High Energy Astrophysical Phenomena Publications (50)

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High Energy Astrophysical Phenomena Publications

We show that observations of solar $\gamma$-ray fluxes offer a novel probe of dark matter, in scenarios where interactions with the visible sector proceed via a long-lived mediator. As a proof of principle, we demonstrate that there exists a class of models which yield solar $\gamma$-ray lines observable with the next generation of $\gamma$-ray telescopes, while being allowed by a large variety of experimental constraints. Our results suggest that fluxes of solar $\gamma$-ray lines can be up to two orders of magnitude higher than the ones from the galactic center, and are subject to very low backgrounds. Read More


The gamma-ray binary 1FGL J1018.6-5856 is known to be composed of a massive star with a compact object with an orbital period of 16.54 days. Read More


2017Mar
Affiliations: 1Astro Space Center of Lebedev Physical Institute, Moscow, Russia, 2Astro Space Center of Lebedev Physical Institute, Moscow, Russia, 3Max-Planck-Institut für Radioastronomie, Bonn, Germany, 4Aalto University Metsähovi Radio Observatory, Kylmälä, Finland, 5Astro Space Center of Lebedev Physical Institute, Moscow, Russia

We present a comprehensive 5-43 GHz VLBA study of the blazar 3C 273 initiated after an onset of a strong $\gamma$-ray flare in this source. We have analyzed the kinematics of new-born components, light curves, and position of the apparent core to pinpoint the location of the $\gamma$-ray emission. Estimated location of the $\gamma$-ray emission zone is close to the jet apex, 2 pc to 7 pc upstream from the observed 7 mm core. Read More


Great advances have been made in the study of ultra-high energy cosmic rays (UHECR) in the past two decades. These include the discovery of the spectral cut-off near 5 x 10^19 eV and complex structure at lower energies, as well as increasingly precise information about the composition of cosmic rays as a function of energy. Important improvements in techniques, including extensive surface detector arrays and high resolution air fluorescence detectors, have been instrumental in facilitating this progress. Read More


We report the detection of a dust scattering halo around a recently discovered X-ray transient, Swift J174540.7-290015, which in early February of 2016 underwent one of the brightest outbursts (F_X ~ 5e-10 erg/cm^2/s) observed from a compact object in the Galactic Center field. We analyze four Chandra images that were taken as follow-up observations to Swift discoveries of new Galactic Center transients. Read More


GRB 120323A is a very intense short Gamma Ray Burst (GRB) detected simultaneously during its prompt gamma-ray emission phase with the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope and the Konus experiment on board the Wind satellite. GBM and Konus operate in the keV--MeV regime, however, the GBM range is broader both toward the low and the high parts of the gamma-ray spectrum. Analysis of such bright events provide a unique opportunity to check the consistency of the data analysis as well as cross-calibrate the two instruments. Read More


2017Mar
Affiliations: 1Harvard/CfA, 2Harvard/CfA, 3Harvard/CfA, 4Harvard/CfA, 5Northwestern University, 6Ohio University, 7Harvard/CfA, 8Harvard/CfA, 9Carnegie Observatories

[Abridged] We present observations of PS16dtm, a luminous transient that occurred at the nucleus of a known Narrow-line Seyfert 1 galaxy hosting a 10$^6$ M$_\odot$ black hole. The transient was previously claimed to be a Type IIn SLSN due to its luminosity and hydrogen emission lines. The light curve shows that PS16dtm brightened by about two magnitudes in ~50 days relative to the archival host brightness and then exhibited a plateau phase for about 100 days followed by the onset of fading in the UV. Read More


Cosmic rays interacting in the solar atmosphere produce showers that result in a flux of high-energy neutrinos from the Sun. These form an irreducible background to indirect solar WIMP co-annihilation searches, which look for heavy dark matter particles annihilating into final states containing neutrinos in the Solar core. This background will eventually create a sensitivity floor for indirect WIMP co-annihilation searches analogous to that imposed by low-energy solar neutrino interactions for direct dark matter detection experiments. Read More


2017Mar

It is often assumed that gravitational wave (GW) events resulting from the merger of stellar-mass black holes are unlikely to produce electromagnetic (EM) counterparts. We point out that the progenitor binary has probably shed a mass $\gtrsim 10\,{\rm M}_{\odot}$ during its prior evolution. If a tiny fraction of this gas is retained until the merger, the recoil and sudden mass loss of the merged black hole shocks and heats it within hours of the GW event. Read More


The HAWC gamma-ray observatory is a wide field of view and high duty cycle $\gamma$-ray detector investigating the 0.1 - 100 TeV energy range. It has detected supermassive black holes in the near Universe, and is seeking to detect black hole related objects like gamma-ray bursts, Galactic binary systems, primordial black holes and gravitational wave mergers. Read More


The Jeans analysis is studied in the first post-Newtonian limit. In other words, the relativistic effects on the local gravitational instability are considered for systems where characteristic velocity of the system and corresponding gravitational field are higher than what permitted in Newtonian limit. The dispersion relation for propagation of small perturbations is found in the post-Newtonian approximation using two different techniques. Read More


