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1,160 results on '"Croft, S."'

1. Results of the follow-up of ANTARES neutrino alerts

Author

Albert, A., Alves, S., André, M., Ardid, M., Ardid, S., Aubert, J. -J., Aublin, J., Baret, B., Basa, S., Becherini, Y., Belhorma, B., Bendahman, M., Benfenati, F., Bertin, V., Biagi, S., Bissinger, M., Boumaaza, J., Bouta, M., Bouwhuis, M. C., Brânzas, H., Bruijn, R., Brunner, J., Busto, J., Caiffi, B., Calvo, D., Campion, S., Capone, A., Caramete, L., Carenini, F., Carr, J., Carretero, V., Celli, S., Cerisy, L., Chabab, M., Moursli, R. Cherkaoui El, Chiarusi, T., Circella, M., Coelho, J. A. B., Coleiro, A., Coniglione, R., Coyle, P., Creusot, A., Cruz, A. S. M., Díaz, A. F., De Martino, B., Distefano, C., Di Palma, I., Donzaud, C., Dornic, D., Drouhin, D., Eberl, T., van Eeden, T., van Eijk, D., Hedri, S. El, Khayati, N. El, Enzenhöfer, A., Fermani, P., Ferrara, G., Filippini, F., Fusco, L., Gagliardini, S., García, J., Oliver, C. Gatius, Gay, P., Geißelbrecht, N., Glotin, H., Gozzini, R., Ruiz, R. Gracia, Graf, K., Guidi, C., Haegel, L., Hallmann, S., van Haren, H., Heijboer, A. J., Hello, Y., Hennig, L., Hernández-Rey, J. J., Hößl, J., Hofestädt, J., Huang, F., Illuminati, G., James, C. W., Jisse-Jung, B., de Jong, M., de Jong, P., Kadler, M., Kalekin, O., Katz, U., Kouchner, A., Kreykenbohm, I., Kulikovskiy, V., Lahmann, R., Lamoureux, M., Lazo, A., Lefèvre, D., Leonora, E., Levi, G., Stum, S. Le, Loucatos, S., Maderer, L., Manczak, J., Marcelin, M., Margiotta, A., Marinelli, A., Martínez-Mora, J. A., Migliozzi, P., Moussa, A., Muller, R., Navas, S., Nezri, E., Fearraigh, B. Ó, Oukacha, E., Pāun, A., Pāvālas, G. E., Peña-Martínez, S., Perrin-Terrin, M., Piattelli, P., Popa, V., Pradier, T., Randazzo, N., Real, D., Riccobene, G., Romanov, A., Sánchez-Losa, A., Saina, A., Greus, F. Salesa, Samtleben, D. F. E., Sanguineti, M., Sapienza, P., Schnabel, J., Schumann, J., Schüssler, F., Seneca, J., Spurio, M., Stolarczyk, Th., Taiuti, M., Tayalati, Y., Tingay, S. J., Vallage, B., Vannoye, G., Van Elewyck, V., Viola, S., Vivolo, D., Wilms, J., Zavatarelli, S., Zegarelli, A., Zornoza, J. D., Zúñiga, J., Lipunov, V., Antipov, G., Balanutsa, P., Buckley, D., Budnev, N., Chasovnikov, A., Cheryasov, D., Francile, C., Gabovich, A., Gorbovskoy, E., Gorbunov, I., Gress, O., Kornilov, V., Kuznetsov, A., Iyudin, A., Podesta, R., Podesta, F., Lopez, R. Rebolo, Senik, V., Sierra-Rucart, M., Svertilov, S., Tiurina, N., Vlasenko, D., Yashin, I., Zhirkov, K., Croft, S., Kaplan, D. L., Anderson, G. E., Williams, A., Dobie, D., Bannister, K. W., Hancock, P. J., Evans, P. A., Kennea, J. A., Osborne, J. P., Cenko, S. B., Antier, S., Atteia, J. L., Boër, M., Klotz, A., Chaty, S., Hodapp, K., and Savchenko, V.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

High-energy neutrinos could be produced in the interaction of charged cosmic rays with matter or radiation surrounding astrophysical sources. To look for transient sources associated with neutrino emission, a follow-up program of neutrino alerts has been operating within the ANTARES Collaboration since 2009. This program, named TAToO, has triggered robotic optical telescopes (MASTER, TAROT, ROTSE and the SVOM ground based telescopes) immediately after the detection of any relevant neutrino candidate and scheduled several observations in the weeks following the detection. A subset of ANTARES events with highest probabilities of being of cosmic origin has also been followed by the Swift and the INTEGRAL satellites, the Murchison Widefield Array radio telescope and the H.E.S.S. high-energy gamma-ray telescope. The results of twelve years of observations are reported. No optical counterpart has been significantly associated with an ANTARES candidate neutrino signal during image analysis. Constraints on transient neutrino emission have been set. In September 2015, ANTARES issued a neutrino alert and during the follow-up, a potential transient counterpart was identified by Swift and MASTER. A multi-wavelength follow-up campaign has allowed to identify the nature of this source and has proven its fortuitous association with the neutrino. The return of experience is particularly important for the design of the alert system of KM3NeT, the next generation neutrino telescope in the Mediterranean Sea., Comment: 27 pages, 14 figures, submitted to JCAP

Published
2024

2. Observations and Simulations of Radio Emission and Magnetic Fields in Minkowski's Object

Author

Nolting, C., Lacy, M., Croft, S., Fragile, P. C., Linden, S. T., Nyland, K., and Patil, P.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies
Abstract

We combine new data from the Karl G. Jansky Very Large Array with previous radio observations to create a more complete picture of the ongoing interactions between the radio jet from galaxy NGC 541 and the star-forming system known as Minkowski's Object (MO). We then compare those observations with synthetic radio data generated from a new set of magnetohydrodynamic simulations of a jet-cloud interaction specifically tailored to the parameters of MO. The combination of radio intensity, polarization, and spectral index measurements all convincingly support the interaction scenario and provide additional constraints on the local dynamical state of the intracluster medium and the time since the jet-cloud interaction first began. In particular, we show that only a simulation with a bent radio jet can reproduce the observations., Comment: 17 pages, 6 figures, links to simulation movies in figure captions, accepted for publication in ApJ

Published
2022
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7. A broadband radio view of transient jet ejecta in the black hole candidate X-ray binary MAXI J1535-571

Author

Chauhan, J., Miller-Jones, J. C. A., Anderson, G. E., Paduano, A., Sokolowski, M., Flynn, C., Hancock, P. J., Hurley-Walker, N., Kaplan, D. L., Russell, T. D., Bahramian, A., Duchesne, S. W., Altamirano, D., Croft, S., Krimm, H. A., Sivakoff, G. R., Soria, R., Trott, C. M., Wayth, R. B., Gupta, V., Johnston-Hollitt, M., and Tingay, S. J.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We present a broadband radio study of the transient jets ejected from the black hole candidate X-ray binary MAXI J1535-571, which underwent a prolonged outburst beginning on 2 September 2017. We monitored MAXI J1535-571 with the Murchison Widefield Array (MWA) at frequencies from 119 to 186 MHz over six epochs from 20 September to 14 October 2017. The source was quasi-simultaneously observed over the frequency range 0.84-19 GHz by UTMOST (the upgraded Molonglo Observatory Synthesis Telescope), the Australian Square Kilometre Array Pathfinder, the Australia Telescope Compact Array (ATCA), and the Australian Long Baseline Array (LBA). Using the LBA observations from 23 September 2017, we measured the source size to be $34\pm1$ mas. During the brightest radio flare on 21 September 2017, the source was detected down to 119 MHz by the MWA, and the radio spectrum indicates a turnover between 250 and 500 MHz, which is most likely due to synchrotron self-absorption (SSA). By fitting the radio spectrum with a SSA model and using the LBA size measurement, we determined various physical parameters of the jet knot (identified in ATCA data), including the jet opening angle (= $4.5\pm1.2^{\circ}$) and the magnetic field strength (= $104^{+80}_{-78}$ mG). Our fitted magnetic field strength agrees reasonably well with that inferred from the standard equipartition approach, suggesting the jet knot to be close to equipartition. Our study highlights the capabilities of the Australian suite of radio telescopes to jointly probe radio jets in black hole X-ray binaries (BH-XRBs) via simultaneous observations over a broad frequency range, and with differing angular resolutions. This suite allows us to determine the physical properties of XRB jets. Finally, our study emphasizes the potential contributions that can be made by the low-frequency part of the Square Kilometre Array (SKA-Low) in the study of BH-XRBs., Comment: This article has been accepted for publication in PASA. This article has 16 pages, 7 figures and 1 table

Published
2021
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8. Space Telescope and Optical Reverberation Mapping Project. XII. Broad-Line Region Modeling of NGC 5548

Author

Williams, P. R., Pancoast, A., Treu, T., Brewer, B. J., Peterson, B. M., Barth, A. J., Malkan, M. A., De Rosa, G., Horne, Keith, Kriss, G. A., Arav, N., Bentz, M. C., Cackett, E. M., Bontà, E. Dalla, Dehghanian, M., Done, C., Ferland, G. J., Grier, C. J., Kaastra, J., Kara, E., Kochanek, C. S., Mathur, S., Mehdipour, M., Pogge, R. W., Proga, D., Vestergaard, M., Waters, T., Adams, S. M., Anderson, M. D., Arévalo, P., Beatty, T. G., Bennert, V. N., Bigley, A., Bisogni, S., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., Brotherton, M., Brown, J. E., Brown, J. S., Canalizo, G., Carini, M. T., Clubb, K. I., Comerford, J. M., Corsini, E. M., Crenshaw, D. M., Croft, S., Croxall, K. V., Deason, A. J., De Lorenzo-Cáceres, A., Denney, K. D., Dietrich, M., Edelson, R., Efimova, N. V., Ely, J., Evans, P. A., Fausnaugh, M. M., Filippenko, A. V., Flatland, K., Fox, O. D., Gardner, E., Gates, E. L., Gehrels, N., Geier, S., Gelbord, J. M., Gonzalez, L., Gorjian, V., Greene, J. E., Grupe, D., Gupta, A., Hall, P. B., Henderson, C. B., Hicks, S., Holmbeck, E., Holoien, T. W. -S., Hutchison, T., Im, M., Jensen, J. J., Johnson, C. A., Joner, M. D., Jones, J., Kaspi, S., Kelly, P. L., Kennea, J. A., Kim, M., Kim, S., Kim, S. C., King, A., Klimanov, S. A., Knigge, C., Krongold, Y., Lau, M. W., Lee, J. C., Leonard, D. C., Li, Miao, Lira, P., Lochhaas, C., Ma, Zhiyuan, Manne-Nicholas, E. R., MacInnis, F., Mauerhan, J. C., McGurk, R., Hardy, I. M. Mc, Montuori, C., Morelli, L., Mosquera, A., Mudd, D., Müller-Sánchez, F., Nazarov, S. V., Norris, R. P., Nousek, J. A., Nguyen, M. L., Ochner, P., Okhmat, D. N., Papadakis, I., Parks, J. R., Pei, L., Penny, M. T., Pizzella, A., Poleski, R., Pott, J. -U., Rafter, S. E., Rix, H. -W., Runnoe, J., Saylor, D. A., Schimoia, J. S., Scott, B., Sergeev, S. G., Shappee, B. J., Shivvers, I., Siegel, M., Simonian, G. V., Siviero, A., Skielboe, A., Somers, G., Spencer, M., Starkey, D., Stevens, D. J., Sung, H. -I., Tayar, J., Tejos, N., Turner, C. S., Uttley, P., Van Saders, J., Vaughan, S. A., Vican, L., Villanueva Jr., S., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., Young, S., Yuk, H., Zheng, W., Zhu, W., and Zu, Y.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We present geometric and dynamical modeling of the broad line region for the multi-wavelength reverberation mapping campaign focused on NGC 5548 in 2014. The dataset includes photometric and spectroscopic monitoring in the optical and ultraviolet, covering the H$\beta$, C IV, and Ly$\alpha$ broad emission lines. We find an extended disk-like H$\beta$ BLR with a mixture of near-circular and outflowing gas trajectories, while the C IV and Ly$\alpha$ BLRs are much less extended and resemble shell-like structures. There is clear radial structure in the BLR, with C IV and Ly$\alpha$ emission arising at smaller radii than the H$\beta$ emission. Using the three lines, we make three independent black hole mass measurements, all of which are consistent. Combining these results gives a joint inference of $\log_{10}(M_{\rm BH}/M_\odot) = 7.64^{+0.21}_{-0.18}$. We examine the effect of using the $V$ band instead of the UV continuum light curve on the results and find a size difference that is consistent with the measured UV-optical time lag, but the other structural and kinematic parameters remain unchanged, suggesting that the $V$ band is a suitable proxy for the ionizing continuum when exploring the BLR structure and kinematics. Finally, we compare the H$\beta$ results to similar models of data obtained in 2008 when the AGN was at a lower luminosity state. We find that the size of the emitting region increased during this time period, but the geometry and black hole mass remain unchanged, which confirms that the BLR kinematics suitably gauge the gravitational field of the central black hole., Comment: 26 pages, 19 figures, 1 table, accepted for publication in ApJ

