J. W. Hessels - ASTRON

J. W. Hessels
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J. W. Hessels

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High Energy Astrophysical Phenomena (41)
Instrumentation and Methods for Astrophysics (16)
Solar and Stellar Astrophysics (9)
Cosmology and Nongalactic Astrophysics (6)
Astrophysics of Galaxies (4)
General Relativity and Quantum Cosmology (3)
Earth and Planetary Astrophysics (1)
High Energy Physics - Phenomenology (1)
Computer Science - Distributed; Parallel; and Cluster Computing (1)
High Energy Physics - Experiment (1)

Publications Authored By J. W. Hessels

Affiliations: 1UC Berkeley, 2Haverford College, 3ASTRON, 4ASIA-A, 5NRAO-Socorro, 6NRAO-Socorro, 7JBCA, 8Cambridge, 9Cornell, 10Cornell, 11NRAO-Socorro, 12UNM, 13Oxford, 14Amsterdam, 15JBCA, 16ASTRON, 17UC Berkeley, 18McGill, 19JPL, 20WVU, 21ASTRON, 22Oxford, 23Cambridge, 24NRAO-Charlottesville, 25Cambridge, 26DRAO, 27JBCA, 28Cambridge, 29DRAO, 30Arecibo, 31MPIfR, 32NRAO-Socorro, 33McGill, 34Cambridge, 35Cornell, 36Harvard-Smithsonian CfA

We present results of the coordinated observing campaign that made the first subarcsecond localization of a Fast Radio Burst, FRB 121102. During this campaign, we made the first simultaneous detection of an FRB burst by multiple telescopes: the VLA at 3 GHz and the Arecibo Observatory at 1.4 GHz. Read More

Affiliations: 1ASTRON, 2McGill, 3ASTRON, 4ASTRON, 5Columbia, 6ASIAA, 7NRAO/WVU, 8NRAO, 9Cornell, 10Cornell, 11ASTRON/Amsterdam, 12McGill, 13Berkeley, 14JIVE, 15JIVE, 16NRAO, 17DRAO, 18MPIfR, 19JIVE/Leiden

We present optical, near- and mid-infrared imaging of the host galaxy of FRB 121102 with the Gemini North telescope, the Hubble Space Telescope and the Spitzer Space Telescope. The FRB 121102 host galaxy is resolved, revealing a bright star forming region located in the outskirts of the irregular, low-metallicity dwarf galaxy. The star forming region has a half-light radius of 0. Read More

We undertook coordinated campaigns with the Green Bank, Effelsberg, and Arecibo radio telescopes during Chandra X-ray Observatory and XMM-Newton observations of the repeating fast radio burst FRB 121102 in late 2016 and early 2017 to search for simultaneous radio and X-ray bursts. We find 12 radio bursts from FRB 121102 during these 70 ks total of X-ray observations. We detect no X-ray photons at the times of radio bursts from FRB 121102 and further detect no X-ray bursts above the measured background at any time. Read More

Affiliations: 1API, U. of Amsterdam, 2ASTRON, 3API, U. of Amsterdam, 4API, U. of Amsterdam, 5Curtin University, 6API, U. of Amsterdam, 7API, U. of Amsterdam, 8API, U. of Amsterdam, 9U. of Southampton

We present quasi-simultaneous radio (VLA) and X-ray ($Swift$) observations of the neutron star low-mass X-ray binary (NS-LMXB) 1RXS J180408.9$-$342058 (J1804) during its 2015 outburst. We found that the radio jet of J1804 was bright ($232 \pm 4 \mu$Jy at $10$ GHz) during the initial hard X-ray state, before being quenched by more than an order of magnitude during the soft X-ray state ($19 \pm 4 \mu$Jy). Read More

In outburst, neutron star X-ray binaries produce less powerful jets than black holes at a given X-ray luminosity. This has made them more difficult to study as they fade towards quiescence. To explore whether neutron stars power jets at low accretion rates ($L_{\rm X} \lesssim 10^{36}$ erg s$^{-1}$), we investigate the radio and X-ray properties of three accreting millisecond X-ray pulsars (IGR J17511-3057, SAX J1808. Read More

