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131 results on '"Hessels, J.W.T."'

1. Discovery and timing of ten new millisecond pulsars in the globular cluster Terzan 5

Author

Padmanabh, P.V., primary, Ransom, S.M., additional, Freire, P.C., additional, Ridolfi, A., additional, Taylor, J.D., additional, Choza, C., additional, Clark, C.J., additional, Abbate, F., additional, Bailes, M., additional, Barr, E.D., additional, Buchner, S., additional, Burgay, M., additional, DeCesar, M.E., additional, Chen, W., additional, Corongiu, A., additional, Champion, D.J., additional, Dutta, A., additional, Geyer, M., additional, Hessels, J.W.T., additional, Kramer, M., additional, Possenti, A., additional, Stairs, I.H., additional, Stappers, B.W., additional, Venkatraman Krishnan, V., additional, Vleeschower, L., additional, and Zhang, L., additional

Published
2024
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3. Possible discovery of Calvera's supernova remnant

Author

Arias de Saavedra Benitez, M., Botteon, A., Bassa, C.G., Jagt, S. van der, Weeren, R.J. van, O'Sullivan, S.P., Bosschaart, Q., Dullaart, R.S., Hardcastle, M.J., Hessels, J.W.T., Shimwell, T., Slob, M.M., Sturm, J.A., Tasse, C., Theijssen, N.C.M.A., Vink, J., High Energy Astrophys. & Astropart. Phys (API, FNWI), and Gravitation and Astroparticle Physics Amsterdam

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Pulsars: individual: 1RXS J141256.0+792204, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), H II regions, FOS: Physical sciences, Astronomy and Astrophysics, Surveys, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies, ISM: supernova remnants, ISM: general
Abstract

We report the discovery of a ring of low surface brightness radio emission around the Calvera pulsar, a high Galactic latitude, isolated neutron star, in the LOFAR Two-metre Sky Survey (LoTSS). It is centered at $\alpha=14\mathrm{h}11\mathrm{m}12.6\mathrm{s}$, $\delta=+79^\mathrm{o}23'15"$, has inner and outer radii of $14.2'$ and $28.4'$, and an integrated flux density at 144 MHz of $1.08\pm0.15$ Jy. The ring center is offset by $4.9'$ from the location of the Calvera pulsar. H$\alpha$ observations with the Isaac Newton Telescope show no coincident optical emission, but do show a small ($\sim20"$) optical structure internal to the ring. We consider three possible interpretations for the ring: that it is an H~II region, a supernova remnant (SNR), or an Odd Radio Circle (ORC). The positional coincidence of the ring, the pulsar, and an X-ray-emitting non-equilibrium ionisation plasma previously detected, lead us to prefer the SNR interpretation. If the source is indeed a SNR and its association with the Calvera pulsar is confirmed, then Calvera's SNR, or G118.4+37.0, will be one of few SNRs in the Galactic halo., Comment: Accepted in A&A

Published
2022

4. PRECISE detects high activity from FRB 20220912A at 1.4 GHz but no bursts at 5 GHz using the Effelsberg telescope

Author

Kirsten, F., Hessels, J.W.T., Hewitt, D.M., Ould Boukattine, O.S., Snelders, M.P., Gopinath, A., Nimmo, K., Karuppusamy, R., Herrmann, W., Yang, J., Gawronski, M., Blaauw, R., Buttaccio, S.T., Maccaferri, G., Bach, U., Feiler, R., Bray, J., Williams, D., Wrigley, N., Marcote, B., Keimpema, A., Paragi, Z., Burgay, M., Corongiu, A., Giroletti, M., Kramer, M., Pilia, M., Spitler, L., Surcis, G., Trudu, M., Yuan, J., Wang, N., Bezrukovs, V., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Abstract

We observed the recently discovered FRB 20220912A (ATel #15679) with an ad-hoc VLBI network as part of the PRECISE project. We targeted the source on three occasions: 22 Oct UT 00:00-04:30, 24-25 Oct UT 21:00-02:00, and 26-27 Oct UT 23:00-04:30.

Published
2022

5. A repeating fast radio burst

Author

Spitler, L.G., Scholz, P., Hessels, J.W.T., Bogdanov, S., Brazier, A., Camilo, F., Chatterjee, S., Cordes, J.M., Crawford, F., Deneva, J., Ferdman, R.D., Freire, P.C.C., Kaspi, V.M., Lazarus, P., Lynch, R., Madsen, E.C., McLaughlin, M.A., Patel, C., Ransom, S.M., Seymour, A., Stairs, I.H., Stappers, B.W., van Leeuwen, J., and Zhu, W.W.

Subjects
Radio waves -- Observations, Wave-motion, Theory of -- Observations, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances (1-8). Previous follow-up observations have failed to find additional bursts at [...]

Published
2016

6. Searching for pulsars associated with polarised point sources using LOFAR: Initial discoveries from the TULIPP project

Author

Sobey, C, Bassa, C.G., O’Sullivan, S.P., Callingham, J.R., Tan, C.M., Hessels, J.W.T., Kondratiev, V.I., Stappers, B.W., Tiburzi, C., Heald, G., Shimwell, T., Breton, R.P., Kirwan, M., Vedantham, H.K., Carretti, E., Grießmeier, J.-M., Haverkorn, M., Karastergiou, A., Sobey, C, Bassa, C.G., O’Sullivan, S.P., Callingham, J.R., Tan, C.M., Hessels, J.W.T., Kondratiev, V.I., Stappers, B.W., Tiburzi, C., Heald, G., Shimwell, T., Breton, R.P., Kirwan, M., Vedantham, H.K., Carretti, E., Grießmeier, J.-M., Haverkorn, M., and Karastergiou, A.

Abstract

Contains fulltext : 249740.pdf (Publisher’s version ) (Open Access)

Published
2022

7. Subsequent detection of three more bursts from FRB 20201124A using the Westerbork-RT1 25-m telescope

Author

Ould-Boukattine, O.S., Kirsten, F., Nimmo, K., Snelders, M.P., Hessels, J.W.T., Blaauw, R., Gawronski, M., Ruiten, R.J. van, Sluman, J.J., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Abstract

Following ATel #15190, we report the subsequent detection of three additional bursts from FRB 20201124A using the Westerbork-RT1 25-m telescope. Observations were done at a central frequency of 1323.49 MHz using a bandwidth of 128 MHz. We use a DM of 410.775 pc cm^-3, as determined in our analysis of bursts discovered using the Onsala telescope (ATel #14605, Kirsten et al., in prep.).

Published
2022

8. Burst detection from FRB 20201124A using the Westerbork-RT1 25-m telescope

Author

Ould-Boukattine, O.S., Kirsten, F., Nimmo, K., Snelders, M.P., Hessels, J.W.T., Blaauw, R., Gawronski, M., Sluman, J.J., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Abstract

We report the detection of a fast radio burst from FRB 20201124A using the Westerbork-RT1 25-m telescope. Observations were done at a central frequency of 1323.49 MHz using a bandwidth of 128 MHz. We use a DM of 410.775 pc cm^-3, as determined in our analysis of bursts discovered using the Onsala telescope (ATel #14605, Kirsten et al., in prep.).

Published
2022

9. A millisecond pulsar in a stellar triple system

Author

Ransom, S.M., Stairs, I.H., Archibald, A.M., Hessels, J.W.T., Kaplan, D.L., van Kerkwijk, M.H., Boyles, J., Deller, A.T., Chatterjee, S., Schechtman-Rook, A., Berndsen, A., Lynch, R.S., Lorimer, D.R., Karako-Argaman, C., Kaspi, V.M., Kondratiev, V.I., McLaughlin, M.A., van Leeuwen, J., Rosen, R., Roberts, M.S.E., and Stovall, K.

