伽玛暴(Gamma-Ray Burst)笔记。记录有关伽玛暴的新文章,另外也包括看的老文章、自己的想法、以及跟天文相关的一些东西。 Feel free to leave me a message by comments or by email.

星期二, 十一月 30, 2010

Carballido 2010 磁化的中微子冷却盘可能是伽马暴的能源机制

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Title:
Characterizing the time variability in magnetized neutrino--cooled accretion disks: signatures of the gamma-ray burst central engine
Authors:
Carballido, Augusto; Lee, William H.
Publication:
eprint arXiv:1011.5515
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - High Energy Astrophysical Phenomena
Comment:
Accepted for publication in ApJ Letters
Bibliographic Code:
2010arXiv1011.5515C

Abstract

The central engine of Gamma Ray Bursts is hidden from direct probing with photons mainly due to the high densities involved. Inferences on their properties are thus made from their cosmological setting, energetics, low-energy counterparts and variability. If GRBs are powered by hypercritical accretion onto compact objects, on small spatial scales the flow will exhibit fluctuations, which could in principle be reflected in the power output of the central engine and ultimately in the high energy prompt emission. Here we address this issue by characterizing the variability in neutrino cooled accretion flows through local shearing box simulations with magnetic fields, and then convolving them on a global scale with large scale dynamical simulations of accretion disks. The resulting signature is characteristic, and sensitive to the details of the cooling mechanism, providing in principle a discriminant for GRB central engine properties.
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Pignata 2010 Ic型超新星 SN 2009bb的观测

主要内容:
没看到对应的伽马暴,文章说排除了伽马暴喷流指向大角度(说不定可以呢?)。

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Title:
SN 2009bb: a Peculiar Broad-Lined Type Ic Supernova
Authors:
Pignata, Giuliano; Stritzinger, Maximilian; Soderberg, Alicia; Mazzali, Paolo; Phillips, M. M.; Morrell, Nidia; Anderson, J. P.; Boldt, Luis; Campillay, Abdo; Contreras, Carlos; Folatelli, Gastón; Förster, Francisco; González, Sergio; Hamuy, Mario; Krzeminski, Wojtek; Maza, José; Roth, Miguel; Levesque, Francisco Salgado Emily M.; Rest, Armin; Crain, J. Adam; Foster, Andrew C.; Haislip, Joshua B.; Ivarsen, Kevin M.; LaCluyze, Aaron P.; Nysewander, Melissa C.; Reichart, Daniel E.
Publication:
eprint arXiv:1011.6126
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - Solar and Stellar Astrophysics
Comment:
Accepted for publication in ApJ
Bibliographic Code:
2010arXiv1011.6126P

Abstract

Ultraviolet, optical, and near-infrared photometry and optical spectroscopy of the broad-lined Type Ic supernova (SN) 2009bb are presented, following the flux evolution from -10 to +285 days past B-band maximum. Thanks to the very early discovery, it is possible to place tight constraints on the SN explosion epoch. The expansion velocities measured from near maximum spectra are found to be only slightly smaller than those measured from spectra of the prototype broad-lined SN 1998bw associated with GRB 980425. Fitting an analytical model to the pseudo-bolometric light curve of SN 2009bb suggests that 4.1+-1.9 Msun of material was ejected with 0.22 +-0.06 Msun of it being 56Ni. The resulting kinetic energy is 1.8+-0.7x10^52 erg. This, together with an absolute peak magnitude of MB=-18.36+-0.44, places SN 2009bb on the energetic and luminous end of the broad-lined Type Ic (SN Ic) sequence. Detection of helium in the early time optical spectra accompanied with strong radio emission, and high metallicity of its environment makes SN 2009bb a peculiar object. Similar to the case for GRBs, we find that the bulk explosion parameters of SN 2009bb cannot account for the copious energy coupled to relativistic ejecta, and conclude that another energy reservoir (a central engine) is required to power the radio emission. Nevertheless, the analysis of the SN 2009bb nebular spectrum suggests that the failed GRB detection is not imputable to a large angle between the line-of-sight and the GRB beamed radiation. Therefore, if a GRB was produced during the SN 2009bb explosion, it was below the threshold of the current generation of gamma-ray instruments.
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Beloborodov 2010 极端相对论外流在光球层的辐射转移