We report on unusually very hard spectral states in three confirmed neutron-star low-mass X-ray binaries (1RXS J180408.9-342058, EXO 1745-248, and IGR J18245-2452) at a luminosity between ~ 10^{36-37} erg s^{-1}. When fitting the Swift X-ray spectra (0. Read More

Plasma lenses in the host galaxies of fast radio bursts (FRBs) can strongly modulate FRB amplitudes for a wide range of distances, including the $\sim $ Gpc distance of the repeater FRB121102. To produce caustics, the lens' dispersion-measure depth (${\rm DM}_{\ell}$), scale size ($a$), and distance from the source ($d_{\rm sl}$) must satisfy ${\rm DM}_{\ell} d_{\rm sl} / a^2 \gtrsim 0.65~ {\rm pc^2 \ AU^{-2} \ cm^{-3}}$. Read More

Affiliations: 1GWU, 2GWU, 3ASTRON, 4Rice University, 5GWU, 6NASA/Goddard, 7ASTRON, 8NASA/Goddard, 9The Open University, 10New York University, 11The Open University, 12Sabancı University, 13Beijing Normal University

We analyzed broad-band X-ray and radio data of the magnetar SGR J1935+2154 taken in the aftermath of its 2014, 2015, and 2016 outbursts. The source soft X-ray spectrum <10 keV is well described with a BB+PL or 2BB model during all three outbursts. NuSTAR observations revealed a hard X-ray tail, $\Gamma=0. Read More

We report on a search for Fast Radio Bursts (FRBs) with the Green Bank Northern Celestial Cap (GBNCC) Pulsar Survey at 350 MHz. Pointings amounting to a total on-sky time of 61 days were searched to a DM of 3000 pc cm$^{-3}$ while the rest (23 days; 29% of the total time) were searched to a DM of 500 pc cm$^{-3}$. No FRBs were detected in the pointings observed through May 2016. Read More

Fast radio bursts are astronomical radio flashes of unknown physical nature with durations of milliseconds. Their dispersive arrival times suggest an extragalactic origin and imply radio luminosities orders of magnitude larger than any other kind of known short-duration radio transient. Thus far, all FRBs have been detected with large single-dish telescopes with arcminute localizations, and attempts to identify their counterparts (source or host galaxy) have relied on contemporaneous variability of field sources or the presence of peculiar field stars or galaxies. Read More

Affiliations: 1JIVE, 2JIVE, 3ASTRON, 4JIVE, 5JIVE, 6Carleton College, 7ASTRON, 8Columbia U, 9ASIAA, 10NRAO Socorro, 11NRAO Socorro, 12JIVE, 13Cornell U, 14Cornell U, 15NRAO Socorro, 16U. of Manchester, 17NAIC Arecibo, 18McGill U, 19UC Berkeley, 20NASA JPL, 21U. of West Virginia Dept. of Physics and Astronomy, 22NRAO CV, 23NAIC Arecibo, 24DRAO, 25NAIC Arecibo, 26UC Berkeley, 27MPIfR, 28McGill U, 29Cornell U

The millisecond-duration radio flashes known as Fast Radio Bursts (FRBs) represent an enigmatic astrophysical phenomenon. Recently, the sub-arcsecond localization (~ 100mas precision) of FRB121102 using the VLA has led to its unambiguous association with persistent radio and optical counterparts, and to the identification of its host galaxy. However, an even more precise localization is needed in order to probe the direct physical relationship between the millisecond bursts themselves and the associated persistent emission. Read More

Affiliations: 1McGill U., 2ASTRON, 3Cornell U., 4ASIAA, 5UC Berkeley, 6Cornell U., 7ASTRON, 8Columbia U., 9NRAO, WVU, 10NRAO, 11NRAO, 12ASTRON, API, 13McGill U., 14JPL, 15ASTRON, 16JIVE, 17WVU, 18JIVE, 19NRAO, 20DRAO, 21Arecibo, 22MPIfR, 23JIVE, Leiden, 24Cornell U.