Subjects
Star formation -- Research, Astronomical research, Pulsars -- Observations, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Gravitationally bound three-body systems have been studied for hundreds of years (1,2) and are common in our Galaxy (3,4). They show complex orbital interactions, which can constrain the compositions, masses and interior structures of the bodies (5) and test theories of gravity (6), if sufficiently precise measurements are available. A triple system containing a radio pulsar could provide such measurements, but the only previously known such system, PSR B1620-26 (refs (7,8); with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of several decades), shows only weak interactions. Here we report precision timing and multiwavelength observations of PSR J0337+1715, a millisecond pulsar in ahierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar (1.4378(13)[M.sub.[dot in a circle]], where [M.sub.[dot in a circle]] is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15)[M.sub.[dot in a circle]] and 0.4101(3)[M.sub.[dot in a circle]]), as well as the inclinations of the orbits (both about 39.2°). The unexpectedly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from those of known stellar systems. The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity., Millisecond pulsars (MSPs) are neutron stars that rotate hundreds of times per second and emit beams of radio waves much as a lighthouse emits light. They are thought to form [...]

Published
2014
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10. Two bright bursts from FRB 20201124A with the Onsala 25-m telescope at 1.4 GHz, with no simultaneous emission detected at 330 MHz with Westerbork 25-m

Author

Kirsten, F., Ould-Boukattine, O.S., Nimmo, K., Hessels, J.W.T., Yang, J., Gawronski, M., Snelders, M.P., Feiler, R., Marcote, B., Forssen, O., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Abstract

We are running a multi-telescope, multi-band observing campaign on the recently announced fast radio burst source FRB 20201124A (ATel #14497). The participating stations are the 25-m telescope at Onsala Space Observatory (OSO, observing between 1360-1488 MHz), the 25-m dish at Westerbork RT1 (300-364 MHz) and the 32-m telescope in Torun (4550-4806 MHz).

Published
2021

11. VLBI localization of FRB 20201124A and absence of persistent emission on milliarcsecond scales

Author

Marcote, B., Kirsten, F., Hessels, J.W.T., Nimmo, K., Keimpema, A., Paragi, Z., Bach, U., Burgay, M., Corongiu, A., Feiler, R., Forssén, O., Gawronski, M., Giroletti, M., Gopinath, A., Hewitt, D.M., Karuppusamy, R., Kramer, M., Ould-Boukattine, O.S., Pilia, M., Snelders, M.P., Spitler, L., Surcis, G., Trudu, M., Yang, J., High Energy Astrophys. & Astropart. Phys (API, FNWI), and Faculty of Science

Abstract

We observed the field of FRB 20201124A (ATel #14497) as part of the PRECISE project with an ad-hoc interferometric array composed of dishes that are part of the European VLBI Network (EVN).

Published
2021

12. Swings between rotation and accretion power in a binary millisecond pulsar

Author

Papitto, A., Ferrigno, C., Bozzo, E., Rea, N., Pavan, L., Burderi, L., Burgay, M., Campanas, S., DiSalvo, T., Falanga, M., Filipovic, M.D., Freire, P.C.C., Hessels, J.W.T., Possenti, A., Ransom, S.M., Riggio, A., Romano, P., Sarkissian, J.M., Stairs, I.H., Stella, L., Torres, D.F., Wieringa, M.H., and Wong, G.F.

Subjects
XMM-Newton (Artificial satellite) -- Usage, Neutrons -- Research, Magnetic fields -- Research, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods (1-3). During the accretion stage, the system is called a low-mass X-ray binary, and bright X-ray emission is observed. When the rate of mass transfer decreases in the later evolutionary stages, these binaries host a radio millisecond pulsar (4-5) whose emission is powered by the neutron star's rotating magnetic field (6). This evolutionary model is supported by the detection of millisecond X-ray pulsations from several accreting neutron stars (7-8) and also by the evidence for a past accretion disc in a rotation-powered millisecond pulsar (9). It has been proposed that a rotation-powered pulsar may temporarily switch on (10-12) during periods of low mass inflow (13) in some such systems. Only indirect evidence for this transition has hitherto been observed (14-18). Here we report observations of accretion-powered, millisecond X-ray pulsations from a neutron star previously seen as a rotation-powered radio pulsar. Within a few days after a month-long X-ray outburst, radio pulses were again detected. This not only shows the evolutionary link between accretion and rotation-powered millisecond pulsars, but also that some systems can swing between the two states on very short timescales., The X-ray transient IGR J18245-2452 was first detected by INTEGRAL on 28 March 2013 and is located in the globular cluster M28 (see Supplementary Information). The X-ray luminosity of 3.5 [...]

Published
2013

13. VLA radio non-detection of IGR J17379-3747 as the X-ray flux drops

Author

Gusinskaia, N.V., Hessels, J.W.T., Jaodand, A.D., Miller-Jones, J.C.A., Degenaar, N., Deller, A.T., Russell, T.D., Bogdanov, S., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics
Abstract

IGR J17379-3747 is an accreting millisecond X-ray pulsar (AMXP). During its previous outburst in 2018, it revealed a few remarkable properties (Bult et al. 2019, ApJ, 877, 70B) that are similar to those of transitional millisecond pulsars (tMSPs) -- binary neutron stars that switch between being active as a radio millisecond pulsar and looking like an AMXP.

Published
2020

14. Quasi-simultaneous radio and X-ray observations of Aql X-1: Probing low luminosities

Author

Gusinskaia, N.V., Hessels, J.W.T., Degenaar, N., Deller, A.T., Miller-Jones, James, Archibald, A.M., Heinke, C.O., Moldón, J., Patruno, A., Tomsick, J.A., Wijnands, R., Gusinskaia, N.V., Hessels, J.W.T., Degenaar, N., Deller, A.T., Miller-Jones, James, Archibald, A.M., Heinke, C.O., Moldón, J., Patruno, A., Tomsick, J.A., and Wijnands, R.

Abstract

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society Aql X-1 is one of the best-studied neutron star low-mass X-ray binaries. It was previously targeted using quasi-simultaneous radio and X-ray observations during at least seven different accretion outbursts. Such observations allow us to probe the interplay between accretion inflow (X-ray) and jet outflow (radio). Thus far, these combined observations have only covered one order of magnitude in radio and X-ray luminosity range; this means that any potential radio-X-ray luminosity correlation, LR ∝ LXβ, is not well constrained (β ≈ 0.4-0.9, based on various studies) or understood. Here we present quasi-simultaneous Very Large Array and Swift-XRT observations of Aql X-1's 2016 outburst, with which we probe one order of magnitude fainter in radio and X-ray luminosity compared to previous studies (6 × 1034 erg s−1 < LX <3 × 1035 erg s−1, i.e. the intermediate to low-luminosity regime between outburst peak and quiescence). The resulting radio non-detections indicate that Aql X-1's radio emission decays more rapidly at low X-ray luminosities than previously assumed - at least during the 2016 outburst. Assuming similar behaviour between outbursts, and combining all available data in the hard X-ray state, this can be modelled as a steep β =1.17+−003021 power-law index or as a sharp radio cut-off at LX ≲ 5 × 1035 erg s−1 (given our deep radio upper limits at X-ray luminosities below this value). We discuss these results in the context of other similar studies.

Published
2020

15. Radio and X-ray monitoring of the accreting millisecond X-ray pulsar IGR J17591-2342 in outburst

Author

Gusinskaia, N.V., Russell, T.D., Hessels, J.W.T., Bogdanov, S., Degenaar, N., Deller, A.T., Van Den Eijnden, J., Jaodand, A.D., Miller-Jones, James, Wijnands, R., Gusinskaia, N.V., Russell, T.D., Hessels, J.W.T., Bogdanov, S., Degenaar, N., Deller, A.T., Van Den Eijnden, J., Jaodand, A.D., Miller-Jones, James, and Wijnands, R.

Abstract

© 2019 The Author(s). IGR J17591-2342 is a new accreting millisecond X-ray pulsar that was recently discovered in outburst in 2018. Early observations revealed that the source's radio emission is brighter than that of any other known neutron star low-mass X-ray binary (NS-LMXB) at comparable X-ray luminosity, and assuming its likely >~6 kpc distance. It is comparably radio bright to black hole LMXBs at similar X-ray luminosities. In this work, we present the results of our extensive radio and X-ray monitoring campaign of the 2018 outburst of IGR J17591-2342. In total, we collected 10 quasi-simultaneous radio (VLA, ATCA) and X-ray (Swift-XRT) observations, which make IGR J17591-2342 one of the best-sampled NS-LMXBs. We use these to fit a power-law correlation index β = 0.37+0.42-0.40 between observed radio and X-ray luminosities (LR α LXβ ). However, our monitoring revealed a large scatter in IGR J17591-2342's radio luminosity (at a similar X-ray luminosity, LX ~1036 erg s-1, and spectral state), with LR ~ 4 × 1029 erg s-1 during the first three reported observations, and up to a factor of 4 lower LR during later radio observations. None the less, the average radio luminosity of IGR J17591-2342 is still one of the highest among NS-LMXBs, and we discuss possible reasons for the wide range of radio luminosities observed in such systems during outburst.We found no evidence for radio pulsations from IGR J17591-2342 in our Green Bank Telescope observations performed shortly after the source returned to quiescence. None the less, we cannot rule out that IGR J17591-2342 becomes a radio millisecond pulsar during quiescence.