2017Mar
Authors: M. L. Ahnen1, S. Ansoldi2, L. A. Antonelli3, C. Arcaro4, A. Babić5, B. Banerjee6, P. Bangale7, U. Barres de Almeida8, J. A. Barrio9, J. Becerra González10, W. Bednarek11, E. Bernardini12, A. Berti13, B. Biasuzzi14, A. Biland15, O. Blanch16, S. Bonnefoy17, G. Bonnoli18, F. Borracci19, T. Bretz20, R. Carosi21, A. Carosi22, A. Chatterjee23, P. Colin24, E. Colombo25, J. L. Contreras26, J. Cortina27, S. Covino28, P. Cumani29, P. Da Vela30, F. Dazzi31, A. De Angelis32, B. De Lotto33, E. de Oña Wilhelmi34, F. Di Pierro35, M. Doert36, A. Domínguez37, D. Dominis Prester38, D. Dorner39, M. Doro40, S. Einecke41, D. Eisenacher Glawion42, D. Elsaesser43, M. Engelkemeier44, V. Fallah Ramazani45, A. Fernández-Barral46, D. Fidalgo47, M. V. Fonseca48, L. Font49, C. Fruck50, D. Galindo51, R. J. García López52, M. Garczarczyk53, M. Gaug54, P. Giammaria55, N. Godinović56, D. Gora57, D. Guberman58, D. Hadasch59, A. Hahn60, T. Hassan61, M. Hayashida62, J. Herrera63, J. Hose64, D. Hrupec65, G. Hughes66, W. Idec67, K. Ishio68, K. Kodani69, Y. Konno70, H. Kubo71, J. Kushida72, D. Lelas73, E. Lindfors74, S. Lombardi75, F. Longo76, M. López77, P. Majumdar78, M. Makariev79, K. Mallot80, G. Maneva81, M. Manganaro82, K. Mannheim83, L. Maraschi84, M. Mariotti85, M. Martínez86, D. Mazin87, U. Menzel88, R. Mirzoyan89, A. Moralejo90, E. Moretti91, D. Nakajima92, V. Neustroev93, A. Niedzwiecki94, M. Nievas Rosillo95, K. Nilsson96, K. Nishijima97, K. Noda98, L. Nogués99, M. Nöthe100, S. Paiano101, J. Palacio102, D. Paneque103, R. Paoletti104, J. M. Paredes105, X. Paredes-Fortuny106, G. Pedaletti107, M. Peresano108, L. Perri109, M. Persic110, J. Poutanen111, P. G. Prada Moroni112, E. Prandini113, I. Puljak114, J. R. Garcia115, I. Reichardt116, W. Rhode117, M. Ribó118, J. Rico119, T. Saito120, K. Satalecka121, S. Schroeder122, T. Schweizer123, S. N. Shore124, A. Sillanpää125, J. Sitarek126, I. Šnidarić127, D. Sobczynska128, A. Stamerra129, M. Strzys130, T. Surić131, L. Takalo132, F. Tavecchio133, P. Temnikov134, T. Terzić135, D. Tescaro136, M. Teshima137, D. F. Torres138, N. Torres-Albà139, T. Toyama140, A. Treves141, G. Vanzo142, M. Vazquez Acosta143, I. Vovk144, J. E. Ward145, M. Will146, M. H. Wu147, F. Krauß148, R. Schulz149, M. Kadler150, J. Wilms151, E. Ros152, U. Bach153, T. Beuchert154, M. Langejahn155, C. Wendel156, N. Gehrels157, W. H. Baumgartner158, C. B. Markwardt159, C. Müller160, V. Grinberg161, T. Hovatta162, J. Magill163
Affiliations: 1ETH Zurich, Institute for Particle Physics, Zurich, Switzerland, 2Università di Udine and INFN, sezione di Trieste, Italy, Udine, Italy, 3INAF - National Institute for Astrophysics, Roma, Italy, 4Dipartimento di Fisica ed Astronomia, Università di Padova and INFN sez. di Padova, Padova, Italy, 5Croatian MAGIC Consortium: Rudjer Boskovic Institute, University of Rijeka, University of Split - FESB, University of Zagreb-FER, University of Osijek, Split, Croatia, 6Saha Institute of Nuclear Physics, HBNI, Kolkata, India, 7Max-Planck-Institut für Physik, München, Germany, 8Max-Planck-Institut für Physik, München, Germany, 9Grupo de Altas Energias, Universidad Complutense, Madrid, Madrid, Spain, 10Instituto de Astrofisica de Canarias, La Laguna, 11Division of Astrophysics, University of Lodz, Lodz, Poland, 12Deutsches Elektronen-Synchrotron, 13Università di Udine and INFN, sezione di Trieste, Italy, Udine, Italy, 14Università di Udine and INFN, sezione di Trieste, Italy, Udine, Italy, 15ETH Zurich, Institute for Particle Physics, Zurich, Switzerland, 16Institut de Fisica d'Altes Energies, 17Grupo de Altas Energias, Universidad Complutense, Madrid, Madrid, Spain, 18Dipartimento di Fisica, Università di Siena and INFN sez. di Pisa, Siena, Italy, 19Max-Planck-Institut für Physik, München, Germany, 20Institut für Theoretische Physik und Astrophysik - Fakultät für Physik und Astronomie - Universität Würzburg, Würzburg, Germany, 21Dipartimento di Fisica, Università di Siena and INFN sez. di Pisa, Siena, Italy, 22INAF - National Institute for Astrophysics, Roma, Italy, 23Saha Institute of Nuclear Physics, HBNI, Kolkata, India, 24Max-Planck-Institut für Physik, München, Germany, 25Instituto de Astrofisica de Canarias, La Laguna, 26Grupo de Altas Energias, Universidad Complutense, Madrid, Madrid, Spain, 27Institut de Fisica d'Altes Energies, 28INAF - National Institute for Astrophysics, Roma, Italy, 29Institut de Fisica d'Altes Energies, 30Dipartimento di Fisica, Università di Siena and INFN sez. di Pisa, Siena, Italy, 31Max-Planck-Institut für Physik, München, Germany, 32Dipartimento di Fisica ed