主要内容:
分物质为主和辐射为主两种情形。

应该是辐射转移的一个很好的应用的例子。

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Title:
Radiative transfer in ultra-relativistic outflows and photospheres of gamma-ray bursts
Authors:
, Andrei M.
Publication:
eprint arXiv:1011.6005
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - High Energy Astrophysical Phenomena
Comment:
13 pages, 8 figures, submitted to ApJ
Bibliographic Code:
2010arXiv1011.6005B

Abstract

Emission of gamma-ray bursts involves radiative transfer in ultra-relativistic jets. The corresponding transfer equation is solved. The solution describes the initial trapping of radiation in the opaque outflow, its adiabatic cooling, and the transition to transparency. Two opposite regimes are examined: (1) Baryon-dominated outflow. Surprisingly, radiation develops enormous anisotropy in the fluid frame before decoupling from the fluid. The radiation is strongly polarized. (2) Radiation-dominated outflow. The transfer occurs as if radiation propagated in vacuum, preserving the angular distribution and the blackbody shape of the spectrum. The observed photospheric spectrum is blackbody if (and only if) the outflow energy is dominated by radiation up to the photospheric radius.
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Inoue 2010 三维的MHD数值模拟伽马暴的激波

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Title:
Three-Dimensional Simulations of MHD Turbulence Behind Relativistic Shock Waves and Their Implications for GRBs
Authors:
Inoue, Tsuyoshi; Asano, Katsuaki; Ioka, Kunihito
Publication:
eprint arXiv:1011.6350
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - High Energy Astrophysical Phenomena
Comment:
13 pages, 12 figures. Submitted to ApJ
Bibliographic Code:
2010arXiv1011.6350I

Abstract

Relativistic astrophysical phenomena such as gamma-ray bursts (GRBs) and active galactic nuclei often require long-lived strong magnetic field that cannot be achieved by shock compression alone. Here, we report on three-dimensional special-relativistic magnetohydrodynamic (MHD) simulations that we performed using a second-order Godunov-type conservative code, to explore the amplification and decay of macroscopic turbulence dynamo excited by the so-called Richtmyer-Meshkov instability (RMI; a Rayleigh-Taylor type instability). This instability is an inevitable outcome of interactions between shock and ambient density fluctuations. We find that the magnetic energy grows exponentially in a few eddy turnover times, because of field-line stretching, and then, following the decay of kinetic turbulence, decays with a temporal power-law exponent of -0.7. The magnetic-energy fraction can reach $epsilon_B \sim$ 0.1 but depends on the initial magnetic field strength, which can diversify the observed phenomena. We find that the magnetic energy grows by at least two orders of magnitude compared to the magnetic energy immediately behind the shock. This minimum degree of the amplification does not depend on the amplitude of the initial density fluctuations, while the growth timescale and the maximum magnetic energy depend on the degree of inhomogeneity in the density. The transition from Kolmogorov cascade to MHD critical balance cascade occurs at $\sim$ 1/10th the initial inhomogeneity scale, which limits the maximum synchrotron polarization to less than 2%. New results include the avoidance of electron cooling with RMI turbulence, the turbulent photosphere model via RMI, the shallow decay of the early afterglow from RMI, and the impossibility of the relativistic turbulent model by Narayan & Kumar because of fast shock dissipation.
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星期五, 十一月 26, 2010

Drout 2010 Ibc型超新星的多波段光变统计

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Title:
The First Systematic Study of Type Ibc Supernova Multi-color Light-curves
Authors:
Drout, Maria R.; Soderberg, Alicia M.; Gal-Yam, A.; Cenko, S. B.; Fox, D. B.; Leonard, D. C.; Sand, D. J.; Moon, D. -S.; Arcavi, I.; Green, Y.
Publication:
eprint arXiv:1011.4959
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:
43 pages, 23 figures, 6 tables, submitted to ApJ. High resolution figures and light-curves available at http://www.cfa.harvard.edu/~asoderberg/SNeIbc
Bibliographic Code:
2010arXiv1011.4959D