Published
2020

16. Detection of Multiple Radio Bursts from FRB 121102 using the Deep Space Network

Author

Pearlman, A.B., Majid, W.A., Prince, T.A., Naudet, C.J., Hessels, J.W.T., Nimmo, K., Kocz, J., Horiuchi, S., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Abstract

We report the detection of multiple bright radio bursts from therepeating fast radio burst (FRB) source FRB 121102 using the 70 mdiameter Deep Space Network (DSN) radio telescope (DSS-43) inTidbinbilla, Australia [1]. We carried out a continuous 5.7 hour observation of the position of FRB 121102 [2, 3], starting at 06 September 2019 17:27:55 UTC, following alerts that the source is now in an active state (e.g., ATels #13064, #13073, #13090, #13098).

Published
2019

18. Low-frequency Faraday rotation measures towards pulsars using LOFAR: probing the 3D Galactic halo magnetic field

Author

Sobey, C, Bilous, A.V., Grießmeier, J.M., Hessels, J.W.T., Karastergiou, A., Keane, E.F., Kondratiev, V.I., Kramer, M., Michilli, D., Noutsos, A., Pilia, M., Polzin, E.J., Stappers, B.W., Tan, C.M., van Leeuwen, J., Verbiest, J.P.W., Weltevrede, P., Heald, G., Alves, M.I.R., Carretti, E., Enßlin, T., Haverkorn, M., Iacobelli, M., Reich, W., Eck, C. Van, Sobey, C, Bilous, A.V., Grießmeier, J.M., Hessels, J.W.T., Karastergiou, A., Keane, E.F., Kondratiev, V.I., Kramer, M., Michilli, D., Noutsos, A., Pilia, M., Polzin, E.J., Stappers, B.W., Tan, C.M., van Leeuwen, J., Verbiest, J.P.W., Weltevrede, P., Heald, G., Alves, M.I.R., Carretti, E., Enßlin, T., Haverkorn, M., Iacobelli, M., Reich, W., and Eck, C. Van

Abstract

Contains fulltext : 201595.pdf (preprint version ) (Open Access)

Published
2019

19. A two-solar-mass neutron star measured using Shapiro delay

Author

Demorest, P.B., Pennucci, T., Ransom, S.M., Roberts, M.S.E., and Hessels, J.W.T.

Subjects
Specific gravity -- Measurement, Neutron stars -- Composition -- Measurement, Mass (Physics) -- Measurement, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Neutron stars are composed of the densest form of matter known to exist in our Universe, the composition and properties of which are still theoretically uncertain. Measurements of the masses or radii of these objects can strongly constrain the neutron star matter equation of state and rule out theoretical models of their composition (1,2). The observed range of neutron star masses, however, has hitherto been too narrow to rule out many predictions of 'exotic' non-nucleonic components (3-6). The Shapiro delay is a general-relativistic increase in light travel time through the curved space-time near a massive body (7). For highly inclined (nearly edge-on) binary millisecond radio pulsar systems, this effect allows us to infer the masses of both the neutron star and its binary companion to high precision (8,9). Here we present radio timing observations of the binary millisecond pulsar J1614-223010,11 that show a strong Shapiro delay signature. We calculate the pulsar mass to be (1.97 ± 0.04)[M.sub.[dot encircle]], which rules out almost all currently proposed (2-5) hyperon or boson condensate equations of state ([M.sub.[dot encircle]], solar mass). Quark matter can support a star this massive only if the quarks are strongly interacting and are therefore not 'free' quarks (12)., In March 2010, we performed a dense set of observations of J1614-2230 with the National Radio Astronomy Observatory Green Bank Telescope (GBT), timed to follow the system through one complete [...]

Published
2010
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20. First EVN measurements of the transient FIRST J141918.9+394036 on milliarcsecond scales

Author

Marcote, B., Paragi, Z., Hessels, J.W.T., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

FIRST J141918.9+394036 has been reported as a slowly-evolving extragalactic radio transient (Law et al. 2018, arXiv:1808.08964), consistent with a fading orphan long gamma-ray burst (LGRB).

Published
2018

22. Tests of gravitational symmetries with pulsar binary J1713+0747

Author

Jessner, A., Krieger, A., Champion, D.J., Graikou, E., Desvignes, G., Lazaridis, K., Liu, K., Lazarus, P., Karuppusamy, R., Caballero, R.N., Wex, N., Tiburzi, C., Verbiest, J.P.W., Osłowski, S., Zhu, W.W., Lee, K.J., Shaifullah, G., McKee, J.W., Kramer, M., Ransom, S.M., Stairs, I.H., Crowter, K., Gonzalez, M.E., Arzoumanian, Z., Possenti, A., Perrodin, D., Burgay, M., Cognard, I., Guillemot, L., Theureau, G., Dolch, T., Ferdman, R.D., Jones, M.L., Fonseca, E., Jones, G., McLaughlin, M.A., Lam, M.T., Pennucci, T., Swiggum, J., Stovall, K., Demorest, P.B., Ellis, J.A., Bassa, C.G., Smits, R, Hessels, J.W.T., Janssen, G.H., Lyne, A.G., Stappers, B.W., Jordan, C., Levin, L., Sanidas, S., Lentati, L., Nice, D.J., Jessner, A., Krieger, A., Champion, D.J., Graikou, E., Desvignes, G., Lazaridis, K., Liu, K., Lazarus, P., Karuppusamy, R., Caballero, R.N., Wex, N., Tiburzi, C., Verbiest, J.P.W., Osłowski, S., Zhu, W.W., Lee, K.J., Shaifullah, G., McKee, J.W., Kramer, M., Ransom, S.M., Stairs, I.H., Crowter, K., Gonzalez, M.E., Arzoumanian, Z., Possenti, A., Perrodin, D., Burgay, M., Cognard, I., Guillemot, L., Theureau, G., Dolch, T., Ferdman, R.D., Jones, M.L., Fonseca, E., Jones, G., McLaughlin, M.A., Lam, M.T., Pennucci, T., Swiggum, J., Stovall, K., Demorest, P.B., Ellis, J.A., Bassa, C.G., Smits, R, Hessels, J.W.T., Janssen, G.H., Lyne, A.G., Stappers, B.W., Jordan, C., Levin, L., Sanidas, S., Lentati, L., and Nice, D.J.

Abstract

Contains fulltext : 201620.pdf (Publisher’s version ) (Open Access)

Published
2018

23. LOFAR 150-MHz observations of SS 433 and W 50

Author

Broderick, J.W., Fender, R.P., Miller-Jones, J.C.A., Trushkin, S.A., Stewart, A.J., Anderson, G.E., Staley, T.D., Blundell, K.M., Pietka, M., Markoff, S., Rowlinson, A., Swinbank, J.D., Horst, A.J.v.d., Bell, M.E., Breton, R.P., Carbone, D., Corbel, S., Eislöffel, J., Falcke, H., Grießmeier, J.M., Hessels, J.W.T., Kondratiev, V.I., Law, C.J., Molenaar, G.J., Serylak, M, Stappers, B.W., Leeuwen, J. van, Wijers, R.A.M.J., Wijnands, R., Wise, M.W., Zarka, P., Broderick, J.W., Fender, R.P., Miller-Jones, J.C.A., Trushkin, S.A., Stewart, A.J., Anderson, G.E., Staley, T.D., Blundell, K.M., Pietka, M., Markoff, S., Rowlinson, A., Swinbank, J.D., Horst, A.J.v.d., Bell, M.E., Breton, R.P., Carbone, D., Corbel, S., Eislöffel, J., Falcke, H., Grießmeier, J.M., Hessels, J.W.T., Kondratiev, V.I., Law, C.J., Molenaar, G.J., Serylak, M, Stappers, B.W., Leeuwen, J. van, Wijers, R.A.M.J., Wijnands, R., Wise, M.W., and Zarka, P.