Astronomia, Università di Padova and INFN sez. di Padova, Padova, Italy, 33Università di Udine and INFN, sezione di Trieste, Italy, Udine, Italy, 34Institut de Ciencies de l'Espai, 35INAF - National Institute for Astrophysics, Roma, Italy, 36Technische Universität Dortmund, Dortmund, Germany, 37Grupo de Altas Energias, Universidad Complutense, Madrid, Madrid, Spain, 38Croatian MAGIC Consortium: Rudjer Boskovic Institute, University of Rijeka, University of Split - FESB, University of Zagreb-FER, University of Osijek, Split, Croatia, 39Institut für Theoretische Physik und Astrophysik - Fakultät für Physik und Astronomie - Universität Würzburg, Würzburg, Germany, 40Dipartimento di Fisica ed Astronomia, Università di Padova and INFN sez. di Padova, Padova, Italy, 41Technische Universität Dortmund, Dortmund, Germany, 42Institut für Theoretische Physik und Astrophysik - Fakultät für Physik und Astronomie - Universität Würzburg, Würzburg, Germany, 43Technische Universität Dortmund, Dortmund, Germany, 44Technische Universität Dortmund, Dortmund, Germany, 45Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, Piikkiö, Finland, 46Institut de Fisica d'Altes Energies, 47Grupo de Altas Energias, Universidad Complutense, Madrid, Madrid, Spain, 48Grupo de Altas Energias, Universidad Complutense, Madrid, Madrid, Spain, 49Universitat Autònoma de Barcelona, Barcelona, Spain, 50Max-Planck-Institut für Physik, München, Germany, 51Universitat de Barcelona, Barcelona, Spain, 52Instituto de Astrofisica de Canarias, La Laguna, 53Deutsches Elektronen-Synchrotron, 54Universitat Autònoma de Barcelona, Barcelona, Spain, 55INAF - National Institute for Astrophysics, Roma, Italy, 56Croatian MAGIC Consortium: Rudjer Boskovic Institute, University of Rijeka, University of Split - FESB, University of Zagreb-FER, University of Osijek, Split, Croatia, 57Deutsches Elektronen-Synchrotron, 58Institut de Fisica d'Altes Energies, 59Japanese MAGIC Consortium, Kyoto, Japan, 60Max-Planck-Institut für Physik, München, Germany, 61Institut de Fisica d'Altes Energies, 62Japanese MAGIC Consortium, Kyoto, Japan, 63Instituto de Astrofisica de Canarias, La Laguna, 64Max-Planck-Institut für Physik, München, Germany, 65Croatian MAGIC Consortium: Rudjer Boskovic Institute, University of Rijeka, University of Split - FESB, University of Zagreb-FER, University of Osijek, Split, Croatia, 66ETH Zurich, Institute for Particle Physics, Zurich, Switzerland, 67Division of Astrophysics, University of Lodz, Lodz, Poland, 68Max-Planck-Institut für Physik, München, Germany, 69Japanese MAGIC Consortium, Kyoto, Japan, 70Japanese MAGIC Consortium, Kyoto, Japan, 71Japanese MAGIC Consortium, Kyoto, Japan, 72Japanese MAGIC Consortium, Kyoto, Japan, 73Croatian MAGIC Consortium: Rudjer Boskovic Institute, University of Rijeka, University of Split - FESB, University of Zagreb-FER, University of Osijek, Split, Croatia, 74Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, Piikkiö, Finland, 75INAF - National Institute for Astrophysics, Roma, Italy, 76Università di Udine and INFN, sezione di Trieste, Italy, Udine, Italy, 77Grupo de Altas Energias, Universidad Complutense, Madrid, Madrid, Spain, 78Saha Institute of Nuclear Physics, HBNI, Kolkata, India, 79Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria, 80Deutsches Elektronen-Synchrotron, 81Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria, 82Instituto de Astrofisica de Canarias, La Laguna, 83Institut für Theoretische Physik und Astrophysik - Fakultät für Physik und Astronomie - Universität Würzburg, Würzburg, Germany, 84INAF - National Institute for Astrophysics, Roma, Italy, 85Dipartimento di Fisica ed Astronomia, Università di Padova and INFN sez. di Padova, Padova, Italy, 86Institut de Fisica d'Altes Energies, 87Max-Planck-Institut für Physik, München, Germany, 88Max-Planck-Institut für Physik, München, Germany, 89Max-Planck-Institut für Physik, München, Germany, 90Institut de Fisica d'Altes Energies, 91Max-Planck-Institut für Physik, München, Germany, 92Japanese MAGIC Consortium, Kyoto, Japan, 93Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, Piikkiö, Finland, 94Division of Astrophysics, University of Lodz, Lodz, Poland, 95Grupo de Altas Energias, Universidad Complutense, Madrid, Madrid, Spain, 96Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, Piikkiö, Finland, 97Japanese MAGIC Consortium, Kyoto, Japan, 98Max-Planck-Institut für Physik, München, Germany, 99Institut de Fisica d'Altes Energies, 100Technische Universität Dortmund, Dortmund, Germany, 101Dipartimento di Fisica ed Astronomia, Università di Padova and