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Bing Zhang - One of the best experts on this subject based on the ideXlab platform.

  • contribution of dark matter annihilation to gamma ray burst Afterglows near massive galaxy centers
    arXiv: High Energy Astrophysical Phenomena, 2020
    Co-Authors: Baoquan Huang, Tong Liu, Feng Huang, Dabin Lin, Bing Zhang
    Abstract:

    Gamma-ray bursts (GRBs) are believed to be powered by ultrarelativistic jets. If these jets encounter and accelerate excess electrons and positrons produced by particle dark matter (DM) annihilation, the observed electromagnetic radiation would be enhanced. In this paper, we study GRB afterglow emission with the presence of abundant DM under the weakly interacting massive particle annihilation conditions. We calculate the light curves and spectra of the GRB Afterglows with different parameters, i.e., DM density, particle DM mass, annihilation channel, and electron density of the interstellar medium. We find that the effect of DM may become noticeable in the afterglow spectra if the circumburst has a low electron number density ($n \lesssim 0.1~\rm cm^{-3}$) and if the DM has a high number density ($\rho_\chi \gtrsim 10^3~\rm GeV~cm^{-3}$). According to the standard galaxy DM density profile, GRB Afterglows with DM contribution might occur at distances of several to tens of parsecs from the centers of massive galaxies.

  • bright broadband Afterglows of gravitational wave bursts from mergers of binary neutron stars
    The Astrophysical Journal, 2013
    Co-Authors: Bing Zhang, He Gao, Xuan Ding, Zigao Dai
    Abstract:

    If double neutron star mergers leave behind a massive magnetar rather than a black hole, then a bright early afterglow can follow the gravitational wave burst (GWB) even if there is no short gamma-ray burst (SGRB)-GWB association or if there is an association but the SGRB does not beam toward Earth. Besides directly dissipating the proto-magnetar wind, as suggested by Zhang, here we suggest that the magnetar wind could push the ejecta launched during the merger process and, under certain conditions, would reach a relativistic speed. Such a magnetar-powered ejecta, when interacting with the ambient medium, would develop a bright broadband afterglow due to synchrotron radiation. We study this physical scenario in detail and present the predicted X-ray, optical, and radio light curves for a range of magnetar and ejecta parameters. We show that the X-ray and optical light curves usually peak around the magnetar spin-down timescale (similar to 10(3)-10(5) s), reaching brightnesses readily detectable by wide-field X-ray and optical telescopes, and remain detectable for an extended period. The radio afterglow peaks later, but is much brighter than the case without a magnetar energy injection. Therefore, such bright broadband Afterglows, if detected and combined with GWBs in the future, would be a probe of massive millisecond magnetars and stiff equations of state for nuclear matter.

  • bright broad band Afterglows of gravitational wave bursts from mergers of binary neutron stars
    arXiv: High Energy Astrophysical Phenomena, 2013
    Co-Authors: He Gao, Bing Zhang, Xuan Ding, Zigao Dai
    Abstract:

    If double neutron star mergers leave behind a massive magnetar rather than a black hole, a bright early afterglow can follow the gravitational wave burst (GWB) even if there is no short gamma-ray burst (SGRB) - GWB association or there is an association but the SGRB does not beam towards earth. Besides directly dissipating the proto-magnetar wind as suggested by Zhang, we here suggest that the magnetar wind could push the ejecta launched during the merger process, and under certain conditions, would reach a relativistic speed. Such a magnetar-powered ejecta, when interacting with the ambient medium, would develop a bright broad-band afterglow due to synchrotron radiation. We study this physical scenario in detail, and present the predicted X-ray, optical and radio light curves for a range of magnetar and ejecta parameters. We show that the X-ray and optical lightcurves usually peak around the magnetar spindown time scale (10^3-10^5s), reaching brightness readily detectable by wide-field X-ray and optical telescopes, and remain detectable for an extended period. The radio afterglow peaks later, but is much brighter than the case without a magnetar energy injection. Therefore, such bright broad-band Afterglows, if detected and combined with GWBs in the future, would be a probe of massive millisecond magnetars and stiff equation-of-state for nuclear matter.