Abstract

We present detailed optical photometry for 25 Type Ibc supernovae within d~150 Mpc obtained with the robotic Palomar 60-inch telescope in 2004-2007. This study represents the first uniform, systematic, and statistical sample of multi-color SNe Ibc light-curves available to date. We correct the light-curves for host galaxy extinction using a new technique based on the photometric color evolution, namely, we show that the (V-R) color of extinction-corrected SNe Ibc at t~10 days after V-band maximum is tightly distributed, (V-R)=0.26+-0.06 mag. Using this technique, we find that SNe Ibc typically suffer from significant host galaxy extinction, E(B-V)~0.4 mag. A comparison of the extinction-corrected light-curves for SNe Ib and Ic reveals that they are statistically indistinguishable, both in luminosity and decline rate. We report peak absolute magnitudes of M_R=-17.9+-0.9 mag and M_R=-18.3+-0.6 mag for SNe Ib and Ic, respectively. Focusing on the broad-lined SNe Ic, we find that they are more luminous than the normal SNe Ibc sample, M_R=-19.0+-1.1 mag, with a probability of only 1.6% that they are drawn from the same population of explosions. By comparing the peak absolute magnitudes of SNe Ic-BL with those inferred for local engine-driven explosions (GRB-SN 1998bw, XRF-SN 2006aj, and SN2009bb) we find a 25% probability that they are drawn from the SNe Ic-BL population. Finally, we fit analytic models to the light-curves to derive typical Ni-56 masses of M_Ni ~0.2 and 0.5 M_sun for SNe Ibc and SNe Ic-BL, respectively. With reasonable assumptions for the photospheric velocities, we extract kinetic energy and ejecta mass values of M_ej ~ 2 M_sun and E_K~1e+51 erg for SNe Ibc, while for SNe Ic-BL we find higher values, M_ej~5~M_sun and E_K~1e+52 erg. We discuss the implications for the progenitors of SNe Ibc and their relation to engine-driven explosions [ABRIDGED].
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Karg 2010 IceCube的初期结果

主要内容:
仪器快要完工了
已经观测到了2万个中微子了。

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Title:
The IceCube neutrino observatory: Status and initial results
Authors:
Karg, Timo; for the IceCube Collaboration
Publication:
eprint arXiv:1011.5027
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - High Energy Astrophysical Phenomena
Comment:
Proceedings of ECRS 2010, Turku, Finland, August 2010
Bibliographic Code:
2010arXiv1011.5027K

Abstract

The IceCube collaboration is building a cubic kilometer scale neutrino telescope at a depth of 2 km at the geographic South Pole, utilizing the clear Antarctic ice as a Cherenkov medium to detect cosmic neutrinos. The IceCube observatory is complemented by IceTop, a square kilometer air shower array on top of the in-ice detector. The construction of the detector is nearly finished with 79 of a planned 86 strings and 73 of 80 IceTop stations deployed. Its completion is expected in the winter 2010/11. Using data from the partially built detector, we present initial results of searches for neutrinos from astrophysical sources such as supernova remnants, active galactic nuclei, and gamma ray bursts, for anisotropies in cosmic rays, and constraints on the dark matter scattering cross section. Further, we discuss future plans and R&D activities towards new neutrino detection techniques.
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Thompson 2010 一个三星系统产生超新星、伽马暴等的爆发的机制

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Title:
Accelerating Compact Object Mergers in Triple Systems with the Kozai Resonance: A Mechanism for "Prompt'' Type Ia Supernovae, Gamma-Ray Bursts, and Other Exotica
Authors:
Thompson, Todd A.
Publication:
eprint arXiv:1011.4322
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:
13 pages, submitted to ApJ
Bibliographic Code:
2010arXiv1011.4322T