INFN sez. di Padova, Padova, Italy, 102Institut de Fisica d'Altes Energies, 103Max-Planck-Institut für Physik, München, Germany, 104Dipartimento di Fisica, Università di Siena and INFN sez. di Pisa, Siena, Italy, 105Universitat de Barcelona, Barcelona, Spain, 106Universitat de Barcelona, Barcelona, Spain, 107Deutsches Elektronen-Synchrotron, 108Università di Udine and INFN, sezione di Trieste, Italy, Udine, Italy, 109INAF - National Institute for Astrophysics, Roma, Italy, 110Università di Udine and INFN, sezione di Trieste, Italy, Udine, Italy, 111Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, Piikkiö, Finland, 112Universita di Pisa, and INFN Pisa, Pisa, Italy, 113Dipartimento di Fisica ed Astronomia, Università di Padova and INFN sez. di Padova, Padova, Italy, 114Croatian MAGIC Consortium: Rudjer Boskovic Institute, University of Rijeka, University of Split - FESB, University of Zagreb-FER, University of Osijek, Split, Croatia, 115Max-Planck-Institut für Physik, München, Germany, 116Dipartimento di Fisica ed Astronomia, Università di Padova and INFN sez. di Padova, Padova, Italy, 117Technische Universität Dortmund, Dortmund, Germany, 118Universitat de Barcelona, Barcelona, Spain, 119Institut de Fisica d'Altes Energies, 120Japanese MAGIC Consortium, Kyoto, Japan, 121Deutsches Elektronen-Synchrotron, 122Technische Universität Dortmund, Dortmund, Germany, 123Max-Planck-Institut für Physik, München, Germany, 124Universita di Pisa, and INFN Pisa, Pisa, Italy, 125Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, Piikkiö, Finland, 126Division of Astrophysics, University of Lodz, Lodz, Poland, 127Croatian MAGIC Consortium: Rudjer Boskovic Institute, University of Rijeka, University of Split - FESB, University of Zagreb-FER, University of Osijek, Split, Croatia, 128Division of Astrophysics, University of Lodz, Lodz, Poland, 129INAF - National Institute for Astrophysics, Roma, Italy, 130Max-Planck-Institut für Physik, München, Germany, 131Croatian MAGIC Consortium: Rudjer Boskovic Institute, University of Rijeka, University of Split - FESB, University of Zagreb-FER, University of Osijek, Split, Croatia, 132Finnish MAGIC Consortium, Tuorla Observatory, University of Turku and Astronomy Division, University of Oulu, Finland, Piikkiö, Finland, 133INAF - National Institute for Astrophysics, Roma, Italy, 134Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria, 135Croatian MAGIC Consortium: Rudjer Boskovic Institute, University of Rijeka, University of Split - FESB, University of Zagreb-FER, University of Osijek, Split, Croatia, 136Dipartimento di Fisica ed Astronomia, Università di Padova and INFN sez. di Padova, Padova, Italy, 137Max-Planck-Institut für Physik, München, Germany, 138ICREA and Institut de Ciencies de l'Espai, 139Universitat de Barcelona, Barcelona, Spain, 140Max-Planck-Institut für Physik, München, Germany, 141Università di Udine and INFN, sezione di Trieste, Italy, Udine, Italy, 142Instituto de Astrofisica de Canarias, La Laguna, 143Instituto de Astrofisica de Canarias, La Laguna, 144Max-Planck-Institut für Physik, München, Germany, 145Institut de Fisica d'Altes Energies, 146Instituto de Astrofisica de Canarias, La Laguna, 147Institut de Ciencies de l'Espai, 148GRAPPA and Anton Pannekoek Institute for Astronomy, University of Amsterdam, The Netherlands, 149ASTRON, the Netherlands Institute for Radio Astronomy, Dwingeloo, Netherlands, 150Institut für Theoretische Physik und Astrophysik - Fakultät für Physik und Astronomie - Universität Würzburg, Würzburg, Germany, 151Dr. Remeis Sternwarte and ECAP, Universität Erlangen-Nürnberg, Bamberg, Germany, 152Max-Planck-Institut für Radioastronomie, Bonn, Germany, 153Max-Planck-Institut für Radioastronomie, Bonn, Germany, 154Dr. Remeis Sternwarte and ECAP, Universität Erlangen-Nürnberg, Bamberg, Germany, 155Institut für Theoretische Physik und Astrophysik - Fakultät für Physik und Astronomie - Universität Würzburg, Würzburg, Germany, 156Institut für Theoretische Physik und Astrophysik - Fakultät für Physik und Astronomie - Universität Würzburg, Würzburg, Germany, 157NASA, Goddard Space Flight Center, Greenbelt, USA, 158NASA, Goddard Space Flight Center, Greenbelt, USA, 159NASA, Goddard Space Flight Center, Greenbelt, USA, 160Department of Astrophysics/IMAPP, Radboud University Nijmegen, Nijmegen, the Netherlands, 161Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research, Cambridge, USA, 162Aalto University Metsähovi Radio Observatory, Kylmälä, Finland, 163Department of Physics and Department of Astronomy, University of Maryland, College Park, USA)