Published
2020
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9. Space Telescope and Optical Reverberation Mapping Project. IX. Velocity-Delay Maps for Broad Emission Lines in NGC 5548

Author

Horne, Keith, De Rosa, G., Peterson, B. M., Barth, A. J., Ely, J., Fausnaugh, M. M., Kriss, G. A., Pei, L., Adams, S. M., Anderson, M. D., Arevalo, P., Beatty, T G., Bennert, V. N., Bentz, M. C., Bigley, A., Bisogni, S., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., Brotherton, M., Brown, J. E., Brown, J. S., Cackett, E. M., Canalizo, G., Carini, M. T., Clubb, K. I., Comerford, J. M., Corsini, E. M., Crenshaw, D. M., Croft, S., Croxall, K. V., Bonta, E. Dalla, Deason, A. J., Dehghanian, M., De Lorenzo-Caceres, A., Denney, K. D., Dietrich, M., Done, C., Edelson, R., Efimova, N. V., Eracleous, M., Evans, P. A., Ferland, G. J., Filippenko, A. V., Flatland, K., Fox, O. D., Gardner, E., Gates, E. L., Gehrels, N., Geier, S., Gelbord, J. M., Goad, M. R., Gonzalez, L., Gorjian, V., Greene, J. E., Grier, C. J., Grupe, D., Gupta, A., Hall, P. B., Henderson, C. B., Hicks, S., Holmbeck, E., Holoien, T. W. -S., Hutchison, T., Im, M., Jensen, J. J., Johnson, C. A., Joner, M. D., Jones, J., Kaastra, J., Kaspi, S., Kelly, P. L., Kennea, J. A., Kim, M., Kim, S., Kim, S. C., King, A., Klimanov, S. A., Kochanek, C. S., Korista, K. T., Krongold, Y., Lau, M. W., Lee, J. C., Leonard, D. C., Li, Miao, Lira, P., Lochhaas, C., Ma, Zhiyuan, MacInnis, F., Malkan, M. A., Manne-Nicholas, E. R., Mathur, S., Mauerhan, J. C., McGurk, R., Hardy, I. M. Mc, Montuori, C., Morelli, L., Mosquera, A., Mudd, D., Mueller-Sanchez, F., Nazarov, S. V., Netzer, H., Norris, R. P., Nousek, J. A., Nguyen, M. L., Ochner, P., Okhmat, D. N., Pancoast, A., Papadakis, I., Parks, J. R., Penny, M. T., Pizzella, A., Pogge, R. W., Poleski, R., Pott, J. -U., Proga, D., Rafter, S. E., Rix, H. -W., Runnoe, J., Saylor, D. A., Schimoia, J. S., Schnuelle, K., Scott, B., Sergeev, S. G., Shappee, B. J., Shivvers, I., Siegel, M., Simonian, G. V., Siviero, A., Skielboe, A., Somers, G., Spencer, M., Starkey, D., Stevens, D. J., Strauss, M. A., Sung, H. -I., Tayar, J., Teems, K. G., Tejos, N., Treu, T., Turner, C. S., Uttley, P., Van Saders, J ., Vestergaard, M., Vican, L., Villanueva Jr, S., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., Young, S., Yuk, H., Zakamska, N. L., Zheng, W., Zhu, W., and Zu, Y.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We report velocity-delay maps for prominent broad emission lines, Ly_alpha, CIV, HeII and H_beta, in the spectrum of NGC5548. The emission-line responses inhabit the interior of a virial envelope. The velocity-delay maps reveal stratified ionization structure. The HeII response inside 5-10 light-days has a broad single-peaked velocity profile. The Ly_alpha, CIV, and H_beta responses peak inside 10 light-days, extend outside 20 light-days, and exhibit a velocity profile with two peaks separated by 5000 km/s in the 10 to 20 light-day delay range. The velocity-delay maps show that the M-shaped lag vs velocity structure found in previous cross-correlation analysis is the signature of a Keplerian disk with a well-defined outer edge at R=20 light-days. The outer wings of the M arise from the virial envelope, and the U-shaped interior of the M is the lower half of an ellipse in the velocity-delay plane. The far-side response is weaker than that from the near side, so that we see clearly the lower half, but only faintly the upper half, of the velocity--delay ellipse. The delay tau=(R/c)(1-sin(i))=5 light-days at line center is from the near edge of the inclined ring, giving the inclination i=45 deg. A black hole mass of M=7x10^7 Msun is consistent with the velocity-delay structure. A barber-pole pattern with stripes moving from red to blue across the CIV and possibly Ly_alpha line profiles suggests the presence of azimuthal structure rotating around the far side of the broad-line region and may be the signature of precession or orbital motion of structures in the inner disk. Further HST observations of NGC 5548 over a multi-year timespan but with a cadence of perhaps 10 days rather than 1 day could help to clarify the nature of this new AGN phenomenon., Comment: 19 pages, 9 figures, ApJ in press

Published
2020
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10. Space Telescope and Optical Reverberation Mapping Project. IX. Velocity–Delay Maps for Broad Emission Lines in NGC 5548

Author

Horne, Keith, De Rosa, G, Peterson, BM, Barth, AJ, Ely, J, Fausnaugh, MM, Kriss, GA, Pei, L, Bentz, MC, Cackett, EM, Edelson, R, Eracleous, M, Goad, MR, Grier, CJ, Kaastra, J, Kochanek, CS, Krongold, Y, Mathur, S, Netzer, H, Proga, D, Tejos, N, Vestergaard, M, Villforth, C, Adams, SM, Anderson, MD, Arévalo, P, Beatty, TG, Bennert, VN, Bigley, A, Bisogni, S, Borman, GA, Boroson, TA, Bottorff, MC, Brandt, WN, Breeveld, AA, Brotherton, M, Brown, JE, Brown, JS, Canalizo, G, Carini, MT, Clubb, KI, Comerford, JM, Corsini, EM, Crenshaw, DM, Croft, S, Croxall, KV, Bontà, E Dalla, Deason, AJ, Dehghanian, M, De Lorenzo-Cáceres, A, Denney, KD, Dietrich, M, Done, C, Efimova, NV, Evans, PA, Ferland, GJ, Filippenko, AV, Flatland, K, Fox, OD, Gardner, E, Gates, EL, Gehrels, N, Geier, S, Gelbord, JM, Gonzalez, L, Gorjian, V, Greene, JE, Grupe, D, Gupta, A, Hall, PB, Henderson, CB, Hicks, S, Holmbeck, E, Holoien, TW-S, Hutchison, T, Im, M, Jensen, JJ, Johnson, CA, Joner, MD, Jones, J, Kaspi, S, Kelly, PL, Kennea, JA, Kim, M, Kim, S, Kim, SC, King, A, Klimanov, SA, Korista, KT, Lau, MW, Lee, JC, Leonard, DC, Li, Miao, Lira, P, Lochhaas, C, Ma, Zhiyuan, MacInnis, F, Malkan, MA, Manne-Nicholas, ER, and Mauerhan, JC

Subjects
astro-ph.GA, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

In this contribution, we achieve the primary goal of the active galactic nucleus (AGN) STORM campaign by recovering velocity-delay maps for the prominent broad emission lines (Lyα, C iv, He ii, and Hβ) in the spectrum of NGC 5548. These are the most detailed velocity-delay maps ever obtained for an AGN, providing unprecedented information on the geometry, ionization structure, and kinematics of the broad-line region. Virial envelopes enclosing the emission-line responses show that the reverberating gas is bound to the black hole. A stratified ionization structure is evident. The He ii response inside 5-10 lt-day has a broad single-peaked velocity profile. The Lyα, C iv, and Hβ responses extend from inside 2 to outside 20 lt-day, with double peaks at ±2500 km s-1 in the 10-20 lt-day delay range. An incomplete ellipse in the velocity-delay plane is evident in Hβ. We interpret the maps in terms of a Keplerian disk with a well-defined outer rim at R = 20 lt-day. The far-side response is weaker than that from the near side. The line-center delay days gives the inclination i ≈ 45°. The inferred black hole mass is M BH ≈ 7 × 107 M o˙. In addition to reverberations, the fit residuals confirm that emission-line fluxes are depressed during the "BLR Holiday"identified in previous work. Moreover, a helical "Barber-Pole"pattern, with stripes moving from red to blue across the C iv and Lyα line profiles, suggests azimuthal structure rotating with a 2 yr period that may represent precession or orbital motion of inner-disk structures casting shadows on the emission-line region farther out.

Published
2021

11. Science with the Murchison Widefield Array: Phase I Results and Phase II Opportunities

Author

Beardsley, A. P., Johnston-Hollitt, M., Trott, C. M., Pober, J. C., Morgan, J., Oberoi, D., Kaplan, D. L., Lynch, C. R., Anderson, G. E., McCauley, P. I., Croft, S., James, C. W., Wong, O. I., Tremblay, C. D., Norris, R. P., Cairns, I. H., Lonsdale, C. J., Hancock, P. J., Gaensler, B. M., Bhat, N. D. R., Li, W., Hurley-Walker, N., Callingham, J. R., Seymour, N., Yoshiura, S., Joseph, R. C., Takahashi, K., Sokolowski, M., Miller-Jones, J. C. A., Chauhan, J. V., Bojičić, I., Filipović, M. D., Leahy, D., Su, H., Tian, W. W., McSweeney, S. J., Meyers, B. W., Kitaeff, S., Vernstrom, T., Gürkan, G., Heald, G., Xue, M., Riseley, C. J., Duchesne, S. W., Bowman, J. D., Jacobs, D. C., Crosse, B., Emrich, D., Franzen, T. M. O., Horsley, L., Kenney, D., Morales, M. F., Pallot, D., Steele, K., Tingay, S. J., Walker, M., Wayth, R. B., Williams, A., and Wu, C.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

The Murchison Widefield Array (MWA) is an open access telescope dedicated to studying the low frequency (80$-$300 MHz) southern sky. Since beginning operations in mid 2013, the MWA has opened a new observational window in the southern hemisphere enabling many science areas. The driving science objectives of the original design were to observe 21\,cm radiation from the Epoch of Reionisation (EoR), explore the radio time domain, perform Galactic and extragalactic surveys, and monitor solar, heliospheric, and ionospheric phenomena. All together 60$+$ programs recorded 20,000 hours producing 146 papers to date. In 2016 the telescope underwent a major upgrade resulting in alternating compact and extended configurations. Other upgrades, including digital back-ends and a rapid-response triggering system, have been developed since the original array was commissioned. In this paper we review the major results from the prior operation of the MWA, and then discuss the new science paths enabled by the improved capabilities. We group these science opportunities by the four original science themes, but also include ideas for directions outside these categories., Comment: 38 pages, 12 figures, accepted for publication in PASA

Published
2019
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12. Space Telescope and Optical Reverberation Mapping Project. VIII. Time Variability of Emission and Absorption in NGC 5548 Based on Modeling the Ultraviolet Spectrum