Abstract

Contains fulltext : 184318.pdf (publisher's version ) (Open Access)

Published
2018

25. An extreme magneto-ionic environment associated with the fast radio burst source FRB 121102

Author

Michilli, D., Seymour, A., Hessels, J.W.T., Spitler, L.G., Gajjar, V., Archibald, A.M., Siemion, A.P.V., Wharton, R.S., Whitlow, D., Michilli, D., Seymour, A., Hessels, J.W.T., Spitler, L.G., Gajjar, V., Archibald, A.M., Siemion, A.P.V., Wharton, R.S., and Whitlow, D.

Abstract

Contains fulltext : 182144.pdf (preprint version ) (Closed access)

Published
2018

26. Disc–jet coupling in low-luminosity accreting neutron stars

Author

Tudor, V., Miller-Jones, J.C.A., Patruno, A., D'Angelo, C.R., Jonker, P.G., Russell, D.M., Russell, T.D., Bernardini, F., Lewis, F., Deller, A.T., Hessels, J.W.T., Migliari, S., Plotkin, R.M., Soria, R., Wijnands, R., Tudor, V., Miller-Jones, J.C.A., Patruno, A., D'Angelo, C.R., Jonker, P.G., Russell, D.M., Russell, T.D., Bernardini, F., Lewis, F., Deller, A.T., Hessels, J.W.T., Migliari, S., Plotkin, R.M., Soria, R., and Wijnands, R.

Abstract

Contains fulltext : 176385.pdf (publisher's version ) (Open Access)

Published
2017

27. A 350-MHz GBT Survey of 50 Faint Fermi γ-ray Sources for Radio Millisecond Pulsars

Author

Hessels, J.W.T., Roberts, M.S.E., McLaughlin, M.A., Ray, P.S., Bangale, P., Ransom, S.M., Kerr, M., Camilo, F., Decesar, M.E., Burgay, M., D'Amico, N., Esposito, P., Pellizzoni, A., Possenti, A., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Millisecond pulsar, Astrophysics::High Energy Astrophysical Phenomena, Green Bank Telescope, Gamma ray, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

We have used the Green Bank Telescope at 350MHz to search 50 faint, unidentified Fermi Gamma-ray sources for radio pulsations. So far, these searches have resulted in the discovery of 10 millisecond pulsars, which are plausible counterparts to these unidentified Fermi sources. Here we briefly describe this survey and the characteristics of the newly discovered MSPs., 4 pages, 2 figures, to appear in AIP Conference Proceedings of Pulsar Conference 2010 "Radio Pulsars: a key to unlock the secrets of the Universe", Sardinia, October 2010

Published
2011
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28. Potential cooling of an accretion-heated neutron star crust in the low-mass X-ray binary 1RXS J180408.9−342058

Author

Parikh, A.S., primary, Wijnands, R., additional, Degenaar, N., additional, Ootes, L.S., additional, Page, D., additional, Altamirano, D., additional, Cackett, E.M., additional, Deller, A.T., additional, Gusinskaia, N., additional, Hessels, J.W.T., additional, Homan, J., additional, Linares, M., additional, Miller, J.M., additional, and Miller-Jones, J.C.A., additional

Published
2017
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29. Low-radio-frequency eclipses of the redback pulsar J2215+5135 observed in the image plane with LOFAR

Author

Broderick, J.W., Fender, R.P., Breton, R.P., Stewart, A.J., Rowlinson, A., Swinbank, J.D., Hessels, J.W.T., Staley, T.D., Horst, A.J. van der, Bell, M.E., Carbone, D., Cendes, Y.N., Corbel, S., Eislöffel, J., Falcke, H., Grießmeier, J.-M., Hassall, T.E., Jonker, P., Kramer, M., Kuniyoshi, M., Law, C.J., Markoff, S., Molenaar, G.J., Pietka, M., Scheers, L.H.A. (Bart), Serylak, M., Stappers, B.W., Veen, S. (Sander) ter, Leeuwen, J. van, Wijers, R.A.M.J. (Ralph), Wijnands, R., Wise, M.W. (Michael), Zarka, P., Broderick, J.W., Fender, R.P., Breton, R.P., Stewart, A.J., Rowlinson, A., Swinbank, J.D., Hessels, J.W.T., Staley, T.D., Horst, A.J. van der, Bell, M.E., Carbone, D., Cendes, Y.N., Corbel, S., Eislöffel, J., Falcke, H., Grießmeier, J.-M., Hassall, T.E., Jonker, P., Kramer, M., Kuniyoshi, M., Law, C.J., Markoff, S., Molenaar, G.J., Pietka, M., Scheers, L.H.A. (Bart), Serylak, M., Stappers, B.W., Veen, S. (Sander) ter, Leeuwen, J. van, Wijers, R.A.M.J. (Ralph), Wijnands, R., Wise, M.W. (Michael), and Zarka, P.

Abstract

The eclipses of certain types of binary millisecond pulsars (i.e. ‘black widows’ and ‘redbacks’) are often studied using high-time-resolution, ‘beamformed’ radio observations. However, they may also be detected in images generated from interferometric data. As part of a larger imaging project to characterize the variable and transient sky at radio frequencies <200 MHz, we have blindly detected the redback system PSR J2215+5135 as a variable source of interest with the Low-Frequency Array (LOFAR). Using observations with cadences of two weeks – six months, we find preliminary evidence that the eclipse duration is frequency dependent (∝ν−0.4), such that the pulsar is eclipsed for longer at lower frequencies, in broad agreement with beamformed studies of other similar sources. Furthermore, the detection of the eclipses in imaging data suggests an eclipsing medium that absorbs the pulsed emission, rather than scattering it. Our study is also a demonstration of the prospects of finding pulsars in wide-field imaging surveys with the current generation of low-frequency radio telescopes.

Published
2016
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30. A LOFAR census of millisecond pulsars

Author

Kondratiev, V.I., Verbiest, J.P.W., Hessels, J.W.T., Bilous, A., Stappers, B.W., Kramer, M., Keane, E.F., Noutsos, A., Osłowski, S., Breton, R.P., Hassall, T.E., Alexov, A., Cooper, S., Falcke, H., Grießmeier, J.-M., Karastergiou, A., Kuniyoshi, M., Pilia, M., Sobey, C, Veen, S. ter, Leeuwen, J. van, Weltevrede, P., Bell, M.E., Broderick, J.W., Corbel, S., Eislöffel, J., Markoff, S., Rowlinson, A., Swinbank, J.D., Wijers, R.A.M.J., Wijnands, R., Zarka, P., Kondratiev, V.I., Verbiest, J.P.W., Hessels, J.W.T., Bilous, A., Stappers, B.W., Kramer, M., Keane, E.F., Noutsos, A., Osłowski, S., Breton, R.P., Hassall, T.E., Alexov, A., Cooper, S., Falcke, H., Grießmeier, J.-M., Karastergiou, A., Kuniyoshi, M., Pilia, M., Sobey, C, Veen, S. ter, Leeuwen, J. van, Weltevrede, P., Bell, M.E., Broderick, J.W., Corbel, S., Eislöffel, J., Markoff, S., Rowlinson, A., Swinbank, J.D., Wijers, R.A.M.J., Wijnands, R., and Zarka, P.

