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1. LOFAR 144-MHz follow-up observations of GW170817

Author

Broderick JW, Shimwell TW, Gourdji K, Rowlinson A, Nissanke S, Hotokezaka K, Jonker PG, Tasse C, Hardcastle MJ, Oonk JBR, Fender RP, Wijers RAMJ, Shulevski A, Stewart AJ, ter Veen S, Moss VA, van der Wiel MHD, Nichols DA, Piette A, Bell ME, Carbone D, Corbel S, Eisloeffel J, Griessmeier J-M, Keane EF, Law CJ, Munoz-Darias T, Pietka M, Serylak M, van der Horst AJ, van Leeuwen J, Wijnands R, Zarka P, Anderson JM, Bentum MJ, Blaauw R, Brouw WN, Brueggen M, Ciardi B, de Vos M, Duscha S, Fallows RA, Franzen TMO, Garrett MA, Gunst AW, Hoeft M, Hoerandel JR, Iacobelli M, Juette E, Koopmans LVE, Krankowski A, Maat P, Mann G, Mulder H, Nelles A, Paas H, Pandey-Pommier M, Pekal R, Reich W, Roettgering HJA, Schwarz DJ, Smirnov O, Soida M, Toribio MC, van Haarlem MP, van Weeren RJ, Vocks C, Wucknitz O, Zucca P, Broderick JW, Shimwell TW, Gourdji K, Rowlinson A, Nissanke S, Hotokezaka K, Jonker PG, Tasse C, Hardcastle MJ, Oonk JBR, Fender RP, Wijers RAMJ, Shulevski A, Stewart AJ, ter Veen S, Moss VA, van der Wiel MHD, Nichols DA, Piette A, Bell ME, Carbone D, Corbel S, Eisloeffel J, Griessmeier J-M, Keane EF, Law CJ, Munoz-Darias T, Pietka M, Serylak M, van der Horst AJ, van Leeuwen J, Wijnands R, Zarka P, Anderson JM, Bentum MJ, Blaauw R, Brouw WN, Brueggen M, Ciardi B, de Vos M, Duscha S, Fallows RA, Franzen TMO, Garrett MA, Gunst AW, Hoeft M, Hoerandel JR, Iacobelli M, Juette E, Koopmans LVE, Krankowski A, Maat P, Mann G, Mulder H, Nelles A, Paas H, Pandey-Pommier M, Pekal R, Reich W, Roettgering HJA, Schwarz DJ, Smirnov O, Soida M, Toribio MC, van Haarlem MP, van Weeren RJ, Vocks C, Wucknitz O, and Zucca P

Published
2020

2. Cosmology with Phase 1 of the Square Kilometre Array: Red Book 2018: Technical specifications and performance forecasts

Author

Bacon, DJ, Battye, RA, Bull, P, Camera, S, Ferreira, PG, Harrison, I, Parkinson, D, Pourtsidou, A, Santos, MG, Wolz, L, Abdalla, F, Akrami, Y, Alonso, D, Andrianomena, S, Ballardini, M, Bernal, JL, Bertacca, D, Bengaly, CAP, Bonaldi, A, Bonvin, C, Brown, ML, Chapman, E, Chen, S, Chen, X, Cunnington, S, Davis, TM, Dickinson, C, Fonseca, J, Grainge, K, Harper, S, Jarvis, MJ, Maartens, R, Maddox, N, Padmanabhan, H, Pritchard, JR, Raccanelli, A, Rivi, M, Roychowdhury, S, Sahlen, M, Schwarz, DJ, Siewert, TM, Viel, M, Villaescusa-Navarro, F, Xu, Y, Yamauchi, D, Zuntz, J, Group, Square Kilometre Array Cosmology Science Working, Laboratoire de physique de l'ENS - ENS Paris (LPENS (UMR_8023)), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), SKA, Astrophysique, Laboratoire de physique de l'ENS - ENS Paris (LPENS), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), European Commission, and European Research Council

Subjects
cosmological model, Cosmology and Nongalactic Astrophysics (astro-ph.CO), cosmology, galaxy redshift surveys, intensity mapping, radio telescopes, weak lensing, General relativity, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, baryon: oscillation: acoustic, 01 natural sciences, Cosmology, Metric expansion of space, NO, General Relativity and Quantum Cosmology, statistical analysis, gravitation: lens, 0103 physical sciences, general relativity, Cluster analysis, 010303 astronomy & astrophysics, Weak gravitational lensing, STFC, Physics, 010308 nuclear & particles physics, PE9_14, Astrophysics::Instrumentation and Methods for Astrophysics, Intensity mapping, RCUK, Astronomy and Astrophysics, ST/P000649/1, Galaxy, observatory, Computer Science::Graphics, Space and Planetary Science, Physics::Space Physics, non-Gaussianity, Dark energy, astro-ph.CO, radio telescopes, cosmology, galaxy redshift surveys, weak lensing, intensity mapping, galaxy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Cosmology and Nongalactic Astrophysics, dark energy: equation of state
Abstract