The precise localization of the repeating fast radio burst (FRB 121102) has provided the first unambiguous association (chance coincidence probability $p\lesssim3\times10^{-4}$) of an FRB with an optical and persistent radio counterpart. We report on optical imaging and spectroscopy of the counterpart and find that it is an extended ($0.6^{\prime\prime}-0. Read More

The objective of this paper is to present the main characteristics of a wide-field MFAA precursor that we envisage to be built at the SKA site in South Africa. Known as MANTIS (the Mid-Frequency Aperture Array Transient and Intensity-Mapping System), this ambitious instrument will represent the next logical step towards the MFAA based SKA telescope. The goal is to use innovative aperture array technology at cm wavelengths, in order to demonstrate the feasibility of deploying huge collecting areas at modest construction and operational cost. Read More

We report on simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822-09 with ESA's XMM-Newton and the WSRT, GMRT and Lovell radio telescopes. PSR B1822-09 switches between a radio-bright and radio-quiet mode, and we discovered a relationship between the durations of its modes and a known underlying radio-modulation timescale within the modes. We discovered X-ray (energies 0. Read More

Over the past decade the discovery of three unique stellar populations and a large number of confirmed pulsars within the globular cluster Terzan 5 has raised questions over its classification. Using the long-term radio pulsar timing of 36 millisecond pulsars in the cluster core, we provide new measurements of key physical properties of the system. As Terzan 5 is located within the galactic bulge, stellar crowding and reddening make optical and near infrared observations difficult. Read More

Affiliations: 1Leiden Observatory, 2ASTRON, 3SRON, 4U. Amsterdam, 5ASTRON, 6Southampton, 7Leicester, 8U. Amsterdam, 9U. Amsterdam

The accreting millisecond X-ray pulsar (AMXP) SAX J1808.4-3658, shows a peculiar orbital evolution that proceeds at a much faster pace than predicted by conservative binary evolution models. It is important to identify the underlying mechanism responsible for this behavior because it can help to understand how this system evolves. Read More

Transitional millisecond pulsars (tMSPs) switch, on roughly multi-year timescales, between rotation-powered radio millisecond pulsar (RMSP) and accretion-powered low-mass X-ray binary (LMXB) states. The tMSPs have raised several questions related to the nature of accretion flow in their LMXB state and the mechanism that causes the state switch. The discovery of coherent X-ray pulsations from PSR J1023+0038 (while in the LMXB state) provides us with the first opportunity to perform timing observations and to compare the neutron star's spin variation during this state to the measured spin-down in the RMSP state. Read More

We report the discovery and timing results for five millisecond pulsars (MSPs) from the Arecibo PALFA survey: PSRs J1906+0055, J1914+0659, J1933+1726, J1938+2516, and J1957+2516. Timing observations of the 5 pulsars were conducted with the Arecibo and Lovell telescopes for time spans ranging from 1.5 to 3. Read More

We report on the discovery and timing observations of 29 distant long-period pulsars discovered in the ongoing Arecibo PALFA pulsar survey. Following discovery with the Arecibo Telescope, confirmation and timing observations of these pulsars over several years at Jodrell Bank Observatory have yielded high-precision positions and measurements of rotation and radiation properties. We have used multi-frequency data to measure the interstellar scattering properties of some of these pulsars. Read More

We report the discovery of two long-term intermittent radio pulsars in the ongoing Arecibo PALFA pulsar survey. Following discovery with the Arecibo Telescope, extended observations of these pulsars over several years at Jodrell Bank Observatory have revealed the details of their rotation and radiation properties. PSRs J1910+0517 and J1929+1357 show long-term extreme bi-modal intermittency, switching between active (ON) and inactive (OFF) emission states and indicating the presence of a large, hitherto unrecognised, underlying population of such objects. Read More