Abstract

The mechanism of Type Ia supernovae and gamma-ray bursts (GRBs) is unknown, but a subset of both may be due to white dwarf-white dwarf (WD-WD) and neutron star-neutron star (NS-NS) mergers, respectively. A general problem with this picture is the production of binaries with semi-major axes small enough to merge via gravitational wave (GW) emission in significantly less than the Hubble time (t_H), and thus accommodate the observation that these events closely follow episodes of star formation in time. I explore the possibility that such systems are not binaries at all, but actually coeval, or dynamical formed, hierarchical triple systems. The tertiary induces Kozai oscillations in the inner binary, driving it to high eccentricity, and dramatically reducing its GW merger timescale. This effect significantly increases the allowed range of binary period P such that the merger time is t_merge < t_H. I find that Chandrasehkar mass binaries with P as large as ~300 days can in fact merge in < t_H if they contain a prograde solar-mass tertiary at high enough inclination. For systems with retrograde tertiaries, the allowed range of P such that t_merge < t_H is yet larger. In contrast, P < 0.3 days is required in the absence of a tertiary. I discuss implications of these findings for the production of Ia supernovae via WD-WD mergers, as well as GRBs formed via binary mergers composed of NSs, black holes, and WDs. Based on the statistics of solar-type binaries, I argue that nearly many tight WD-WD binaries should be in triple systems affected by the Kozai resonance. In analogy, the tightest NS-NS binaries may also have formed in triples. If true, expectations for the mHz GW signal from individual sources, the diffuse background, and the foreground for GW experiments like LISA are modified. This work motivates future studies of the triple fraction of intermediate mass A/B stars and massive O stars.
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Mannucci 2010 长暴的宿主星系的金属丰度和低质量星系的金属丰度

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Title:
The metallicity of the long GRB hosts and the Fundamental Metallicity Relation of low-mass galaxies
Authors:
Mannucci, F.; Salvaterra, R.; Campisi, M. A.
Publication:
eprint arXiv:1011.4506
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:
6 pages, submitted to MNRAS
Bibliographic Code:
2010arXiv1011.4506M

Abstract

We investigate the metallicity properties of host galaxies of long Gamma-ray Bursts (GRBs) in the light of the Fundamental Metallicity Relation (FMR), the tight dependence of metallicity on mass and SFR recently discovered for SDSS galaxies with stellar masses above 10^9.2 Msun. As most of the GRB hosts have masses below this limit, the FMR can only be used after an extension towards lower masses. At this aim, we study the FMR for galaxies with masses down to ~10^8.3 Msun, finding that the FMR does extend smoothly at lower masses, albeit with a much larger scatter. We then compare the resulting FMR with the metallicity properties of 18 host galaxies of long GRBs. While the GRB hosts show a systematic offset with respect to the mass-metallicity relation, they are fully consistent with the FMR. This shows that the difference with the mass-metallicity relation is due to higher than average SFRs, and that GRBs do not preferentially select low-metallicity hosts among the star-forming galaxies. The apparent low metallicity is therefore a consequence of the occurrence of long GRB in low mass, actively star-forming galaxies, known to dominate the current cosmic SFR.
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Ukwatta 2010 一个新的长暴的频率和光度的关系

主要内容:
功率密度谱的频率和光度的关系,也不致密。

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Title:
A New Frequency-Luminosity Relation for Long GRBs?
Authors:
Ukwatta, T. N.; Dhuga, K. S.; Morris, D. C.; MacLachlan, G.; Parke, W. C.; Maximon, L. C.; Eskandarian, A.; Gehrels, N.; Norris, J. P.; Shenoy, A.
Publication:
eprint arXiv:1011.4342
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - High Energy Astrophysical Phenomena
Comment:
9 pages, 17 figures, 1 table; Accepted for publication in MNRAS
Bibliographic Code:
2010arXiv1011.4342U