Square Kilometre Array Cosmology Science Working Group: et al., arXiv:1811.02743v1, We present a detailed overview of the cosmological surveys that we aim to carry out with Phase 1 of the Square Kilometre Array (SKA1) and the science that they will enable. We highlight three main surveys: a medium-deep continuum weak lensing and low-redshift spectroscopic HI galaxy survey over 5 000 deg2; a wide and deep continuum galaxy and HI intensity mapping (IM) survey over 20 000 deg2 from to 3; and a deep, high-redshift HI IM survey over 100 deg2 from to 6. Taken together, these surveys will achieve an array of important scientific goals: measuring the equation of state of dark energy out to with percent-level precision measurements of the cosmic expansion rate; constraining possible deviations from General Relativity on cosmological scales by measuring the growth rate of structure through multiple independent methods; mapping the structure of the Universe on the largest accessible scales, thus constraining fundamental properties such as isotropy, homogeneity, and non-Gaussianity; and measuring the HI density and bias out to z = 6. These surveys will also provide highly complementary clustering and weak lensing measurements that have independent systematic uncertainties to those of optical and near-infrared (NIR) surveys like Euclid, LSST, and WFIRST leading to a multitude of synergies that can improve constraints significantly beyond what optical or radio surveys can achieve on their own. This document, the 2018 Red Book, provides reference technical specifications, cosmological parameter forecasts, and an overview of relevant systematic effects for the three key surveys and will be regularly updated by the Cosmology Science Working Group in the run up to start of operations and the Key Science Programme of SKA1., RB, CD, and SH acknowledge support from an STFC Consolidated Grant (ST/P000649/1). SC is supported by the Italian Ministry of Education, University and Research (MIUR) through Rita Levi Montalcini project ‘PROMETHEUS—Probing and Relating Observables with Multi-wavelength Experiments To Help Enlightening the Universe’s Structure’, and by the ‘Departments of Excellence 2018-2022’ Grant awarded by MIUR (L. 232/2016). PGF acknowledges support from ERC Grant No: 693024, the Beecroft Trust and STFC. RM and MGS acknowledge support from the South African Square Kilometre Array Project and National Research Foundation (Grant Nos. 75415 and 84156). LW is supported by an ARC Discovery Early Career Researcher Award (DE170100356). YA acknowledges support from the Netherlands Organization for Scientific Research (NWO) and the Dutch Ministry of Education, Culture and Science (OCW), and also from the D-ITP consortium, a programme of the NWO that is funded by the OCW. YA is also supported by LabEx ENS-ICFP: ANR-10-LABX-0010/ANR-10-IDEX0001-02 PSL∗. HP’s research is supported by the Tomalla Foundation. AR has received funding from the People Programme (Marie Curie Actions) of the European Union H2020 Programme under REA grant agreement number 706896 (COSMOFLAGS). TS and DJS gratefully acknowledge support from the Deutsche Forschungsgemeinschaft (DFG) within the Research Training Group 1620 ‘Models of Gravity’.

Published
2018
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3. Shock location and CME 3D reconstruction of a solar type II radio burst with LOFAR

Author

Zucca, P, Morosan, DE, Rouillard, AP, Fallows, R, Gallagher, PT, Magdalenic, J, Klein, KL, Mann, G, Vocks, C, Carley, EP, Bisi, MM, Kontar, EP, Rothkaehl, H, Dabrowski, B, Krankowski, A, Anderson, J, Asgekar, A, Bell, ME, Bentum, MJ, Best, P, Blaauw, R, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Ciardi, B, De Geus, E, Deller, A, Duscha, S, Eislöffel, J, Garrett, MA, Grießmeier, JM, Gunst, AW, Heald, G, Hoeft, M, Hörandel, J, Iacobelli, M, Juette, E, Karastergiou, A, Van Leeuwen, J, McKay-Bukowski, D, Mulder, H, Munk, H, Nelles, A, Orru, E, Paas, H, Pandey, VN, Pekal, R, Pizzo, R, Polatidis, AG, Reich, W, Rowlinson, A, Schwarz, DJ, Shulevski, A, Sluman, J, Smirnov, O, Sobey, C, Soida, M, Thoudam, S, Toribio, MC, Vermeulen, R, Van Weeren, RJ, Wucknitz, O, Zarka, P, Zucca, P, Morosan, DE, Rouillard, AP, Fallows, R, Gallagher, PT, Magdalenic, J, Klein, KL, Mann, G, Vocks, C, Carley, EP, Bisi, MM, Kontar, EP, Rothkaehl, H, Dabrowski, B, Krankowski, A, Anderson, J, Asgekar, A, Bell, ME, Bentum, MJ, Best, P, Blaauw, R, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Ciardi, B, De Geus, E, Deller, A, Duscha, S, Eislöffel, J, Garrett, MA, Grießmeier, JM, Gunst, AW, Heald, G, Hoeft, M, Hörandel, J, Iacobelli, M, Juette, E, Karastergiou, A, Van Leeuwen, J, McKay-Bukowski, D, Mulder, H, Munk, H, Nelles, A, Orru, E, Paas, H, Pandey, VN, Pekal, R, Pizzo, R, Polatidis, AG, Reich, W, Rowlinson, A, Schwarz, DJ, Shulevski, A, Sluman, J, Smirnov, O, Sobey, C, Soida, M, Thoudam, S, Toribio, MC, Vermeulen, R, Van Weeren, RJ, Wucknitz, O, and Zarka, P

