Metzger 2008 致密星并合所形成的吸积盘

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文章信息:

· arXiv e-print (arXiv:0805.4415)

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Title:		Time-Dependent Models of Accretion Disks Formed from Compact Object Mergers
Authors:		Metzger, B. D.; Piro, A. L.; Quataert, E.
Publication:		eprint arXiv:0805.4415
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		18 pages, 14 figures; submitted to MNRAS
Bibliographic Code:		2008arXiv0805.4415M

Abstract

We present time-dependent models of the accretion disks created during compact object mergers, focusing on the energy available from accretion at late times and the composition of the disk and its outflows. We calculate the dynamics near the outer edge of the disk, which contains the majority of the mass and sets the accretion rate onto the central black hole. This allows us to follow the evolution over much longer timescales than current hydrodynamic simulations. At late times the disk becomes advective and its properties asymptote to self-similar solutions with accretion rate dM/dt ~ t^(-4/3) (neglecting outflows). This late-time accretion can in principle provide sufficient energy to power the late-time activity observed from some short-duration gamma-ray bursts (GRBs). However, because outflows during the advective phase unbind the majority of the remaining mass, it is difficult for the remnant disk alone to produce significant accretion power well beyond the onset of the advective phase. Unless the viscosity is quite low (alpha ~1e-3), this occurs before the start of observed flaring at ~ 30 s; continued mass inflow thus appears required to explain the late-time activity from short GRBs. We show that the composition of the disk freezes-out relatively neutron-rich (electron fraction Ye ~ 0.3). Roughly 1e-2 Msun of this neutron-rich material is ejected by winds at late times. During earlier, neutrino-cooled phases of accretion, neutrino irradiation of the disk produces a wind with Ye ~ 0.5, which synthesizes at most ~ 1e-3 Msun of Ni56. We highlight what conditions are favorable for Ni56 production and predict, in the best cases, optical and infrared transients peaking ~ 0.5-2 days after the burst, with fluxes a factor of ~ 10 below the current observational limits.

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Palmer 2008 Swift观测到SGR 1627-41的活动

主要内容:
GCN观测报告, GCN 7777 and 7778
一共有四个SGR来着，除了两个有名的，还有一个是SGR 0526-66
见维基百科 http://en.wikipedia.org/wiki/Soft_gamma_repeater

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文章信息:

Reactivation of SGR 1627-41	?
	GCN 7777

SOURCE: GCN
TITLE: GCN CIRCULAR
NUMBER: 7777
SUBJECT: Reactivation of SGR 1627-41
DATE: 08/05/29 00:34:50 GMT
FROM: David Palmer at LANL

D. Palmer (LANL), P. Esposito (INAF-IASF Milano), S. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), G. L. Israel (INAF-OA Roma), H. Krimm (GSFC/USRA), T. Sakamoto (GSFC/ORAU), R. Starling (U. of Leicester)
Swift has detected the resumption of activity of Soft Gamma Repeater SGR 1627-41 after a 9.8-year long quiescent period. BAT detected the initial burst on 2008-05-28 at 08:21:43 UT, and a larger burst at 09:53:00. This was followed by a 'forest' of dozens of bursts extending at least to 10:25:54. The brightest burst seen thus far has a 15-50 keV flux of 550 times the Crab, averaged over a 0.128 second time interval. Following the BAT detection, Swift observed the source with XRT on 2008 May 28th, starting from 12:58:14 UT. This SGR was discovered in 1998 June when it emitted over 100 bursts clustered within 6 weeks (Kouveliotou et al. 1998, IAU Circ. 6944, 2; Woods et al. 1999, ApJ 519, L139); no further burst emission has been reported to date. Preliminary results, based on the first 2 ks XRT observation, found a persistent and relatively constant X-ray source with a count rate of 0.06 +/- 0.01 cts/s at a position RA, Dec = 16 35 51.9, -47 35 23.0 (J2000) with an uncertainty of 4.1 arcsec (radius, 90% confidence level). This position is consistent with the Chandra coordinates of the SGR (Wachter et al. 2004, ApJ 615, 887). The paucity of detected photons did not allow us to carry out a sensitive search for coherent pulsations (upper limits > 100% pulsed fraction at 3 sigma c.l.). A single absorbed black body model fits well the spectrum with nH=6.8x10^22 cm^-2 and kT=0.8 keV (Mereghetti et al. 2006, A&A 450, 759). The observed flux is 6.5x10^-12 erg/cm2/s (unabsorbed: 7.3x10^-11). This persistent luminosity is the highest ever recorded from this source (and a factor ~50 higher than the September 2004 XMM-Newton values; Mereghetti et al. 2006). Analysis of data from this burst is continuing, and will be reported in later circulars. A plot of the BAT light curve for the forest can be seen at <http://gcn.gsfc.nasa.gov/gcn/other/SGR1627-41_timeline_2008.png>. The timeline of the previous outbursts can be seen at <http://gcn.gsfc.nasa.gov/gcn/other/SGR1627-41_timeline.gif>. We thank the Swift Operations Duty Scientist and Flight Operations Team for performing a rapid ToO. This GCN is also being submitted as an ATEL.