Abstract

Contains fulltext : 155764.pdf (preprint version ) (Open Access)

Published
2016

31. LOFAR MSSS: detection of a low-frequency radio transient in 400 h of monitoring of the North Celestial Pole

Author

Stewart, A.J., Fender, R.P., Broderick, J.W., Hassall, T.E., Muñoz-Darias, T., Rowlinson, A., Swinbank, J.D., Staley, T.D., Molenaar, G.J., Scheers, B., Grobler, T.L., Pietka, M., Heald, G., McKean, J.P., Bell, M.E., Bonafede, A., Breton, R.P., Carbone, D., Cendes, Y., Clarke, A.O., Corbel, S., Gasperin, F. de, Eislöffel, J., Falcke, H., Ferrari, C., Grießmeier, J.-M., Hardcastle, M.J., Heesen, V., Hessels, J.W.T., Horneffer, A., Iacobelli, M., Jonker, P.G., Karastergiou, A., Kokotanekov, G., Kondratiev, V.I., Kuniyoshi, M., Law, C.J., Leeuwen, J. van, Markoff, S., Miller-Jones, J.C.A., Mulcahy, D., Orru, E., Pandey-Pommier, M., Pratley, L., Rol, E., Röttgering, H.J.A., Scaife, A.M.M., Shulevski, A., Sobey, C.A., Stappers, B.W., Tasse, C., Horst, A.J. van der, Velzen, S. van, Weeren, R.J. van, Wijers, R.A.M.J., Wijnands, R., Wise, M., Zarka, P., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Breitling, F., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., Corstanje, A., Geus, A. de, Deller, A., Duscha, S., Frieswijk, W., Garrett, M.A., Gunst, A.W., Haarlem, M.P. van, Hoeft, M., Hörandel, J., Juette, E., Kuper, G., Loose, M., Maat, P., McFadden, R., McKay-Bukowski, D., Moldon, J., Munk, H., Norden, M.J., Paas, H., Polatidis, A.G., Schwarz, D., Sluman, J., Smirnov, O., Steinmetz, M., Thoudam, S., Toribio, M.C., Vermeulen, R., Vocks, C., Wijnholds, S.J., Wucknitz, O., Yatawatta, S., Stewart, A.J., Fender, R.P., Broderick, J.W., Hassall, T.E., Muñoz-Darias, T., Rowlinson, A., Swinbank, J.D., Staley, T.D., Molenaar, G.J., Scheers, B., Grobler, T.L., Pietka, M., Heald, G., McKean, J.P., Bell, M.E., Bonafede, A., Breton, R.P., Carbone, D., Cendes, Y., Clarke, A.O., Corbel, S., Gasperin, F. de, Eislöffel, J., Falcke, H., Ferrari, C., Grießmeier, J.-M., Hardcastle, M.J., Heesen, V., Hessels, J.W.T., Horneffer, A., Iacobelli, M., Jonker, P.G., Karastergiou, A., Kokotanekov, G., Kondratiev, V.I., Kuniyoshi, M., Law, C.J., Leeuwen, J. van, Markoff, S., Miller-Jones, J.C.A., Mulcahy, D., Orru, E., Pandey-Pommier, M., Pratley, L., Rol, E., Röttgering, H.J.A., Scaife, A.M.M., Shulevski, A., Sobey, C.A., Stappers, B.W., Tasse, C., Horst, A.J. van der, Velzen, S. van, Weeren, R.J. van, Wijers, R.A.M.J., Wijnands, R., Wise, M., Zarka, P., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Breitling, F., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., Corstanje, A., Geus, A. de, Deller, A., Duscha, S., Frieswijk, W., Garrett, M.A., Gunst, A.W., Haarlem, M.P. van, Hoeft, M., Hörandel, J., Juette, E., Kuper, G., Loose, M., Maat, P., McFadden, R., McKay-Bukowski, D., Moldon, J., Munk, H., Norden, M.J., Paas, H., Polatidis, A.G., Schwarz, D., Sluman, J., Smirnov, O., Steinmetz, M., Thoudam, S., Toribio, M.C., Vermeulen, R., Vocks, C., Wijnholds, S.J., Wucknitz, O., and Yatawatta, S.

Abstract

Contains fulltext : 155770.pdf (preprint version ) (Open Access)

Published
2016

32. A LOFAR census of non-recycled pulsars: average profiles, dispersion measures, flux densities, and spectra⋆

Author

Bilous, A.V., Kondratiev, V.I., Kramer, M., Keane, E.F., Hessels, J.W.T., Stappers, B.W., Malofeev, V.M., Sobey, C, Breton, R.P., Cooper, S., Falcke, H., Karastergiou, A., Michilli, D., Osłowski, S., Sanidas, S., Veen, S. ter, Leeuwen, J. van, Verbiest, J.P.W., Weltevrede, P., Zarka, P., Grießmeier, J.-M., Serylak, M, Bell, M.E., Broderick, J.W., Eislöffel, J., Markoff, S., Rowlinson, A., Bilous, A.V., Kondratiev, V.I., Kramer, M., Keane, E.F., Hessels, J.W.T., Stappers, B.W., Malofeev, V.M., Sobey, C, Breton, R.P., Cooper, S., Falcke, H., Karastergiou, A., Michilli, D., Osłowski, S., Sanidas, S., Veen, S. ter, Leeuwen, J. van, Verbiest, J.P.W., Weltevrede, P., Zarka, P., Grießmeier, J.-M., Serylak, M, Bell, M.E., Broderick, J.W., Eislöffel, J., Markoff, S., and Rowlinson, A.

Abstract

Contains fulltext : 159647.pdf (publisher's version ) (Open Access)

Published
2016

33. New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR

Author

Carbone, D., Horst, A.J. van der, Wijers, R.A.M.J., Swinbank, J.D., Rowlinson, A., Broderick, J.W., Cendes, Y.N., Stewart, A.J., Bell, M.E., Breton, R.P., Corbel, S., Eislöffel, J., Fender, R.P., Grießmeier, J.M., Hessels, J.W.T., Jonker, P.G., Kramer, M., Law, C.J., Miller-Jones, J.C.A., Pietka, M., Scheers, L.H.A., Stappers, B.W., Leeuwen, J. van, Wijnands, R., Wise, M., Zarka, P., Carbone, D., Horst, A.J. van der, Wijers, R.A.M.J., Swinbank, J.D., Rowlinson, A., Broderick, J.W., Cendes, Y.N., Stewart, A.J., Bell, M.E., Breton, R.P., Corbel, S., Eislöffel, J., Fender, R.P., Grießmeier, J.M., Hessels, J.W.T., Jonker, P.G., Kramer, M., Law, C.J., Miller-Jones, J.C.A., Pietka, M., Scheers, L.H.A., Stappers, B.W., Leeuwen, J. van, Wijnands, R., Wise, M., and Zarka, P.

Abstract

Contains fulltext : 157933.pdf (publisher's version ) (Open Access)

Published
2016

34. Intrabinary shock emission from 'black widows' and 'redbacks'

Author

Roberts, M.S.E., McLaughlin, M.A., Gentile, P., Aliu, E., Hessels, J.W.T., Ransom, S.M., Ray, P.S., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Eclipsing millisecond pulsars in close (Pb < 1 day) binary systems provide a different view of pulsar winds and shocks than do isolated pulsars. Since 2009, the numbers of these systems known in the Galactic field has increased enormously. We have been systematically studying many of these newly discovered systems at multiple wavelengths. Typically, the companion is nearly Roche-lobe filling and heated by the pulsar which drives mass loss from the companion. The pulsar wind shocks with this material just above the surface of the companion. We discuss various observational properties of this shock, including radio eclipses, orbitally modulated X-ray emission, and the potential for γ-ray emission. Redbacks, whose companions are likely non-degenerate and significantly more massive, generally have more luminous shocks than black widows which have very low mass companions. This is expected since the more massive redback companions intercept a greater fraction of the pulsar wind. We also compare these systems to accreting millisecond pulsars, which may be progenitors of black widows and in some cases can pass back and forth between redback and accretion phases.

Published
2014

35. The LOFAR Transients Pipeline

Author

Swinbank, J.D., Staley, T.D., Molenaar, G.J., Rol, E., Rowlinson, A., Scheers, B., Spreeuw, H., Bell, M.E., Broderick, J.W., Carbone, D., Garsden, H., Horst, A.J. van der, Law, C.J., Wise, M., Breton, R.P., Cendes, Y., Corbel, S., Eislöffel, J., Falcke, H., Fender, R., Grießmeier, J.M., Hessels, J.W.T., Stappers, B.W., Stewart, A.J., Wijers, R.A.M.J., Wijnands, R., Zarka, P., Swinbank, J.D., Staley, T.D., Molenaar, G.J., Rol, E., Rowlinson, A., Scheers, B., Spreeuw, H., Bell, M.E., Broderick, J.W., Carbone, D., Garsden, H., Horst, A.J. van der, Law, C.J., Wise, M., Breton, R.P., Cendes, Y., Corbel, S., Eislöffel, J., Falcke, H., Fender, R., Grießmeier, J.M., Hessels, J.W.T., Stappers, B.W., Stewart, A.J., Wijers, R.A.M.J., Wijnands, R., and Zarka, P.