The extragalactic VHE gamma-ray sky is rich in blazars. These are jetted active galactic nuclei viewed at a small angle to the line-of-sight. Only a handful of objects viewed at a larger angle are known so far to emit above 100 GeV. Read More


We present MUSE observations of galaxy NGC 7469 from its Science Verification to show how powerful is the combination of high-resolution wide-field integral field spectroscopy with both photometric and spectroscopic observations of supernova (SN) explosions. Using STARLIGHT and HIIexplorer, we selected all Hii regions of the galaxy and produced 2- dimensional maps of the H{\alpha} equivalent width, average luminosity-weighted stellar age, and oxygen abundance. We measured deprojected galactocentric distances for all Hii regions, and radial gradients for all above-mentioned parameters. Read More


Solar $\gamma$ ray events measured near Earth can last several hours during so-called Long Duration Gamma Ray Flares (LDGRFs). LDGRFs suggest that a particle-acceleration mechanism operates over many hours to produce energetic protons that stream continually towards the solar surface. Coronal shocks, driven by the expansion of Coronal Mass Ejections (CMEs), could be the source of these energetic particles. Read More


2017Mar
Affiliations: 1School of Physics and Astronomy, Monash University, 2School of Physics and Astronomy, Monash University, 3X-ray Astrophysics Laboratory, Astrophysics Science Division, NASA/GSFC

We present a sample of observations of thermonuclear (type-I) X-ray bursts, selected for comparison with numerical models. Provided are examples of four distinct cases of thermonuclear ignition: He-ignition in mixed H/He fuel (case 1 of Fujimoto et al. 1981); He-ignition in pure He fuel, following exhaustion of accreted H by steady burning (case 2); ignition in (almost) pure He accumulated from an evolved donor in an ultracompact system; and an example of a superburst, thought to arise from ignition of a layer of carbon fuel produced as a by-product of more frequent bursts. Read More


Supermassive primordial stars are now suspected to be the progenitors of the most massive quasars at z~6. Previous studies of such stars were either unable to resolve hydrodynamical timescales or considered stars in isolation, not in the extreme accretion flows in which they actually form. Therefore, they could not self-consistently predict their final masses at collapse, or those of the resulting supermassive black hole seeds, but rather invoked comparison to simple polytropic models. Read More


2017Mar
Affiliations: 1CIERA/Northwestern, 2Caltech, 3UW e-Science Institute, 4Oskar Klein Centre - Physics, 5Weizmann Institute, 6IPAC, 7Caltech, 8IPAC, 9LBNL, 10Dark Cosmology Centre, 11Oskar Klein Centre - Physics, 12SDSU, 13JPL, 14Oskar Klein Centre - Astronomy, 15Oskar Klein Centre - Astronomy, 16Caltech

Modern wide-field, optical time-domain surveys must solve a basic optimization problem: maximize the number of transient discoveries or minimize the follow-up needed for the new discoveries. Here, we describe the Color Me Intrigued experiment, the first from the intermediate Palomar Transient Factory (iPTF) to search for transients simultaneously in the $g_\mathrm{PTF}$- and $R_\mathrm{PTF}$-bands. During the course of this experiment we discovered iPTF$\,$16fnm, a new member of the 02cx-like subclass of type Ia supernovae (SNe). Read More


Recently, the author proposed an alternative vector theory of gravity. To the best of our knowledge, vector gravity also passes available tests of gravity, and, in addition, predicts the correct value of the cosmological constant without free parameters. It is important to find a new feasible test which can distinguish between vector gravity and general relativity and determine whether gravity has a vector or a tensor origin. Read More


Cosmic Rays (CR) are high energy particles which come from the universe. When one of those particles enters to the atmosphere of the earth it produces an air shower, conformed by secondary particles in which the initial energy is distributed. The Pierre Auger Observatory, located in Argentina, is dedicated to the study of those events. Read More