Wachter 2008 SGR 1900+14的红外环

主要内容:
看到了环状结构

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文章信息:

Letter

Nature 453, 626-628 (29 May 2008) | doi:10.1038/nature06987; Received 16 January 2008; Accepted 1 April 2008

An infrared ring around the magnetar SGR 1900+14

S. Wachter¹, E. Ramirez-Ruiz², V. V. Dwarkadas³, C. Kouveliotou⁴, J. Granot⁵, S. K. Patel⁶ & D. Figer⁷

Correspondence to: S. Wachter¹ Correspondence and requests for materials should be addressed to S.W. (Email: wachter@ipac.caltech.edu).

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Magnetars^{1, 2} are a special class of slowly rotating (period 5–12 s) neutron stars with extremely strong magnetic fields (>10¹⁴ G)—at least an order of magnitude larger than those of the 'normal' radio pulsars. The potential evolutionary links and differences between these two types of object are still unknown; recent studies, however, have provided circumstantial evidence connecting magnetars with very massive progenitor stars^{3, 4, 5}. Here we report the discovery of an infrared elliptical ring or shell surrounding the magnetar SGR 1900+14. The appearance and energetics of the ring are difficult to interpret within the framework of the progenitor's stellar mass loss or the subsequent evolution of the supernova remnant. We suggest instead that a dust-free cavity was produced in the magnetar environment by the giant flare emitted by the source in August 1998. Considering the total energy released in the flare, the theoretical dust-destruction radius matches well with the observed dimensions of the ring. We conclude that SGR 1900+14 is unambiguously associated with a cluster of massive stars, thereby solidifying the link between magnetars and massive stars.

Salvaterra 2008 长暴函数存在演化的证据

主要内容:
“GRBs were more luminous in the past as we see them today.”什么意思？

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文章信息:

· arXiv e-print (arXiv:0805.4104)

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Title:		Evidence for Luminosity Evolution of Long Gamma-ray Bursts in Swift Data
Authors:		Salvaterra, R.; Guidorzi, C.; Campana, S.; Chincarini, G.; Tagliaferri, G.
Publication:		eprint arXiv:0805.4104
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		5 pages, 2 figures, submitted to MNRAS
Bibliographic Code:		2008arXiv0805.4104S