  • jet breaks and energetics of swift gamma ray burst x ray Afterglows
    The Astrophysical Journal, 2009
    Co-Authors: J L Racusin, Bing Zhang, T Sakamoto, D N Burrows, Enwei Liang, A Falcone, B Zhang, P A Evans, J P Osborne
    Abstract:

    We present a systematic temporal and spectral study of all Swift-X-ray Telescope observations of gamma-ray burst (GRB) Afterglows discovered between 2005 January and 2007 December. After constructing and fitting all light curves and spectra to power-law models, we classify the components of each afterglow in terms of the canonical X-ray afterglow and test them against the closure relations of the forward shock models for a variety of parameter combinations. The closure relations are used to identify potential jet breaks with characteristics including the uniform jet model with and without lateral spreading and energy injection, and a power-law structured jet model, all with a range of parameters. With this technique, we survey the X-ray Afterglows with strong evidence for jet breaks (∼12% of our sample), and reveal cases of potential jet breaks that do not appear plainly from the light curve alone (another ∼30%), leading to insight into the missing jet break problem. Those Xray light curves that do not show breaks or have breaks that are not consistent with one of the jet models are explored to place limits on the times of unseen jet breaks. The distribution of jet break times ranges from a few hours to a few weeks with a median of ∼1 day, similar to what was found pre-Swift. On average, Swift GRBs have lower isotropic equivalent γ -ray energies, which in turn result in lower collimation corrected γ -ray energies than those of pre-Swift GRBs. Finally, we explore the implications for GRB jet geometry and energetics.

  • jet breaks and energetics of swift grb x ray Afterglows
    arXiv: Astrophysics, 2008
    Co-Authors: J L Racusin, Bing Zhang, T Sakamoto, D N Burrows, Enwei Liang, A Falcone, B Zhang, P A Evans, J P Osborne
    Abstract:

    We present a systematic temporal and spectral study of all Swift-XRT observations of GRB Afterglows discovered between 2005 January and 2007 December. After constructing and fitting all light curves and spectra to power-law models, we classify the components of each afterglow in terms of the canonical X-ray afterglow and test them against the closure relations of the forward shock models for a variety of parameter combinations. The closure relations are used to identify potential jet breaks with characteristics including the uniform jet model with and without lateral spreading and energy injection, and a power-law structured jet model, all with a range of parameters. With this technique, we survey the X-ray Afterglows with strong evidence for jet breaks (~12% of our sample), and reveal cases of potential jet breaks that do not appear plainly from the light curve alone (another ~30%), leading to insight into the missing jet break problem. Those X-ray light curves that do not show breaks or have breaks that are not consistent with one of the jet models are explored to place limits on the times of unseen jet breaks. The distribution of jet break times ranges from a few hours to a few weeks with a median of ~1 day, similar to what was found pre-Swift. On average Swift GRBs have lower isotropic equivalent gamma-ray energies, which in turn results in lower collimation corrected gamma-ray energies than those of pre-Swift GRBs. Finally, we explore the implications for GRB jet geometry and energetics.

Ehud Nakar - One of the best experts on this subject based on the ideXlab platform.

  • Detectability of neutron star merger Afterglows
    Monthly Notices of the Royal Astronomical Society, 2019
    Co-Authors: Ore Gottlieb, Ehud Nakar, Tsvi Piran
    Abstract:

    VLBI and JVLA observations revealed that GW170817 involved a narrow jet ($ \theta_j \approx 4^\circ $) that dominated the afterglow peak at our viewing angle, $ \theta_{\rm obs} \approx 20^\circ $. This implies that at the time of the afterglow peak, the observed signal behaved like an afterglow of a top-hat jet seen at $ \theta_{\rm obs} \gg \theta_j $, and it can be modeled by analytic expressions that describe such jets. We use a set of numerical simulations to calibrate these analytic relations and obtain generic equations for the peak time and flux of such an afterglow as seen from various observing angles. Using the calibrated equations and the estimated parameters of GW170817, we estimate the detectability of Afterglows from future double neutron star mergers during the Advanced LIGO/Virgo observation run O3. GW170817 took place at a relatively low-density environment. Afterglows of similar events will be detectable only at small viewing angles, $ \theta_{\rm obs} \lesssim 20^\circ $, and only $\sim 20\% $ of the GW detections of these events will be accompanied by a detectable afterglow. At higher densities, more typical to sGRB sites, up to $ 70\% $ of the GW detections are expected to be followed by a detectable afterglow, typically at $ \theta_{\rm obs} \sim 30^\circ $. We also provide the latest time one should expect an afterglow detection. We find that for typical parameters, if the jet emission had not been detected within about a year after the merger, it is unlikely to be ever detected.

