The Experts below are selected from a list of 3282 Experts worldwide ranked by ideXlab platform
C Hanna - One of the best experts on this subject based on the ideXlab platform.
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utility of galaxy catalogs for following up gravitational waves from binary neutron star mergers with wide field telescopes
The Astrophysical Journal, 2014Co-Authors: C Hanna, Ilya Mandel, W D VousdenAbstract:The first detections of gravitational waves from binary neutron star mergers with advanced LIGO and Virgo observatories are anticipated in the next five years. These detections could pave the way for multi-messenger gravitational-wave (GW) and electromagnetic (EM) astronomy if GW triggers are successfully followed up with targeted EM observations. However, GW sky localization is relatively poor, with expected localization areas of ~10-100 deg2; this presents a challenge for following up GW signals from compact binary mergers. Even for wide-field instruments, tens or hundreds of pointings may be required. Prioritizing pointings based on the relative probability of successful imaging is important since it may not be possible to tile the entire gravitational-wave localization region in a timely fashion. Galaxy catalogs were effective at narrowing down regions of the sky to search in initial attempts at joint GW/EM observations. The relatively limited range of initial GW instruments meant that few galaxies were present per pointing and galaxy catalogs were complete within the search volume. The next generation of GW detectors will have a 10-fold increase in range thereby increasing the expected number of galaxies per Unit Solid Angle by a factor of ~1000. As an additional complication, catalogs will be highly incomplete. Nevertheless, galaxy catalogs can still play an important role in prioritizing pointings for the next era of GW searches. We show how to quantify the advantages of using galaxy catalogs to prioritize wide-field follow-ups as a function of only two parameters: the three-dimensional volume within the field of view of a telescope after accounting for the GW distance measurement uncertainty, and the fraction of the GW sky localization uncertainty region that can be covered with telescope pointings. We find that the use of galaxy catalogs can improve the probability of successful imaging by ~10% to ~300% relative to follow-up strategies that do not utilize such catalogs for the scenarios we considered. We determine that catalogs with a 75% completeness perform comparably to complete catalogs in most cases, while 33%-complete catalogs can lead to lower follow-up success rates than complete catalogs for small fields of view, though still providing an advantage over strategies that do not use a catalog at all.
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utility of galaxy catalogs for following up gravitational waves from binary neutron star mergers with wide field telescopes
arXiv: High Energy Astrophysical Phenomena, 2013Co-Authors: C Hanna, Ilya Mandel, W D VousdenAbstract:The first detections of gravitational waves from binary neutron star mergers with advanced LIGO and Virgo observatories are anticipated in the next five years. These detections could pave the way for multi-messenger gravitational-wave (GW) and electromagnetic (EM) astronomy if GW triggers are successfully followed up with targeted EM observations. However, GW sky localization is relatively poor, with expected localization areas of ~10--100 square degrees; this presents a challenge for following up GW signals from compact binary mergers. Prioritizing wide-field follow-ups based on the probability of successful imaging is important when it is impossible to tile the entire gravitational-wave localization region. Galaxy catalogs were effective at narrowing down regions of the sky to search in initial attempts at joint GW/EM observations. The next generation of GW detectors will have a ten-fold increase in range thereby increasing the expected number of galaxies per Unit Solid Angle a thousand-fold. As an additional complication, catalogs may be highly incomplete. We show how to quantify the advantages of using galaxy catalogs as a function of only two parameters: the three-dimensional volume within the field of view of a telescope after accounting for the GW distance measurement uncertainty, and the fraction of the GW sky localization uncertainty region that can be followed up. We find that the use of galaxy catalogs can improve success rates by ~10% to a factor of 4 relative to follow-up strategies that do not utilize such catalogs for the scenarios we considered. We determine that catalogs with a 75% completeness perform comparably to complete catalogs in most cases, while 33%-complete catalogs can lead to lower follow-up success rates than complete catalogs for small fields of view, though still providing an advantage over strategies that do not use a catalog at all.
