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Post Info TOPIC: FRB 121102

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Posts: 131433
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 RE: FRB 121102 Permalink Title: FRB 121102 is coincident with a star forming region in its host galaxy Author: C.G. Bassa (ASTRON), S.P. Tendulkar (McGill), E.A.K. Adams (ASTRON), N. Maddox (ASTRON), S. Bogdanov (Columbia), G.C. Bower (ASIAA), S. Burke-Spolaor (NRAO/WVU), B.J. Butler (NRAO), S. Chatterjee (Cornell), J.M. Cordes (Cornell), J.W.T. Hessels (ASTRON/Amsterdam), V.M. Kaspi (McGill), C.J. Law (Berkeley), B. Marcote (JIVE), Z. Paragi (JIVE), S.M. Ransom (NRAO), P. Scholz (DRAO), L.G. Spitler (MPIfR), H.J. van Langevelde (JIVE/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 0.68 kpc (0.20 arcsec), encompassing the projected location of the compact (<0.7 pc), persistent radio source that is associated with FRB 121102. The half-light diameter of the dwarf galaxy is 5 to 7 kpc, and broadband spectral energy distribution fitting indicates that it has a total stellar mass of M*~10^8 Msun. The metallicity of the host galaxy is low, 12+log10 ([O/H])=8.0±0.1. The properties of the host galaxy of FRB 121102 are comparable to those of extreme emission line galaxies, also known to host hydrogen-poor superluminous supernovae and long-duration gamma-ray bursts. The projected location of FRB 121102 within the star forming region supports the proposed connection of FRBs with newly born neutron stars or magnetars.Read more (465kb, PDF) __________________

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Posts: 131433
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 Permalink Title: A model for the repeating FRB 121102 in the AGN scenario Author: Florencia L. Vieyro, Gustavo E. Romero, Valentí Bosch-Ramon, Benito Marcote, María V. del Valle Fast radio bursts, or FRBs, are transient sources of unknown origin. Recent radio and optical observations have provided strong evidence for an extragalactic origin of the phenomenon and the precise localization of the repeating FRB 121102. Observations using the Karl G. Jansky Very Large Array (VLA) and very-long-baseline interferometry (VLBI) have revealed the existence of a continuum non-thermal radio source consistent with the location of the bursts in a dwarf galaxy. All these new data rule out several models that were previously proposed, and impose stringent constraints to new models. We aim to model FRB 121102 in light of the new observational results in the active galactic nucleus (AGN) scenario. We propose a model for repeating FRBs in which a non-steady relativistic e^±-beam, accelerated by an impulsive magnetohydrodynamic (MHD)-driven mechanism, interacts with a cloud at the centre of a star-forming dwarf galaxy. The interaction generates regions of high electrostatic field called cavitons in the plasma cloud. Turbulence is also produced in the beam. These processes, plus particle isotropization, the interaction scale, and light retardation effects, provide the necessary ingredients for short-lived, bright coherent radiation bursts. The mechanism studied in this work explains the general properties of FRB 121102, and may also be applied to other repetitive FRBs. Coherent emission from electrons and positrons accelerated in cavitons provides a plausible explanation of FRBs. Read more (37kb, PDF) __________________

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Posts: 131433
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 Permalink Title: A flaring magnetar in FRB 121102? Author: Andrei M. Beloborodov (Columbia University) The persistent radio counterpart of FRB 121102 is estimated to have N~10^52 particles, energy EN~10^48 erg, and size R~10^17 cm. The source can be a nebula inflated and heated by an intermittent outflow from a magnetar -- a neutron star powered by its magnetic (rather than rotational) energy. The object is young and frequently liberating energy in magnetic flares driven by accelerated ambipolar diffusion in the neutron star core, feeding the nebula and producing bright millisecond bursts. The particle number in the nebula is consistent with ion ejecta from giant flares. The nebula should also contain the freeze-out of electron-positron pairs N±~1051 created months after the neutron star birth; the same mechanism offers an explanation for N± in the Crab nebula. The persistent source around FRB 121102 is likely heated by magnetic dissipation and internal waves excited by the magnetar ejecta. The volumetric heating by waves explains the nebula's enormous efficiency in producing radio emission. The repeating radio bursts are suggested to occur much closer to the magnetar, whose flaring magnetosphere drives ultrarelativistic internal shocks into the magnetar wind. The shocks are mediated by Larmor rotation that forms a GHz maser of observed duration <1 ms. Furthermore, the flare ejecta can become charge-starved and then convert to electromagnetic waves.Read more (14kb, PDF) __________________

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Posts: 131433
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 Fast Radio Burst 121102 Permalink Title: FRB 121102 Casts New Light on the Photon Mass Author: Luca Bonetti, John Ellis, Nikolaos E. Mavromatos, Alexander S. Sakharov, Edward K. Sarkisyan-Grinbaum, Alessandro D.A.M. Spallicci The photon mass, m_\gamma, can in principle be constrained using measurements of the dispersion measures (DMs) of fast radio bursts (FRBs), once the FRB redshifts are known. The DM of the repeating FRB 121102 is known to <1%, a host galaxy has now been identified with high confidence,and its redshift, z, has now been determined with high accuracy: z=0.19273(8). Taking into account the plasma contributions to the DM from the Intergalactic medium (IGM) and the Milky Way, we use the data on FRB 121102 to derive the constraint m_\gamma \lesssim 2.2 x 10^-14 eV c^-2 (3.9 x 10^-50 kg). Since the plasma and photon mass contributions to DMs have different redshift dependences, they could in principle be distinguished by measurements of more FRB redshifts, enabling the sensitivity to m to be improved. Read more (168kb, PDF) __________________

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Posts: 131433
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 RE: FRB 121102 Permalink Title: Millisecond Magnetar Birth Connects FRB 121102 to Superluminous Supernovae and Long Duration Gamma-ray Bursts Author: Brian D. Metzger, Edo Berger, Ben Margalit Sub-arcsecond localization of the repeating fast radio burst FRB 121102 revealed its coincidence with a dwarf host galaxy and a steady (quiescent') non-thermal radio source. We show that the properties of the host galaxy are consistent with those of long-duration gamma-ray bursts (LGRB) and hydrogen-poor superluminous supernovae (SLSNe-I). Both LGRBs and SLSNe-I were previously hypothesized to be powered by the electromagnetic spin-down of newly-formed, strongly-magnetized neutron stars with millisecond birth rotation periods (millisecond magnetars'). This motivates considering a scenario whereby the repeated bursts from FRB 121102 originate from a young magnetar remnant embedded within a young hydrogen-poor supernova remnant. Requirements on the GHz free-free optical depth through the expanding supernova ejecta (accounting for photo-ionization by the rotationally-powered magnetar nebula), energetic constraints on the bursts, and constraints on the size of the quiescent source all point to an age of less than a few decades. The quiescent radio source can be attributed to radio synchrotron emission from the shock interaction between the fast outer layer of the supernova ejecta with the surrounding wind of the progenitor star, or from deeper within the magnetar wind nebula. Alternatively, the radio emission could be an orphan radio afterglow from an initially off-axis LGRB jet, though this might require the source to be too young. We propose future tests of the SLSNe-I/LGRB/FRB connection, such as searches for FRBs from nearby SLSNe-I/LGRB on timescales of decades after their explosions. Read more (1084kb, PDF) __________________

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