  • the Afterglows of swift era gamma ray bursts i comparing pre swift and swift era long soft type ii grb optical Afterglows
    The Astrophysical Journal, 2010
    Co-Authors: D A Kann, S Klose, Ehud Nakar, Nathaniel R Butler, D Malesani, A C Wilson, B B Zhang, A S Pozanenko, P Jakobsson
    Abstract:

    We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) Afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB Afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host-galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z = 1 system and compared their luminosities with a sample of pre-Swift Afterglows. The results of a former study, which showed that GRB Afterglows clustered and exhibited a bimodal distribution in luminosity space, are weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) is very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at 1 day after the GRB in the z = 1 system. A comparative study of the optical luminosities of GRB Afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without, reveals no indication that the former are statistically significantly more luminous. Furthermore, we propose the existence of an upper ceiling on afterglow luminosities and study the luminosity distribution at early times, which was not accessible before the advent of the Swift satellite. Most GRBs feature Afterglows that are dominated by the forward shock from early times on. Finally, we present the first indications of a class of long GRBs, which form a bridge between the typical high-luminosity, high-redshift events and nearby low-luminosity events (which are also associated with spectroscopic supernovae) in terms of energetics and observed redshift distribution, indicating a continuous distribution overall.

  • the Afterglows of swift era gamma ray bursts ii type i grb versus type ii grb optical Afterglows
    arXiv: Astrophysics, 2008
    Co-Authors: D A Kann, S Klose, Ehud Nakar, Bing Zhang, S Covino, Nathaniel R Butler, D Malesani, A C Wilson, L A Antonelli, G Chincarini
    Abstract:

    We use a large sample of GRB afterglow and prompt-emission data (adding further GRB afterglow observations in this work) to compare the optical Afterglows (or the lack thereof) of Type I GRBs with those of Type II GRBs. In comparison to the Afterglows of Type II GRBs, we find that those of Type I GRBs have a lower average luminosity and show an intrinsic spread of luminosities at least as wide. From late and deep upper limits on the optical transients, we establish limits on the maximum optical luminosity of any associated supernova, confirming older works and adding new results. We use deep upper limits on Type I GRB optical Afterglows to constrain the parameter space of possible mini-SN emission associated with a compact-object merger. Using the prompt emission data, we search for correlations between the parameters of the prompt emission and the late optical afterglow luminosities. We find tentative correlations between the bolometric isotropic energy release and the optical afterglow luminosity at a fixed time after trigger (positive), and between the host offset and the luminosity (negative), but no significant correlation between the isotropic energy release and the duration of the GRBs. We also discuss three anomalous GRBs, GRB 060505, GRB 060614, and GRB 060121, in the light of their optical afterglow luminosities. (Abridged)

  • the Afterglows of swift era gamma ray bursts i comparing pre swift and swift era long soft type ii grb optical Afterglows
    arXiv: Astrophysics, 2007
    Co-Authors: D A Kann, S Klose, Ehud Nakar, Nathaniel R Butler, D Malesani, A C Wilson, B B Zhang, A S Pozanenko, P Jakobsson
    Abstract:

    We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) Afterglows including GRBs up to September 2009, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB Afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z=1 system and compared their luminosities with a sample of pre-Swift Afterglows. The results of a former study, which showed that GRB Afterglows clustered and exhibited a bimodal distribution in luminosity space, is weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) are very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at one day after the GRB in the z=1 system. A comparative study of the optical luminosities of GRB Afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without reveals no indication that the former are statistically significantly more luminous. (abridged)

  • smooth light curves from a bumpy ride relativistic blast wave encounters a density jump
    Monthly Notices of the Royal Astronomical Society, 2007
    Co-Authors: Ehud Nakar, Jonathan Granot
    Abstract:

