The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
B Giacomazzo - One of the best experts on this subject based on the ideXlab platform.
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short gamma ray bursts from the merger of two black holes
The Astrophysical Journal, 2016Co-Authors: Rosalba Perna, Davide Lazzati, B GiacomazzoAbstract:This is the publisher’s final pdf. The article is copyrighted by the American Astronomical Society and published by IOP Publishing. It can be found at: http://iopscience.iop.org/journal/2041-8205
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short gamma ray bursts from the merger of two black holes
arXiv: High Energy Astrophysical Phenomena, 2016Co-Authors: Rosalba Perna, Davide Lazzati, B GiacomazzoAbstract:Short Gamma-Ray Bursts (GRBs) are explosions of cosmic origin believed to be associated with the merger of two compact objects, either two neutron stars, or a neutron star and a black hole. The presence of at least one neutron star has long been thought to be an essential element of the model: its tidal disruption provides the needed baryonic material whose rapid accretion onto the post-merger black hole powers the burst. The recent tentative detection by the Fermi satellite of a short GRB in association with the gravitational wave signal GW150914 produced by the merger of two black holes has challenged this standard paradigm. Here we show that the evolution of two high-mass, low-metallicity stars with main sequence rotational speeds a few tens of percent of the critical speed eventually undergoing a weak supernova explosion {\em can} produce a short gamma-ray burst. The outer layers of the envelope of the last exploding star remain bound and circularize at large radii. With time, the disk cools and becomes neutral, suppressing the magneto-rotational instability, and hence the viscosity. The disk remains 'long-lived dead' until tidal torques and shocks during the pre-merger phase heat it up and re-ignite accretion, rapidly consuming the disk and powering the short gamma-ray burst.
Scott J Kenyon - One of the best experts on this subject based on the ideXlab platform.
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the elm survey v merging massive white dwarf binaries
The Astrophysical Journal, 2013Co-Authors: Warren R Brown, Mukremin Kilic, Carlos Allende Prieto, A Gianninas, Scott J KenyonAbstract:We present the discovery of 17 low mass white dwarfs (WDs) in short-period P ≤ 1 day binaries. Our sample includes four objects with remarkable logg ≃ 5 surface gravities and orbital solutions that require them to be double degenerate binaries. All of the lowest surface gravity WDs have metal lines in their spectra implying long gravitational settling times or on-going accretion. Notably, six of the WDs in our sample have binary merger times <10 Gyr. Four have &0.9 M⊙ companions. If the companions are massive WDs, these four binaries will evolve into stable mass transfer AM CVn systems and possibly explode as underluminous supernovae. If the companions are neutron stars, then these may be milli-second pulsar binaries. These discoveries increase the number of detached, double degenerate binaries in the ELM Survey to 54; 31 of these binaries will merge within a Hubble time. Subject headings: binaries: close — Galaxy: stellar content — Stars: individual: SDSS J0751-0141, SDSS J0811+0225 — Stars: neutron — white dwarfs
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the elm survey ii twelve binary white dwarf merger systems
arXiv: Astrophysics of Galaxies, 2010Co-Authors: Mukremin Kilic, Warren R Brown, Carlos Allende Prieto, Marcel A Agueros, C O Heinke, Scott J KenyonAbstract:We describe new radial velocity and X-ray observations of extremely low-mass white dwarfs (ELM WDs, ~0.2 Msol) in the Sloan Digital Sky Survey Data Release 4 and the MMT Hypervelocity Star survey. We identify four new short period binaries, including two merger systems. These observations bring the total number of short period binary systems identified in our survey to 20. No main-sequence or neutron star companions are visible in the available optical photometry, radio, and X-ray data. Thus, the companions are most likely WDs. Twelve of these systems will merge within a Hubble time due to gravitational wave radiation. We have now tripled the number of known merging WD systems. We discuss the characteristics of this merger sample and potential links to underluminous supernovae, extreme helium stars, AM CVn systems, and other merger products. We provide new observational tests of the WD mass-period distribution and cooling models for ELM WDs. We also find evidence for a new formation channel for single low-mass WDs through binary mergers of two lower mass objects.
Carlos Allende Prieto - One of the best experts on this subject based on the ideXlab platform.