We report on simultaneous X-ray and radio observations of the mode-switching pulsar PSR B0943+10 obtained with the XMM-Newton satellite and the LOFAR, LWA and Arecibo radio telescopes in November 2014. We confirm the synchronous X-ray/radio switching between a radio-bright (B) and a radio-quiet (Q) mode, in which the X-ray flux is a factor ~2.4 higher than in the B-mode. Read More

1RXS J180408.9-342058 is a transient neutron star low-mass X-ray binary that exhibited a bright accretion outburst in 2015. We present Nustar, Swift, and Chandra observations obtained around the peak of this outburst. Read More

We present an implementation of the coherent dedispersion algorithm capable of dedispersing high-time-resolution radio observations to many different dispersion measures (DMs). This approach allows the removal of the dispersive effects of the interstellar medium and enables searches for pulsed emission from pulsars and other millisecond-duration transients at low observing frequencies and/or high DMs where time broadening of the signal due to dispersive smearing would otherwise severely reduce the sensitivity. The implementation, called 'cdmt', for Coherent Dispersion Measure Trials, exploits the parallel processing capability of general-purpose graphics processing units to accelerate the computations. Read More

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

We present an archival search for transient gravitational-wave bursts in coincidence with 27 single pulse triggers from Green Bank Telescope pulsar surveys, using the LIGO, Virgo and GEO interferometer network. We also discuss a check for gravitational-wave signals in coincidence with Parkes Fast Radio Bursts using similar methods. Data analyzed in these searches were collected between 2007 and 2013. Read More

We report on radio and X-ray observations of the only known repeating Fast Radio Burst (FRB) source, FRB 121102. We have detected six additional radio bursts from this source: five with the Green Bank Telescope at 2 GHz, and one at 1.4 GHz at the Arecibo Observatory for a total of 17 bursts from this source. Read More