Author

Kriss, G. A., De Rosa, G., Ely, J., Peterson, B. M., Kaastra, J., Mehdipour, M., Ferland, G. J., Dehghanian, M., Mathur, S., Edelson, R., Korista, K. T., Arav, N., Barth, A. J., Bentz, M. C., Brandt, W. N., Crenshaw, D. M., Bontà, E. Dalla, Denney, K. D., Done, C., Eracleous, M., Fausnaugh, M. M., Gardner, E., Goad, M. R., Grier, C. J., Horne, Keith, Kochanek, C. S., Mchardy, I. M., Netzer, H., Pancoast, A., Pei, L., Pogge, R. W., Proga, D., Silva, C., Tejos, N., Vestergaard, M., Adams, S. M., Anderson, M. D., Arévalo, P., Beatty, T G., Behar, E., Bennert, V. N., Bianchi, S., Bigley, A., Bisogni, S., Boissay-Malaquin, R., Borman, G. A., Bottorff, M. C., Breeveld, A. A., Brotherton, M., Brown, J. E., Brown, J. S., Cackett, E. M., Canalizo, G., Cappi, M., Carini, M. T., Clubb, K. I., Comerford, J. M., Coker, C. T., Corsini, E. M., Costantini, E., Croft, S., Croxall, K. V., Deason, A. J., De Lorenzo-Cáceres, A., De Marco, B., Dietrich, M., Di Gesu, L., Ebrero, J., Evans, P. A., Filippenko, A. V., Flatland, K., Gates, E. L., Gehrels, N., Geier, Z S., Gelbord, J. M., Gonzalez, L., Gorjian, V., Grupe, D., Gupta, A., Hall, P. B., Henderson, C. B., Hicks, S., Holmbeck, E., Holoien, T. W. -S., Hutchison, T. A., Im, M., Jensen, J. J., Johnson, C. A., Joner, M. D., Kaspi, S., Kelly, B. C., Kelly, P. L., Kennea, J. A., Kim, M., Kim, S. C., Kim, S. Y., King, A., Klimanov, S. A., Krongold, Y., Lau, M. W., Lee, J. C., Leonard, D. C., Li, Miao, Lira, P., Lochhaas, C., Ma, Zhiyuan, Macinnis, F., Malkan, M. A., Manne-Nicholas, E. R., Matt, G., Mauerhan, J. C., Mcgurk, R., Montuori, C., Morelli, L., Mosquera, A., Mudd, D., Müller-Sánchez, F., Nazarov, S. V., Norris, R. P., Nousek, J. A., Nguyen, M. L., Ochner, P., Okhmat, D. N., Paltani, S., Parks, J. R., Pinto, C., Pizzella, A., Poleski, R., Ponti, G., Pott, J. -U., Rafter, S. E., Rix, H. -W., Runnoe, J., Saylor, D. A., Schimoia, J. S., Schnülle, K., Scott, B., Sergeev, S. G., Shappee, B. J., Shivvers, I., Siegel, M., Simonian, G. V., Siviero, A., Skielboe, A., Somers, G., Spencer, M., Starkey, D., Stevens, D. J., Sung, H. -I., Tayar, J., Teems, K. G., Treu, T., Turner, C. S., Uttley, P., Van Saders, J ., Vican, L., Villforth, C., Villanueva Jr., S., Walton, D. J., Waters, T., Weiss, Y., Woo, J. -H., Yan, H., Yuk, H., Zheng, W., Zhu, W., and Zu, Y.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We model the ultraviolet spectra of the Seyfert 1 galaxy NGC~5548 obtained with the Hubble Space Telescope during the 6-month reverberation-mapping campaign in 2014. Our model of the emission from NGC 5548 corrects for overlying absorption and deblends the individual emission lines. Using the modeled spectra, we measure the response to continuum variations for the deblended and absorption-corrected individual broad emission lines, the velocity-dependent profiles of Ly$\alpha$ and C IV, and the narrow and broad intrinsic absorption features. We find that the time lags for the corrected emission lines are comparable to those for the original data. The velocity-binned lag profiles of Ly$\alpha$ and C IV have a double-peaked structure indicative of a truncated Keplerian disk. The narrow absorption lines show delayed response to continuum variations corresponding to recombination in gas with a density of $\sim 10^5~\rm cm^{-3}$. The high-ionization narrow absorption lines decorrelate from continuum variations during the same period as the broad emission lines. Analyzing the response of these absorption lines during this period shows that the ionizing flux is diminished in strength relative to the far-ultraviolet continuum. The broad absorption lines associated with the X-ray obscurer decrease in strength during this same time interval. The appearance of X-ray obscuration in $\sim\,2012$ corresponds with an increase in the luminosity of NGC 5548 following an extended low state. We suggest that the obscurer is a disk wind triggered by the brightening of NGC 5548 following the decrease in size of the broad-line region during the preceding low-luminosity state., Comment: 50 pages, 30 figures, uses aastex62.cls. Accepted for publication in ApJ, 07/06/2019. High-level products page in MAST will go live after 7/15/2019. Replaced Figure 4 on 7/12/2019 to be more red/green color-blind friendly

Published
2019
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13. A Fast Radio Burst with frequency-dependent polarization detected during Breakthrough Listen observations

Author

Price, D. C., Foster, G., Geyer, M., van Straten, W., Gajjar, V., Hellbourg, G., Karastergiou, A., Keane, E. F., Siemion, A. P. V., Arcavi, I., Bhat, R., Caleb, M., Chang, S-W., Croft, S., DeBoer, D., de Pater, I., Drew, J., Enriquez, J. E., Farah, W., Gizani, N., Green, J. A., Isaacson, H., Hickish, J., Jameson, A., Lebofsky, M., MacMahon, D. H. E., Möller, A., Onken, C. A., Petroff, E., Werthimer, D., Wolf, C., Worden, S. P., and Zhang, Y. G.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

Here, we report on the detection and verification of Fast Radio Burst FRB 180301, which occurred on UTC 2018 March 1 during the Breakthrough Listen observations with the Parkes telescope. Full-polarization voltage data of the detection were captured--a first for non-repeating FRBs--allowing for coherent de-dispersion and additional verification tests. The coherently de-dispersed dynamic spectrum of FRB 180301 shows complex, polarized frequency structure over a small fractional bandwidth. As FRB 180301 was detected close to the geosynchronous satellite band during a time of known 1-2 GHz satellite transmissions, we consider whether the burst was due to radio interference emitted or reflected from an orbiting object. Based on the preponderance of our verification tests, we find that FRB 180301 is likely of astrophysical origin, but caution that anthropogenic sources cannot conclusively be ruled out., Comment: Submitted to MNRAS

Published
2019
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14. Space Telescope and Optical Reverberation Mapping Project. XII. Broad-line Region Modeling of NGC 5548

Author

Williams, PR, Pancoast, A, Treu, T, Brewer, BJ, Peterson, BM, Barth, AJ, Malkan, MA, Rosa, GD, Horne, K, Kriss, GA, Arav, N, Bentz, MC, Cackett, EM, Bontà, ED, Dehghanian, M, Done, C, Ferland, GJ, Grier, CJ, Kaastra, J, Kara, E, Kochanek, CS, Mathur, S, Mehdipour, M, Pogge, RW, Proga, D, Vestergaard, M, Waters, T, Adams, SM, Anderson, MD, Arévalo, P, Beatty, TG, Bennert, VN, Bigley, A, Bisogni, S, Borman, GA, Boroson, TA, Bottorff, MC, Brandt, WN, Breeveld, AA, Brotherton, M, Brown, JE, Brown, JS, Canalizo, G, Carini, MT, Clubb, KI, Comerford, JM, Corsini, EM, Crenshaw, DM, Croft, S, Croxall, KV, Deason, AJ, Lorenzo-Cáceres, AD, Denney, KD, Dietrich, M, Edelson, R, Efimova, NV, Ely, J, Evans, PA, Fausnaugh, MM, Filippenko, AV, Flatland, K, Fox, OD, Gardner, E, Gates, EL, Gehrels, N, Geier, S, Gelbord, JM, Gonzalez, L, Gorjian, V, Greene, JE, Grupe, D, Gupta, A, Hall, PB, Henderson, CB, Hicks, S, Holmbeck, E, Holoien, TWS, Hutchison, T, Im, M, Jensen, JJ, Johnson, CA, Joner, MD, Jones, J, Kaspi, S, Kelly, PL, Kennea, JA, Kim, M, Kim, S, Kim, SC, King, A, Klimanov, SA, Knigge, C, Krongold, Y, Lau, MW, Lee, JC, Leonard, DC, Li, M, Lira, P, Lochhaas, C, and Ma, Z

Subjects
Active galaxies, Active galactic nuclei, Reverberation mapping, Seyfert galaxies, astro-ph.GA, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

We present geometric and dynamical modeling of the broad line region (BLR) for the multi-wavelength reverberation mapping campaign focused on NGC 5548 in 2014. The data set includes photometric and spectroscopic monitoring in the optical and ultraviolet, covering the Hβ, C iv, and Ly broad emission lines. We find an extended disk-like Hβ BLR with a mixture of near-circular and outflowing gas trajectories, while the C iv and Ly BLRs are much less extended and resemble shell-like structures. There is clear radial structure in the BLR, with C iv and Ly emission arising at smaller radii than the Hβ emission. Using the three lines, we make three independent black hole mass measurements, all of which are consistent. Combining these results gives a joint inference of . We examine the effect of using the V band instead of the UV continuum light curve on the results and find a size difference that is consistent with the measured UV-optical time lag, but the other structural and kinematic parameters remain unchanged, suggesting that the V band is a suitable proxy for the ionizing continuum when exploring the BLR structure and kinematics. Finally, we compare the Hβ results to similar models of data obtained in 2008 when the active galactic nucleus was at a lower luminosity state. We find that the size of the emitting region increased during this time period, but the geometry and black hole mass remained unchanged, which confirms that the BLR kinematics suitably gauge the gravitational field of the central black hole.

Published
2020

16. The Murchison Widefield Array Transients Survey (MWATS). A search for low frequency variability in a bright Southern hemisphere sample

Author

Bell, M. E., Murphy, Tara, Hancock, P. J., Callingham, J. R., Johnston, S., Kaplan, D. L., Hunstead, R. W., Sadler, E. M., Croft, S., White, S. V., Hurley-Walker, N., Chhetri, R., Morgan, J. S., Edwards, P. G., Rowlinson, A., Offringa, A. R., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Deshpande, A. A., Gaensler, B. M., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Lonsdale, C. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Wayth, R. B., Webster, R. L., Williams, A., and Williams, C. L.

Subjects
Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report on a search for low-frequency radio variability in 944 bright (> 4Jy at 154 MHz) unresolved, extragalactic radio sources monitored monthly for several years with the Murchison Widefield Array. In the majority of sources we find very low levels of variability with typical modulation indices < 5%. We detect 15 candidate low frequency variables that show significant long term variability (>2.8 years) with time-averaged modulation indices M = 3.1 - 7.1%. With 7/15 of these variable sources having peaked spectral energy distributions, and only 5.7% of the overall sample having peaked spectra, we find an increase in the prevalence of variability in this spectral class. We conclude that the variability seen in this survey is most probably a consequence of refractive interstellar scintillation and that these objects must have the majority of their flux density contained within angular diameters less than 50 milli-arcsec (which we support with multi-wavelength data). At 154 MHz we demonstrate that interstellar scintillation time-scales become long (~decades) and have low modulation indices, whilst synchrotron driven variability can only produce dynamic changes on time-scales of hundreds of years, with flux density changes less than one milli-jansky (without relativistic boosting). From this work we infer that the low frequency extra-galactic southern sky, as seen by SKA-Low, will be non-variable on time-scales shorter than one year., Comment: 19 pages, 11 figures

Published
2018
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17. Highest-frequency detection of FRB 121102 at 4-8 GHz using the Breakthrough Listen Digital Backend at the Green Bank Telescope

Author

Gajjar, V., Siemion, A. P. V., Price, D. C., Law, C. J., Michilli, D., Hessels, J. W. T., Chatterjee, S., Archibald, A. M., Bower, G. C., Brinkman, C., Burke-Spolaor, S., Cordes, J. M., Croft, S., Enriquez, J. Emilio, Foster, G., Gizani, N., Hellbourg, G., Isaacson, H., Kaspi, V. M., Lazio, T. J. W., Lebofsky, M., Lynch, R. S., MacMahon, D., McLaughlin, M. A., Ransom, S. M., Scholz, P., Seymour, A., Spitler, L. G., Tendulkar, S. P., Werthimer, D., and Zhang, Y. G.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report the first detections of the repeating fast radio burst source FRB 121102 above 5.2 GHz. Observations were performed using the 4$-$8 GHz receiver of the Robert C. Byrd Green Bank Telescope with the Breakthrough Listen digital backend. We present the spectral, temporal and polarization properties of 21 bursts detected within the first 60 minutes of a total 6-hour observations. These observations comprise the highest burst density yet reported in the literature, with 18 bursts being detected in the first 30 minutes. A few bursts clearly show temporal sub-structures with distinct spectral properties. These sub-structures superimpose to provide enhanced peak signal-to-noise ratio at higher trial dispersion measures. Broad features occur in $\sim 1$ GHz wide subbands that typically differ in peak frequency between bursts within the band. Finer-scale structures ($\sim 10-50$ MHz) within these bursts are consistent with that expected from Galactic diffractive interstellar scintillation. The bursts exhibit nearly 100% linear polarization, and a large average rotation measure of 9.359$\pm$0.012 $\times$ 10$^{\rm 4}$ rad m$^{\rm -2}$ (in the observer's frame). No circular polarization was found for any burst. We measure an approximately constant polarization position angle in the 13 brightest bursts. The peak flux densities of the reported bursts have average values (0.2$\pm$0.1 Jy), similar to those seen at lower frequencies ($<3$ GHz), while the average burst widths (0.64$\pm$0.46 ms) are relatively narrower., Comment: Accepted for publication in ApJ

Published
2018
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18. A Serendipitous MWA Search for Narrow-band and Broad-band Low Frequency Radio Transmissions from 1I/2017 U1 'Oumuamua

Author

Tingay, S. J., Kaplan, D. L., Lenc, E., Croft, S., McKinley, B., Beardsley, A., Crosse, B., Emrich, D., Franzen, T. M. O., Gaensler, B. M., Horsley, L., Johnston-Hollitt, M., Kenney, D., Morales, M. F., Pallot, D., Steele, K., Trott, C. M., Walker, M., Wayth, R. B., Williams, A., and Wu, C.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

We examine data from the Murchison Widefield Array (MWA) in the frequency range 72 -- 102 MHz for a field-of-view that serendipitously contained the interstellar object 'Oumuamua on 2017 November 28. Observations took place with time resolution of 0.5 s and frequency resolution of 10 kHz. %This observation was undertaken for another purpose but due to the MWA's extremely large field-of-view, 'Oumuamua was serendipitously observed simultaneously. Based on the interesting but highly unlikely suggestion that 'Oumuamua is an interstellar spacecraft, due to some unusual orbital and morphological characteristics, we examine our data for signals that might indicate the presence of intelligent life associated with 'Oumuamua. We searched our radio data for: 1) impulsive narrow-band signals; 2) persistent narrow-band signals; and 3) impulsive broadband signals. We found no such signals with non-terrestrial origins and make estimates of the upper limits on Equivalent Isotropic Radiated Power (EIRP) for these three cases of approximately 7 kW, 840 W, and 100 kW, respectively. These transmitter powers are well within the capabilities of human technologies, and are therefore plausible for alien civilizations. While the chances of positive detection in any given Search for Extraterrestrial Intelligence (SETI) experiment are vanishingly small, the characteristics of new generation telescopes such as the MWA (and in the future, the Square Kilometre Array) make certain classes of SETI experiment easy, or even a trivial by-product of astrophysical observations. This means that the future costs of SETI experiments are very low, allowing large target lists to partially balance the low probability of a positive detection., Comment: Nine pages, four figures. Accepted for publication in ApJ

Published
2018
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19. A search for Extraterrestrial Intelligence (SETI) toward the Galactic Anticenter with the Murchison Widefield Array

Author

Tingay, S. J., Tremblay, C. D., and Croft, S.