Published
2018

4. Low-frequency radio absorption in Cassiopeia A

Author

Arias, M, Vink, J, De Gasperin, F, Salas, P, Oonk, JBR, Van Weeren, RJ, Van Amesfoort, AS, Anderson, J, Beck, R, Bell, ME, Bentum, MJ, Best, P, Blaauw, R, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Ciardi, B, De Geus, E, Deller, A, Van Dijk, PCG, Duscha, S, Eislöffel, J, Garrett, MA, Grießmeier, JM, Gunst, AW, Van Haarlem, MP, Heald, G, Hessels, J, Hörandel, J, Holties, HA, Van Der Horst, AJ, Iacobelli, M, Juette, E, Krankowski, A, Van Leeuwen, J, Mann, G, McKay-Bukowski, D, McKean, JP, Mulder, H, Nelles, A, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pekal, R, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Rothkaehl, H, Schwarz, DJ, Smirnov, O, Soida, M, Steinmetz, M, Tagger, M, Thoudam, S, Toribio, MC, Vocks, C, Van Der Wiel, MHD, Wijers, RAMJ, Wucknitz, O, Zarka, P, Zucca, P, Arias, M, Vink, J, De Gasperin, F, Salas, P, Oonk, JBR, Van Weeren, RJ, Van Amesfoort, AS, Anderson, J, Beck, R, Bell, ME, Bentum, MJ, Best, P, Blaauw, R, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Ciardi, B, De Geus, E, Deller, A, Van Dijk, PCG, Duscha, S, Eislöffel, J, Garrett, MA, Grießmeier, JM, Gunst, AW, Van Haarlem, MP, Heald, G, Hessels, J, Hörandel, J, Holties, HA, Van Der Horst, AJ, Iacobelli, M, Juette, E, Krankowski, A, Van Leeuwen, J, Mann, G, McKay-Bukowski, D, McKean, JP, Mulder, H, Nelles, A, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pekal, R, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Rothkaehl, H, Schwarz, DJ, Smirnov, O, Soida, M, Steinmetz, M, Tagger, M, Thoudam, S, Toribio, MC, Vocks, C, Van Der Wiel, MHD, Wijers, RAMJ, Wucknitz, O, Zarka, P, and Zucca, P

Abstract

© ESO 2018. Context. Cassiopeia A is one of the best-studied supernova remnants. Its bright radio and X-ray emission is due to shocked ejecta. Cas A is rather unique in that the unshocked ejecta can also be studied: through emission in the infrared, the radio-active decay of 44Ti, and the low-frequency free-free absorption caused by cold ionised gas, which is the topic of this paper. Aims. Free-free absorption processes are affected by the mass, geometry, temperature, and ionisation conditions in the absorbing gas. Observations at the lowest radio frequencies can constrain a combination of these properties. Methods. We used Low Frequency Array (LOFAR) Low Band Antenna observations at 30-77 MHz and Very Large Array (VLA) L-band observations at 1-2 GHz to fit for internal absorption as parametrised by the emission measure. We simultaneously fit multiple UV-matched images with a common resolution of 17″ (this corresponds to 0.25 pc for a source t the distance of Cas A). The ample frequency coverage allows us separate the relative contributions from the absorbing gas, the unabsorbed front of the shell, and the absorbed back of the shell to the emission spectrum. We explored the effects that a temperature lower than the ~100-500 K proposed from infrared observations and a high degree of clumping can have on the derived physical properties of the unshocked material, such as its mass and density. We also compiled integrated radio flux density measurements, fit for the absorption processes that occur in the radio band, and considered their effect on the secular decline of the source. Results. We find a mass in the unshocked ejecta of M = 2.95 ± 0.48 MȮ for an assumed gas temperatureof T = 100 K. This estimate is reduced for colder gas temperatures and, most significantly, if the ejecta are clumped. We measure the reverse shock to have a radius of 114″± 6″ and be centred at 23:23:26, +58:48:54 (J2000). We also find that a decrease in the amount of mass in the unshocked eject