Authors: S. Buitink1, A. Corstanje2, H. Falcke3, J. R. Hörandel4, T. Huege5, A. Nelles6, J. P. Rachen7, L. Rossetto8, P . Schellart9, O. Scholten10, S. ter Veen11, S. Thoudam12, T. N. G. Trinh13, J. Anderson14, A. Asgekar15, I. M. Avruch16, M. E. Bell17, M. J. Bentum18, G. Bernardi19, P. Best20, A. Bonafede21, F. Breitling22, J. W. Broderick23, W. N. Brouw24, M. Brüggen25, H. R. Butcher26, D. Carbone27, B. Ciardi28, J. E. Conway29, F. de Gasperin30, E. de Geus31, A. Deller32, R. -J. Dettmar33, G. van Diepen34, S. Duscha35, J. Eislöffel36, D. Engels37, J. E. Enriquez38, R. A. Fallows39, R. Fender40, C. Ferrari41, W. Frieswijk42, M. A. Garrett43, J. M. Griessmeier44, A. W. Gunst45, M. P. van Haarlem46, T. E. Hassall47, G. Heald48, J. W. T. Hessels49, M. Hoeft50, A. Horneffer51, M. Iacobelli52, H. Intema53, E. Juette54, A. Karastergiou55, V. I. Kondratiev56, M. Kramer57, M. Kuniyoshi58, G. Kuper59, J. van Leeuwen60, G. M. Loose61, P. Maat62, G. Mann63, S. Markoff64, R. McFadden65, D. McKay-Bukowski66, J. P. McKean67, M. Mevius68, D. D. Mulcahy69, H. Munk70, M. J. Norden71, E. Orru72, H. Paas73, M. Pandey-Pommier74, V. N. Pandey75, M. Pietka76, R. Pizzo77, A. G. Polatidis78, W. Reich79, H. J. A. Röttgering80, A. M. M. Scaife81, D. J. Schwarz82, M. Serylak83, J. Sluman84, O. Smirnov85, B. W. Stappers86, M. Steinmetz87, A. Stewart88, J. Swinbank89, M. Tagger90, Y. Tang91, C. Tasse92, M. C. Toribio93, R. Vermeulen94, C. Vocks95, C. Vogt96, R. J. van Weeren97, R. A. M. J. Wijers98, S. J. Wijnholds99, M. W. Wise100, O. Wucknitz101, S. Yatawatta102, P. Zarka103, J. A. Zensus104
Affiliations: 1Astrophysical Institute, Vrije Universiteit Brussel, 2Department of Astrophysics/IMAPP, Radboud University Nijmegen, 3Department of Astrophysics/IMAPP, Radboud University Nijmegen, 4Department of Astrophysics/IMAPP, Radboud University Nijmegen, 5IKP, Karlsruhe Institute of Technology, 6Department of Astrophysics/IMAPP, Radboud University Nijmegen, 7Department of Astrophysics/IMAPP, Radboud University Nijmegen, 8Department of Astrophysics/IMAPP, Radboud University Nijmegen, 9Department of Astrophysics/IMAPP, Radboud University Nijmegen, 10KVI CART, University of Groningen, 11ASTRON, Netherlands Institute for Radio Astronomy, 12Department of Astrophysics/IMAPP, Radboud University Nijmegen, 13KVI CART, University of Groningen, 14Helmholtz-Zentrum Potsdam, DeutschesGeoForschungsZentrum GFZ, 15ASTRON, Netherlands Institute for Radio Astronomy, 16SRON Netherlands Insitute for Space Research, 17CSIRO Australia Telescope National Facility, 18ASTRON, Netherlands Institute for Radio Astronomy, 19Harvard-Smithsonian Center for Astrophysics, 20Institute for Astronomy, University of Edinburgh, 21University of Hamburg, 22Leibniz-Institut, 23School of Physics and Astronomy, University of Southampton, 24ASTRON, Netherlands Institute for Radio Astronomy, 25University of Hamburg, 26Research School of Astronomy and Astrophysics, Australian National University, 27Anton Pannekoek Institute for Astronomy, University of Amsterdam, 28Max Planck Institute for Astrophysics, 29Onsala Space Observatory, Dept. of Earth and Space Sciences, Chalmers University of Technology, 30University of Hamburg, 31ASTRON, Netherlands Institute for Radio Astronomy, 32ASTRON, Netherlands Institute for Radio Astronomy, 33Astronomisches Institut der Ruhr-Universität Bochum, 34ASTRON, Netherlands Institute for Radio Astronomy, 35ASTRON, Netherlands Institute for Radio Astronomy, 36Thüringer Landessternwarte, 37Hamburger Sternwarte, 38Department of Astrophysics/IMAPP, Radboud University Nijmegen, 39ASTRON, Netherlands Institute for Radio Astronomy, 40Astrophysics, University of Oxford, 41Laboratoire Lagrange, Université Côte d'Azur, 42ASTRON, Netherlands Institute for Radio Astronomy, 43ASTRON, Netherlands Institute for Radio Astronomy, 44LPC2E - Universite d'Orleans/CNRS, 45ASTRON, Netherlands Institute for Radio Astronomy, 46ASTRON, Netherlands Institute for Radio Astronomy, 47School of Physics and Astronomy, University of Southampton, 48ASTRON, Netherlands Institute for Radio Astronomy, 49ASTRON, Netherlands Institute for Radio Astronomy, 50Thüringer Landessternwarte, 51Max-Planck-Institut für Radioastronomie, 52ASTRON, Netherlands Institute for Radio Astronomy, 53Leiden Observatory, Leiden University, 54Astronomisches Institut der Ruhr-Universität Bochum, 55Astrophysics, University of Oxford, 56ASTRON, Netherlands Institute for Radio Astronomy, 57Max-Planck-Institut für Radioastronomie, 58National Astronomical Observatory of Japan, Japan, 59ASTRON, Netherlands Institute for Radio Astronomy, 60ASTRON, Netherlands Institute for Radio Astronomy, 61ASTRON, Netherlands Institute for Radio Astronomy, 62ASTRON, Netherlands Institute for Radio Astronomy, 63Leibniz-Institut, 64Anton Pannekoek Institute for Astronomy, University of Amsterdam, 65ASTRON, Netherlands Institute for Radio Astronomy, 66Sodankylä Geophysical Observatory, University of Oulu, 67ASTRON, Netherlands Institute for Radio Astronomy, 68ASTRON, Netherlands Institute for Radio Astronomy, 69School of Physics and Astronomy, University of Southampton, 70ASTRON, Netherlands Institute for Radio Astronomy, 71ASTRON, Netherlands Institute for Radio Astronomy, 72ASTRON, Netherlands Institute for Radio Astronomy, 73Center for Information Technology, 74Centre de Recherche Astrophysique de Lyon, Observatoire de Lyon, 75ASTRON, Netherlands Institute for Radio Astronomy, 76Astrophysics, University of Oxford, 77ASTRON, Netherlands Institute for Radio Astronomy, 78ASTRON, Netherlands Institute for Radio Astronomy, 79Max-Planck-Institut für Radioastronomie, 80Leiden Observatory, Leiden University, 81School of Physics and Astronomy, University of Southampton, 82Fakultät für Physik, Universität Bielefeld, 83Astrophysics, University of Oxford, 84ASTRON, Netherlands Institute for Radio Astronomy, 85Department of Physics and Electronics, Rhodes University, 86Jodrell Bank Center for Astrophysics, School of Physics and Astronomy, The University of Manchester, 87Leibniz-Institut, 88Astrophysics, University of Oxford, 89Anton Pannekoek Institute for Astronomy, University of Amsterdam, 90LPC2E - Universite d'Orleans/CNRS, 91ASTRON, Netherlands Institute for Radio Astronomy, 92Department of Physics and Electronics, Rhodes University, 93ASTRON, Netherlands Institute for Radio Astronomy, 94ASTRON, Netherlands Institute for Radio Astronomy, 95Leibniz-Institut, 96ASTRON, Netherlands Institute for Radio Astronomy, 97Harvard-Smithsonian Center for Astrophysics, 98Anton Pannekoek Institute for Astronomy, University of Amsterdam, 99ASTRON, Netherlands Institute for Radio Astronomy, 100ASTRON, Netherlands Institute for Radio Astronomy, 101Max-Planck-Institut für Radioastronomie, 102ASTRON, Netherlands Institute for Radio Astronomy, 103LESIA, 104Max-Planck-Institut für Radioastronomie