Subjects
Physics - Popular Physics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

Following from the results of the first systematic modern low frequency Search for Extraterrestrial Intelligence (SETI) using the Murchison Widefield Array (MWA), which was directed toward a Galactic Center field, we report a second survey toward a Galactic Anticenter field. Using the MWA in the frequency range of 99 to 122 MHz over a three hour period, a 625 sq. deg. field centered on Orion KL (in the general direction of the Galactic Anticenter) was observed with a frequency resolution of 10 kHz. Within this field, 22 exoplanets are known. At the positions of these exoplanets, we searched for narrow band signals consistent with radio transmissions from intelligent civilisations. No such signals were found with a 5-sigma detection threshold. Our sample is significantly different to the 45 exoplanets previously studied with the MWA toward the Galactic Center Tingay et al.(2016), since the Galactic Center sample is dominated by exoplanets detected using microlensing, hence at much larger distances compared to the exoplants toward the Anticenter, found via radial velocity and transit detection methods. Our average effective sensitivity to extraterrestrial transmiter power is therefore much improved for the Anticenter sample. Added to this, our data processing techniques have improved, reducing our observational errors, leading to our best detection limit being reduced by approximately a factor of four compared to our previously published results., Comment: Six pages, two figures. Accepted for publication in ApJ

Published
2018
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20. Breakthrough Listen Observations of 1I/'Oumuamua with the GBT

Author

Enriquez, J. E., Siemion, A., Lazio, T. J. W., Lebofsky, M., MacMahon, D. H. E., Park, R. S., Croft, S., DeBoer, D., Gizani, N., Gajjar, V., Hellbourg, G., Isaacson, H., and Price, D. C.

Subjects
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

We have conducted a search for radio emission consistent with an artificial source targeting 1I/'Oumuamua with the Robert C. Byrd Green Bank Telescope (GBT) between 1.1 and 11.6 GHz. We searched the data for narrowband signals and found none. Given the close proximity to this interstellar object, we can place limits to putative transmitters with extremely low power (0.08 W)., Comment: 1 table, Submitted to RN of AAS

Published
2018

21. Space Telescope and Optical Reverberation Mapping Project. VIII. Time Variability of Emission and Absorption in NGC 5548 Based on Modeling the Ultraviolet Spectrum

Author

Kriss, GA, De Rosa, G, Ely, J, Peterson, BM, Kaastra, J, Mehdipour, M, Ferland, GJ, Dehghanian, M, Mathur, S, Edelson, R, Korista, KT, Arav, N, Barth, AJ, Bentz, MC, Brandt, WN, Crenshaw, DM, Bontà, E Dalla, Denney, KD, Done, C, Eracleous, M, Fausnaugh, MM, Gardner, E, Goad, MR, Grier, CJ, Horne, Keith, Kochanek, CS, McHardy, IM, Netzer, H, Pancoast, A, Pei, L, Pogge, RW, Proga, D, Silva, C, Tejos, N, Vestergaard, M, Adams, SM, Anderson, MD, Arévalo, P, Beatty, TG, Behar, E, Bennert, VN, Bianchi, S, Bigley, A, Bisogni, S, Boissay-Malaquin, R, Borman, GA, Bottorff, MC, Breeveld, AA, Brotherton, M, Brown, JE, Brown, JS, Cackett, EM, Canalizo, G, Cappi, M, Carini, MT, Clubb, KI, Comerford, JM, Coker, CT, Corsini, EM, Costantini, E, Croft, S, Croxall, KV, Deason, AJ, De Lorenzo-Cáceres, A, De Marco, B, Dietrich, M, Di Gesu, L, Ebrero, J, Evans, PA, Filippenko, AV, Flatland, K, Gates, EL, Gehrels, N, Geier, S, Gelbord, JM, Gonzalez, L, Gorjian, V, Grupe, D, Gupta, A, Hall, PB, Henderson, CB, Hicks, S, Holmbeck, E, Holoien, TW-S, Hutchison, TA, Im, M, Jensen, JJ, Johnson, CA, Joner, MD, Kaspi, S, Kelly, BC, Kelly, PL, Kennea, JA, Kim, M, Kim, SC, Kim, SY, King, A, Klimanov, SA, Krongold, Y, and Lau, MW

Subjects
galaxies: active, galaxies: individual, galaxies: nuclei, galaxies: Seyfert, astro-ph.GA, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

We model the ultraviolet spectra of the Seyfert 1 galaxy NGC 5548 obtained with the Hubble Space Telescope during the 6 month reverberation mapping campaign in 2014. Our model of the emission from NGC 5548 corrects for overlying absorption and deblends the individual emission lines. Using the modeled spectra, we measure the response to continuum variations for the deblended and absorption-corrected individual broad emission lines, the velocity-dependent profiles of Ly and C iv, and the narrow and broad intrinsic absorption features. We find that the time lags for the corrected emission lines are comparable to those for the original data. The velocity-binned lag profiles of Ly and C iv have a double-peaked structure indicative of a truncated Keplerian disk. The narrow absorption lines show a delayed response to continuum variations corresponding to recombination in gas with a density of ∼105 cm-3. The high-ionization narrow absorption lines decorrelate from continuum variations during the same period as the broad emission lines. Analyzing the response of these absorption lines during this period shows that the ionizing flux is diminished in strength relative to the far-ultraviolet continuum. The broad absorption lines associated with the X-ray obscurer decrease in strength during this same time interval. The appearance of X-ray obscuration in ∼2012 corresponds with an increase in the luminosity of NGC 5548 following an extended low state. We suggest that the obscurer is a disk wind triggered by the brightening of NGC 5548 following the decrease in size of the broad-line region during the preceding low-luminosity state.

Published
2019

22. Breakthrough Listen Follow-up of the Reported Transient Signal Observed at the Arecibo Telescope in the Direction of Ross 128

Author

Enriquez, J. E., Siemion, A., Dana, R., Croft, S., Méndez, A., Xu, A., DeBoer, D., Gajjar, V., Hellbourg, G., Isaacson, H., Lebofsky, M., MacMahon, D. H. E., Price, D. C., Werthimer, D., and Zuluaga, J.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We undertook observations with the Green Bank Telescope, simultaneously with the 300m telescope in Arecibo, as a follow-up of a possible flare of radio emission from Ross 128. We report here the non-detections from the GBT observations in C band (4-8 GHz), as well as non-detections in archival data at L band (1.1-1.9 GHz). We suggest that a likely scenario is that the emission comes from one or more satellites passing through the same region of the sky., Comment: 6 pages, 2 figures. Accepted to International Journal of Astrobiology

Published
2017

23. Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the UV anomaly in NGC 5548 with X-Ray Spectroscopy

Author

Mathur, S., Gupta, A., Page, K., Pogge, R. W., Krongold, Y., Goad, M. R., Adams, S. M., Anderson, M. D., Arevalo, P., Barth, A. J., Bazhaw, C., Beatty, T. G., Bentz, M. C., Bigley, A., Bisogni, S., Borman, G. A., Boroson, T. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., Brown, J. E., Brown, J. S., Cackett, E. M., Canalizo, G., Carini, M. T., Clubb, K. I., Comerford, J. M., Coker, C. T., Corsini, E. M., Crenshaw, D. M., Croft, S., Croxall, K. V., Bonta, E. Dalla, Deason, A. J., Denney, K. D., De Lorenzo-Caceres, A., De Rosa, G., Dietrich, M., Edelson, R., Ely, J., Eracleous, M., Evans, P. A., Fausnaugh, M. M., Ferland, G. J., Filippenko, A. V., Flatland, K., Fox, O. D., Gates, E. L., Gehrels, N., Geier, S., Gelbord, J. M., Gorjian, V., Greene, J. E., Grier, C. J., Grupe, D., Hall, P. B., Henderson, C. B., Hicks, S., Holmbeck, E., Holoien, T. W. -S., Horenstein, D., Horne, Keith, Hutchison, T., Im, M., Jensen, J. J., Johnson, C. A., Joner, M. D., Jones, J., Kaastra, J., Kaspi, S., Kelly, B. C., Kelly, P. L., Kennea, J. A., Kim, M., Kim, S., Kim, S. C., King, A., Klimanov, S. A., Kochanek, C. S., Korista, K. T., Kriss, G. A., Lau, M. W., Lee, J. C., Leonard, D. C., Li, M., Lira, P., Ma, Z., MacInnis, F., Manne-Nicholas, E. R., Malkan, M. A., Mauerhan, J. C., McGurk, R., McHardy, I. M., Montouri, C., Morelli, L., Mosquera, A., Mudd, D., Muller-Sanchez, F., Musso, R., Nazarov, S. V., Netzer, H., Nguyen, M. L., Norris, R. P., Nousek, J. A., Ochner, P., Okhmat, D. N., Ou-Yang, B., Pancoast, A., Papadakis, I., Parks, J. R., Pei, L., Peterson, B. M., Pizzella, A., Poleski, R., Pott, J. -U., Rafter, S. E., Rix, H. -W., Runnoe, J., Saylor, D. A., Schimoia, J. S., Schnülle, K., Sergeev, S. G., Shappee, B. J., Shivvers, I., Siegel, M., Simonian, G. V., Siviero, A., Skielboe, A., Somers, G., Spencer, M., Starkey, D., Stevens, D. J., Sung, H. -I., Tayar, J., Tejos, N., Turner, C. S., Uttley, P., Van Saders, J., Vestergaard, M., Vican, L., VillanuevaJr., S., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., Young, S., Yuk, H., Zheng, W., Zhu, W., and Zu, Y.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

During the Space Telescope and Optical Reverberation Mapping Project (STORM) observations of NGC 5548, the continuum and emission-line variability became de-correlated during the second half of the 6-month long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as a part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than being due to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all the three observations: the UV emission line flux decrease, the soft-excess increase, and the emission line anomaly., Comment: ApJ in press. Replaced with the accepted version

Published
2017
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24. Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-Line Analysis for NGC 5548

Author

Pei, L., Fausnaugh, M. M., Barth, A. J., Peterson, B. M., Bentz, M. C., De Rosa, G., Denney, K. D., Goad, M. R., Kochanek, C. S., Korista, K. T., Kriss, G. A., Pogge, R. W., Bennert, V. N., Brotherton, M., Clubb, K. I., Bontà, E. Dalla, Filippenko, A. V., Greene, J. E., Grier, C. J., Vestergaard, M., Zheng, W., Adams, Scott M., Beatty, Thomas G., Bigley, A., Brown, Jacob E., Brown, Jonathan S., Canalizo, G., Comerford, J. M., Coker, Carl T., Corsini, E. M., Croft, S., Croxall, K. V., Deason, A. J., Eracleous, Michael, Fox, O. D., Gates, E. L., Henderson, C. B., Holmbeck, E., Holoien, T. W. -S., Jensen, J. J., Johnson, C. A., Kelly, P. L., Kim, S., King, A., Lau, M. W., Li, Miao, Lochhaas, Cassandra, Ma, Zhiyuan, Manne-Nicholas, E. R., Mauerhan, J. C., Malkan, M. A., McGurk, R., Morelli, L., Mosquera, Ana, Mudd, Dale, Sanchez, F. Muller, Nguyen, M. L., Ochner, P., Ou-Yang, B., Pancoast, A., Penny, Matthew T., Pizzella, A., Poleski, Radosław, Runnoe, Jessie, Scott, B., Schimoia, Jaderson S., Shappee, B. J., Shivvers, I., Simonian, Gregory V., Siviero, A., Somers, Garrett, Stevens, Daniel J., Strauss, M. A., Tayar, Jamie, Tejos, N., Treu, T., Van Saders, J., Vican, L., Villanueva Jr., S., Yuk, H., Zakamska, N. L., Zhu, W., Anderson, M. D., Arévalo, P., Bazhaw, C., Bisogni, S., Borman, G. A., Bottorff, M. C., Brandt, W. N., Breeveld, A. A., Cackett, E. M., Carini, M. T., Crenshaw, D. M., De Lorenzo-Cáceres, A., Dietrich, M., Edelson, R., Efimova, N. V., Ely, J., Evans, P. A., Ferland, G. J., Flatland, K., Gehrels, N., Geier, S., Gelbord, J. M., Grupe, D., Gupta, A., Hall, P. B., Hicks, S., Horenstein, D., Horne, Keith, Hutchison, T., Im, M., Joner, M. D., Jones, J., Kaastra, J., Kaspi, S., Kelly, B. C., Kennea, J. A., Kim, M., Kim, S. C., Klimanov, S. A., Lee, J. C., Leonard, D. C., Lira, P., MacInnis, F., Mathur, S., McHardy, I. M., Montouri, C., Musso, R., Nazarov, S. V., Netzer, H., Norris, R. P., Nousek, J. A., Okhmat, D. N., Papadakis, I., Parks, J. R., Pott, J. -U., Rafter, S. E., Rix, H. -W., Saylor, D. A., Schnülle, K., Sergeev, S. G., Siegel, M., Skielboe, A., Spencer, M., Starkey, D., Sung, H. -I., Teems, K. G., Turner, C. S., Uttley, P., Villforth, C., Weiss, Y., Woo, J. -H., Yan, H., Young, S., and Zu, Y.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multi-wavelength reverberation mapping campaign. The campaign spanned six months and achieved an almost daily cadence with observations from five ground-based telescopes. The H$\beta$ and He II $\lambda$4686 broad emission-line light curves lag that of the 5100 $\AA$ optical continuum by $4.17^{+0.36}_{-0.36}$ days and $0.79^{+0.35}_{-0.34}$ days, respectively. The H$\beta$ lag relative to the 1158 $\AA$ ultraviolet continuum light curve measured by the Hubble Space Telescope is roughly $\sim$50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is $\sim$50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for H$\beta$ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the H$\beta$ and He II $\lambda$4686 emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C IV, Ly $\alpha$, He II(+O III]), and Si IV(+O IV]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured H$\beta$ lag is a factor of five shorter than the expected value implied by the $R_\mathrm{BLR} - L_\mathrm{AGN}$ relation based on the past behavior of NGC 5548., Comment: 22 pages, 13 figures, accepted to ApJ