Abstract

Contains fulltext : 143840.pdf (preprint version ) (Open Access)

Published
2015

36. Limits on fast radio bursts at 145 MHz with artemis, a real-time software backend

Author

Karastergiou, A., Chennamangalam, J., Armour, W., Williams, C., Mort, B., Dulwich, F., Salvini, S., Magro, A., Roberts, S., Serylak, M, Doo, A., Bilous, A.V., Breton, R.P., Falcke, H., Grießmeier, J.-M., Hessels, J.W.T., Keane, E.F., Kondratiev, V.I., Kramer, M., Leeuwen, J. van, Noutsos, A., Osłowski, S., Sobey, C, Stappers, B.W., Weltevrede, P., Karastergiou, A., Chennamangalam, J., Armour, W., Williams, C., Mort, B., Dulwich, F., Salvini, S., Magro, A., Roberts, S., Serylak, M, Doo, A., Bilous, A.V., Breton, R.P., Falcke, H., Grießmeier, J.-M., Hessels, J.W.T., Keane, E.F., Kondratiev, V.I., Kramer, M., Leeuwen, J. van, Noutsos, A., Osłowski, S., Sobey, C, Stappers, B.W., and Weltevrede, P.

Abstract

Contains fulltext : 143747.pdf (publisher's version ) (Open Access)

Published
2015

37. Pulsar polarisation below 200 MHz: Average profiles and propagation effects

Author

Noutsos, A., Sobey, C.A., Kondratiev, V.I., Weltevrede, P., Verbiest, J.P.W., Karastergiou, A., Kramer, M., Kuniyoshi, M., Alexov, A., Breton, R.P., Bilous, A.V., Cooper, S., Falcke, H., Grießmeier, J.-M., Hassall, T.E., Hessels, J.W.T., Keane, E.F., Oslowski, S., Pilia, M., Serylak, M., Stappers, B.W., Veen, S. (Sander) ter, Leeuwen, J. (Joeri) van, Zagkouris, K., Anderson, K., Baehren, L., Bell, M.E., Broderick, J.W., Carbone, D., Cendes, Y.N., Coenen, T., Corbel, S., Eislöffel, J., Fender, R.P., Garsden, H., Jonker, P., Law, C.J., Markoff, S., Masters, J., Miller-Jones, J.C.A., Molenaar, G.J., Osten, R., Pietka, M., Rol, E., Rowlinson, A., Scheers, L.H.A. (Bart), Spreeuw, H., Staley, T.D., Stewart, A.J., Swinbank, J.D., Wijers, R.A.M.J. (Ralph), Wijnands, R., Wise, M.W. (Michael), Zarka, P., Horst, A.J. van der, Noutsos, A., Sobey, C.A., Kondratiev, V.I., Weltevrede, P., Verbiest, J.P.W., Karastergiou, A., Kramer, M., Kuniyoshi, M., Alexov, A., Breton, R.P., Bilous, A.V., Cooper, S., Falcke, H., Grießmeier, J.-M., Hassall, T.E., Hessels, J.W.T., Keane, E.F., Oslowski, S., Pilia, M., Serylak, M., Stappers, B.W., Veen, S. (Sander) ter, Leeuwen, J. (Joeri) van, Zagkouris, K., Anderson, K., Baehren, L., Bell, M.E., Broderick, J.W., Carbone, D., Cendes, Y.N., Coenen, T., Corbel, S., Eislöffel, J., Fender, R.P., Garsden, H., Jonker, P., Law, C.J., Markoff, S., Masters, J., Miller-Jones, J.C.A., Molenaar, G.J., Osten, R., Pietka, M., Rol, E., Rowlinson, A., Scheers, L.H.A. (Bart), Spreeuw, H., Staley, T.D., Stewart, A.J., Swinbank, J.D., Wijers, R.A.M.J. (Ralph), Wijnands, R., Wise, M.W. (Michael), Zarka, P., and Horst, A.J. van der

Abstract

Aims: We present the highest-quality polarisation profiles to date of 16 non-recycled pulsars and four millisecond pulsars, observed below 200 MHz with the LOFAR high-band antennas. Based on the observed profiles, we perform an initial investigation of expected observational effects resulting from the propagation of polarised emission in the pulsar magnetosphere and the interstellar medium. Methods: The polarisation data presented in this paper have been calibrated for the geometric-projection and beam-shape effects that distort the polarised information as detected with the LOFAR antennas. We have used RM Synthesis to determine the amount of Faraday rotation in the data at the time of the observations. The ionospheric contribution to the measured Faraday rotation was estimated using a model of the ionosphere. To study the propagation effects, we have compared our low-frequency polarisation observations with archival data at 240, 400, 600, and 1400 MHz. Results: The predictions of magnetospheric birefringence in pulsars have been tested using spectra of the pulse width and fractional polarisation from multifrequency data. The derived spectra offer only partial support for the expected effects of birefringence on the polarisation properties, with only about half of our sample being consistent with the model's predictions. It is noted that for some pulsars these measurements are contaminated by the effects of interstellar scattering. For a number of pulsars in our sample, we have observed significant variations in the amount of Faraday rotation as a function of pulse phase, which is possibly an artefact of scattering. These variations are typically two orders of magnitude smaller than that observed at 1400 MHz by Noutsos et al. (2009), for a different sample of southern pulsars. In this paper we present a possible explanation for the difference in magnitude of this effect between the two frequencies, based on scattering. Finally, we have estimated the magnetospheric e

Published
2015

38. Probing atmospheric electric fields in thunderstorms through radio emission from cosmic-ray-induced air showers

Author

Schellart, P., Trinh, T.N.G., Buitink, S., Corstanje, A., Enriquez, J.E., Falcke, H., Hörandel, J.R., Nelles, A., Rachen, J.P., Rossetto, L., Scholten, O., ter Veen, S., Thoudam, S., Ebert, U., Koehn, C., Rutjes, C., Alexov, A., Anderson, J.M., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Butcher, H.R., Ciardi, B., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Fallows, R.A., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Heald, G., Hessels, J.W.T., Hoeft, M., Holties, H.A., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Mann, G., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mevius, M., Moldon, J., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D.J., Serylak, M., Smirnov, O., Steinmetz, M., Swinbank, J., Tagger, M., Tasse, C., Toribio, M.C., van Weeren, R.J., Vermeulen, R., Vocks, C., Wise, M.W., Wucknitz, O., Zarka, P., Schellart, P., Trinh, T.N.G., Buitink, S., Corstanje, A., Enriquez, J.E., Falcke, H., Hörandel, J.R., Nelles, A., Rachen, J.P., Rossetto, L., Scholten, O., ter Veen, S., Thoudam, S., Ebert, U., Koehn, C., Rutjes, C., Alexov, A., Anderson, J.M., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Butcher, H.R., Ciardi, B., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Fallows, R.A., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Heald, G., Hessels, J.W.T., Hoeft, M., Holties, H.A., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Mann, G., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mevius, M., Moldon, J., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D.J., Serylak, M., Smirnov, O., Steinmetz, M., Swinbank, J., Tagger, M., Tasse, C., Toribio, M.C., van Weeren, R.J., Vermeulen, R., Vocks, C., Wise, M.W., Wucknitz, O., and Zarka, P.

Abstract

We present measurements of radio emission from cosmic ray air showers that took place during thunderstorms. The intensity and polarization patterns of these air showers are radically different from those measured during fair-weather conditions. With the use of a simple two-layer model for the atmospheric electric field, these patterns can be well reproduced by state-of-the-art simulation codes. This in turn provides a novel way to study atmospheric electric fields.