Cosmic rays are the highest energy particles found in nature. Measurements of the mass composition of cosmic rays between 10^{17} eV and 10^{18} eV are essential to understand whether this energy range is dominated by 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. Read More

Affiliations: 1MPIfR, 2McGill U, 3ASTRON, 4Columbia U, 5Cornell U, 6Columbia U, 7Cornell U, 8Cornell U, 9Franklin and Marshall College, 10NRL, 11McGill U, 12MPIfR, 13McGill U, 14MPIfR, 15NRAO GB, 16McGill U, 17West Virginia U, 18McGill U, 19NRAO CV, 20NAIC Arecibo Observatory, 21U. British Columbia, 22U. Manchester, 23ASTRON, 24MPIfR

Fast Radio Bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measures (i.e. Read More

We analyse the stochastic properties of the 49 pulsars that comprise the first International Pulsar Timing Array (IPTA) data release. We use Bayesian methodology, performing model selection to determine the optimal description of the stochastic signals present in each pulsar. In addition to spin-noise and dispersion-measure (DM) variations, these models can include timing noise unique to a single observing system, or frequency band. Read More

The highly stable spin of neutron stars can be exploited for a variety of (astro-)physical investigations. In particular arrays of pulsars with rotational periods of the order of milliseconds can be used to detect correlated signals such as those caused by gravitational waves. Three such "Pulsar Timing Arrays" (PTAs) have been set up around the world over the past decades and collectively form the "International" PTA (IPTA). Read More

We present the first X-ray observations of three recently discovered millisecond pulsars (MSPs) with interesting characteristics: PSR J0337+1715, PSR J0636+5129, and PSR J0645+5158. PSR J0337+1715 is a fast-spinning, bright, and so-far unique MSP in a hierarchical triple system with two white dwarf (WD) companions. PSR J0636+5129 is a MSP in a very tight 96-min orbit with a low-mass, 8 $M_J$ companion. Read More