Published
2018

5. Tracking of an electron beam through the solar corona with LOFAR

Author

Mann, G, Breitling, F, Vocks, C, Aurass, H, Steinmetz, M, Strassmeier, KG, Bisi, MM, Fallows, RA, Gallagher, P, Kerdraon, A, Mackinnon, A, Magdalenic, J, Rucker, H, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bîrzan, L, Bonafede, A, Broderick, JW, Brüggen, M, Butcher, HR, Ciardi, B, Corstanje, A, Gasperin, FD, Geus, ED, Deller, A, Duscha, S, Eislöffel, J, Engels, D, Falcke, H, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, J, Gunst, AW, Haarlem, MV, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Hörandel, J, Horneffer, A, Juette, E, Karastergiou, A, Klijn, WFA, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Maat, P, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mulcahy, DD, Munk, H, Nelles, A, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pizzo, R, Polatidis, AG, Rafferty, D, Reich, W, Röttgering, H, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Tagger, M, Tang, Y, Tasse, C, Veen, ST, Thoudam, S, Toribio, MC, Vermeulen, R, Weeren, RJV, Wise, MW, Wucknitz, O, Yatawatta, S, Zarka, P, Zensus, JA, Mann, G, Breitling, F, Vocks, C, Aurass, H, Steinmetz, M, Strassmeier, KG, Bisi, MM, Fallows, RA, Gallagher, P, Kerdraon, A, Mackinnon, A, Magdalenic, J, Rucker, H, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bîrzan, L, Bonafede, A, Broderick, JW, Brüggen, M, Butcher, HR, Ciardi, B, Corstanje, A, Gasperin, FD, Geus, ED, Deller, A, Duscha, S, Eislöffel, J, Engels, D, Falcke, H, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, J, Gunst, AW, Haarlem, MV, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Hörandel, J, Horneffer, A, Juette, E, Karastergiou, A, Klijn, WFA, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Maat, P, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mulcahy, DD, Munk, H, Nelles, A, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pizzo, R, Polatidis, AG, Rafferty, D, Reich, W, Röttgering, H, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Tagger, M, Tang, Y, Tasse, C, Veen, ST, Thoudam, S, Toribio, MC, Vermeulen, R, Weeren, RJV, Wise, MW, Wucknitz, O, Yatawatta, S, Zarka, P, and Zensus, JA

Abstract

© ESO 2018. The Sun's activity leads to bursts of radio emission, among other phenomena. An example is type-III radio bursts. They occur frequently and appear as short-lived structures rapidly drifting from high to low frequencies in dynamic radio spectra. They are usually interpreted as signatures of beams of energetic electrons propagating along coronal magnetic field lines. Here we present novel interferometric LOFAR (LOw Frequency ARray) observations of three solar type-III radio bursts and their reverse bursts with high spectral, spatial, and temporal resolution. They are consistent with a propagation of the radio sources along the coronal magnetic field lines with nonuniform speed. Hence, the type-III radio bursts cannot be generated by a monoenergetic electron beam, but by an ensemble of energetic electrons with a spread distribution in velocity and energy. Additionally, the density profile along the propagation path is derived in the corona. It agrees well with three-fold coronal density model by (1961, ApJ, 133, 983).

Published
2018

6. A large light-mass component of cosmic rays at 1017-1017.5 electronvolts from radio observations

Author

Buitink, S, Corstanje, A, Falcke, H, Hörandel, JR, Huege, T, Nelles, A, Rachen, JP, Rossetto, L, Schellart, P, Scholten, O, Ter Veen, S, Thoudam, S, Trinh, TNG, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bonafede, A, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Carbone, D, Ciardi, B, Conway, JE, De Gasperin, F, De Geus, E, Deller, A, Dettmar, RJ, Van Diepen, G, Duscha, S, Eislöffel, J, Engels, D, Enriquez, JE, Fallows, RA, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, JM, Gunst, AW, Van Haarlem, MP, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Horneffer, A, Iacobelli, M, Intema, H, Juette, E, Karastergiou, A, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Van Leeuwen, J, Loose, GM, Maat, P, Mann, G, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mevius, M, Mulcahy, DD, Munk, H, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pietka, M, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Steinmetz, M, Stewart, A, Swinbank, J, Tagger, M, Tang, Y, Tasse, C, Toribio, MC, Vermeulen, R, Vocks, C, Vogt, C, Van Weeren, RJ, Wijers, RAMJ, Wijnholds, SJ, and Wise, MW

Subjects
General Science & Technology, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract

© 2016 Macmillan Publishers Limited. All rights reserved. Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017-1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate air showers - cascades of secondary particles in the atmosphere - and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. Current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017-1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017-1017.5 electronvolt range.