Abstract

We compute the luminosity function (LF) and the formation rate of long gamma ray bursts (GRBs) by fitting the observed differential peak flux distribution obtained by the BATSE satellite in two different scenarios: i) the GRB luminosity evolves with redshift and ii) GRBs form preferentially in low-metallicity environments. In both cases, model predictions are consistent with the Swift number counts and with the number of detections at z>2.5 and z>3.5. To discriminate between the two evolutionary scenarios, we compare the model results with the number of luminous bursts (i.e. with isotropic peak luminosity in excess of 10^53 erg s^-1) detected by Swift in its first three years of mission. Our sample conservatively contains only bursts with good redshift determination and measured peak energy. We find that models in which GRBs are characterised by a constant LF are ruled out, underproducing the number of luminous GRBs. Only for a metallicity threshold for GRB formation as low as 1/10 \Zsun, the model is marginally consistent with the observed number of bright GRBs. Using these new constraints, we derive robust upper limits on the bright-end of the GRB LF, showing that this can not be steeper than ~2.5. In conclusion, we find that available Swift observations (both the number of high-z GRBs and of bright GRBs) point to a scenario in which GRBs were more luminous in the past as we see them today.

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Sokolov 2008 引力坍缩作为伽玛暴的能源机制

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文章信息:

arXiv:0805.3262 [ps, pdf, other]

Title: Gravitational collapse as the source of gamma-ray bursts

Authors: V.V.Sokolov

Comments: 12 pages, no figures. To be published in Proceedings of the Conference "Problems of Practical Cosmology", see this http URL

Subjects: Astrophysics (astro-ph)

If the threshold for $e^{-}e^{+}$ pair production depends on an angle between photon momenta, and if the $\gamma$-rays are collimated right in gamma-ray burst (GRB) source then another solution of the compactness problem is possible. The list of basic assumptions of the scenario describing the GRB with energy release $<>

Prochaska 2008 用余辉的谱探测暴周环境

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文章信息:

arXiv:0805.2989 [ps, pdf, other]

Title: Resolving The ISM Surrounding GRBs with Afterglow Spectroscopy

Authors: Jason X. Prochaska (1), Hsiao-Wen Chen (2), Miroslava Dessauges-Zavadsky (3), Joshua S. Bloom (4) ((1) UCO/Lick Observatory, UC Santa Cruz, (2) U. Chicago, (3) Observatoire de Geneve, (4) UC Berkeley)

Comments: Conference procedings for Gamma Ray Bursts 2007 November 5-9, 2007 Santa Fe, New Mexico (8 pages, 4 figures)

Subjects: Astrophysics (astro-ph)

We review current research related to spectroscopy of gamma-ray burst (GRB) afterglows with particular emphasis on the interstellar medium (ISM) of the galaxies hosting these high redshift events. These studies reveal the physical conditions of star-forming galaxies and yield clues to the nature of the GRB progenitor. We offer a pedagogical review of the experimental design and review current results. The majority of sightlines are characterized by large HI column densities, negligible molecular fraction, the ubiquitous detection of UV pumped fine-structure transitions, and metallicities ranging from 1/100 to nearly solar abundance.

Galli 2008 X射线耀发和余辉阶段的高能辐射

主要内容:
以及MAGIC的探测率

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文章信息:

arXiv:0805.2884 [ps, pdf, other]

Title: Prospects for detection of very high energy emission from GRB in the context of the External Shock model

Authors: A. Galli, L. Piro (INAF/Isaf-Roma)

Comments: 5 pages, 2 color figures, submitted to A&A letters

Subjects: Astrophysics (astro-ph)

The detection of the 100 GeV-TeV emission by a Gamma-Ray Burst (GRB) will provide an unprecedented opportunity to enlighten the nature of the central engine and the interaction between the relativistic flow and the environment of the burst progenitor. In this paper we show that there are exciting prospects of detecting by MAGIC high energy (HE) emission from the burst during the "early" X-ray flaring activity and, later, during the "normal" afterglow phase. We also identify the best observational strategy (trigger conditions and time period of observation). We determine the expected HE emission from the flaring and afterglow phases of GRBs in the context of the External Shock scenario and compare them with the MAGIC threshold. We find that a X-ray flare with the average properties of the class, can be detected in the 100 GeV range by MAGIC provided that z<1.> a few cm^{-3}. In this case the MAGIC observation shall extend to about 10-20 ksec. We provide recipes to tailor this prediction to the observational properties of each burst, in particular the fluence in the prompt emission and the redshift, thus allowing an almost "real time" decision procedure to decide whether to continue the follow up observation of a burst at late times.