    In the standard forward shock model for gamma-ray burst (GRB) afterglow, the observed afterglow emission is synchrotron radiation from a quasi-spherical, adiabatic, self-similar, relativistic blast wave, that propagates into the external medium. This model predicts a smooth light curve where the flux scales as a power law in time, and may at most smoothly transition to a different power law. However, some GRB afterglow light curves show significant variability, which often includes episodes of rebrightening. Such temporal variability had been attributed in several cases to a large enhancement in the external density, or a density 'bump', that is encountered by the self-similar adiabatic blast wave. Here we examine the effect of a sharp increase in the external density on the afterglow light curve in this scenario by considering, for the first time, a full treatment of both the hydrodynamic evolution and the radiation. To this end we develop a semi-analytic model for the light curve and carry out numerical simulations using a one-dimensional hydrodynamic code together with a synchrotron radiation code. Two spherically symmetric cases are explored in detail - a density jump in a uniform external medium (which is used to constrain the effect of a density clump) and a wind termination shock. We find that even a very sharp (modelled as a step function) and large (by a factor of a > 1) increase in the external density does not produce sharp features in the light curve, and cannot account for significant temporal variability in GRB Afterglows in the forward shock model. For a wind termination shock, the light curve smoothly transitions between the asymptotic power laws over about one decade in time, and there is no rebrightening in the optical or X-rays that could serve as a clear observational signature. For a sharp jump in a uniform density profile, we find that the maximal deviation Delta alpha(max) of the temporal decay index alpha from its asymptotic value (at early and late times) is bounded (e.g, Delta alpha(max) < 0.4 for a = 10); Delta alpha(max) slowly increases with a, converging to Delta alpha(max) approximate to 1 at very large a values. Therefore, no optical rebrightening is expected in this case as well. In the X-rays, while the asymptotic flux is unaffected by the density jump, the fluctuations in alpha are found to be comparable to those in the optical. Finally, we discuss the implications of our results for the origin of the observed fluctuations in several GRB Afterglows.

D A Kann - One of the best experts on this subject based on the ideXlab platform.

  • the seds and host galaxies of the dustiest grb Afterglows
    Astronomy and Astrophysics, 2011
    Co-Authors: T Kruhler, J Greiner, P Schady, S Savaglio, P Afonso, C Clemens, J Elliot, R Filgas, D Gruber, D A Kann
    Abstract:

    Context. The Afterglows and host galaxies of long gamma-ray bursts (GRBs) offer unique opportunities to study star-forming galaxies in the high-z Universe. Until recently, however, the information inferred from GRB follow-up observations was mostly limited to optically bright Afterglows, biasing all demographic studies against sight-lines that contain large amounts of dust. Aims. Here we present afterglow and host observations for a sample of bursts that are exemplary of previously missed ones because of high visual extinction (A GRB 1 mag) along the sight-line. This facilitates an investigation of the properties, geometry, and location of the absorbing dust of these poorly-explored host galaxies, and a comparison to hosts from optically-selected samples. Methods. This work is based on GROND optical/NIR and Swift/XRT X-ray observations of the Afterglows, and multi-color imaging for eight GRB hosts. The afterglow and galaxy spectral energy distributions yield detailed insight into physical properties such as the dust and metal content along the GRB sight-line and galaxy-integrated characteristics such as the host’s stellar mass, luminosity, color-excess, and star-formation rate. Results. For the eight Afterglows considered in this study, we report for the first time the redshift of GRB 081109 (z = 0.9787±0.0005), and the visual extinction towards GRBs 081109 (A GRB = 3.4 +0.4 −0.3 mag) and 100621A (A GRB V = 3.8 ± 0.2 mag), which are among the largest ever derived for GRB Afterglows. Combined with non-extinguished GRBs, there is a strong anti-correlation between the afterglow’s metal-to-dust ratio and visual extinction. The hosts of the dustiest Afterglows are diverse in their properties, but on average redder (� (R − K)AB �∼ 1.6 mag), more luminous (� L �∼ 0.9L ∗ ), and massive (� log M∗[M� ] �∼ 9.8) than the hosts of optically-bright events. Hence, we probe a different galaxy population, suggesting that previous host samples miss most of the massive and metal-rich members. This also indicates that the dust along the sight-line is often related to host properties, and thus probably located in the diffuse ISM or interstellar clouds and not in the immediate GRB environment. Some of the hosts in our sample, are blue, young, or of low stellar mass illustrating that even apparently non-extinguished galaxies possess very dusty sight-lines owing to a patchy dust distribution. Conclusions. The Afterglows and host galaxies of the dustiest GRBs provide evidence of a complex dust geometry in star-forming galaxies. In addition, they establish a population of luminous, massive, and correspondingly chemically evolved GRB hosts. This suggests that GRBs trace the global star-formation rate better than studies based on optically selected host samples indicate, and that the previously claimed deficiency of high-mass hosts was at least partially a selection effect.