Published
2015

7. The association of a J -burst with a solar jet

Author

Morosan, DE, Gallagher, PT, Fallows, RA, Reid, H, Mann, G, Bisi, MM, Magdalenić, J, Rucker, HO, Thidé, B, Vocks, C, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Best, P, Blaauw, R, Bonafede, A, Breitling, F, Broderick, JW, Brüggen, M, Cerrigone, L, Ciardi, B, De Geus, E, Duscha, S, Eislöffel, J, Falcke, H, Garrett, MA, Grießmeier, JM, Gunst, AW, Hoeft, M, Iacobelli, M, Juette, E, Kuper, G, McFadden, R, McKay-Bukowski, D, McKean, JP, Mulcahy, DD, Munk, H, Nelles, A, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pizzo, R, Polatidis, AG, Reich, W, Schwarz, DJ, Sluman, J, Smirnov, O, Steinmetz, M, Tagger, M, Ter Veen, S, Thoudam, S, Toribio, MC, Vermeulen, R, Van Weeren, RJ, Wucknitz, O, Zarka, P, Morosan, DE, Gallagher, PT, Fallows, RA, Reid, H, Mann, G, Bisi, MM, Magdalenić, J, Rucker, HO, Thidé, B, Vocks, C, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Best, P, Blaauw, R, Bonafede, A, Breitling, F, Broderick, JW, Brüggen, M, Cerrigone, L, Ciardi, B, De Geus, E, Duscha, S, Eislöffel, J, Falcke, H, Garrett, MA, Grießmeier, JM, Gunst, AW, Hoeft, M, Iacobelli, M, Juette, E, Kuper, G, McFadden, R, McKay-Bukowski, D, McKean, JP, Mulcahy, DD, Munk, H, Nelles, A, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pizzo, R, Polatidis, AG, Reich, W, Schwarz, DJ, Sluman, J, Smirnov, O, Steinmetz, M, Tagger, M, Ter Veen, S, Thoudam, S, Toribio, MC, Vermeulen, R, Van Weeren, RJ, Wucknitz, O, and Zarka, P

Abstract

© ESO, 2017. Context. The Sun is an active star that produces large-scale energetic events such as solar flares and coronal mass ejections, and numerous smaller scale events such as solar jets. These events are often associated with accelerated particles that can cause emission at radio wavelengths. The reconfiguration of the solar magnetic field in the corona is believed to be the cause of the majority of solar energetic events and accelerated particles. Aims. Here, we investigate a bright J-burst that was associated with a solar jet and the possible emission mechanism causing these two phenomena. Methods. We used data from the Solar Dynamics Observatory (SDO) to observe a solar jet and radio data from the Low Frequency Array (LOFAR) and the Nançay Radioheliograph (NRH) to observe a J-burst over a broad frequency range (33-173 MHz) on 9 July 2013 at ~11:06 UT. Results. The J-burst showed fundamental and harmonic components and was associated with a solar jet observed at extreme ultraviolet wavelengths with SDO. The solar jet occurred in the northern hemisphere at a time and location coincident with the radio burst and not inside a group of complex active regions in the southern hemisphere. The jet occurred in the negative polarity region of an area of bipolar plage. Newly emerged positive flux in this region appeared to be the trigger of the jet. Conclusions. Magnetic reconnection between the overlying coronal field lines and the newly emerged positive field lines is most likely the cause of the solar jet. Radio imaging provides a clear association between the jet and the J-burst, which shows the path of the accelerated electrons. These electrons travelled from a region in the vicinity of the solar jet along closed magnetic field lines up to the top of a closed magnetic loop at a height of ~360 Mm. Such small-scale complex eruptive events arising from magnetic reconnection could facilitate accelerated electrons to produce continuously the large numbers of Type III

Published
2017

8. A large light-mass component of cosmic rays at 1017-1017.5 electronvolts from radio observations

Author

Buitink, S, Corstanje, A, Falcke, H, Hörandel, JR, Huege, T, Nelles, A, Rachen, JP, Rossetto, L, Schellart, P, Scholten, O, Ter Veen, S, Thoudam, S, Trinh, TNG, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bonafede, A, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Carbone, D, Ciardi, B, Conway, JE, De Gasperin, F, De Geus, E, Deller, A, Dettmar, RJ, Van Diepen, G, Duscha, S, Eislöffel, J, Engels, D, Enriquez, JE, Fallows, RA, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, JM, Gunst, AW, Van Haarlem, MP, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Horneffer, A, Iacobelli, M, Intema, H, Juette, E, Karastergiou, A, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Van Leeuwen, J, Loose, GM, Maat, P, Mann, G, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mevius, M, Mulcahy, DD, Munk, H, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pietka, M, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Steinmetz, M, Stewart, A, Swinbank, J, Tagger, M, Tang, Y, Tasse, C, Toribio, MC, Vermeulen, R, Vocks, C, Vogt, C, Van Weeren, RJ, Wijers, RAMJ, Wijnholds, SJ, Wise, MW, Buitink, S, Corstanje, A, Falcke, H, Hörandel, JR, Huege, T, Nelles, A, Rachen, JP, Rossetto, L, Schellart, P, Scholten, O, Ter Veen, S, Thoudam, S, Trinh, TNG, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bonafede, A, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Carbone, D, Ciardi, B, Conway, JE, De Gasperin, F, De Geus, E, Deller, A, Dettmar, RJ, Van Diepen, G, Duscha, S, Eislöffel, J, Engels, D, Enriquez, JE, Fallows, RA, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, JM, Gunst, AW, Van Haarlem, MP, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Horneffer, A, Iacobelli, M, Intema, H, Juette, E, Karastergiou, A, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Van Leeuwen, J, Loose, GM, Maat, P, Mann, G, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mevius, M, Mulcahy, DD, Munk, H, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pietka, M, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Steinmetz, M, Stewart, A, Swinbank, J, Tagger, M, Tang, Y, Tasse, C, Toribio, MC, Vermeulen, R, Vocks, C, Vogt, C, Van Weeren, RJ, Wijers, RAMJ, Wijnholds, SJ, and Wise, MW

Abstract

© 2016 Macmillan Publishers Limited. All rights reserved. Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017-1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate air showers - cascades of secondary particles in the atmosphere - and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. Current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017-1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017-1017.5 electronvolt range.