Published
2017
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25. Highest Frequency Detection of FRB 121102 at 4–8 GHz Using the Breakthrough Listen Digital Backend at the Green Bank Telescope

Author

Gajjar, V, Siemion, APV, Price, DC, Law, CJ, Michilli, D, Hessels, JWT, Chatterjee, S, Archibald, AM, Bower, GC, Brinkman, C, Burke-Spolaor, S, Cordes, JM, Croft, S, Enriquez, J Emilio, Foster, G, Gizani, N, Hellbourg, G, Isaacson, H, Kaspi, VM, Lazio, TJW, Lebofsky, M, Lynch, RS, MacMahon, D, McLaughlin, MA, Ransom, SM, Scholz, P, Seymour, A, Spitler, LG, Tendulkar, SP, Werthimer, D, and Zhang, YG

Subjects
radio continuum: stars, stars: neutron, supernovae: general, astro-ph.HE, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

We report the first detections of the repeating fast radio burst source FRB 121102 above 5.2 GHz. Observations were performed using the 4-8 GHz receiver of the Robert C. Byrd Green Bank Telescope with the Breakthrough Listen digital backend. We present the spectral, temporal, and polarization properties of 21 bursts detected within the first 60 minutes of a total of 6 hr of observations. These observations comprise the highest burst density yet reported in the literature, with 18 bursts being detected in the first 30 minutes. A few bursts clearly show temporal sub-structure with distinct spectral properties. These sub-structures superimpose to provide an enhanced peak signal-to-noise ratio at higher trial dispersion measures. Broad features occur in ∼1 GHz wide subbands that typically differ in peak frequency between bursts within the band. Finer-scale structures (∼10-50 MHz) within these bursts are consistent with the structure expected from Galactic diffractive interstellar scintillation. The bursts exhibit nearly 100% linear polarization, and a large average rotation measure of 9.359 ± 0.012 ×104 rad m-2 (in the observer's frame). No circular polarization was found for any burst. We measure an approximately constant polarization position angle in the 13 brightest bursts. The peak flux densities of the reported bursts have average values (0.2 ± 0.1 Jy) similar to those seen at lower frequencies (

Published
2018

27. Strategies for Finding Prompt Radio Counterparts to Gravitational Wave Transients with the Murchison Widefield Array

Author

Kaplan, D. L., Murphy, T., Rowlinson, A., Croft, S. D., Wayth, R. B., and Trott, C. M.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

We present and evaluate several strategies to search for prompt, low-frequency radio emission associated with gravitational wave transients using the Murchison Widefield Array (MWA). As we are able to repoint the MWA on timescales of tens of seconds, we can search for the dispersed radio signal that has been predicted to originate along with or shortly after a neutron star-neutron star merger. We find that given the large, 600 deg^2 instantaneous field-of-view of the MWA we can cover a significant fraction of the predicted gravitational wave error region, although due to the complicated geometry of the latter we only cover >50% of the error region for approximately 5% of events, and roughly 15% of events will be located <10 deg from the MWA pointing center such that they will be covered in the radio images. For optimal conditions our limiting flux density for a 10-s long transient would be 0.1 Jy, increasing to about 1 Jy for a wider range of events. This corresponds to luminosity limits of 1e38-1e39 erg/s based on expectations for the distances of the gravitational wave transients, which should be sufficient to detect or significantly constrain a range of models for prompt emission., Comment: 9 pages, 5 figures. Accepted for publication in PASA

Published
2016
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28. Time-domain and spectral properties of pulsars at 154 MHz

Author

Bell, M. E., Murphy, Tara, Johnston, S., Kaplan, D. L., Croft, S., Hancock, P., Callingham, J. R., Zic, A., Dobie, D., Swiggum, J. K., Rowlinson, A., Hurley-Walker, N., Offringa, A. R., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Deshpande, A. A., Gaensler, B. M., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Lonsdale, C. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Wayth, R. B., Webster, R. L., Williams, A., and Williams, C. L.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We present 154 MHz Murchison Widefield Array imaging observations and variability information for a sample of pulsars. Over the declination range $-80^{\circ} < {\delta} < 10^{\circ}$ we detect 17 known pulsars with mean flux density greater than 0.3 Jy. We explore the variability properties of this sample on timescales of minutes to years. For three of these pulsars, PSR J0953+0755, PSR J0437-4715 and PSR J0630-2834 we observe interstellar scintillation and variability on timescales of greater than 2 minutes. One further pulsar, PSR J0034-0721, showed significant variability, the physical origins of which are difficult to determine. The dynamic spectra for PSR J0953+0755 and PSR J0437-4715 show discrete time and frequency structure consistent with diffractive interstellar scintillation and we present the scintillation bandwidth and timescales from these observations. The remaining pulsars within our sample were statistically non-variable. We also explore the spectral properties of this sample and find spectral curvature in pulsars PSR J0835-4510, PSR J1752-2806 and PSR J0437-4715.

Published
2016
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29. Supplement: Localization and broadband follow-up of the gravitational-wave transient GW150914