McGlynn 2008 短暴GRB070707的观测

主要内容:
是第一个被INTEGRAL观测到的短暴。

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文章信息:

arXiv:0805.2880 [ps, pdf, other]

Title: GRB 070707: the first short gamma-ray burst observed by INTEGRAL

Authors: S. McGlynn (1,2), S. Foley (1), S. McBreen (3), L. Hanlon (1), R. O'Connor (1), A. Martin Carrillo (1), B. McBreen (1) ((1) University College Dublin, (2) Royal Institute of Technology (KTH), Stockholm (3) MPE Garching)

Comments: 7 pages, 3 figures, accepted for publication in A&A

Subjects: Astrophysics (astro-ph)

INTEGRAL has observed 47 long-duration GRBs (T_90 > 2s) and 1 short-duration GRB (T_90 < alpha =" -1.19">~ 25 for GRB 070707, assuming the typical redshift for short GRBs of z=0.35. This limit is consistent with previous estimates for short GRBs and is smaller than the lower limits of Gamma >~ 100 calculated for long GRBs. If GRB 070707 is a member of the recently postulated class of short GRBs at z ~ 1, the lower limit on Gamma increases to Gamma >~ 35.

Kruhler 2008 GRB070802的余辉观测

主要内容:
说可能有dust的信号

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文章信息:

arXiv:0805.2824 [ps, pdf, other]

Title: The 2175 A dust feature in a Gamma Ray Burst afterglow at redshift 2.45

Authors: T. Krühler, A. Küpcü Yoldaş, J. Greiner, C. Clemens, S. McBreen, N. Primak, S. Savaglio, A. Yoldaş, G. P. Szokoly

Comments: 21 pages, 3 figures, accepted for publication by ApJ

Subjects: Astrophysics (astro-ph)

We present optical and near-infrared photometry of the afterglow of the long Gamma-Ray Burst GRB 070802 at redshift 2.45 obtained with the ESO/MPI 2.2 m telescope equipped with the multi-channel imager GROND. Follow-up observations in g'r'i'z' and JHK_S bands started ~17 min and extended up to 28 h post burst. We find an increase in brightness of the afterglow at early times, which can be explained by the superposition of reverse and forward shock (FS) emission or the onset of the afterglow FS. Additionally, we detect a strong broad-band absorption feature in the i' band, which we interpret as extinction from the redshifted 2175 A bump in the GRB host galaxy. This is one of the first and clearest detections of the 2175 A feature at high redshift. It is strong evidence for a carbon rich environment, indicating that Milky Way or Large Magellanic Cloud like dust was already formed in substantial amounts in a galaxy at z=2.45.

Sonabas 2008 GRB060218/SN2006aj的超新星阶段的观测

主要内容:
可以看到星风包层的信号。

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文章信息:

arXiv:0805.2657 [ps, pdf, other]

Title: The stellar-wind envelope around the supernova XRF/GRB060218/SN2006aj massive progenitor star

Authors: E. Sonbas, A.S. Moskvitin, T.A. Fatkhullin, V.V. Sokolov, A. Castro-Tirado, A. de Ugarte Postigo, J. Gorosabel, S. Guziy, M. Jelinek, T.N. Sokolova, V.N. Chernenkov

Comments: 26 pages, 7 figures, 3 tables, Accepted for publication in Astrophysical Bulletin, 2008, v. 63, No 3

Subjects: Astrophysics (astro-ph)