Published
2016

9. Associations of Usual and Fast Gait Speed With Physical Performance and Balance Confidence in Community-Dwelling Older Adults: Implications for Assessment.

Author

Tiernan C, Schwarz DJ, and Goldberg A

Subjects
Humans, Female, Aged, Male, Cross-Sectional Studies, Aged, 80 and over, Middle Aged, Muscle Strength physiology, Walk Test, Postural Balance physiology, Walking Speed physiology, Independent Living, Accidental Falls prevention & control, Physical Functional Performance, Geriatric Assessment methods
Abstract

Background and Purpose: Gait speed is a robust measure that offers many advantages clinically. However, decisions concerning its utilization exist, including whether to assess usual or fast gait speed. The current study aimed to identify whether usual or fast gait speed was more strongly associated with physical performance measures and balance confidence. A secondary aim was to explore these relationships within subgroups based on fall risk status., Methods: This was an observational study with a cross-sectional design involving 57 community-dwelling older adults (77.2% female; mean age = 68.8, SD = 6.5 years, range = 60-87 years) who were assessed on the following variables: usual and fast gait speed, knee extension strength, step execution time, 6-minute walk test (6MWT), and Activities-specific Balance Confidence Scale (ABC-6). Spearman ρ correlations were computed to determine bivariate associations of usual and fast gait speed with physical performance measures and balance confidence for the whole sample and within subgroups based on fall risk [lower fall risk (n = 28) vs higher fall risk (n = 29)]. Multiple linear regression models were estimated with either usual or fast gait speed as key predictors of knee extension strength, step execution time, 6MWT, and ABC-6., Results and Discussion: Stronger correlations were observed for fast gait speed compared with usual gait speed with all physical performance measures and balance confidence for the entire sample and within the higher fall risk group. Multiple regression results indicated that models with fast rather than usual gait speed as the key predictor explained more of the variance in 6MWT ( R2 = 64.5% vs 45.6%), ABC-6 ( R2 = 28.5% vs 25.4%), step execution time ( R2 = 24.9% vs 19.0%), and knee extension strength ( R2 = 15.7% vs 7.2%)., Conclusions: Fast gait speed showed stronger associations and better predictive capabilities compared with usual gait speed with physical performance measures and balance confidence in older adults. Despite being measured less often than usual gait speed, fast gait speed assessment warrants additional consideration., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2024 APTA Geriatrics, An Academy of the American Physical Therapy Association.)

Published
2024
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10. Searching for Axionlike Particles under Strong Gravitational Lenses.

Author

Basu A, Goswami J, Schwarz DJ, and Urakawa Y

Abstract

We establish strong gravitational lens systems as robust probes of axionlike particles (ALPs)-a candidate for dark matter. A tiny interaction of photons with ALPs induces birefringence. Multiple images of gravitationally lensed polarized objects allow measurement of differential birefringence, alleviating systematics and astrophysical dependencies. We apply this novel method to the lens system CLASS B1152+199 and constrain the ALP-photon coupling ≤9.2×10^{-11} to 7.7×10^{-8}  GeV^{-1} (95% C.L.) for an ALP mass between 3.6×10^{-21} and 4.6×10^{-18}  eV. A larger sample will improve the constraints.

Published
2021
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11. Needle-like structures discovered on positively charged lightning branches.

Author

Hare BM, Scholten O, Dwyer J, Trinh TNG, Buitink S, Ter Veen S, Bonardi A, Corstanje A, Falcke H, Hörandel JR, Huege T, Mitra P, Mulrey K, Nelles A, Rachen JP, Rossetto L, Schellart P, Winchen T, Anderson J, Avruch IM, Bentum MJ, Blaauw R, Broderick JW, Brouw WN, Brüggen M, Butcher HR, Ciardi B, Fallows RA, de Geus E, Duscha S, Eislöffel J, Garrett MA, Grießmeier JM, Gunst AW, van Haarlem MP, Hessels JWT, Hoeft M, van der Horst AJ, Iacobelli M, Koopmans LVE, Krankowski A, Maat P, Norden MJ, Paas H, Pandey-Pommier M, Pandey VN, Pekal R, Pizzo R, Reich W, Rothkaehl H, Röttgering HJA, Rowlinson A, Schwarz DJ, Shulevski A, Sluman J, Smirnov O, Soida M, Tagger M, Toribio MC, van Ardenne A, Wijers RAMJ, van Weeren RJ, Wucknitz O, Zarka P, and Zucca P