  • the Afterglows of swift era gamma ray bursts i comparing pre swift and swift era long soft type ii grb optical Afterglows
    The Astrophysical Journal, 2010
    Co-Authors: D A Kann, S Klose, Ehud Nakar, Nathaniel R Butler, D Malesani, A C Wilson, B B Zhang, A S Pozanenko, P Jakobsson
    Abstract:

    We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) Afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB Afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host-galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z = 1 system and compared their luminosities with a sample of pre-Swift Afterglows. The results of a former study, which showed that GRB Afterglows clustered and exhibited a bimodal distribution in luminosity space, are weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) is very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at 1 day after the GRB in the z = 1 system. A comparative study of the optical luminosities of GRB Afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without, reveals no indication that the former are statistically significantly more luminous. Furthermore, we propose the existence of an upper ceiling on afterglow luminosities and study the luminosity distribution at early times, which was not accessible before the advent of the Swift satellite. Most GRBs feature Afterglows that are dominated by the forward shock from early times on. Finally, we present the first indications of a class of long GRBs, which form a bridge between the typical high-luminosity, high-redshift events and nearby low-luminosity events (which are also associated with spectroscopic supernovae) in terms of energetics and observed redshift distribution, indicating a continuous distribution overall.

  • on dust extinction of gamma ray burst host galaxies
    The Astrophysical Journal, 2008
    Co-Authors: Aigen Li, S L Liang, D A Kann, S Klose, Y J Wang
    Abstract:

    Although it is well recognized that gamma-ray burst (GRB) Afterglows are obscured and reddened by dust in their host galaxies, the wavelength dependence and quantity of dust extinction are still poorly known. Current studies on this mostly rely on fitting the afterglow spectral energy distributions (SEDs) with template extinction models. The inferred extinction (both quantity and wavelength dependence) and dust-to-gas ratios are often in disagreement with that obtained from dust depletion and X-ray spectroscopy studies. We argue that this discrepancy could result from the prior assumption of a template extinction law. We propose an analytical formula to approximate the GRB host extinction law. With the template extinction laws self-contained, and the capability of revealing extinction laws differing from the conventional ones, it is shown that this is a powerful approach in modeling the afterglow SEDs to derive GRB host extinction.

  • the Afterglows of swift era gamma ray bursts ii type i grb versus type ii grb optical Afterglows
    arXiv: Astrophysics, 2008
    Co-Authors: D A Kann, S Klose, Ehud Nakar, Bing Zhang, S Covino, Nathaniel R Butler, D Malesani, A C Wilson, L A Antonelli, G Chincarini
    Abstract:

    We use a large sample of GRB afterglow and prompt-emission data (adding further GRB afterglow observations in this work) to compare the optical Afterglows (or the lack thereof) of Type I GRBs with those of Type II GRBs. In comparison to the Afterglows of Type II GRBs, we find that those of Type I GRBs have a lower average luminosity and show an intrinsic spread of luminosities at least as wide. From late and deep upper limits on the optical transients, we establish limits on the maximum optical luminosity of any associated supernova, confirming older works and adding new results. We use deep upper limits on Type I GRB optical Afterglows to constrain the parameter space of possible mini-SN emission associated with a compact-object merger. Using the prompt emission data, we search for correlations between the parameters of the prompt emission and the late optical afterglow luminosities. We find tentative correlations between the bolometric isotropic energy release and the optical afterglow luminosity at a fixed time after trigger (positive), and between the host offset and the luminosity (negative), but no significant correlation between the isotropic energy release and the duration of the GRBs. We also discuss three anomalous GRBs, GRB 060505, GRB 060614, and GRB 060121, in the light of their optical afterglow luminosities. (Abridged)