In this paper, we study the parallelization of the dedispersion algorithm on many-core accelerators, including GPUs from AMD and NVIDIA, and the Intel Xeon Phi. An important contribution is the computational analysis of the algorithm, from which we conclude that dedispersion is inherently memory-bound in any realistic scenario, in contrast to earlier reports. We also provide empirical proof that, even in unrealistic scenarios, hardware limitations keep the arithmetic intensity low, thus limiting performance. Read More

Analogously to globular clusters, the dense stellar environment of the Galactic center has been proposed to host a large population of as-yet undetected millisecond pulsars (MSPs). Recently, this hypothesis found support in the analysis of gamma rays from the inner Galaxy seen by the Large Area Telescope (LAT) aboard the Fermi satellite, which revealed a possible excess of diffuse GeV photons in the inner 15 deg about the Galactic center (Fermi GeV excess). The excess can be interpreted as the collective emission of thousands of MSPs in the Galactic bulge, with a spherical distribution that strongly peaks towards the Galactic center. Read More


We present the results of a four-month campaign searching for low-frequency radio transients near the North Celestial Pole with the Low-Frequency Array (LOFAR), as part of the Multifrequency Snapshot Sky Survey (MSSS). The data were recorded between 2011 December and 2012 April and comprised 2149 11-minute snapshots, each covering 175 deg^2. We have found one convincing candidate astrophysical transient, with a duration of a few minutes and a flux density at 60 MHz of 15-25 Jy. Read More

We present first results from a LOFAR census of non-recycled pulsars. The census includes almost all such pulsars known (194 sources) at declinations ${\rm Dec}> 8^\circ$ and Galactic latitudes $|{\rm Gb}| > 3^\circ$, regardless of their expected flux densities and scattering times. Each pulsar was observed for $\geq 20$ minutes in the contiguous frequency range of 110--188 MHz. Read More

LOFAR offers the unique capability of observing pulsars across the 10-240 MHz frequency range with a fractional bandwidth of roughly 50%. This spectral range is well-suited for studying the frequency evolution of pulse profile morphology caused by both intrinsic and extrinsic effects: such as changing emission altitude in the pulsar magnetosphere or scatter broadening by the interstellar medium, respectively. The magnitude of most of these effects increases rapidly towards low frequencies. Read More

Dense, continuous pulsar timing observations over a 24-hr period provide a method for probing intermediate gravitational wave (GW) frequencies from 10 microhertz to 20 millihertz. The European Pulsar Timing Array (EPTA), the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), the Parkes Pulsar Timing Array (PPTA), and the combined International Pulsar Timing Array (IPTA) all use millisecond pulsar observations to detect or constrain GWs typically at nanohertz frequencies. In the case of the IPTA's nine-telescope 24-Hour Global Campaign on millisecond pulsar J1713+0747, GW limits in the intermediate frequency regime can be produced. Read More

We have searched for continuous gravitational wave (CGW) signals produced by individually resolvable, circular supermassive black hole binaries (SMBHBs) in the latest EPTA dataset, which consists of ultra-precise timing data on 41 millisecond pulsars. We develop frequentist and Bayesian detection algorithms to search both for monochromatic and frequency-evolving systems. None of the adopted algorithms show evidence for the presence of such a CGW signal, indicating that the data are best described by pulsar and radiometer noise only. Read More