Abstract

Lightning is a dangerous yet poorly understood natural phenomenon. Lightning forms a network of plasma channels propagating away from the initiation point with both positively and negatively charged ends-called positive and negative leaders 1 . Negative leaders propagate in discrete steps, emitting copious radio pulses in the 30-300-megahertz frequency band 2-8 that can be remotely sensed and imaged with high spatial and temporal resolution 9-11 . Positive leaders propagate more continuously and thus emit very little high-frequency radiation 12 . Radio emission from positive leaders has nevertheless been mapped 13-15 , and exhibits a pattern that is different from that of negative leaders 11-13,16,17 . Furthermore, it has been inferred that positive leaders can become transiently disconnected from negative leaders 9,12,16,18-20 , which may lead to current pulses that both reconnect positive leaders to negative leaders 11,16,17,20-22 and cause multiple cloud-to-ground lightning events 1 . The disconnection process is thought to be due to negative differential resistance 18 , but this does not explain why the disconnections form primarily on positive leaders 22 , or why the current in cloud-to-ground lightning never goes to zero 23 . Indeed, it is still not understood how positive leaders emit radio-frequency radiation or why they behave differently from negative leaders. Here we report three-dimensional radio interferometric observations of lightning over the Netherlands with unprecedented spatiotemporal resolution. We find small plasma structures-which we call 'needles'-that are the dominant source of radio emission from the positive leaders. These structures appear to drain charge from the leader, and are probably the reason why positive leaders disconnect from negative ones, and why cloud-to-ground lightning connects to the ground multiple times.

Published
2019
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12. Cosmic QCD Epoch at Nonvanishing Lepton Asymmetry.

Author

Wygas MM, Oldengott IM, Bödeker D, and Schwarz DJ

Abstract

We investigate how a lepton asymmetry impacts the cosmic trajectory in the QCD phase diagram. We study the evolution of chemical potentials during the QCD epoch of the early Universe using susceptibilities from lattice QCD to interpolate between an ideal quark gas and an ideal hadron resonance gas. The lepton asymmetry affects the evolution of all chemical potentials. The standard cosmic trajectory is obtained assuming tiny lepton and baryon asymmetries. For larger lepton asymmetry, the charge chemical potential exceeds the baryon chemical potential before pion annihilation.

Published
2018
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13. Corrigendum: A large light-mass component of cosmic rays at 10 17 -10 17.5 electronvolts from radio observations.

Author

Buitink S, Corstanje A, Falcke H, Hörandel JR, Huege T, Nelles A, Rachen JP, Rossetto L, Schellart P, Scholten O, Ter Veen S, Thoudam S, Trinh TN, Anderson J, Asgekar A, Avruch IM, Bell ME, Bentum MJ, Bernardi G, Best P, Bonafede A, Breitling F, Broderick JW, Brouw WN, Brüggen M, Butcher HR, Carbone D, Ciardi B, Conway JE, de Gasperin F, de Geus E, Deller A, Dettmar RJ, van Diepen G, Duscha S, Eislöffel J, Engels D, Enriquez JE, Fallows RA, Fender R, Ferrari C, Frieswijk W, Garrett MA, Grießmeier JM, Gunst AW, van Haarlem MP, Hassall TE, Heald G, Hessels JW, Hoeft M, Horneffer A, Iacobelli M, Intema H, Juette E, Karastergiou A, Kondratiev VI, Kramer M, Kuniyoshi M, Kuper G, van Leeuwen J, Loose GM, Maat P, Mann G, Markoff S, McFadden R, McKay-Bukowski D, McKean JP, Mevius M, Mulcahy DD, Munk H, Norden MJ, Orru E, Paas H, Pandey-Pommier M, Pandey VN, Pietka M, Pizzo R, Polatidis AG, Reich W, Röttgering HJ, Scaife AM, Schwarz DJ, Serylak M, Sluman J, Smirnov O, Stappers BW, Steinmetz M, Stewart A, Swinbank J, Tagger M, Tang Y, Tasse C, Toribio MC, Vermeulen R, Vocks C, Vogt C, van Weeren RJ, Wijers RA, Wijnholds SJ, Wise MW, Wucknitz O, Yatawatta S, Zarka P, and Zensus JA

Published
2016
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14. A large light-mass component of cosmic rays at 10(17)-10(17.5) electronvolts from radio observations.