  • the Afterglows of swift era gamma ray bursts i comparing pre swift and swift era long soft type ii grb optical Afterglows
    arXiv: Astrophysics, 2007
    Co-Authors: D A Kann, S Klose, Ehud Nakar, Nathaniel R Butler, D Malesani, A C Wilson, B B Zhang, A S Pozanenko, P Jakobsson
    Abstract:

    We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) Afterglows including GRBs up to September 2009, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB Afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z=1 system and compared their luminosities with a sample of pre-Swift Afterglows. The results of a former study, which showed that GRB Afterglows clustered and exhibited a bimodal distribution in luminosity space, is weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) are very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at one day after the GRB in the z=1 system. A comparative study of the optical luminosities of GRB Afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without reveals no indication that the former are statistically significantly more luminous. (abridged)

P Jakobsson - One of the best experts on this subject based on the ideXlab platform.

  • the properties of the 2175 a extinction feature discovered in grb Afterglows
    The Astrophysical Journal, 2012
    Co-Authors: P Jakobsson, G Leloudas, D Watson, J P U Fynbo, T Kruhler, P Schady, T Zafar, Ardis Eliasdottir, C C Thone
    Abstract:

    The unequivocal, spectroscopic detection of the 2175?? bump in extinction curves outside the Local Group is rare. To date, the properties of the bump have been examined in only two gamma-ray burst (GRB) Afterglows (GRB?070802 and GRB?080607). In this work, we analyze in detail the detections of the 2175?? extinction bump in the optical spectra of two further GRB Afterglows: GRB?080605 and 080805. We gather all available optical/near-infrared photometric, spectroscopic, and X-ray data to construct multi-epoch spectral energy distributions (SEDs) for both GRB Afterglows. We fit the SEDs with the Fitzpatrick & Massa model with a single or broken power law. We also fit a sample of 38 GRB Afterglows, known to prefer a Small Magellanic Cloud (SMC)-type extinction curve, with the same model. We find that the SEDs of GRB?080605 and GRB?080805 at two epochs are fit well with a single power law with a derived extinction of AV = 0.52+0.13 ? 0.16 and 0.50+0.13 ? 0.10, and 2.1+0.7 ? 0.6 and 1.5 ? 0.2, respectively. While the slope of the extinction curve of GRB?080805 is not well constrained, the extinction curve of GRB?080605 has an unusual very steep far-UV rise together with the 2175?? bump. Such an extinction curve has previously been found in only a small handful of sightlines in the Milky Way. One possible explanation of such an extinction curve may be dust arising from two different regions with two separate grain populations, however we cannot distinguish the origin of the curve. We finally compare the four 2175?? bump sightlines to the larger GRB afterglow sample and to Local Group sightlines. We find that while the width and central positions of the bumps are consistent with what is observed in the Local Group, the relative strength of the detected bump (A bump) for GRB Afterglows is weaker for a given AV than for almost any Local Group sightline. Such dilution of the bump strength may offer tentative support to a dual dust-population scenario.

  • the Afterglows of swift era gamma ray bursts i comparing pre swift and swift era long soft type ii grb optical Afterglows
    The Astrophysical Journal, 2010
    Co-Authors: D A Kann, S Klose, Ehud Nakar, Nathaniel R Butler, D Malesani, A C Wilson, B B Zhang, A S Pozanenko, P Jakobsson
    Abstract:

    We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) Afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB Afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host-galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z = 1 system and compared their luminosities with a sample of pre-Swift Afterglows. The results of a former study, which showed that GRB Afterglows clustered and exhibited a bimodal distribution in luminosity space, are weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) is very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at 1 day after the GRB in the z = 1 system. A comparative study of the optical luminosities of GRB Afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without, reveals no indication that the former are statistically significantly more luminous. Furthermore, we propose the existence of an upper ceiling on afterglow luminosities and study the luminosity distribution at early times, which was not accessible before the advent of the Swift satellite. Most GRBs feature Afterglows that are dominated by the forward shock from early times on. Finally, we present the first indications of a class of long GRBs, which form a bridge between the typical high-luminosity, high-redshift events and nearby low-luminosity events (which are also associated with spectroscopic supernovae) in terms of energetics and observed redshift distribution, indicating a continuous distribution overall.