Abstract

We have studied power density spectra (PDS) of 206 long Gamma-Ray Bursts (GRBs). We fitted the PDS with a simple power-law and extracted the exponent of the power-law (alpha) and the noise-crossing threshold frequency (f_th). We find that the distribution of the extracted alpha peaks around -1.4 and that of f_th around 1 Hz. In addition, based on a sub-set of 58 bursts with known redshifts, we show that the redshift-corrected threshold frequency is positively correlated with the isotropic peak luminosity. The correlation coefficient is 0.57 +/- 0.03.
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De Cia 2010 GRB 080210的余辉观测

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Title:
Probing GRB environments with time variability: ULTRASPEC fast imaging of GRB 080210
Authors:
De Cia, A.; Jakobsson, P.; Björnsson, G.; Vreeswijk, P. M.; Dhillon, V. S.; Marsh, T. R.; Chapman, R.; Fynbo, J. P. U.; Ledoux, C.; Littlefair, S. P.; Malesani, D.; Schulze, S.; Smette, A.; Zafar, T.; Gudmundsson, E. H.
Publication:
eprint arXiv:1011.4239
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:
14 pages, 8 figures; accepted for publication in MNRAS
Bibliographic Code:
2010arXiv1011.4239D

Abstract

We present high time resolution (1.09 s) photometry of GRB 080210 obtained with ULTRASPEC mounted on the ESO/3.6-m telescope, starting 68.22 min after the burst and lasting for 26.45 min. The light curve is smooth on both short (down to 2.18 s) and long time scales, confirmed by a featureless power spectrum. On top of the fireball power-law decay, bumps and wiggles at different time scales can, in principle, be produced by density fluctuations in the circumburst medium, substructures in the jet or by refreshed shocks. Comparing our constraints with variability limits derived from kinematic arguments, we exclude under-density fluctuations producing flux dips larger than 1 per cent with time scales \Deltat > 9.2 min (2 per cent on \Deltat > 2.3 min for many fluctuating regions). In addition, we study the afterglow VLT/FORS2 spectrum, the optical-to-X-ray spectral energy distribution (SED) and the time decay. The SED is best fit with a broken power law with slopes {\beta}opt = 0.71 \pm 0.01 and {\beta}X = 1.59 \pm 0.07, in disagreement with the fireball model, suggesting a non-standard afterglow for GRB 080210. We find AV = 0.18 \pm 0.03 mag optical extinction due to SMC-like dust and an excess X-ray absorption of log (NH/cm-2) = 21.58 +0.18 -0.26 assuming Solar abundances. The spectral analysis reveals a damped Ly{\alpha} absorber (log (NH I /cm-2) = 21.90 \pm 0.10) with a low metallicity ([X/H] = -1.21 \pm 0.16), likely associated with the interstellar medium of the GRB host galaxy (z = 2.641).
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Abadie 2010 用LIGO和Virgo找6个磁星的引力波

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没有看到。

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Title:
Search for Gravitational Wave Bursts from Six Magnetars
Authors:
LIGO Scientific Collaboration; Virgo Collaboration
Publication:
eprint arXiv:1011.4079
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Comment:
9 pages, 3 figures
Bibliographic Code:
2010arXiv1011.4079L

Abstract

Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are thought to be magnetars: neutron stars powered by extreme magnetic fields. These rare objects are characterized by repeated and sometimes spectacular gamma-ray bursts. The burst mechanism might involve crustal fractures and excitation of non-radial modes which would emit gravitational waves (GWs). We present the results of a search for GW bursts from six galactic magnetars that is sensitive to neutron star f-modes, thought to be the most efficient GW emitting oscillatory modes in compact stars. One of them, SGR 0501+4516, is likely ~1 kpc from Earth, an order of magnitude closer than magnetars targeted in previous GW searches. A second, AXP 1E 1547.0-5408, gave a burst with an estimated isotropic energy >10^{44} erg which is comparable to the giant flares. We find no evidence of GWs associated with a sample of 1279 electromagnetic triggers from six magnetars occurring between November 2006 and June 2009, in GW data from the LIGO, Virgo, and GEO600 detectors. Our lowest model-dependent GW emission energy upper limits for band- and time-limited white noise bursts in the detector sensitive band, and for f-mode ringdowns (at 1090 Hz), are 3.0x10^{44} d_1^2 erg and 1.4x10^{47} d_1^2 erg respectively, where d_1 = d_{0501} / 1 kpc and d_{0501} is the distance to SGR 0501+4516. These limits on GW emission from f-modes are an order of magnitude lower than any previous, and approach the range of electromagnetic energies seen in SGR giant flares for the first time.
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Kocevski 2010 伽马暴宿主星系的质量-金属丰度关系