Author

Abbott, B. P., Abbott, R., Abbott, T. D., Abernathy, M. R., Acernese, F., Ackley, K., Adams, C., Adams, T., Addesso, P., Adhikari, R. X., Adya, V. B., Affeldt, C., Agathos, M., Agatsuma, K., Aggarwal, N., Aguiar, O. D., Aiello, L., Ain, A., Ajith, P., Allen, B., Allocca, A., Altin, P. A., Anderson, S. B., Anderson, W. G., Arai, K., Araya, M. C., Arceneaux, C. C., Areeda, J. S., Arnaud, N., Arun, K. G., Ascenzi, S., Ashton, G., Ast, M., Aston, S. M., Astone, P., Aufmuth, P., Aulbert, C., Babak, S., Bacon, P., Bader, M. K. M., Baker, P. T., Baldaccini, F., Ballardin, G., Ballmer, S. W., Barayoga, J. C., Barclay, S. E., Barish, B. C., Barker, D., Barone, F., Barr, B., Barsotti, L., Barsuglia, M., Barta, D., Barthelmy, S., Bartlett, J., Bartos, I., Bassiri, R., Basti, A., Batch, J. C., Baune, C., Bavigadda, V., Bazzan, M., Behnke, B., Bejger, M., Bell, A. S., Bell, C. J., Berger, B. K., Bergman, J., Bergmann, G., Berry, C. P. L., Bersanetti, D., Bertolini, A., Betzwieser, J., Bhagwat, S., Bhandare, R., Bilenko, I. A., Billingsley, G., Birch, J., Birney, R., Biscans, S., Bisht, A., Bitossi, M., Biwer, C., Bizouard, M. A., Blackburn, J. K., Blair, C. D., Blair, D. G., Blair, R. M., Bloemen, S., Bock, O., Bodiya, T. P., Boer, M., Bogaert, G., Bogan, C., Bohe, A., Bojtos, P., Bond, C., Bondu, F., Bonnand, R., Boom, B. A., Bork, R., Boschi, V., Bose, S., Bouffanais, Y., Bozzi, A., Bradaschia, C., Brady, P. R., Braginsky, V. B., Branchesi, M., Brau, J. E., Briant, T., Brillet, A., Brinkmann, M., Brisson, V., Brockill, P., Brooks, A. F., Brown, D. A., Brown, D. D., Brown, N. M., Buchanan, C. C., Buikema, A., Bulik, T., Bulten, H. J., Buonanno, A., Buskulic, D., Buy, C., Byer, R. L., Cadonati, L., Cagnoli, G., Cahillane, C., Bustillo, J. C., Callister, T., Calloni, E., Camp, J. B., Cannon, K. C., Cao, J., Capano, C. D., Capocasa, E., Carbognani, F., Caride, S., Diaz, J. C., Casentini, C., Caudill, S., Cavaglià, M., Cavalier, F., Cavalieri, R., Cella, G., Cepeda, C. B., Baiardi, L. C., Cerretani, G., Cesarini, E., Chakraborty, R., Chalermsongsak, T., Chamberlin, S. J., Chan, M., Chao, S., Charlton, P., Chassande-Mottin, E., Chen, H. Y., Chen, Y., Cheng, C., Chincarini, A., Chiummo, A., Cho, H. S., Cho, M., Chow, J. H., Christensen, N., Chu, Q., Chua, S., Chung, S., Ciani, G., Clara, F., Clark, J. A., Cleva, F., Coccia, E., Cohadon, P. -F., Colla, A., Collette, C. G., Cominsky, L., Constancio Jr., M., Conte, A., Conti, L., Cook, D., Corbitt, T. R., Cornish, N., Corsi, A., Cortese, S., Costa, C. A., Coughlin, M. W., Coughlin, S. B., Coulon, J. -P., Countryman, S. T., Couvares, P., Cowan, E. E., Coward, D. M., Cowart, M. J., Coyne, D. C., Coyne, R., Craig, K., Creighton, J. D. E., Cripe, J., Crowder, S. G., Cumming, A., Cunningham, L., Cuoco, E., Canton, T. Dal, Danilishin, S. L., D'Antonio, S., Danzmann, K., Darman, N. S., Dattilo, V., Dave, I., Daveloza, H. P., Davier, M., Davies, G. S., Daw, E. J., Day, R., DeBra, D., Debreczeni, G., Degallaix, J., De Laurentis, M., Deléglise, S., Del Pozzo, W., Denker, T., Dent, T., Dereli, H., Dergachev, V., DeRosa, R. T., De Rosa, R., DeSalvo, R., Dhurandhar, S., Díaz, M. C., Di Fiore, L., Di Giovanni, M., Di Lieto, A., Di Pace, S., Di Palma, I., Di Virgilio, A., Dojcinoski, G., Dolique, V., Donovan, F., Dooley, K. L., Doravari, S., Douglas, R., Downes, T. P., Drago, M., Drever, R. W. P., Driggers, J. C., Du, Z., Ducrot, M., Dwyer, S. E., Edo, T. B., Edwards, M. C., Effler, A., Eggenstein, H. -B., Ehrens, P., Eichholz, J., Eikenberry, S. S., Engels, W., Essick, R. C., Etzel, T., Evans, M., Evans, T. M., Everett, R., Factourovich, M., Fafone, V., Fair, H., Fairhurst, S., Fan, X., Fang, Q., Farinon, S., Farr, B., Farr, W. M., Favata, M., Fays, M., Fehrmann, H., Fejer, M. M., Ferrante, I., Ferreira, E. C., Ferrini, F., Fidecaro, F., Fiori, I., Fiorucci, D., Fisher, R. P., Flaminio, R., Fletcher, M., Fournier, J. -D., Franco, S., Frasca, S., Frasconi, F., Frei, Z., Freise, A., Frey, R., Frey, V., Fricke, T. T., Fritschel, P., Frolov, V. V., Fulda, P., Fyffe, M., Gabbard, H. A. G., Gair, J. R., Gammaitoni, L., Gaonkar, S. G., Garufi, F., Gatto, A., Gaur, G., Gehrels, N., Gemme, G., Gendre, B., Genin, E., Gennai, A., George, J., Gergely, L., Germain, V., Ghosh, A., Ghosh, S., Giaime, J. A., Giardina, K. D., Giazotto, A., Gill, K., Glaefke, A., Goetz, E., Goetz, R., Gondan, L., González, G., Castro, J. M. G., Gopakumar, A., Gordon, N. A., Gorodetsky, M. L., Gossan, S. E., Gosselin, M., Gouaty, R., Graef, C., Graff, P. B., Granata, M., Grant, A., Gras, S., Gray, C., Greco, G., Green, A. C., Groot, P., Grote, H., Grunewald, S., Guidi, G. M., Guo, X., Gupta, A., Gupta, M. K., Gushwa, K. E., Gustafson, E. K., Gustafson, R., Hacker, J. J., Hall, B. R., Hall, E. D., Hammond, G., Haney, M., Hanke, M. M., Hanks, J., Hanna, C., Hannam, M. D., Hanson, J., Hardwick, T., Haris, K., Harms, J., Harry, G. M., Harry, I. W., Hart, M. J., Hartman, M. T., Haster, C. -J., Haughian, K., Heidmann, A., Heintze, M. C., Heitmann, H., Hello, P., Hemming, G., Hendry, M., Heng, I. S., Hennig, J., Heptonstall, A. W., Heurs, M., Hild, S., Hoak, D., Hodge, K. A., Hofman, D., Hollitt, S. E., Holt, K., Holz, D. E., Hopkins, P., Hosken, D. J., Hough, J., Houston, E. A., Howell, E. J., Hu, Y. M., Huang, S., Huerta, E. A., Huet, D., Hughey, B., Husa, S., Huttner, S. H., Huynh-Dinh, T., Idrisy, A., Indik, N., Ingram, D. R., Inta, R., Isa, H. N., Isac, J. -M., Isi, M., Islas, G., Isogai, T., Iyer, B. R., Izumi, K., Jacqmin, T., Jang, H., Jani, K., Jaranowski, P., Jawahar, S., Jiménez-Forteza, F., Johnson, W. W., Jones, D. I., Jones, R., Jonker, R. J. G., Ju, L., Kalaghatgi, C. V., Kalogera, V., Kandhasamy, S., Kang, G., Kanner, J. B., Karki, S., Kasprzack, M., Katsavounidis, E., Katzman, W., Kaufer, S., Kaur, T., Kawabe, K., Kawazoe, F., Kéfélian, F., Kehl, M. S., Keitel, D., Kelley, D. B., Kells, W., Kennedy, R., Key, J. S., Khalaidovski, A., Khalili, F. Y., Khan, I., Khan, S., Khan, Z., Khazanov, E. A., Kijbunchoo, N., Kim, C., Kim, J., Kim, K., Kim, N., Kim, Y. -M., King, E. J., King, P. J., Kinzel, D. L., Kissel, J. S., Kleybolte, L., Klimenko, S., Koehlenbeck, S. M., Kokeyama, K., Koley, S., Kondrashov, V., Kontos, A., Korobko, M., Korth, W. Z., Kowalska, I., Kozak, D. B., Kringel, V., Królak, A., Krueger, C., Kuehn, G., Kumar, P., Kuo, L., Kutynia, A., Lackey, B. D., Landry, M., Lange, J., Lantz, B., Lasky, P. D., Lazzarini, A., Lazzaro, C., Leaci, P., Leavey, S., Lebigot, E. O., Lee, C. H., Lee, H. K., Lee, H. M., Lee, K., Lenon, A., Leonardi, M., Leong, J. R., Leroy, N., Letendre, N., Levin, Y., Levine, B. M., Li, T. G. F., Libson, A., Littenberg, T. B., Lockerbie, N. A., Logue, J., Lombardi, A. L., Lord, J. E., Lorenzini, M., Loriette, V., Lormand, M., Losurdo, G., Lough, J. D., Lück, H., Lundgren, A. P., Luo, J., Lynch, R., Ma, Y., MacDonald, T., Machenschalk, B., MacInnis, M., Macleod, D. M., Magaña-Sandoval, F., Magee, R. M., Mageswaran, M., Majorana, E., Maksimovic, I., Malvezzi, V., Man, N., Mandel, I., Mandic, V., Mangano, V., Mansell, G. L., Manske, M., Mantovani, M., Marchesoni, F., Marion, F., Márka, S., Márka, Z., Markosyan, A. S., Maros, E., Martelli, F., Martellini, L., Martin, I. W., Martin, R. M., Martynov, D. V., Marx, J. N., Mason, K., Masserot, A., Massinger, T. J., Masso-Reid, M., Matichard, F., Matone, L., Mavalvala, N., Mazumder, N., Mazzolo, G., McCarthy, R., McClelland, D. E., McCormick, S., McGuire, S. C., McIntyre, G., McIver, J., McManus, D. J., McWilliams, S. T., Meacher, D., Meadors, G. D., Meidam, J., Melatos, A., Mendell, G., Mendoza-Gandara, D., Mercer, R. A., Merilh, E., Merzougui, M., Meshkov, S., Messenger, C., Messick, C., Meyers, P. M., Mezzani, F., Miao, H., Michel, C., Middleton, H., Mikhailov, E. E., Milano, L., Miller, J., Millhouse, M., Minenkov, Y., Ming, J., Mirshekari, S., Mishra, C., Mitra, S., Mitrofanov, V. P., Mitselmakher, G., Mittleman, R., Moggi, A., Mohan, M., Mohapatra, S. R. P., Montani, M., Moore, B. C., Moore, C. J., Moraru, D., Moreno, G., Morriss, S. R., Mossavi, K., Mours, B., Mow-Lowry, C. M., Mueller, C. L., Mueller, G., Muir, A. W., Mukherjee, A., Mukherjee, D., Mukherjee, S., Mukund, N., Mullavey, A., Munch, J., Murphy, D. J., Murray, P. G., Mytidis, A., Nardecchia, I., Naticchioni, L., Nayak, R. K., Necula, V., Nedkova, K., Nelemans, G., Neri, M., Neunzert, A., Newton, G., Nguyen, T. T., Nielsen, A. B., Nissanke, S., Nitz, A., Nocera, F., Nolting, D., Normandin, M. E. N., Nuttall, L. K., Oberling, J., Ochsner, E., O'Dell, J., Oelker, E., Ogin, G. H., Oh, J. J., Oh, S. H., Ohme, F., Oliver, M., Oppermann, P., Oram, R. J., O'Reilly, B., O'Shaughnessy, R., Ottaway, D. J., Ottens, R. S., Overmier, H., Owen, B. J., Pai, A., Pai, S. A., Palamos, J. R., Palashov, O., Palliyaguru, N., Palomba, C., Pal-Singh, A., Pan, H., Pankow, C., Pannarale, F., Pant, B. C., Paoletti, F., Paoli, A., Papa, M. A., Paris, H. R., Parker, W., Pascucci, D., Pasqualetti, A., Passaquieti, R., Passuello, D., Patricelli, B., Patrick, Z., Pearlstone, B. L., Pedraza, M., Pedurand, R., Pekowsky, L., Pele, A., Penn, S., Perreca, A., Phelps, M., Piccinni, O., Pichot, M., Piergiovanni, F., Pierro, V., Pillant, G., Pinard, L., Pinto, I. M., Pitkin, M., Poggiani, R., Popolizio, P., Post, A., Powell, J., Prasad, J., Predoi, V., Premachandra, S. S., Prestegard, T., Price, L. R., Prijatelj, M., Principe, M., Privitera, S., Prodi, G. A., Prokhorov, L., Puncken, O., Punturo, M., Puppo, P., Pürrer, M., Qi, H., Qin, J., Quetschke, V., Quintero, E. A., Quitzow-James, R., Raab, F. J., Rabeling, D. S., Radkins, H., Raffai, P., Raja, S., Rakhmanov, M., Rapagnani, P., Raymond, V., Razzano, M., Re, V., Read, J., Reed, C. M., Regimbau, T., Rei, L., Reid, S., Reitze, D. H., Rew, H., Reyes, S. D., Ricci, F., Riles, K., Robertson, N. A., Robie, R., Robinet, F., Rocchi, A., Rolland, L., Rollins, J. G., Roma, V. J., Romano, R., Romanov, G., Romie, J. H., Rosińska, D., Rowan, S., Rüdiger, A., Ruggi, P., Ryan, K., Sachdev, S., Sadecki, T., Sadeghian, L., Salconi, L., Saleem, M., Salemi, F., Samajdar, A., Sammut, L., Sanchez, E. J., Sandberg, V., Sandeen, B., Sanders, J. R., Sassolas, B., Sathyaprakash, B. S., Saulson, P. R., Sauter, O., Savage, R. L., Sawadsky, A., Schale, P., Schilling, R., Schmidt, J., Schmidt, P., Schnabel, R., Schofield, R. M. S., Schönbeck, A., Schreiber, E., Schuette, D., Schutz, B. F., Scott, J., Scott, S. M., Sellers, D., Sentenac, D., Sequino, V., Sergeev, A., Serna, G., Setyawati, Y., Sevigny, A., Shaddock, D. A., Shah, S., Shahriar, M. S., Shaltev, M., Shao, Z., Shapiro, B., Shawhan, P., Sheperd, A., Shoemaker, D. H., Shoemaker, D. M., Siellez, K., Siemens, X., Sigg, D., Silva, A. D., Simakov, D., Singer, A., Singh, A., Singh, R., Singhal, A., Sintes, A. M., Slagmolen, B. J. J., Smith, J. R., Smith, N. D., Smith, R. J. E., Son, E. J., Sorazu, B., Sorrentino, F., Souradeep, T., Srivastava, A. K., Staley, A., Steinke, M., Steinlechner, J., Steinlechner, S., Steinmeyer, D., Stephens, B. C., Stone, R., Strain, K. A., Straniero, N., Stratta, G., Strauss, N. A., Strigin, S., Sturani, R., Stuver, A. L., Summerscales, T. Z., Sun, L., Sutton, P. J., Swinkels, B. L., Szczepańczyk, M. J., Tacca, M., Talukder, D., Tanner, D. B., Tápai, M., Tarabrin, S. P., Taracchini, A., Taylor, R., Theeg, T., Thirugnanasambandam, M. P., Thomas, E. G., Thomas, M., Thomas, P., Thorne, K. A., Thorne, K. S., Thrane, E., Tiwari, S., Tiwari, V., Tokmakov, K. V., Tomlinson, C., Tonelli, M., Torres, C. V., Torrie, C. 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Subjects
Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Abstract

This Supplement provides supporting material for arXiv:1602.08492 . We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands., Comment: For the main Letter, see arXiv:1602.08492

Published
2016
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30. Murchison Widefield Array Limits on Radio Emission from ANTARES Neutrino Events

Author

Croft, S., Kaplan, D. L., Tingay, S. J., Murphy, T., Bell, M. E., Rowlinson, A., Adrian-Martinez, S., Ageron, M., Albert, A., Andre, M., Anton, G., Ardid, M., Aubert, J. -J., Avgitas, T., Baret, B., Barrios-Marti, J., Basa, S., Bertin, V., Biagi, S., Bormuth, R., Bouwhuis, M. C., Bruijn, R., Brunner, J., Busto, J., Capone, A., Caramete, L., Carr, J., Chiarusi, T., Circella, M., Coleiro, A., Coniglione, R., Costantini, H., Coyle, P., Creusot, A., Dekeyser, I., Deschamps, A., De Bonis, G., Distefano, C., Donzaud, C., Dornic, D., Drouhin, D., Eberl, T., Bojaddaini, I. El, Elsasser, D., Enzenhofer, A., Fehn, K., Felis, I., Fermani, P., Fusco, L. A., Galata, S., Gay, P., Geisselsoder, S., Geyer, K., Giordano, V., Gleixner, A., Glotin, H., Gracia-Ruiz, R., Graf, K., Hallmann, S., van Haren, H., Heijboer, A. J., Hello, Y., Hernandez-Rey, J. J., Hossl, J., Hofestadt, J., Hugon, C., James, C. W, de Jong, M., Kadler, M., Kalekin, O., Katz, U., Kiessling, D., Kooijman, P., Kouchner, A., Kreter, M., Kreykenbohm, I., Kulikovskiy, V., Lachaud, C., Lahmann, R., Lefevre, D., Leonora, E., Loucatos, S., Marcelin, M., Margiotta, A., Marinelli, A., Martinez-Mora, J. A., Mathieu, A., Michael, T., Migliozzi, P., Moussa, A., Mueller, C., Nezri, E., Pavalas, G. E., Pellegrino, C., Perrina, C., Piattelli, P., Popa, V., Pradier, T., Racca, C., Riccobene, G., Roensch, K., Saldana, M., Samtleben, D. F. E., Sanchez-Losa, A., Sanguineti, M., Sapienza, P., Schmid, J., Schnabel, J., Schussler, F., Seitz, T., Sieger, C., Spurio, M., Steijger, J. J. M., Stolarczyk, T., Taiuti, M., Tamburini, C., Trovato, A., Tselengidou, M., Turpin, D., Tonnis, C., Vallage, B., Vallee, C., Van Elewyck, V., Visser, E., Vivolo, D., Wagner, S., Wilms, J., Zornoza, J. D., Zuniga, J., Klotz, A., Boer, M., Van Suu, A. Le, Akerlof, C., and Zheng, W.