O S Salafia - One of the best experts on this subject based on the ideXlab platform.
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structure of gamma ray burst jets intrinsic versus apparent properties
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: O S Salafia, A Pescalli, Gabriele Ghisellini, Giovanna Ghirlanda, Fabio NappoAbstract:With this paper we introduce the concept of apparent structure of a GRB jet, as opposed to its intrinsic structure. The latter is customarily defined specifying the functions ( ) (the energy emitted per jet Unit Solid Angle) and ( ) (the Lorentz factor of the emitting material); the apparent structure is instead defined by us as the isotropic equivalent energy Eiso( v) as a function of the viewing Angle v. We show how to predict the apparent structure of a jet given its intrinsic structure. We find that a Gaussian intrinsic structure yields a power law apparent structure: this opens a new viewpoint on the Gaussian (which can be understood as a proxy for a realistic narrow, well collimated jet structure) as a possible candidate for a quasi-universal GRB jet structure. We show that such a model (a) is consistent with recent constraints on the observed luminosity function of GRBs; (b) implies fewer orphan afterglows with respect to the standard uniform model; (c) can break out the progenitor star (in the collapsar scenario) without wasting an unreasonable amount of energy; (d) is compatible with the explanation of the Amati correlation as a viewing Angle effect; (e) can be very standard in energy content, and still yield a very wide range of observed isotropic equivalent energies.
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luminosity function and jet structure of gamma ray burst
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: O S Salafia, A Pescalli, Gabriele Ghisellini, Giovanna Ghirlanda, Fabio Nappo, R SalvaterraAbstract:The structure of Gamma Ray Burst (GRB) jets impacts on their prompt and afterglow emission properties. The jet of GRBs could be uniform, with constant energy per Unit Solid Angle within the jet aperture, or it could instead be structured, namely with energy and velocity that depend on the angular distance from the axis of the jet. We try to get some insight about the still unknown structure of GRBs by studying their luminosity function. We show that low (1e46-1e48 erg/s) and high (i.e. with L > 1e50 erg/s) luminosity GRBs can be described by a unique luminosity function, which is also consistent with current lower limits in the intermediate luminosity range (1e48-1e50} erg/s). We derive analytical expressions for the luminosity function of GRBs in uniform and structured jet models and compare them with the data. Uniform jets can reproduce the entire luminosity function with reasonable values of the free parameters. A structured jet can also fit adequately the current data, provided that the energy within the jet is relatively strongly structured, i.e. E propto theta^{-k} with k > 4. The classical E propto theta^{-2} structured jet model is excluded by the current data.
W D Vousden - One of the best experts on this subject based on the ideXlab platform.
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utility of galaxy catalogs for following up gravitational waves from binary neutron star mergers with wide field telescopes
The Astrophysical Journal, 2014Co-Authors: C Hanna, Ilya Mandel, W D VousdenAbstract:The first detections of gravitational waves from binary neutron star mergers with advanced LIGO and Virgo observatories are anticipated in the next five years. These detections could pave the way for multi-messenger gravitational-wave (GW) and electromagnetic (EM) astronomy if GW triggers are successfully followed up with targeted EM observations. However, GW sky localization is relatively poor, with expected localization areas of ~10-100 deg2; this presents a challenge for following up GW signals from compact binary mergers. Even for wide-field instruments, tens or hundreds of pointings may be required. Prioritizing pointings based on the relative probability of successful imaging is important since it may not be possible to tile the entire gravitational-wave localization region in a timely fashion. Galaxy catalogs were effective at narrowing down regions of the sky to search in initial attempts at joint GW/EM observations. The relatively limited range of initial GW instruments meant that few galaxies were present per pointing and galaxy catalogs were complete within the search volume. The next generation of GW detectors will have a 10-fold increase in range thereby increasing the expected number of galaxies per Unit Solid Angle by a factor of ~1000. As an additional complication, catalogs will be highly incomplete. Nevertheless, galaxy catalogs can still play an important role in prioritizing pointings for the next era of GW searches. We show how to quantify the advantages of using galaxy catalogs to prioritize wide-field follow-ups as a function of only two parameters: the three-dimensional volume within the field of view of a telescope after accounting for the GW distance measurement uncertainty, and the fraction of the GW sky localization uncertainty region that can be covered with telescope pointings. We find that the use of galaxy catalogs can improve the probability of successful imaging by ~10% to ~300% relative to follow-up strategies that do not utilize such catalogs for the scenarios we considered. We determine that catalogs with a 75% completeness perform comparably to complete catalogs in most cases, while 33%-complete catalogs can lead to lower follow-up success rates than complete catalogs for small fields of view, though still providing an advantage over strategies that do not use a catalog at all.