According to magnetohydrodynamics (MHD), the encounter of two collisional magnetized plasmas at high velocity gives rise to shock waves. Investigations conducted so far have found that the same conclusion still holds in the case of collisionless plasmas. For the case of a flow-aligned field, MHD stipulates that the field and the fluid are disconnected, so that the shock produced is independent of the field. Read More


2017Mar
Affiliations: 1Università degli Studi di Palermo, Palermo, Italy, 2INAF, Osservatorio Astronomico di Roma, Monte Porzio Catone, 3Università degli Studi di Palermo, Palermo, Italy, 4ISDC Data Centre for Astrophysics, Versoix, Switzerland, 5Institut de Ciencies de l'Espai, 6Università degli Studi di Palermo, Palermo, Italy, 7Università degli Studi di Cagliari, Dipartimento di Fisica, Monserrato, Italy, 8Institut de Ciencies de l'Espai, 9Osservatorio Astronomico di Capodimonte, Napoli, Italy, 10ESA/ESAC, Science Operations Department Villanueva de la Canada Madrid, Spain, 11Università degli Studi di Palermo, Palermo, Italy, 12ISDC Data Centre for Astrophysics, Versoix, Switzerland, 13INAF, Osservatorio Astronomico di Roma, Monte Porzio Catone

CONTEXT - Transient low-mass X-ray binaries (LMXBs) often show outbursts lasting typically a few-weeks and characterized by a high X-ray luminosity ($L_{x} \approx 10^{36}-10^{38}$ erg/sec), while for most of the time they are found in X-ray quiescence ($L_X\approx10^{31} -10^{33}$ erg/sec). EXO 1745-248 is one of them. AIMS - The broad-band coverage, and the sensitivity of instrument on board of {\xmm} and {\igr}, offers the opportunity to characterize the hard X-ray spectrum during {\exo} outburst. Read More


We considered a model for the prompt phase of Gamma-Ray Burst (GRB) emission arising from a magnetized jet undergoing gradual energy dissipation due to magnetic reconnection. The dissipated magnetic energy is translated to bulk kinetic energy and to acceleration of particles. The energy in these particles is released via synchrotron radiation as they gyrate around the strong magnetic fields in the jet. Read More


2017Mar
Affiliations: 1Dipartimento di Fisica e Astronomia, Università di Bologna, INAF-Istituto di Radioastronomia, 2Instituto de Astrofisica de Canarias, Departamento de Astrofisica, Universidad de La Laguna, 3INAF-Osservatorio Astrofisico di Torino, 4INAF-Osservatorio Astrofisico di Torino, 5Department of Physics and Astronomy, University of Southampton, 6INAF-Istituto di Radioastronomia, 7Instituto de Astrofisica de Canarias, Departamento de Astrofisica, Universidad de La Laguna

The discovery of gamma-ray emission from radio-loud narrow-line Seyfert 1 (NLSy1) galaxies has questioned the need for large black hole masses (> 10^8 solar masses) to launch relativistic jets. We present near-infrared data of the gamma-ray emitting NLSy1 FBQS J1644+2619 which were collected using the camera CIRCE at the 10.4 m Gran Telescopio Canarias to investigate the structural properties of its host galaxy and to infer the black hole mass. Read More


Weakly Interacting Massive Particles (WIMPs) are among the best-motivated dark matter candidates. In light of no conclusive detection signal yet despite an extensive search program that combines, often in a complementary way, direct, indirect, and collider probes, we find it timely to give a broad overview of the WIMP paradigm. In particular, we review here the theoretical foundations of the WIMP paradigm, discuss status and prospects of various detection strategies, and explore future experimental challenges and opportunities. Read More


Axion-like particles (ALPs) and photons can quantum mechanically interconvert when propagating through magnetic fields, and ALP-photon conversion may induce oscillatory features in the spectra of astrophysical sources. We use deep (370 ks), short frame time Chandra observations of the bright nucleus at the centre of the radio galaxy M87 in the Virgo cluster to search for signatures of light ALPs. The absence of substantial irregularities in the X-ray power-law spectrum leads to a new upper limit on the photon-ALP coupling, $g_{a\gamma}$: using a conservative model of the cluster magnetic field consistent with Faraday rotation measurements from M87 and M84, we find $g_{a \gamma} < 1. Read More


Clustering methods are an important tool to enumerate and describe the different coherent kinds of Gamma Ray Bursts (GRBs). But their performance can be affected by a number of factors such as the choice of clustering algorithm and inherent associated assumptions, the inclusion of variables in clustering, nature of initialization methods used or the iterative algorithm or the criterion used to judge the optimal number of groups supported by the data. We analyzed GRBs from the BATSE 4Br catalog using $k$-means and Gaussian Mixture Models-based clustering methods and found that after accounting for all the above factors, all six variables -- different subsets of which have been used in the literature -- and that are, namely, the flux duration variables ($T_{50}$, $T_{90}$), the peak flux ($P_{256}$) measured in 256-millisecond bins, the total fluence ($F_t$) and the spectral hardness ratios ($H_{32}$ and $H_{321}$) contain information on clustering. Read More