Subjects
Astrophysics - High Energy Astrophysical Phenomena
Abstract

We present a search, using the Murchison Widefield Array (MWA), for electromagnetic counterparts to two candidate high energy neutrino events detected by the ANTARES neutrino telescope in 2013 November and 2014 March. These events were selected by ANTARES because they are consistent, within 0.4 degrees, with the locations of galaxies within 20 Mpc of Earth. Using MWA archival data at frequencies between 118 and 182 MHz, taken ~20 days prior to, at the same time as, and up to a year after the neutrino triggers, we look for transient or strongly variable radio sources consistent with the neutrino positions. No such counterparts are detected, and we set a 5 sigma upper limit for low-frequency radio emission of ~1E37 erg/s for progenitors at 20 Mpc. If the neutrino sources are instead not in nearby galaxies, but originate in binary neutron star coalescences, our limits place the progenitors at z > 0.2. While it is possible, due to the high background from atmospheric neutrinos, that neither event is astrophysical, the MWA observations are nevertheless among the first to follow up neutrino candidates in the radio, and illustrate the promise of wide-field instruments like MWA to detect electromagnetic counterparts to such events., Comment: 7 pages, 2 figures, accepted for publication in ApJL

Published
2016
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31. Localization and broadband follow-up of the gravitational-wave transient GW150914

Author

Abbott, B. P., Abbott, R., Abbott, T. D., Abernathy, M. R., Acernese, F., Ackley, K., Adams, C., Adams, T., Addesso, P., Adhikari, R. X., Adya, V. B., Affeldt, C., Agathos, M., Agatsuma, K., Aggarwal, N., Aguiar, O. D., Aiello, L., Ain, A., Ajith, P., Allen, B., Allocca, A., Altin, P. A., Anderson, S. B., Anderson, W. G., Arai, K., Araya, M. C., Arceneaux, C. C., Areeda, J. S., Arnaud, N., Arun, K. G., Ascenzi, S., Ashton, G., Ast, M., Aston, S. M., Astone, P., Aufmuth, P., Aulbert, C., Babak, S., Bacon, P., Bader, M. K. M., Baker, P. T., Baldaccini, F., Ballardin, G., Ballmer, S. W., Barayoga, J. C., Barclay, S. E., Barish, B. C., Barker, D., Barone, F., Barr, B., Barsotti, L., Barsuglia, M., Barta, D., Barthelmy, S., Bartlett, J., Bartos, I., Bassiri, R., Basti, A., Batch, J. C., Baune, C., Bavigadda, V., Bazzan, M., Behnke, B., Bejger, M., Bell, A. S., Bell, C. J., Berger, B. K., Bergman, J., Bergmann, G., Berry, C. P. L., Bersanetti, D., Bertolini, A., Betzwieser, J., Bhagwat, S., Bhandare, R., Bilenko, I. A., Billingsley, G., Birch, J., Birney, R., Biscans, S., Bisht, A., Bitossi, M., Biwer, C., Bizouard, M. A., Blackburn, J. K., Blair, C. D., Blair, D. G., Blair, R. M., Bloemen, S., Bock, O., Bodiya, T. P., Boer, M., Bogaert, G., Bogan, C., Bohe, A., Bojtos, P., Bond, C., Bondu, F., Bonnand, R., Boom, B. A., Bork, R., Boschi, V., Bose, S., Bouffanais, Y., Bozzi, A., Bradaschia, C., Brady, P. R., Braginsky, V. B., Branchesi, M., Brau, J. E., Briant, T., Brillet, A., Brinkmann, M., Brisson, V., Brockill, P., Brooks, A. F., Brown, D. A., Brown, D. D., Brown, N. M., Buchanan, C. C., Buikema, A., Bulik, T., Bulten, H. J., Buonanno, A., Buskulic, D., Buy, C., Byer, R. L., Cadonati, L., Cagnoli, G., Cahillane, C., Bustillo, J. C., Callister, T., Calloni, E., Camp, J. B., Cannon, K. C., Cao, J., Capano, C. D., Capocasa, E., Carbognani, F., Caride, S., Diaz, J. 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R., Bhalerao, V., Miller, A. A., Barlow, T., Bellm, E., Manulis, I., Rana, J., Laher, R., Masci, F., Surace, J., Rebbapragada, U., Van Sistine, A., Sesar, B., Perley, D., Ferreti, R., Prince, T., Kendrick, R., Horesh, A., Hurley, K., Golenetskii, S. V., Aptekar, R. L., Frederiks, D. D., Svinkin, D. S., Rau, A., Zhang, X., Smith, D. M., Cline, T., Krimm, H., Abe, F., Doi, M., Fujisawa, K., Kawabata, K. S., Morokuma, T., Motohara, K., Tanaka, M., Ohta, K., Yanagisawa, K., Yoshida, M., Baltay, C., Rabinowitz, D., Ellman, N., Rostami, S., Bersier, D. F., Bode, M. F., Collins, C. A., Copperwheat, C. M., Darnley, M. J., Galloway, D. K., Gomboc, A., Kobayashi, S., Mazzali, P., Mundell, C. G., Piascik, A. S., Pollacco, Don, Steele, I. A., Ulaczyk, K., Broderick, J. W., Fender, R. P., Jonker, P. G., Rowlinson, A., Stappers, B. W., Wijers, R. A. M. J., Lipunov, V., Gorbovskoy, E., Tyurina, N., Kornilov, V., Balanutsa, P., Kuznetsov, A., Buckley, D., Rebolo, R., Serra-Ricart, M., Israelian, G., Budnev, N. M., Gress, O., Ivanov, K., Poleshuk, V., Tlatov, A., Yurkov, V., Kawai, N., Serino, M., Negoro, H., Nakahira, S., Mihara, T., Tomida, H., Ueno, S., Tsunemi, H., Matsuoka, M., Croft, S., Feng, L., Franzen, T. M. O., Gaensler, B. M., Johnston-Hollitt, M., Kaplan, D. L., Morales, M. F., Tingay, S. J., Wayth, R. B., Williams, A., Smartt, S. J., Chambers, K. C., Smith, K. W., Huber, M. E., Young, D. R., Wright, D. E., Schultz, A., Denneau, L., Flewelling, H., Magnier, E. A., Primak, N., Rest, A., Sherstyuk, A., Stalder, B., Stubbs, C. W., Tonry, J., Waters, C., Willman, M., E., F. Olivares, Campbell, H., Kotak, R., Sollerman, J., Smith, M., Dennefeld, M., Anderson, J. P., Botticella, M. T., Chen, T. -W., Valle, M. D., Elias-Rosa, N., Fraser, M., Inserra, C., Kankare, E., Kupfer, T., Harmanen, J., Galbany, L., Guillou, L. Le, Lyman, J. D., Maguire, K., Mitra, A., Nicholl, M., Razza, A., Terreran, G., Valenti, S., Gal-Yam, A., Ćwiek, A., Ćwiok, M., Mankiewicz, L., Opiela, R., Zaremba, M., Żarnecki, A. F., Onken, C. A., Scalzo, R. A., Schmidt, B. P., Wolf, C., Yuan, F., Evans, P. A., Kennea, J. A., Burrows, D. N., Campana, S., Cenko, S. B., Marshall, F. E., Nousek, J., O'Brien, P., Osborne, J. P., Palmer, D., Perri, M., Siegel, M., Tagliaferri, G., Klotz, A., Turpin, D., Laugier, R., Beroiz, M., Peñuela, T., Macri, L. M., Oelkers, R. J., Lambas, D. G., Vrech, R., Cabral, J., Colazo, C., Dominguez, M., Sanchez, B., Gurovich, S., Lares, M., Marshall, J. L., DePoy, D. L., Padilla, N., Pereyra, N. A., Benacquista, M., Tanvir, N. R., Wiersema, K., Levan, A. J., Steeghs, D., Hjorth, J., Fynbo, J. P. U., Malesani, D., Milvang-Jensen, B., Watson, D., Irwin, M., Fernandez, C. G., McMahon, R. G., Banerji, M., Gonzalez-Solares, E., Schulze, S., Postigo, A. de U., Thoene, C. C., Cano, Z., and Rosswog, S.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Abstract

A gravitational-wave (GW) transient was identified in data recorded by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) detectors on 2015 September 14. The event, initially designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the GW data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network circulars, giving an overview of the participating facilities, the GW sky localization coverage, the timeline and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic (EM) signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the EM data and results of the EM follow-up campaign are being disseminated in papers by the individual teams., Comment: For Supplement, see https://arxiv.org/abs/1604.07864

Published
2016
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32. A Deep Search for Prompt Radio Emission from the Short GRB 150424A With The Murchison Widefield Array

Author

Kaplan, D. L., Rowlinson, A., Bannister, K. W., Bell, M. E., Croft, S. D., Murphy, T., Tingay, S. J., Wayth, R. B., and Williams, A.

Subjects
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We present a search for prompt radio emission associated with the short-duration gamma-ray burst (GRB) 150424A using the Murchison Widefield Array (MWA) at frequencies from 80-133 MHz. Our observations span delays of 23 s-30 min after the GRB, corresponding to dispersion measures of 100-7700 pc/cm^3. We see no excess flux in images with timescales of 4 s, 2 min, or 30 min, and set a 3 sigma flux density limit of 3.0 Jy at 132 MHz on the shortest timescales: some of the most stringent limits to date on prompt radio emission from any type of GRB. We use these limits to constrain a number of proposed models for coherent emission from short-duration GRBs, although we show that our limits are not particularly constraining for fast radio bursts because of reduced sensitivity for this pointing. Finally, we discuss the prospects for using the MWA to search for prompt radio emission from gravitational wave transients and find that while the flux density and luminosity limits are likely to be very constraining, the latency of the gravitational wave alert may limit the robustness of any conclusions., Comment: 6 pages, 4 figures. ApJ Letters, in press

Published
2015
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37. Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

Author

Mathur, S, Gupta, A, Page, K, Pogge, RW, Krongold, Y, Goad, MR, Adams, SM, Anderson, MD, Arévalo, P, Barth, AJ, Bazhaw, C, Beatty, TG, Bentz, MC, Bigley, A, Bisogni, S, Borman, GA, Boroson, TA, Bottorff, MC, Brandt, WN, Breeveld, AA, Brown, JE, Brown, JS, Cackett, EM, Canalizo, G, Carini, MT, Clubb, KI, Comerford, JM, Coker, CT, Corsini, EM, Crenshaw, DM, Croft, S, Croxall, KV, Bontà, E Dalla, Deason, AJ, Denney, KD, De Lorenzo-Cáceres, A, De Rosa, G, Dietrich, M, Edelson, R, Ely, J, Eracleous, M, Evans, PA, Fausnaugh, MM, Ferland, GJ, Filippenko, AV, Flatland, K, Fox, OD, Gates, EL, Gehrels, N, Geier, S, Gelbord, JM, Gorjian, V, Greene, JE, Grier, CJ, Grupe, D, Hall, PB, Henderson, CB, Hicks, S, Holmbeck, E, Holoien, TW-S, Horenstein, D, Horne, Keith, Hutchison, T, Im, M, Jensen, JJ, Johnson, CA, Joner, MD, Jones, J, Kaastra, J, Kaspi, S, Kelly, BC, Kelly, PL, Kennea, JA, Kim, M, Kim, S, Kim, SC, King, A, Klimanov, SA, Kochanek, CS, Korista, KT, Kriss, GA, Lau, MW, Lee, JC, Leonard, DC, Li, M, Lira, P, Ma, Z, MacInnis, F, Manne-Nicholas, ER, Malkan, MA, Mauerhan, JC, McGurk, R, McHardy, IM, Montouri, C, Morelli, L, Mosquera, A, Mudd, D, Muller-Sanchez, F, Musso, R, and Nazarov, SV

Subjects
galaxies: active, galaxies: individual, X-rays: galaxies, X-rays: individual, astro-ph.GA, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.

Published
2017

38. Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-line Analysis for NGC 5548

Author

Pei, L, Fausnaugh, MM, Barth, AJ, Peterson, BM, Bentz, MC, De Rosa, G, Denney, KD, Goad, MR, Kochanek, CS, Korista, KT, Kriss, GA, Pogge, RW, Bennert, VN, Brotherton, M, Clubb, KI, Bontà, E Dalla, Filippenko, AV, Greene, JE, Grier, CJ, Vestergaard, M, Zheng, W, Adams, Scott M, Beatty, Thomas G, Bigley, A, Brown, Jacob E, Brown, Jonathan S, Canalizo, G, Comerford, JM, Coker, Carl T, Corsini, EM, Croft, S, Croxall, KV, Deason, AJ, Eracleous, Michael, Fox, OD, Gates, EL, Henderson, CB, Holmbeck, E, Holoien, TW-S, Jensen, JJ, Johnson, CA, Kelly, PL, Kim, S, King, A, Lau, MW, Li, Miao, Lochhaas, Cassandra, Ma, Zhiyuan, Manne-Nicholas, ER, Mauerhan, JC, Malkan, MA, McGurk, R, Morelli, L, Mosquera, Ana, Mudd, Dale, Sanchez, F Muller, Nguyen, ML, Ochner, P, Ou-Yang, B, Pancoast, A, Penny, Matthew T, Pizzella, A, Poleski, Radosław, Runnoe, Jessie, Scott, B, Schimoia, Jaderson S, Shappee, BJ, Shivvers, I, Simonian, Gregory V, Siviero, A, Somers, Garrett, Stevens, Daniel J, Strauss, MA, Tayar, Jamie, Tejos, N, Treu, T, Van Saders, J, Vican, L, Villanueva, S, Yuk, H, Zakamska, NL, Zhu, W, Anderson, MD, Arévalo, P, Bazhaw, C, Bisogni, S, Borman, GA, Bottorff, MC, Brandt, WN, Breeveld, AA, Cackett, EM, Carini, MT, Crenshaw, DM, De Lorenzo-Cáceres, A, Dietrich, M, Edelson, R, Efimova, NV, Ely, J, Evans, PA, and Ferland, GJ

Subjects
galaxies: active, galaxies: individual, galaxies: nuclei, galaxies: Seyfert, astro-ph.GA, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multiwavelength reverberation mapping campaign. The campaign spanned 6 months and achieved an almost daily cadence with observations from five ground-based telescopes. The Hβ and He ii λ4686 broad emission-line light curves lag that of the 5100 +-optical continuum by 4.17+0.36-0.36 and 0.79+0.35-0.34 days, respectively. The Hβ lag relative to the 1158 ultraviolet continuum light curve measured by the Hubble Space Telescope is ∼50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is ∼50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for Hβ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the Hβ and He ii emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C iv, Lyα, He ii(+O iii]), and Si iv(+O iv]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured Hβ lag is a factor of five shorter than the expected value implied by the R BLR-L AGN relation based on the past behavior of NGC 5548.