In BTA spectra of the supernova SN2006aj, identified with the X-ray flash (XRF) and gamma-ray burst XRF/GRB060218/SN2006aj, we detected details interpreted as hydrogen lines, which is a sign of stellar-wind envelope around a massive progenitor star of the gamma-ray burst. Results of modeling two early spectra obtained with the BTA in 2.55 and 3.55 days after the explosion of Type Ic supernova SN2006aj (z=0.0331) are presented. The spectra were modeled in the Sobolev approximation with the SYNOW code (Branch et al. 2001; Elmhamdi et al. 2006). In the spectra of the optical afterglow of the X-ray flash XRF/GRB060218 we detected spectral features interpreted as (1) the H_alpha PCyg profile for the velocity 33000 km s$^{-1}$ -- a wide and almost unnoticeable deformation of continuum in the range of $\simeq5600 - 6600\AA$ for the first epoch (2.55 days) and (2) a part (``remnant'') of the H_alpha PCyg profile in absorption blueshifted by 24000 km s$^{-1}$ -- a wide spectral feature with a minimum at $\simeq6100\AA$ (the rest wavelength) for the second epoch (3.55 days). Taking into consideration early BTA observations and spectra obtained with other telescopes (ESO Lick, ESO VLT, NOT) before 2006 Feb. 23 UT, it can be said that we observe evolution of optical spectra of Type Ic core-collapse supernova SN 2006aj during {\it transition} from the short phase related to the shock breakout to outer layers of the stellar-wind envelope to spectra of the phase of increasing brightness corresponding to radioactive heating. Signs of hydrogen in spectra of the gamma-ray burst afterglow were detected for the first time.

Perley 2008 GRB 071003的观测

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文章信息:

· arXiv e-print (arXiv:0805.2394)

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Title:		GRB 071003: Broadband Follow-up Observations of a Very Bright Gamma-Ray Burst in a Galactic Halo
Authors:		Perley, D. A.; Li, W.; Chornock, R.; Prochaska, J. X.; Butler, N. R.; Chandra, P.; Pollack, L. K.; Bloom, J. S.; Filippenko, A. V.; Akerlof, C.; Auger, M. W.; Cenko, S. B.; Chen, H. -W.; Fassnacht, C. D.; Fox, D.; Frail, D.; Johansson, E. M.; Le Mignant, D.; Modjaz, M.; Skinner, M. A.; Smith, G. H.; Swan, H.; van Dam, M. A.; Yuan, F.
Publication:		eprint arXiv:0805.2394
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		Submitted to astro-ph
Bibliographic Code:		2008arXiv0805.2394P

Abstract

The optical afterglow of long-duration gamma-ray burst (GRB) 071003 is among the brightest yet to be detected from any GRB, with R ~ 12 mag in Katzman Automatic Imaging Telescope observations starting 42 s after the GRB trigger, including filtered detections during prompt emission. However, our high signal-to-noise ratio afterglow spectrum displays only extremely weak absorption lines at what we argue is the host redshift of z=1.60435 - in contrast to the three other, much stronger Mg II absorption systems observed at lower redshifts. Together with Keck Adaptive Optics observations which fail to reveal a host galaxy coincident with the burst position, our observations suggest a halo progenitor and offer a cautionary tale about the use of Mg II for GRB redshift determination. We present early through late-time observations spanning the electromagnetic spectrum, constrain the connection between the prompt emission and early variations in the light curve (we observe no correlation), and discuss possible origins for an unusual, marked rebrightening that occurs a few hours after the burst: likely either a late-time refreshed shock or a wide-angle secondary jet. Analysis of the late-time afterglow is most consistent with a wind environment, suggesting a massive star progenitor. Together with GRB 070125, this may indicate that a small but significant portion of star formation in the early universe occurred far outside what we consider a normal galactic disk.

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Koers 2008 伽玛暴中的中微子产生

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文章信息:

· arXiv e-print (arXiv:0805.2514)

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Title:		Neutrino production in nucleonic interactions in gamma-ray bursters
Authors:		Koers, Hylke B. J.
Publication:		eprint arXiv:0805.2514
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		6 pages, no figures. Contribution to the Rencontres de Moriond 2008 (Electroweak session), La Thuile, Italy, 1-8 March 2008
Bibliographic Code:		2008arXiv0805.2514K

Abstract

Neutrinos produced in gamma-ray bursters (GRBers) may provide a unique probe for the physics of these extreme astrophysical systems. Here we discuss neutrino production in inelastic neutron-proton collisions within the relativistic outflows associated with GRBers. We consider both the widely used fireball model and a recently proposed magneto-hydrodynamic (MHD) model for the GRB outflow.