  • the Afterglows of swift era gamma ray bursts i comparing pre swift and swift era long soft type ii grb optical Afterglows
    arXiv: Astrophysics, 2007
    Co-Authors: D A Kann, S Klose, Ehud Nakar, Nathaniel R Butler, D Malesani, A C Wilson, B B Zhang, A S Pozanenko, P Jakobsson
    Abstract:

    We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) Afterglows including GRBs up to September 2009, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB Afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z=1 system and compared their luminosities with a sample of pre-Swift Afterglows. The results of a former study, which showed that GRB Afterglows clustered and exhibited a bimodal distribution in luminosity space, is weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) are very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at one day after the GRB in the z=1 system. A comparative study of the optical luminosities of GRB Afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without reveals no indication that the former are statistically significantly more luminous. (abridged)

  • the optical afterglow of the short gamma ray burst grb 050709
    Nature, 2005
    Co-Authors: J Hjorth, P Jakobsson, D Watson, J P U Fynbo, P A Price, B L Jensen, U G Jorgensen, D Kubas, J Gorosabel, J Sollerman
    Abstract:

    It has long been known that there are two classes of gamma-ray bursts (GRBs), mainly distinguished by their durations. The breakthrough in our understanding of long-duration GRBs (those lasting more than approximately 2 s), which ultimately linked them with energetic type Ic supernovae, came from the discovery of their long-lived X-ray and optical 'Afterglows', when precise and rapid localizations of the sources could finally be obtained. X-ray localizations have recently become available for short (duration <2 s) GRBs, which have evaded optical detection for more than 30 years. Here we report the first discovery of transient optical emission (R-band magnitude approximately 23) associated with a short burst: GRB 050709. The optical afterglow was localized with subarcsecond accuracy, and lies in the outskirts of a blue dwarf galaxy. The optical and X-ray afterglow properties 34 h after the GRB are reminiscent of the Afterglows of long GRBs, which are attributable to synchrotron emission from ultrarelativistic ejecta. We did not, however, detect a supernova, as found in most nearby long GRB Afterglows, which suggests a different origin for the short GRBs.

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  • Detectability of neutron star merger Afterglows
    Monthly Notices of the Royal Astronomical Society, 2019
    Co-Authors: Ore Gottlieb, Ehud Nakar, Tsvi Piran
    Abstract:

    VLBI and JVLA observations revealed that GW170817 involved a narrow jet ($ \theta_j \approx 4^\circ $) that dominated the afterglow peak at our viewing angle, $ \theta_{\rm obs} \approx 20^\circ $. This implies that at the time of the afterglow peak, the observed signal behaved like an afterglow of a top-hat jet seen at $ \theta_{\rm obs} \gg \theta_j $, and it can be modeled by analytic expressions that describe such jets. We use a set of numerical simulations to calibrate these analytic relations and obtain generic equations for the peak time and flux of such an afterglow as seen from various observing angles. Using the calibrated equations and the estimated parameters of GW170817, we estimate the detectability of Afterglows from future double neutron star mergers during the Advanced LIGO/Virgo observation run O3. GW170817 took place at a relatively low-density environment. Afterglows of similar events will be detectable only at small viewing angles, $ \theta_{\rm obs} \lesssim 20^\circ $, and only $\sim 20\% $ of the GW detections of these events will be accompanied by a detectable afterglow. At higher densities, more typical to sGRB sites, up to $ 70\% $ of the GW detections are expected to be followed by a detectable afterglow, typically at $ \theta_{\rm obs} \sim 30^\circ $. We also provide the latest time one should expect an afterglow detection. We find that for typical parameters, if the jet emission had not been detected within about a year after the merger, it is unlikely to be ever detected.