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utility of galaxy catalogs for following up gravitational waves from binary neutron star mergers with wide field telescopes
arXiv: High Energy Astrophysical Phenomena, 2013Co-Authors: C Hanna, Ilya Mandel, W D VousdenAbstract:The first detections of gravitational waves from binary neutron star mergers with advanced LIGO and Virgo observatories are anticipated in the next five years. These detections could pave the way for multi-messenger gravitational-wave (GW) and electromagnetic (EM) astronomy if GW triggers are successfully followed up with targeted EM observations. However, GW sky localization is relatively poor, with expected localization areas of ~10--100 square degrees; this presents a challenge for following up GW signals from compact binary mergers. Prioritizing wide-field follow-ups based on the probability of successful imaging is important when it is impossible to tile the entire gravitational-wave localization region. Galaxy catalogs were effective at narrowing down regions of the sky to search in initial attempts at joint GW/EM observations. The next generation of GW detectors will have a ten-fold increase in range thereby increasing the expected number of galaxies per Unit Solid Angle a thousand-fold. As an additional complication, catalogs may be highly incomplete. We show how to quantify the advantages of using galaxy catalogs as a function of only two parameters: the three-dimensional volume within the field of view of a telescope after accounting for the GW distance measurement uncertainty, and the fraction of the GW sky localization uncertainty region that can be followed up. We find that the use of galaxy catalogs can improve success rates by ~10% to a factor of 4 relative to follow-up strategies that do not utilize such catalogs for the scenarios we considered. We determine that catalogs with a 75% completeness perform comparably to complete catalogs in most cases, while 33%-complete catalogs can lead to lower follow-up success rates than complete catalogs for small fields of view, though still providing an advantage over strategies that do not use a catalog at all.
A Pescalli - One of the best experts on this subject based on the ideXlab platform.
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structure of gamma ray burst jets intrinsic versus apparent properties
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: O S Salafia, A Pescalli, Gabriele Ghisellini, Giovanna Ghirlanda, Fabio NappoAbstract:With this paper we introduce the concept of apparent structure of a GRB jet, as opposed to its intrinsic structure. The latter is customarily defined specifying the functions ( ) (the energy emitted per jet Unit Solid Angle) and ( ) (the Lorentz factor of the emitting material); the apparent structure is instead defined by us as the isotropic equivalent energy Eiso( v) as a function of the viewing Angle v. We show how to predict the apparent structure of a jet given its intrinsic structure. We find that a Gaussian intrinsic structure yields a power law apparent structure: this opens a new viewpoint on the Gaussian (which can be understood as a proxy for a realistic narrow, well collimated jet structure) as a possible candidate for a quasi-universal GRB jet structure. We show that such a model (a) is consistent with recent constraints on the observed luminosity function of GRBs; (b) implies fewer orphan afterglows with respect to the standard uniform model; (c) can break out the progenitor star (in the collapsar scenario) without wasting an unreasonable amount of energy; (d) is compatible with the explanation of the Amati correlation as a viewing Angle effect; (e) can be very standard in energy content, and still yield a very wide range of observed isotropic equivalent energies.