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Mirabel 2008 微类星体综述

主要内容:
微类星体小综述。

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文章信息:
arXiv e-print (arXiv:0805.2378)
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Title:
Microquasars: summary and outlook
Authors:
Mirabel, I. F.
Publication:
eprint arXiv:0805.2378
Publication Date:
05/2008
Origin:
ARXIV
Keywords:
Astrophysics
Comment:
Review based on courses given at international schools for graduate students and post-docs; 13 pages, 7 color figures
Bibliographic Code:
2008arXiv0805.2378M
AbstractMicroquasars are compact objects (stellar-mass black holes and neutron stars) that mimic, on a smaller scale, many of the phenomena seen in quasars. Their discovery provided new insights into the physics of relativistic jets observed elsewhere in the universe, and in particular, the accretion-jet coupling in black holes. Microquasars are opening new horizons for the understanding of ultraluminous X-ray sources observed in external galaxies, gamma-ray bursts of long duration, and the origin of stellar black holes and neutron stars. Microquasars are one of the best laboratories to probe General Relativity in the limit of the strongest gravitational fields, and as such, have become an area of topical interest for both high energy physics and astrophysics. At present, back hole astrophysics exhibits historical and epistemological similarities with the origins of stellar astrophysics in the last century.
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Fan 2008 伽玛暴的高能辐射

主要内容:
综述了伽玛暴的高能辐射的产生机制。

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文章信息:
· arXiv e-print (arXiv:0805.2221)
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Title:
High energy gamma-ray emission from Gamma-Ray Bursts -- before GLAST
Authors:
Fan, Yi-Zhong; Piran, Tsvi
Publication:
eprint arXiv:0805.2221
Publication Date:
05/2008
Origin:
ARXIV
Keywords:
Astrophysics
Comment:
An invited review article for Front. Phys. China. (Possible prompt and very early GeV-TeV emission from GRB 080319B are discussed in Sec. V)
Bibliographic Code:
2008arXiv0805.2221F
AbstractGamma-ray bursts (GRBs) are short and intense emission of soft gamma-rays, which have fascinated astronomers and astrophysicists since their unexpected discovery in 1960s. The X-ray/optical/radio afterglow observations confirm the cosmological origin of GRBs, support the fireball model, and imply a long-activity of the central engine. The high energy gamma-ray emission (>20 MeV) from GRBs is particularly important because they shed some lights on the radiation mechanisms and can help us to constrain the physical processes giving rise to the early afterglows. In this work, we review observational and theoretical studies of the high energy emission from GRBs. Special attention is given to the expected high energy emission signatures accompanying the canonical early-time X-ray afterglow that was observed by the Swift X-ray Telescope. We also discuss the detection prospect of the upcoming GLAST satellite and the current ground-based Cerenkov detectors.
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Racusin 2008 GRB 080319B的观测

主要内容:
Swift组的文章

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文章信息:

· arXiv e-print (arXiv:0805.1557)