  • high energy afterglow emission from gamma ray bursts
    2013
    Co-Authors: Ramesh Narayan, Tsvi Piran, Yizhong Fan, Daming Wei
    Abstract:

    We calculate the very high energy (sub-GeV to TeV) inverse Compton emission of GRB Afterglows. We argue that this emission provides a powerful test of the currently accepted afterglow model. We focus on two processes: synchrotron self-Compton (SSC) emission within the afterglow blast wave, and external inverse Compton (EIC) emission which occurs when flare photons (produced by an internal process) pass through the blast wave. We show that if our current interpretations of the Swift XRT data are correct, there should be a canonical high energy afterglow emission light curve. Our predictions can be tested with high energy observatories such as GLAST, Whipple, H.E.S.S. and MAGIC. Under favorable conditions we expect afterglow detections in all these detectors.

  • high energy afterglow emission from gamma ray bursts
    Monthly Notices of the Royal Astronomical Society, 2008
    Co-Authors: Ramesh Narayan, Tsvi Piran, Yizhong Fan, Daming Wei
    Abstract:

    We calculate the very high-energy (sub-GeV to TeV) inverse Compton emission of GRB Afterglows. We argue that this emission provides a powerful test of the currently accepted afterglow model. We focus on two processes: synchrotron self-Compton emission within the afterglow blast wave, and external inverse Compton emission which occurs when flare photons (produced by an internal process) pass through the blast wave. We show that if our current interpretations of the Swift X-ray telescope (XRT) data are correct, there should be a canonical high-energy afterglow emission light curve. Our predictions can be tested with high-energy observatories such as GLAST, Whipple, HESS and MAGIC. Under favourable conditions we expect afterglow detections in all these detectors.

  • the afterglow of grb 050709 and the nature of the short hard γ ray bursts
    Nature, 2005
    Co-Authors: Tsvi Piran, D A Frail, S R Kulkarni, P A Price, A M Soderberg, E Berger, D B Fox, S B Cenko
    Abstract:

    The final chapter in the long-standing mystery of the γ-ray bursts (GRBs) centres on the origin of the short-hard class of bursts, which are suspected on theoretical grounds to result from the coalescence of neutron-star or black-hole binary systems. Numerous searches for the Afterglows of short-hard bursts have been made, galvanized by the revolution in our understanding of long-duration GRBs that followed the discovery in 1997 of their broadband (X-ray, optical and radio) afterglow emission. Here we present the discovery of the X-ray afterglow of a short-hard burst, GRB 050709, whose accurate position allows us to associate it unambiguously with a star-forming galaxy at redshift z = 0.160, and whose optical lightcurve definitively excludes a supernova association. Together with results from three other recent short-hard bursts, this suggests that short-hard bursts release much less energy than the long-duration GRBs. Models requiring young stellar populations, such as magnetars and collapsars, are ruled out, while coalescing degenerate binaries remain the most promising progenitor candidates.

  • the physics of gamma ray bursts
    Reviews of Modern Physics, 2005
    Co-Authors: Tsvi Piran
    Abstract:

    Gamma-ray bursts (GRB's), short and intense pulses of low-energy $\ensuremath{\gamma}$ rays, have fascinated astronomers and astrophysicists since their unexpected discovery in the late sixties. During the last decade, several space missions---BATSE (Burst and Transient Source Experiment) on the Compton Gamma-Ray Observatory, BeppoSAX and now HETE II (High-Energy Transient Explorer)---together with ground-based optical, infrared, and radio observatories have revolutionized our understanding of GRB's, showing that they are cosmological, that they are accompanied by long-lasting Afterglows, and that they are associated with core-collapse supernovae. At the same time a theoretical understanding has emerged in the form of the fireball internal-external shocks model. According to this model GRB's are produced when the kinetic energy of an ultrarelativistic flow is dissipated in internal collisions. The afterglow arises when the flow is slowed down by shocks with the surrounding circumburst matter. This model has had numerous successful predictions, like the predictions of the afterglow itself, of jet breaks in the afterglow light curve, and of the optical flash that accompanies the GRB's. This review focuses on the current theoretical understanding of the physical processes believed to take place in GRB's.