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luminosity function and jet structure of gamma ray burst
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: O S Salafia, A Pescalli, Gabriele Ghisellini, Giovanna Ghirlanda, Fabio Nappo, R SalvaterraAbstract:The structure of Gamma Ray Burst (GRB) jets impacts on their prompt and afterglow emission properties. The jet of GRBs could be uniform, with constant energy per Unit Solid Angle within the jet aperture, or it could instead be structured, namely with energy and velocity that depend on the angular distance from the axis of the jet. We try to get some insight about the still unknown structure of GRBs by studying their luminosity function. We show that low (1e46-1e48 erg/s) and high (i.e. with L > 1e50 erg/s) luminosity GRBs can be described by a unique luminosity function, which is also consistent with current lower limits in the intermediate luminosity range (1e48-1e50} erg/s). We derive analytical expressions for the luminosity function of GRBs in uniform and structured jet models and compare them with the data. Uniform jets can reproduce the entire luminosity function with reasonable values of the free parameters. A structured jet can also fit adequately the current data, provided that the energy within the jet is relatively strongly structured, i.e. E propto theta^{-k} with k > 4. The classical E propto theta^{-2} structured jet model is excluded by the current data.
Fabio Nappo - One of the best experts on this subject based on the ideXlab platform.
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structure of gamma ray burst jets intrinsic versus apparent properties
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: O S Salafia, A Pescalli, Gabriele Ghisellini, Giovanna Ghirlanda, Fabio NappoAbstract:With this paper we introduce the concept of apparent structure of a GRB jet, as opposed to its intrinsic structure. The latter is customarily defined specifying the functions ( ) (the energy emitted per jet Unit Solid Angle) and ( ) (the Lorentz factor of the emitting material); the apparent structure is instead defined by us as the isotropic equivalent energy Eiso( v) as a function of the viewing Angle v. We show how to predict the apparent structure of a jet given its intrinsic structure. We find that a Gaussian intrinsic structure yields a power law apparent structure: this opens a new viewpoint on the Gaussian (which can be understood as a proxy for a realistic narrow, well collimated jet structure) as a possible candidate for a quasi-universal GRB jet structure. We show that such a model (a) is consistent with recent constraints on the observed luminosity function of GRBs; (b) implies fewer orphan afterglows with respect to the standard uniform model; (c) can break out the progenitor star (in the collapsar scenario) without wasting an unreasonable amount of energy; (d) is compatible with the explanation of the Amati correlation as a viewing Angle effect; (e) can be very standard in energy content, and still yield a very wide range of observed isotropic equivalent energies.
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luminosity function and jet structure of gamma ray burst
Monthly Notices of the Royal Astronomical Society, 2015Co-Authors: O S Salafia, A Pescalli, Gabriele Ghisellini, Giovanna Ghirlanda, Fabio Nappo, R SalvaterraAbstract:The structure of Gamma Ray Burst (GRB) jets impacts on their prompt and afterglow emission properties. The jet of GRBs could be uniform, with constant energy per Unit Solid Angle within the jet aperture, or it could instead be structured, namely with energy and velocity that depend on the angular distance from the axis of the jet. We try to get some insight about the still unknown structure of GRBs by studying their luminosity function. We show that low (1e46-1e48 erg/s) and high (i.e. with L > 1e50 erg/s) luminosity GRBs can be described by a unique luminosity function, which is also consistent with current lower limits in the intermediate luminosity range (1e48-1e50} erg/s). We derive analytical expressions for the luminosity function of GRBs in uniform and structured jet models and compare them with the data. Uniform jets can reproduce the entire luminosity function with reasonable values of the free parameters. A structured jet can also fit adequately the current data, provided that the energy within the jet is relatively strongly structured, i.e. E propto theta^{-k} with k > 4. The classical E propto theta^{-2} structured jet model is excluded by the current data.