Published
2015

39. LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A

Author

Asgekar, A., Oonk, J.B., Yatawatta, S., Weeren, R.J., McKean, J.P., White, G., Jackson, N., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Bell, M.E., Bell, Michael, Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Braun, R., Breitling, F., Brink, R.H., Broderick, J.W., Brouw, W.N., Brüggen, M., Butcher, H.R., Cappellen, W., Ciardi, B., Conway, J.E., De Gasperin, F., Geus, E., Jong, A., Vos, M., Duscha, S., Eislöffel, J., Falcke, H., Fellows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J.-M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Law, C.J., Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKay-Bukowski, D., Mevins, M., Miller-Jones, J.C.A., Mol, J.D., Morganti, R., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, Varun, Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H.J.A., Scheers, Bart, Schoenmakers, A., Sluman, J., Smirnov, O., Sobey, C.A., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Vocks, C., Wijers, Ralph, Wise, Michael, Wucknitz, O., Zarka, P., Leeuwen, Joeri, and Database Architectures

Subjects
ISM: clouds - radio lines: ISM – ISM: individual objects: Cassiopeia A, Astrophysics::Galaxy Astrophysics
Abstract

Cassiopeia A was observed using the low-band antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) along the line-of-sight to this source. Five carbon alpha RRLs were detected in absorption between 40 and 50 MHz with a signal-to-noise ratio of >5 from two independent LOFAR data sets. The derived line velocities (vLSR ~ - 50 km s-1) and integrated optical depths (~13 s-1) of the RRLs in our spectra, extracted over the whole supernova remnant, are consistent within each LOFAR data set and with those previously reported. For the first time, we are able to extract spectra against the brightest hotspot of the remnant at frequencies below 330 MHz. These spectra show significantly higher (15-80 percent) integrated optical depths, indicating that there is small-scale angular structure of the order of ~1 pc in the absorbing gas distribution over the face of the remnant. We also place an upper limit of 3 × 10-4 on the peak optical depths of hydrogen and helium RRLs. These results demonstrate that LOFAR has the desired spectral stability and sensitivity to study faint recombination lines in the decameter band.

Published
2013

40. Status of LOFAR Data in HDF5 Format

Author

Alexov, A., Schellart, P., Veen, S. ter, Akker, M. van den, Bähren, L., Greissmeier, J.-M., Hessels, J.W.T., Mol, J.D., Renting, G.A., Swinbank, J., Wise, M., Egret, D., Lorente, N.P.F., Ballester, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Netherlands Institute for Radio Astronomy (ASTRON), Radboud university [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), P. Ballester & D. Egret & N.P.F. Lorente, and Ballester, P.

Subjects
[SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU]Sciences of the Universe [physics], Astronomy, Astronomical Society of the Pacific Conference Series
Abstract

International audience; The Hierarchical Data Format, version 5 (HDF5) is a data model, library, and file format for storing and managing data. It is designed for flexible and efficient I/O and for high volume, complex data. The Low Frequency Array (LOFAR) project is solving the challenge of data size and complexity using HDF5. Most of LOFAR's standard data products will be stored using HDF5; the beam-formed time-series data and transient buffer board data have already transitioned from project-specific binary format to HDF5. We report on our effort to pave the way towards new astronomical data encapsulation using HDF5, which can be used by future ground and space projects. The LOFAR project has formed a collaboration with NRAO, the Virtual Astronomical Observatory (VAO) and the HDF Group to obtain funding for a full-time staff member to work on documenting and developing standards for astronomical data written in HDF5. We hope our effort will enhance HDF5 visibility and usage within the community, specifically for LSST, the SKA pathfinders (ASKAP, MeerKAT, MWA, LWA), and other major new radio telescopes such as EVLA, ALMA, and eMERLIN.

Published
2012

41. Observing pulsars and fast transients with LOFAR

Author

Stappers, B.W., Hessels, J.W.T., Scheers, Bart, et al, not, and Database Architectures

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in the lowest 4 octaves of the ionospheric “radio window”: 10–240 MHz, that will greatly facilitate observing pulsars at low radio frequencies. Through the huge collecting area, long baselines, and flexible digital hardware, it is expected that LOFAR will revolutionize radio astronomy at the lowest frequencies visible from Earth. LOFAR is a next-generation radio telescope and a pathfinder to the Square Kilometre Array (SKA), in that it incorporates advanced multi-beaming techniques between thousands of individual elements. We discuss the motivation for low-frequency pulsar observations in general and the potential of LOFAR in addressing these science goals.We present LOFAR as it is designed to perform high-time-resolution observations of pulsars and other fast transients, and outline the various relevant observing modes and data reduction pipelines that are already or will soon be implemented to facilitate these observations. A number of results obtained from commissioning observations are presented to demonstrate the exciting potential of the telescope. This paper outlines the case for low frequency pulsar observations and is also intended to serve as a reference for upcoming pulsar/fast transient science papers with LOFAR.

Published
2011

42. An automated archival Very Large Array transients survey

Author

Bell, M.E., Fender, R.P., Swinbank, J., Miller-Jones, J.C.A., Law, C.J., Scheers, L.H.A., Spreeuw, J.N., Wise, M.W., Stappers, B.W., Wijers, R.A.M.J., Hessels, J.W.T., Masters, J., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Abstract

In this paper we present the results of a survey for radio transients using data obtained from the Very Large Array archive. We have reduced, using a pipeline procedure, 5037 observations of the most common pointings - i.e. the calibrator fields. These fields typically contain a relatively bright point source and are used to calibrate ‘target’ observations: they are therefore rarely imaged themselves. The observations used span a time range ∼1984-2008 and consist of eight different pointings, three different frequencies (8.4, 4.8 and 1.4 GHz) and have a total observing time of 435 h. We have searched for transient and variable radio sources within these observations using components from the prototype LOFAR transient detection system. In this paper we present the methodology for reducing large volumes of Very Large Array data; and we also present a brief overview of the prototype LOFAR transient detection algorithms. No radio transients were detected in this survey, therefore we place an upper limit on the snapshot rate of GHz frequency transients >8.0 mJy to ρ≤ 0.032 deg−2 that have typical time-scales 4.3 to 45.3 d. We compare and contrast our upper limit with the snapshot rates - derived from either detections or non-detections of transient and variable radio sources - reported in the literature. When compared with the current Log N−Log S distribution formed from previous surveys, we show that our upper limit is consistent with the observed population. Current and future radio transient surveys will hopefully further constrain these statistics, and potentially discover dominant transient source populations. In this paper we also briefly explore the current transient commissioning observations with LOFAR, and the impact they will make on the field.

Published
2011

43. LOFAR observations of PSR B0943+10: profile evolution and discovery of a systematically changing profile delay in bright mode

Author

Bilous, A.V., Hessels, J.W.T., Kondratiev, V.I., Leeuwen, J. van, Stappers, B.W., Weltevrede, P., Falcke, H., Hassall, T.E., Pilia, M., Keane, E., Kramer, M., Grießmeier, J.-M., Serylak, M, Bilous, A.V., Hessels, J.W.T., Kondratiev, V.I., Leeuwen, J. van, Stappers, B.W., Weltevrede, P., Falcke, H., Hassall, T.E., Pilia, M., Keane, E., Kramer, M., Grießmeier, J.-M., and Serylak, M

Abstract

Contains fulltext : 134808.pdf (preprint version ) (Open Access)

Published
2014

44. The radio sky on short timescales with LOFAR: pulsars and fast transients

Author

Hessels, J.W.T., Stappers, B.W., van Leeuwen, J., Saikia, D.J., Green, D.A., Gupta, Y., Venturi, T., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

LOFAR, the "low-frequency array", will be one of the first in a new generation of radio telescopes and Square Kilometer Array (SKA) pathfinders that are highly flexible in capability because they are largely software driven. LOFAR will not only open up a mostly unexplored spectral window, the lowest frequency radio light observable from the Earth’s surface, but it will also be an unprecedented tool with which to monitor the transient radio sky over a large field of view and down to timescales of milliseconds or less. Here we discuss LOFAR’s current and upcoming capabilities for observing fast transients and pulsars, and briefly present recent commissioning observations of known pulsars.