We report the identification of a bright hard X-ray source dominating the M31 bulge above 25 keV from a simultaneous NuSTAR-Swift observation. We find that this source is the counterpart to Swift J0042.6+4112, which was previously detected in the Swift BAT All-sky Hard X-ray Survey. Read More


Large-scale extragalactic magnetic fields may induce conversions between very-high-energy photons and axion-like particles (ALPs), thereby shielding the photons from absorption on the extragalactic background light. However, in simplified "cell" models, used so far to represent extragalactic magnetic fields, this mechanism would be strongly suppressed by current astrophysical bounds. Here we consider realistic models of extragalactic magnetic fields obtained from large-scale cosmological simulations. Read More


2017Mar
Affiliations: 1SRON, 2SRON, 3Leiden University, 4Leiden University, 5Monash University, 6UvA, 7UvA, 8MIT

We observed the Rapid Burster with Chandra when it was in the 'banana' state that usually precedes the type-II X-ray bursting 'island' state for which the source is particularly known. We employed the High-Energy Transmission Grating Spectrometer in combination with the ACIS-S detector in continuous clocking mode. The observation yielded 20 thermonuclear type-I X-ray bursts emitted from the neutron star surface with recurrence times between 0. Read More


In the narrow-line Seyfert 1 galaxy 1H 0707-495, recently a transient quasi-periodic oscillation (QPO) signal has been detected at a high statistical significance. Here, we reanalyze the same set of XMM-Newton data measured on 2008 February 4 with the Weighted-Wavelet Z-transform (WWZ) method. In addition to confirm the previous finding we find the other QPO signal in a separated X-ray emission phase at a confidence level of $\sim 4. Read More


We present the results of a multi-epoch and multi-instrument study of the supermassive black hole at the center of the galaxy MCG-05-23-16 aiming at the determination of its spin. We have analyzed high quality X-ray data of MCG-05-23-16 from XMM-Newton, Suzaku, and NuSTAR obtained over a period of about 10~years. We have built a double-reflection spectral model that well describes the observed spectrum based on prior results suggesting that the iron K$\alpha$ line includes both a broad component from the disk's reflection spectrum and a narrow component due to fluorescence and scattering off material by more distant matter. Read More


We report the results from a recent 133 ks XMM-Newton observation of a highly super-Eddington narrow-line Type-1 QSO RX J0439.6-5311. This source has one of the steepest AGN hard X-ray slopes, in addition to a prominent and smooth soft X-ray excess. Read More


In this work, we simulate a set of realizations of local volume dark matter subhalo population based on the distributions and relations derived from Via Lactea II N-body simulation. We calculate the J-factors of these subhalos, and find that the low mass subhalos contribute a lot to the total J-factors. Combining with 91 months of the Fermi LAT observation, we constrain on the cross section of dark matter annihilating directly to two gamma rays. Read More


We carried out the first multi-wavelength (optical/UV and X-ray) photometric reverberation mapping of a tidal disruption flare (TDF) ASASSN-14li. We find that its X-ray variations are correlated with and lag the optical/UV fluctuations by 32$\pm$4 days. Based on the direction and the magnitude of the X-ray time lag, we rule out X-ray reprocessing and direct emission from a standard circular thin disk as the dominant source of its optical/UV emission. Read More


Most of ultraluminous X-ray sources are thought to be objects accreting above their Eddington limits. In the recently identified class of ultraluminous X-ray pulsars, accretor is a neutron star and thus has a fairly small mass with a small Eddington limit. The accretion disc structure around such an object affects important observables such as equilibrium period, period derivative and the size of the magnetosphere. Read More


2017Mar
Authors: A. Albert, R. Alfaro, C. Alvarez, J. D. Álvarez, R. Arceo, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, A. S. Barber, N. Bautista-Elivar, J. Becerra Gonzalez, A. Becerril, E. Belmont-Moreno, S. Y. BenZvi, A. Bernal, J. Braun, C. Brisbois, K. S. Caballero-Mora, T. Capistrán, A. Carramiñana, S. Casanova, M. Castillo, U. Cotti, J. Cotzomi, S. Coutiño de León, C. De León, E. De la Fuente, R. Diaz Hernandez, B. L. Dingus, M. A. DuVernois, J. C. Díaz-Vélez, R. W. Ellsworth, K. Engel, D. W. Fiorino, N. Fraija, J. A. García-González, F. Garfias, M. Gerhardt, A. González Muñoz, M. M. González, J. A. Goodman, Z. Hampel-Arias, J. P. Harding, S. Hernandez, A. Hernandez-Almada, B. Hona, C. M. Hui, P. Hüntemeyer, A. Iriarte, A. Jardin-Blicq, V. Joshi, S. Kaufmann, D. Kieda, A. Lara, R. J. Lauer, W. H. Lee, D. Lennarz, H. León Vargas, J. T. Linnemann, A. L. Longinotti, G. Luis Raya, R. Luna-García, R. López-Coto, K. Malone, S. S. Marinelli, O. Martinez, I. Martinez-Castellanos, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, E. Moreno, M. Mostafá, L. Nellen, M. Newbold, M. U. Nisa, R. Noriega-Papaqui, J. Pretz, E. G. Pérez-Pérez, Z. Ren, C. D. Rho, C. Rivière, D. Rosa-González, M. Rosenberg, E. Ruiz-Velasco, F. Salesa Greus, A. Sandoval, M. Schneider, H. Schoorlemmer, G. Sinnis, A. J. Smith, R. W. Springer, P. Surajbali, I. Taboada, O. Tibolla, K. Tollefson, I. Torres, T. N. Ukwatta, G. Vianello, T. Weisgarber, S. Westerhoff, I. G. Wisher, J. Wood, T. Yapici, P. W. Younk, A. Zepeda, H. Zhou