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Title:
On The Origin Of The Mass-Metallicity Relation For GRB Host Galaxies
Authors:
Kocevski, Daniel; West, Andrew A.
Publication:
eprint arXiv:1011.4060
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Galaxy Astrophysics
Comment:
6 pages, 4 figures, submitted to ApJL
Bibliographic Code:
2010arXiv1011.4060K

Abstract

We investigate the nature of the mass-metallicity (M-Z) relation for long gamma-ray burst (LGRB) host galaxies. Recent studies suggest that the M-Z relation for local LGRB host galaxies may be systematically offset towards lower metallicities relative to the M-Z relation defined by the general star forming galaxy (SDSS) population. The nature of this offset is consistent with suggestions that low metallicity environments may be required to produce high mass progenitors, although the detection of several GRBs in high-mass, high-metallicity galaxies challenges the notion of a strict metallicity cut-off for host galaxies that are capable of producing GRBs. We show that the nature of this reported offset may be explained by a recently proposed anti-correlation between the star formation rate (SFR) and the metallicity of star forming galaxies. If low metallicity galaxies produce more stars than their equally massive, high-metallicity counterparts, then transient events that closely trace the SFR in a galaxy would be more likely to be found in these low metallicity, low mass galaxies. Therefore, the offset between the GRB and SDSS defined M-Z relations may be the result of the different methods used to select their respective galaxy populations, with GRBs being biased towards low metallicity, high SFR, galaxies. We predict that such an offset should not be expected of transient events that do not closely follow the star formation history of their host galaxies, such as short duration GRBs and SN Ia, but should be evident in core collapse SNe found through upcoming untargeted surveys.
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Suarez-Garcia 2010 一个用POLAR定位伽马暴的办法

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Title:
A method to localize gamma-ray bursts using POLAR
Authors:
Suarez-Garcia, E.; Haas, D.; Hajdas, W.; Lamanna, G.; Lechanoine-Leluc, C.; Marcinkowski, R.; Mtchedlishvili, A.; Orsi, S.; Pohl, M.; Produit, N.; Rapin, D.; Rybka, D.; Vialle, J. -P.
Publication:
eprint arXiv:1011.3789
Publication Date:
11/2010
Origin:
ARXIV
Keywords:
Astrophysics - Instrumentation and Methods for Astrophysics
Comment:
13 pages, 10 figures; Nuclear Instruments and Methods in Physics Research Section A, 2010; doi:10.1016/j.nima.2010.10.006
Bibliographic Code:
2010arXiv1011.3789S

Abstract

The hard X-ray polarimeter POLAR aims to measure the linear polarization of the 50-500 keV photons arriving from the prompt emission of gamma-ray bursts (GRBs). The position in the sky of the detected GRBs is needed to determine their level of polarization. We present here a method by which, despite of the polarimeter incapability of taking images, GRBs can be roughly localized using POLAR alone. For this purpose scalers are attached to the output of the 25 multi-anode photomultipliers (MAPMs) that collect the light from the POLAR scintillator target. Each scaler measures how many GRB photons produce at least one energy deposition above 50 keV in the corresponding MAPM. Simulations show that the relative outputs of the 25 scalers depend on the GRB position. A database of very strong GRBs simulated at 10201 positions has been produced. When a GRB is detected, its location is calculated searching the minimum of the chi2 obtained in the comparison between the measured scaler pattern and the database. This GRB localization technique brings enough accuracy so that the error transmitted to the 100% modulation factor is kept below 10% for GRBs with fluence Ftot \geq 10^(-5) erg cm^(-2) . The POLAR localization capability will be useful for those cases where no other instruments are simultaneously observing the same field of view.
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