Published
2009

45. Calibrating high-precision Faraday rotation measurements for LOFAR and the next generation of low-frequency radio telescopes

Author

Sotomayor-Beltran, C., Sobey, C, Hessels, J.W.T., Bruyn, G. de, Noutsos, A., Alexov, A., Anderson, J., Asgekar, A., Avruch, J., Beck, R., Bell, E., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Ciardi, B., Gasperin, F. de, Dettmar, R.-J., Duin, A. van, Duscha, S., Eislöffel, J., Falcke, H.D.E., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, A., Griessmeier, J.M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hoeft, M., Horneffer, A., Iacobelle, M., Juette, E., Karastergiou, A., Orru, E., Pilia, M., Veen, S. ter, Vermeulen, R., Zarka, P., Sotomayor-Beltran, C., Sobey, C, Hessels, J.W.T., Bruyn, G. de, Noutsos, A., Alexov, A., Anderson, J., Asgekar, A., Avruch, J., Beck, R., Bell, E., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Ciardi, B., Gasperin, F. de, Dettmar, R.-J., Duin, A. van, Duscha, S., Eislöffel, J., Falcke, H.D.E., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, A., Griessmeier, J.M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hoeft, M., Horneffer, A., Iacobelle, M., Juette, E., Karastergiou, A., Orru, E., Pilia, M., Veen, S. ter, Vermeulen, R., and Zarka, P.

Abstract

Contains fulltext : 111298.pdf (preprint version ) (Open Access)

Published
2013

46. IGR J19308+0530: Roche lobe overflow on to a compact object from a donor 1.8 times as massive

Author

Ratti, E.M., Grunsven, T.F.J. van, Torres, M.A.P., Jonker, P.G., Miller-Jones, J.C.A., Hessels, J.W.T., Winckel, H. van, Sluys, M. van der, Nelemans, G.A., Ratti, E.M., Grunsven, T.F.J. van, Torres, M.A.P., Jonker, P.G., Miller-Jones, J.C.A., Hessels, J.W.T., Winckel, H. van, Sluys, M. van der, and Nelemans, G.A.

Abstract

Contains fulltext : 111353.pdf (preprint version ) (Open Access)

Published
2013

47. Status of LOFAR Data in HDF5 Format

Author

Ballester, P., Alexov, A., Schellart, P., Veen, S. ter, Akker, M. van den, Bähren, L., Greissmeier, J.-M., Hessels, J.W.T., Mol, J.D., Renting, G.A., Swinbank, J., Wise, M., Egret, D., Lorente, N.P.F., Ballester, P., Alexov, A., Schellart, P., Veen, S. ter, Akker, M. van den, Bähren, L., Greissmeier, J.-M., Hessels, J.W.T., Mol, J.D., Renting, G.A., Swinbank, J., Wise, M., Egret, D., and Lorente, N.P.F.

Abstract

Astronomical Data Analysis Software and Systems XXI Paris Marriott Rive Gauche Conference Center Paris, France 6–10 November 2011, Item does not contain fulltext

Published
2012

48. An automated archival VLA transients survey

Author

Bell, M.E., Fender, R.P., Swinbank, J.D., Miller-Jones, J.C.A., Law, C.J., Scheers, L.H.A. (Bart), Spreeuw, H., Wise, M.W. (Michael), Stappers, B.W., Wijers, R.A.M.J. (Ralph), Hessels, J.W.T., Masters, J., Bell, M.E., Fender, R.P., Swinbank, J.D., Miller-Jones, J.C.A., Law, C.J., Scheers, L.H.A. (Bart), Spreeuw, H., Wise, M.W. (Michael), Stappers, B.W., Wijers, R.A.M.J. (Ralph), Hessels, J.W.T., and Masters, J.

Abstract

In this paper we present the results of a survey for radio transients using data obtained from the Very Large Array archive. We have reduced, using a pipeline procedure, 5037 observations of the most common pointings - i.e. the calibrator fields. These fields typically contain a relatively bright point source and are used to calibrate 'target' observations: they are therefore rarely imaged themselves. The observations used span a time range ˜1984-2008 and consist of eight different pointings, three different frequencies (8.4, 4.8 and 1.4 GHz) and have a total observing time of 435 h. We have searched for transient and variable radio sources within these observations using components from the prototype LOFAR transient detection system. In this paper we present the methodology for reducing large volumes of Very Large Array data; and we also present a brief overview of the prototype LOFAR transient detection algorithms. No radio transients were detected in this survey, therefore we place an upper limit on the snapshot rate of GHz frequency transients >8.0 mJy to ρ≤ 0.032 deg-2 that have typical time-scales 4.3 to 45.3 d. We compare and contrast our upper limit with the snapshot rates - derived from either detections or non-detections of transient and variable radio sources - reported in the literature. When compared with the current Log N-Log S distribution formed from previous surveys, we show that our upper limit is consistent with the observed population. Current and future radio transient surveys will hopefully further constrain these statistics, and potentially discover dominant transient source populations. In this paper we also briefly explore the current transient commissioning observations with LOFAR, and the impact they will make on the field.

Published
2011

49. The Discovery of an Eccentric Millisecond Pulsar in the Galactic Plane

Author

Bassa, C.G., Wang, Z., Cumming, A., Kaspi, V.M., Champion, D.J., Ransom, S.M., Lazarus, P., Camilo, F., Nice, D.J., Freire, P.C.C., Cordes, J.M., Hessels, J.W.T., Lorimer, D.R., Stairs, I.H., Leeuwen, J. van, Arzoumnian, Z., Backer, D.C., Bhat, N.D.R., Chatterjee, S., Crawford, F., Deneva, J.S., Faucher-Giguere, C.-A., Gaensler, B.M., Han, J., Jenet, F.A., Kasian, L., Kondratiev, V.I., Kramer, M., Lazio, J., McLaughlin, M.A., Stappers, B.W., Venkataraman, A., Vlemmings, W., Bassa, C.G., Wang, Z., Cumming, A., Kaspi, V.M., Champion, D.J., Ransom, S.M., Lazarus, P., Camilo, F., Nice, D.J., Freire, P.C.C., Cordes, J.M., Hessels, J.W.T., Lorimer, D.R., Stairs, I.H., Leeuwen, J. van, Arzoumnian, Z., Backer, D.C., Bhat, N.D.R., Chatterjee, S., Crawford, F., Deneva, J.S., Faucher-Giguere, C.-A., Gaensler, B.M., Han, J., Jenet, F.A., Kasian, L., Kondratiev, V.I., Kramer, M., Lazio, J., McLaughlin, M.A., Stappers, B.W., Venkataraman, A., and Vlemmings, W.

Abstract

40 Years of Pulsars: Millisecond Pulsars, Magnetars and More, 12 augustus 2007, Contains fulltext : 72512.pdf (publisher's version ) (Open Access)

Published
2008

50. An Eccentric Binary Millisecond Pulsar in the Galactic Plane

Author

Champion, D.J., Ransom, S.M., Lazarus, P., Camilo, F., Bassa, C.G., Kaspi, V.M., Nice, D.J., Freire, P.C.C., Stairs, I.H., Leeuwen, J. van, Stappers, B.W., Cordes, J.M., Hessels, J.W.T., Lorimer, D.R., Arzoumanian, Z., Backer, D.C., Bhat, N.D.R., Chatterjee, S., Cognard, I., Deneva, J.S., Faucher-Giguere, C.-A., Gaensler, B.M., Han, J., Jenet, F.A., Kasian, L., Kondratiev, V.I., Kramer, M., Lazio, J., McLaughlin, M.A., Venkataraman, A., Vlemmings, W., Champion, D.J., Ransom, S.M., Lazarus, P., Camilo, F., Bassa, C.G., Kaspi, V.M., Nice, D.J., Freire, P.C.C., Stairs, I.H., Leeuwen, J. van, Stappers, B.W., Cordes, J.M., Hessels, J.W.T., Lorimer, D.R., Arzoumanian, Z., Backer, D.C., Bhat, N.D.R., Chatterjee, S., Cognard, I., Deneva, J.S., Faucher-Giguere, C.-A., Gaensler, B.M., Han, J., Jenet, F.A., Kasian, L., Kondratiev, V.I., Kramer, M., Lazio, J., McLaughlin, M.A., Venkataraman, A., and Vlemmings, W.

Abstract

Contains fulltext : 72626.pdf (preprint version ) (Closed access)

Published
2008

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