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the elm survey v merging massive white dwarf binaries
The Astrophysical Journal, 2013Co-Authors: Warren R Brown, Mukremin Kilic, Carlos Allende Prieto, A Gianninas, Scott J KenyonAbstract:We present the discovery of 17 low mass white dwarfs (WDs) in short-period P ≤ 1 day binaries. Our sample includes four objects with remarkable logg ≃ 5 surface gravities and orbital solutions that require them to be double degenerate binaries. All of the lowest surface gravity WDs have metal lines in their spectra implying long gravitational settling times or on-going accretion. Notably, six of the WDs in our sample have binary merger times <10 Gyr. Four have &0.9 M⊙ companions. If the companions are massive WDs, these four binaries will evolve into stable mass transfer AM CVn systems and possibly explode as underluminous supernovae. If the companions are neutron stars, then these may be milli-second pulsar binaries. These discoveries increase the number of detached, double degenerate binaries in the ELM Survey to 54; 31 of these binaries will merge within a Hubble time. Subject headings: binaries: close — Galaxy: stellar content — Stars: individual: SDSS J0751-0141, SDSS J0811+0225 — Stars: neutron — white dwarfs
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the elm survey ii twelve binary white dwarf merger systems
arXiv: Astrophysics of Galaxies, 2010Co-Authors: Mukremin Kilic, Warren R Brown, Carlos Allende Prieto, Marcel A Agueros, C O Heinke, Scott J KenyonAbstract:We describe new radial velocity and X-ray observations of extremely low-mass white dwarfs (ELM WDs, ~0.2 Msol) in the Sloan Digital Sky Survey Data Release 4 and the MMT Hypervelocity Star survey. We identify four new short period binaries, including two merger systems. These observations bring the total number of short period binary systems identified in our survey to 20. No main-sequence or neutron star companions are visible in the available optical photometry, radio, and X-ray data. Thus, the companions are most likely WDs. Twelve of these systems will merge within a Hubble time due to gravitational wave radiation. We have now tripled the number of known merging WD systems. We discuss the characteristics of this merger sample and potential links to underluminous supernovae, extreme helium stars, AM CVn systems, and other merger products. We provide new observational tests of the WD mass-period distribution and cooling models for ELM WDs. We also find evidence for a new formation channel for single low-mass WDs through binary mergers of two lower mass objects.
Christopher Thompson - One of the best experts on this subject based on the ideXlab platform.
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formation of very strongly magnetized neutron stars implications for gamma ray bursts
The Astrophysical Journal, 1992Co-Authors: Robert C Duncan, Christopher ThompsonAbstract:Neutron stars with unusually strong magnetic dipole fields B_dipole ~ 10^14 - 10^15 G, can form when conditions for efficient helical dynamo action are met during the first few seconds after gravitational collapse. Such high-field neutron stars, "magnetars," initially rotate with short periods ~ 1 ms, but quickly lose most of their rotational energy via magnetic braking, giving a large energy boost to the associated supernova explosion. Several mechanisms unique to magnetars can plausibly generate large (~ 1000 km/s) recoil velocities. These include anisotropic neutrino emission, core rotational instability and fragmentation, and/or anisotropic magnetic winds. Magnetars are relatively difficult to detect because they drop below the radio death line faster than ordinary pulsars, and because they probably do not remain bound in binary systems. We conjecture that their main observational signature is gamma-ray bursts powered by their vast reservoirs of magnetic energy. If they acquire large recoils, most magnetars are unbound from the Galaxy or reside in an extended, weakly bound Galactic corona. There is evidence that the soft gamma repeaters are young magnetars. Finally, we note that a convective dynamo can also generate a very strong dipole field after the merger of a neutron star binary, but only if the merged star survives for as long as ~ 10-100 ms.
Rosalba Perna - One of the best experts on this subject based on the ideXlab platform.
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short gamma ray bursts from the merger of two black holes
The Astrophysical Journal, 2016Co-Authors: Rosalba Perna, Davide Lazzati, B GiacomazzoAbstract:This is the publisher’s final pdf. The article is copyrighted by the American Astronomical Society and published by IOP Publishing. It can be found at: http://iopscience.iop.org/journal/2041-8205
-
short gamma ray bursts from the merger of two black holes
arXiv: High Energy Astrophysical Phenomena, 2016Co-Authors: Rosalba Perna, Davide Lazzati, B GiacomazzoAbstract:Short Gamma-Ray Bursts (GRBs) are explosions of cosmic origin believed to be associated with the merger of two compact objects, either two neutron stars, or a neutron star and a black hole. The presence of at least one neutron star has long been thought to be an essential element of the model: its tidal disruption provides the needed baryonic material whose rapid accretion onto the post-merger black hole powers the burst. The recent tentative detection by the Fermi satellite of a short GRB in association with the gravitational wave signal GW150914 produced by the merger of two black holes has challenged this standard paradigm. Here we show that the evolution of two high-mass, low-metallicity stars with main sequence rotational speeds a few tens of percent of the critical speed eventually undergoing a weak supernova explosion {\em can} produce a short gamma-ray burst. The outer layers of the envelope of the last exploding star remain bound and circularize at large radii. With time, the disk cools and becomes neutral, suppressing the magneto-rotational instability, and hence the viscosity. The disk remains 'long-lived dead' until tidal torques and shocks during the pre-merger phase heat it up and re-ignite accretion, rapidly consuming the disk and powering the short gamma-ray burst.