We present results from daily monitoring of gamma rays in the energy range $\sim$0.5 to $\sim$100 TeV with the first 17 months of data from the High Altitude Water Cherenkov (HAWC) Observatory. Its wide field of view of 2 steradians and duty cycle of >95% allow us to observe any source that transits over HAWC for up to $\sim$6 hours each sidereal day. Read More


The two messenger results of the Galactic center gamma-ray excess and the recent analysis of the antiproton flux from the AMS-02 observations suggest the signals may be owing to the same origin of the dark matter (DM) annihilating into $b \bar b$, while these results seem in tension with the dwarf spheroidal galaxy observations. To give a compatible explanation about it, we consider the pseudoscalar DM particles $S_d^+ S_d^-$ annihilating via $S_d^+ S_d^- \rightarrow S_d^0 S_d^0$, with the process mediated by a new scalar $\phi$ and $S_d^0$ quickly decaying into $b \bar{b}$. The particles $S_d^+$, $S_d^-$ and $S_d^0$ are in triplet in hidden sector with degenerate masses, and the annihilation cross section of DM today is linear dependent on the relative velocity $v_r$. Read More


In this paper we study centrifugal acceleration of particles moving along a prescribed rotating curved trajectories. We consider the physical system embedded in an isotropic photon field and study the influence of the photon drag force on the acceleration process. For this purpose we study three major configurations of the field lines: the straight line; the Archimede's spiral and the dipolar field line configuration. Read More


Black hole binaries may form both through isolated binary evolution and through dynamical interactions in dense stellar environments. During the formation and evolution of isolated binaries, several processes can alter the orientation of the black hole spin vectors with respect to the binary's orbital angular momentum. A subset of binary black holes merge through the emission of gravitational radiation and are observable with advanced ground-based gravitational-wave detectors. Read More


A channel for the formation of stellar mass black holes (BHs) is through hierarchical mergers of smaller BHs. Repeated mergers between BHs leave an imprint on the spin of the resulting black hole, since the final BH spin is largely determined by the orbital angular momentum of the merging binary system. It has been shown that a population of supermassive BHs that forms through repeated mergers will have a distribution of spin magnitudes centered around a dimensionless spin magnitude of a ~ 0. Read More


2017Mar
Authors: P. Blasi1
Affiliations: 1INAF/Arcetri, GSSI

The description of the transport of cosmic rays in magnetized media is central to both acceleration and propagation of these particles in our Galaxy and outside. The investigation of the process of particle acceleration, especially at shock waves, has already emphasized that non-linear effects such as self-generation of waves and dynamical reaction of cosmic rays on the background plasmas, are crucial if to achieve a physical understanding of the origin of cosmic rays. Here we discuss how similar non-linear effects on Galactic scales may affect the propagation of cosmic rays, not only through the excitation of plasma waves important for particle scattering, but also by inducing the motion of the interstellar medium in the direction opposite to the gravitational pull exerted by matter in the Galaxy, thereby resulting in the launching of a wind. Read More


We continue our study on the capabilities of present and future X-ray missions to test the nature of astrophysical black hole candidates via X-ray reflection spectroscopy and distinguish Kerr black holes from other solutions of 4-dimensional Einstein's gravity in the presence of a matter field. Here we investigate the case of Kerr black holes with Proca hair [1]. The analysis of a sample of these configurations suggests that even extremely hairy black holes can mimic the iron line profile of the standard Kerr black holes, and, at least for the configurations of our study, we find that current X-ray missions cannot distinguish these objects from Kerr black holes. Read More


The purpose of this article is to alert Astronomers, particularly those using spectroscopic surveys, to the fact that exotic astronomical objects (e.g. quasars or active galactic nuclei) that send ultra-rapid quasi periodic pulses of optical light would generate spectroscopic features that look like emission lines. Read More


We derive stringent constraints on the persistent source associated with FRB 121102: Size $10^{17}$ cm $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


Beaming effect is important for the observational properties of blazars. In this work, we collect 91 $Fermi$ blazars with available radio Doppler factors. $\gamma$-ray Doppler factors are estimated and compared with radio Doppler factors for some sources. Read More