Authors: G. H. Heald, R. F. Pizzo, E. Orrú, R. P. Breton, D. Carbone, C. Ferrari, M. J. Hardcastle, W. Jurusik, G. Macario, D. Mulcahy, D. Rafferty, A. Asgekar, M. Brentjens, R. A. Fallows, W. Frieswijk, M. C. Toribio, B. Adebahr, M. Arts, M. R. Bell, A. Bonafede, J. Bray, J. Broderick, T. Cantwell, P. Carroll, Y. Cendes, A. O. Clarke, J. Croston, S. Daiboo, F. de Gasperin, J. Gregson, J. Harwood, T. Hassall, V. Heesen, A. Horneffer, A. J. van der Horst, M. Iacobelli, V. Jelić, D. Jones, D. Kant, G. Kokotanekov, P. Martin, J. P. McKean, L. K. Morabito, B. Nikiel-Wroczyński, A. Offringa, V. N. Pandey, M. Pandey-Pommier, M. Pietka, L. Pratley, C. Riseley, A. Rowlinson, J. Sabater, A. M. M. Scaife, L. H. A. Scheers, K. Sendlinger, A. Shulevski, M. Sipior, C. Sobey, A. J. Stewart, A. Stroe, J. Swinbank, C. Tasse, J. Trüstedt, E. Varenius, S. van Velzen, N. Vilchez, R. J. van Weeren, S. Wijnholds, W. L. Williams, A. G. de Bruyn, R. Nijboer, M. Wise, A. Alexov, J. Anderson, I. M. Avruch, R. Beck, M. E. Bell, I. van Bemmel, M. J. Bentum, G. Bernardi, P. Best, F. Breitling, W. N. Brouw, M. Brüggen, H. R. Butcher, B. Ciardi, J. E. Conway, E. de Geus, A. de Jong, M. de Vos, A. Deller, R. J. Dettmar, S. Duscha, J. Eislöffel, D. Engels, H. Falcke, R. Fender, M. A. Garrett, J. Grießmeier, A. W. Gunst, J. P. Hamaker, J. W. T. Hessels, M. Hoeft, J. Hörandel, H. A. Holties, H. Intema, N. J. Jackson, E. Jütte, A. Karastergiou, W. F. A. Klijn, V. I. Kondratiev, L. V. E. Koopmans, M. Kuniyoshi, G. Kuper, C. Law, J. van Leeuwen, M. Loose, P. Maat, S. Markoff, R. McFadden, D. McKay-Bukowski, M. Mevius, J. C. A. Miller-Jones, R. Morganti, H. Munk, A. Nelles, J. E. Noordam, M. J. Norden, H. Paas, A. G. Polatidis, W. Reich, A. Renting, H. Röttgering, A. Schoenmakers, D. Schwarz, J. Sluman, O. Smirnov, B. W. Stappers, M. Steinmetz, M. Tagger, Y. Tang, S. ter Veen, S. Thoudam, R. Vermeulen, C. Vocks, C. Vogt, R. A. M. J. Wijers, O. Wucknitz, S. Yatawatta, P. Zarka

We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky LOFAR imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). Read More

We report the detection of 48 millisecond pulsars (MSPs) out of 75 observed thus far using the LOFAR in the frequency range 110-188 MHz. We have also detected three MSPs out of nine observed in the frequency range 38-77 MHz. This is the largest sample of MSPs ever observed at these low frequencies, and half of the detected MSPs were observed for the first time at frequencies below 200 MHz. Read More

The paucity of observed supermassive black hole binaries (SMBHBs) may imply that the gravitational wave background (GWB) from this population is anisotropic, rendering existing analyses sub-optimal. We present the first constraints on the angular distribution of a nanohertz stochastic GWB from circular, inspiral-driven SMBHBs using the $2015$ European Pulsar Timing Array data [Desvignes et al. (in prep. Read More

Fast Radio Bursts (FRBs), are millisecond radio signals that exhibit dispersion larger than what the Galactic electron density can account for. We have conducted a 1446 hour survey for Fast Radio Bursts (FRBs) at 145~MHz, covering a total of 4193 sq. deg on the sky. Read More

We report on the determination of the astrometric, spin and orbital parameters for PSR J1953+1846A, a "black widow" binary millisecond pulsar in the globular cluster M71. By using the accurate position and orbital parameters obtained from radio timing, we identified the optical companion in ACS/Hubble Space Telescope images. It turns out to be a faint (m_F606W>=24, m_F814W>=23) and variable star located at only ~0. Read More