Author

Buitink S, Corstanje A, Falcke H, Hörandel JR, Huege T, Nelles A, Rachen JP, Rossetto L, Schellart P, Scholten O, ter Veen S, Thoudam S, Trinh TN, Anderson J, Asgekar A, Avruch IM, Bell ME, Bentum MJ, Bernardi G, Best P, Bonafede A, Breitling F, Broderick JW, Brouw WN, Brüggen M, Butcher HR, Carbone D, Ciardi B, Conway JE, de Gasperin F, de Geus E, Deller A, Dettmar RJ, van Diepen G, Duscha S, Eislöffel J, Engels D, Enriquez JE, Fallows RA, Fender R, Ferrari C, Frieswijk W, Garrett MA, Grießmeier JM, Gunst AW, van Haarlem MP, Hassall TE, Heald G, Hessels JW, Hoeft M, Horneffer A, Iacobelli M, Intema H, Juette E, Karastergiou A, Kondratiev VI, Kramer M, Kuniyoshi M, Kuper G, van Leeuwen J, Loose GM, Maat P, Mann G, Markoff S, McFadden R, McKay-Bukowski D, McKean JP, Mevius M, Mulcahy DD, Munk H, Norden MJ, Orru E, Paas H, Pandey-Pommier M, Pandey VN, Pietka M, Pizzo R, Polatidis AG, Reich W, Röttgering HJ, Scaife AM, Schwarz DJ, Serylak M, Sluman J, Smirnov O, Stappers BW, Steinmetz M, Stewart A, Swinbank J, Tagger M, Tang Y, Tasse C, Toribio MC, Vermeulen R, Vocks C, Vogt C, van Weeren RJ, Wijers RA, Wijnholds SJ, Wise MW, Wucknitz O, Yatawatta S, Zarka P, and Zensus JA

Abstract

Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 10(17)-10(18) electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate air showers--cascades of secondary particles in the atmosphere-and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. Current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 10(17)-10(17.5) electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 10(17.5) electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 10(17)-10(17.5) electronvolt range.

Published
2016
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15. Probing Atmospheric Electric Fields in Thunderstorms through Radio Emission from Cosmic-Ray-Induced Air Showers.

Author

Schellart P, Trinh TN, Buitink S, Corstanje A, Enriquez JE, Falcke H, Hörandel JR, Nelles A, Rachen JP, Rossetto L, Scholten O, Ter Veen S, Thoudam S, Ebert U, Koehn C, Rutjes C, Alexov A, Anderson JM, Avruch IM, Bentum MJ, Bernardi G, Best P, Bonafede A, Breitling F, Broderick JW, Brüggen M, Butcher HR, Ciardi B, de Geus E, de Vos M, Duscha S, Eislöffel J, Fallows RA, Frieswijk W, Garrett MA, Grießmeier J, Gunst AW, Heald G, Hessels JW, Hoeft M, Holties HA, Juette E, Kondratiev VI, Kuniyoshi M, Kuper G, Mann G, McFadden R, McKay-Bukowski D, McKean JP, Mevius M, Moldon J, Norden MJ, Orru E, Paas H, Pandey-Pommier M, Pizzo R, Polatidis AG, Reich W, Röttgering H, Scaife AM, Schwarz DJ, Serylak M, Smirnov O, Steinmetz M, Swinbank J, Tagger M, Tasse C, Toribio MC, van Weeren RJ, Vermeulen R, Vocks C, Wise MW, 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
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16. Value of H(0) in the inhomogeneous universe.

Author

Ben-Dayan I, Durrer R, Marozzi G, and Schwarz DJ

Abstract

Local measurements of the Hubble expansion rate are affected by structures like galaxy clusters or voids. Here we present a fully relativistic treatment of this effect, studying how clustering modifies the mean distance- (modulus-)redshift relation and its dispersion in a standard cold dark matter universe with a cosmological constant. The best estimates of the local expansion rate stem from supernova observations at small redshifts (0.01

Published
2014
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17. Large-scale suppression from stochastic inflation.

Author

Kühnel F and Schwarz DJ

Abstract

We show nonperturbatively that the power spectrum of a self-interacting scalar field in de Sitter space-time is strongly suppressed on large scales. The cutoff scale depends on the strength of the self-coupling, the number of e folds of quasi-de Sitter evolution, and its expansion rate. As a consequence, the two-point correlation function of field fluctuations is free from infrared divergencies.

Published
2010
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19. Is the low-l microwave background cosmic?

Author

Schwarz DJ, Starkman GD, Huterer D, and Copi CJ

Abstract

The large-angle (low-l) correlations of the cosmic microwave background exhibit several statistically significant anomalies compared to the standard inflationary cosmology. We show that the quadrupole plane and the three octopole planes are far more aligned than previously thought (99.9% C.L.). Three of these planes are orthogonal to the ecliptic at 99.1% C.L., and the normals to these planes are aligned at 99.6% C.L. with the direction of the cosmological dipole and with the equinoxes. The remaining octopole plane is orthogonal to the supergalactic plane at 99.6% C.L.

Published
2004
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20. QCD phase transition in the inhomogeneous universe.

Author

Ignatius J and Schwarz DJ

Abstract

We investigate a new mechanism for the cosmological QCD phase transition: inhomogeneous nucleation. The primordial temperature fluctuations, measured to be deltaT/T approximately 10(-5), are larger than the tiny temperature interval in which bubbles would form in the standard picture of homogeneous nucleation. Thus the bubbles nucleate at cold spots. We find the typical distance between bubble centers to be a few meters. This exceeds the estimates from homogeneous nucleation by 2 orders of magnitude. The resulting baryon inhomogeneities may affect primordial nucleosynthesis.

Published
2001
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