Published
2017

44. Spectropolarimetry with the Allen Telescope Array: Faraday Rotation toward Bright Polarized Radio Galaxies

Author

Law, C. J., Gaensler, B. M., Bower, G. C., Backer, D. C., Bauermeister, A., Croft, S., Forster, R., Gutierrez-Kraybill, C., Harvey-Smith, L., Heiles, C., Hull, C., Keating, G., MacMahon, D., Whysong, D., Williams, P. K. G., and Wright, M.

Subjects
Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We have observed 37 bright, polarized radio sources with the Allen Telescope Array (ATA) to present a novel analysis of their Faraday rotation properties. Each source was observed during the commissioning phase with 2 to 4 100-MHz bands at frequencies ranging from 1 to 2 GHz. These observations demonstrate how the continuous frequency coverage of the ATA's log-periodic receiver can be applied to the study of Faraday rotation measures (RMs). We use RM synthesis to show that wide-bandwidth data can find multiple RM components toward a single source. Roughly a quarter of the sources studied have extra RM components with high confidence (brighter than ~40 mJy), when observing with a RM resolution of roughly 100 rad/m2. These extra components contribute 10%-70% of the total polarized flux. This is the first time multiple RM components have been identified in a large sample of point sources. For our observing configuration, these extra RM components bias the measurement of the peak RM by 10-15 rad/m2 ; more generally, the peak RM cannot be determined more precisely than the RM beam size. Comparing our 1-2 GHz RM spectra to VLBA polarimetric maps shows both techniques can identify complicated Faraday structures in the sources. However, the RM values and fractional polarization are generally smaller at lower frequencies than in the higher-frequency VLBA maps. With a few exceptions, the RMs from this work are consistent with that of earlier, narrow-bandwidth, all-sky surveys. This work also describes the polarimetry calibration procedure and that on-axis ATA observations of linear polarization can be calibrated to an accuracy of 0.2% of Stokes I. Future research directions include studying the time-dependent RM structure in Active Galactic Nuclei (AGNs) and enabling accurate, wide-area RM surveys to test models of Galactic and extragalactic magnetic fields., Comment: Accepted to ApJ, 83 (preprint format) pages, 49 figures

Published
2010
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45. A galaxy populations study of a radio-selected protocluster at z~3.1

Author

Kuiper, E., Hatch, N. A., Rottgering, H. J. A., Miley, G. K., Overzier, R. A., Venemans, B. P., de Breuck, C., Croft, S., Kajisawa, M., Kodama, T., Kurk, J. D., Pentericci, L., Stanford, S. A., Tanaka, I., and Zirm, A. W.

Subjects
Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We present a population study of several types of galaxies within the protocluster surrounding the radio galaxy MRC0316-257 at z~3.1. In addition to the known population of Ly_alpha emitters (LAEs) and [OIII] emitters, we use colour selection techniques to identify protocluster candidates that are Lyman break galaxies (LBG) and Balmer break galaxies (BBGs). The radio galaxy field contains an excess of LBG candidates, with a surface density 1.6\pm0.3 times larger than found for comparable blank fields. This surface overdensity corresponds to an LBG volume overdensity of ~8\pm4. The BBG photometric redshift distribution peaks at the protocluster's redshift, but we detect no significant surface overdensity of BBG. This is not surprising because a volume overdensity similar to the LBGs would have resulted in a surface density of ~1.2 that found in the blank field. This could not have been detected in our sample. Masses and star formation rates of the candidate protocluster galaxies are determined using SED fitting. These properties are not significantly different from those of field galaxies. The galaxies with the highest masses and star formation rates are located near the radio galaxy, indicating that the protocluster environment influences galaxy evolution at z~3. We conclude that the protocluster around MRC0316-257 is still in the early stages of formation., Comment: 19 pages, 20 figures, accepted for publication in MNRAS

Published
2010
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46. Mid-Infrared Variability from the Spitzer Deep, Wide-Field Survey

Author

Kozlowski, Szymon, Kochanek, Christopher S., Stern, Daniel, Ashby, Matthew L. N., Assef, Roberto J., Bock, J. J., Borys, C., Brand, K., Brodwin, M., Brown, M. J. I., Cool, R., Cooray, A., Croft, S., Dey, Arjun, Eisenhardt, P. R., Gonzalez, A., Gorjian, V., Griffith, R., Grogin, N., Ivison, R., Jacob, J., Jannuzi, B. T., Mainzer, A., Moustakas, L., Rottgering, H., Seymour, N., Smith, H. A., Stanford, S. A., Stauffer, J. R., Sullivan, I. S., van Breugel, W., Willner, S. P., and Wright, E. L.

Subjects
Astrophysics - Cosmology and Extragalactic Astrophysics
Abstract

We use the multi-epoch, mid-infrared Spitzer Deep, Wide-Field Survey to investigate the variability of 474,179 objects in 8.1 deg^2 of the NDWFS Bootes field. We perform a Difference Image Analysis of the four available epochs between 2004 and 2008, focusing on the deeper 3.6 and 4.5 micron bands. We find that 1.1% of the studied sample meet our standard selection criteria for being classed as a variable source. We require that the 3.6 and 4.5 micron light-curves are strongly correlated (r>0.8) and that their joint variance exceeds that for all sources with the same magnitude by 2 sigma. We then examine the mid-IR colors of the variable sources and match them with X-ray sources from the XBootes survey, radio catalogs, 24 micron-selected AGN candidates, and spectroscopically identified AGNs from the AGN and Galaxy Evolution Survey (AGES). Based on their mid-IR colors, most of the variable sources are AGNs (76%), with smaller contributions from stars (11%), galaxies (6%), and unclassified objects. Most of the stellar, galaxy and unclassified sources are false positives. For our standard selection criteria, 11-12% of the mid-IR counterparts to X-ray sources, 24 micron-selected AGN candidates and spectroscopically identified AGNs show variability. Mid-IR AGN variability can be well described by a single power-law structure function with a power-law index of 0.5 at both 3.6 and 4.5 microns, and an amplitude of 0.1 mag on rest-frame time scales of 2 years. The variability amplitude is higher for shorter rest-frame wavelengths and lower luminosities. (Abridged), Comment: preprint 38 pages, 10 figures, full catalogs available from http://data.spitzer.caltech.edu/popular/sdwfs/20100503_enhanced/catalogs/

Published
2010
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47. The Spitzer Deep, Wide-Field Survey

Author

Ashby, M. L. N., Stern, D., Brodwin, M., Griffith, R., Eisenhardt, P., Kozlowski, S., Kochanek, C. S., Bock, J. J., Borys, C., Brand, K., Brown, M. J. I., Cool, R., Cooray, A., Croft, S., Dey, A., Eisenstein, D., Gonzalez, A. H., Gorjian, V., Grogin, N. A., Ivison, R. J., Jacob, J., Jannuzi, B. T., Mainzer, A., Moustakas, L. A., Rottgering, H. J. A., Seymour, N., Smith, H. A., Stanford, S. A., Stauffer, J. R., Sullivan, I., van Breugel, W., Willner, S. P., and Wright, E. L.

Subjects
Astrophysics - Cosmology and Extragalactic Astrophysics
Abstract

The Spitzer Deep, Wide-Field Survey (SDWFS) is a four-epoch infrared survey of ten square degrees in the Bootes field of the NOAO Deep Wide-Field Survey using the IRAC instrument on the Spitzer Space Telescope. SDWFS, a Cycle four Spitzer Legacy project, occupies a unique position in the area-depth survey space defined by other Spitzer surveys. The four epochs that make up SDWFS permit -- for the first time -- the selection of infrared-variable and high proper motion objects over a wide field on timescales of years. Because of its large survey volume, SDWFS is sensitive to galaxies out to z~3 with relatively little impact from cosmic variance for all but the richest systems. The SDWFS datasets will thus be especially useful for characterizing galaxy evolution beyond z~1.5. This paper explains the SDWFS observing strategy and data processing, presents the SDWFS mosaics and source catalogs, and discusses some early scientific findings. The publicly-released, full-depth catalogs contain 6.78, 5.23, 1.20, and 0.96 x 10e5 distinct sources detected to the average 5-sigma, 4" diameter, aperture-corrected limits of 19.77, 18.83, 16.50, and 15.82 Vega mag at 3.6, 4.5, 5.8, and 8.0 micron, respectively. The SDWFS number counts and color-color distribution are consistent with other, earlier Spitzer surveys. At the 6 min integration time of the SDWFS IRAC imaging, more than 50% of isolated FIRST radio sources and more than 80% of on-axis XBootes sources are detected out to 8.0 micron. Finally, we present the four highest proper motion IRAC-selected sources identified from the multi-epoch imaging, two of which are likely field brown dwarfs of mid-T spectral class., Comment: 71 pages, 18 figures, accepted for publication in the Astrophysical Journal

Published
2009
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48. The Dynamic Radio Sky: An Opportunity for Discovery

Author

Lazio, J., Bloom, J. S., Bower, G. C., Cordes, J., Croft, S., Hyman, S., Law, C., and McLaughlin, M.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract

The time domain of the sky has been only sparsely explored. Nevertheless, recent discoveries from limited surveys and serendipitous discoveries indicate that there is much to be found on timescales from nanoseconds to years and at wavelengths from meters to millimeters. These observations have revealed unexpected phenomena such as rotating radio transients and coherent pulses from brown dwarfs. Additionally, archival studies have found not-yet identified radio transients without optical or high-energy hosts. In addition to the known classes of radio transients, possible other classes of objects include extrapolations from known classes and exotica such as orphan gamma-ray burst afterglows, radio supernovae, tidally-disrupted stars, flare stars, magnetars, and transmissions from extraterrestrial civilizations. Over the next decade, meter- and centimeter-wave radio telescopes with improved sensitivity, wider fields of view, and flexible digital signal processing will be able to explore radio transient parameter space more comprehensively and systematically., Comment: Astro2010 Decadal Survey Science white paper

Published
2009

50. Protoclusters associated with z > 2 radio galaxies. I. Characteristics of high redshift protoclusters

Author

Venemans, B. P., Rottgering, H. J. A., Miley, G. K., van Breugel, W. J. M., De Breuck, C., Kurk, J. D., Pentericci, L., Stanford, S. A., Overzier, R. A., Croft, S., and Ford, H.

Subjects
Astrophysics
Abstract

[Abridged] We present the results of a large program conducted with the Very Large Telescope and Keck telescope to search for forming clusters of galaxies near powerful radio galaxies at 2.0 < z < 5.2. We obtained narrow- and broad-band images of nine radio galaxies and their surroundings. The imaging was used to select candidate Lyman alpha emitting galaxies in ~3x3 Mpc^2 areas near the radio galaxies. A total of 337 candidate emitters were found with a rest-frame Lyman alpha equivalent width of EW_0 > 15 A and Sigma = EW_0/Delta EW_0 > 3. Follow-up spectroscopy confirmed 168 Lyman alpha emitters near eight radio galaxies. The success rate of our selection procedure is 91%. At least six of our eight fields are overdense in Lyman alpha emitters by a factor 3-5. Also, the emitters show significant clustering in velocity space. In the overdense fields, the width of the velocity distributions of the emitters is a factor 2-5 smaller than the width of the narrow-band filters. Taken together, we conclude that we have discovered six forming clusters of galaxies (protoclusters). We estimate that roughly 75% of powerful (L_2.7GHz > 10^33 erg/s/Hz/sr) high redshift radio galaxies reside in a protocluster, with a sizes of at least 1.75 Mpc. We estimate that the protoclusters have masses in the range 2-9 x 10^14 Msun and they are likely to be progenitors of present-day (massive) clusters of galaxies. For the first time, we have been able to estimate the velocity dispersion of cluster progenitors from z~5 to ~2. The velocity dispersion of the emitters increases with cosmic time, in agreement with the dark matter velocity dispersion in numerical simulations of forming massive clusters., Comment: 30 pages, 20 figures. Published in A&A. The article with high resolution figures is available at http://www.ast.cam.ac.uk/~venemans/research/datapaper/index.html

Published
2006
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