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Title:		GRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe
Authors:		Racusin, J. L.; Karpov, S. V.; Sokolowski, M.; Granot, J.; Wu, X. F.; Pal'shin, V.; Covino, S.; van der Horst, A. J.; Oates, S. R.; Schady, P.; Smith, R. J.; Cummings, J.; Starling, R. L. C.; Piotrowski, L. W.; Zhang, B.; Evans, P. A.; Holland, S. T.; Malek, K.; Page, M. T.; Vetere, L.; Margutti, R.; Guidorzi, C.; Kamble, A.; Curran, P. A.; Beardmore, A.; Kouveliotou, C.; Mankiewicz, L.; Melandri, A.; O'Brien, P. T.; Page, K. L.; Piran, T.; Tanvir, N. R.; Wrochna, G.; Aptekar, R. L.; Bartolini, C.; Barthelmy, S.; Beskin, G. M.; Bondar, S.; Campana, S.; Cucchiara, A.; Cwiok, M.; D'Avanzo, P.; D'Elia, V.; Della Valle, M.; Dominik, W.; Falcone, A.; Fiore, F.; Fox, D. B.; Frederiks, D. D.; Fruchter, A. S.; Fugazza, D.; Garrett, M.; Gehrels, N.; Golenetskii, S.; Gomboc, A.; Greco, G.; Guarnieri, A.; Immler, S.; Kasprowicz, G.; Levan, A. J.; Mazets, E. P.; Molinari, E.; Moretti, A.; Nawrocki, K.; Oleynik, P. P.; Osborne, J. P.; Pagani, C.; Paragi, Z.; Perri, M.; Piccioni, A.; Ramirez-Ruiz, E.; Roming, P. W. A.; Steele, I. A.; Strom, R. G.; Testa, V.; Tosti, G.; Ulanov, M. V.; Wiersema, K.; Wijers, R. A. M. J.; Zarnecki, A. F.; Zerbi, F.; Meszaros, P.; Chincarini, G.; Burrows, D. N.
Publication:		eprint arXiv:0805.1557
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		43 pages, 18 figures, 3 tables, submitted to Nature May 11, 2008
Bibliographic Code:		2008arXiv0805.1557R

Abstract

Long duration gamma-ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of a massive star. Over the last forty years, our understanding of the GRB phenomenon has progressed dramatically; nevertheless, fortuitous circumstances occasionally arise that provide access to a regime not yet probed. GRB 080319B presented such an opportunity, with extraordinarily bright prompt optical emission that peaked at a visual magnitude of 5.3, making it briefly visible with the naked eye. It was captured in exquisite detail by wide-field telescopes, imaging the burst location from before the time of the explosion. The combination of these unique optical data with simultaneous gamma-ray observations provides powerful diagnostics of the detailed physics of this explosion within seconds of its formation. Here we show that the prompt optical and gamma-ray emissions from this event likely arise from different spectral components within the same physical region located at a large distance from the source, implying an extremely relativistic outflow. The chromatic behaviour of the broadband afterglow is consistent with viewing the GRB down the very narrow inner core of a two-component jet that is expanding into a wind-like environment consistent with the massive star origin of long GRBs. These circumstances can explain the extreme properties of this GRB.

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Morgan 2008 Optimal Coaddition技术观测快速变暗的余辉

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文章信息:

· arXiv e-print (arXiv:0805.1426)

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Title:		Optimal Coaddition of Imaging Data for Rapidly Fading Gamma-Ray Burst Afterglows
Authors:		Morgan, A. N.; Vanden Berk, D. E.; Roming, P. W. A.; Nousek, J. A.; Koch, T. S.; Breeveld, A. A.; de Pasquale, M.; Holland, S. T.; Kuin, N. P. M.; Page, M. J.; Still, M.
Publication:		eprint arXiv:0805.1426
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		17 pages, accepted for publication in ApJ
Bibliographic Code:		2008arXiv0805.1426M

Abstract

We present a technique for optimal coaddition of image data for rapidly varying sources, with specific application to gamma-ray burst (GRB) afterglows. Unweighted coaddition of rapidly fading afterglow lightcurve data becomes counterproductive relatively quickly. It is better to stop coaddition of the data once noise dominates late exposures. A better alternative is to optimally weight each exposure to maximize the signal-to-noise ratio (S/N) of the final coadded image data. By using information about GRB lightcurves and image noise characteristics, optimal image coaddition increases the probability of afterglow detection and places the most stringent upper limits on non-detections. For a temporal power law flux decay typical of GRB afterglows, optimal coaddition has the greatest potential to improve the S/N of afterglow imaging data (relative to unweighted coaddition), when the decay rate is high, the source count rate is low, and the background rate is high. The optimal coaddition technique is demonstrated with applications to Swift Ultraviolet/Optical Telescope (UVOT) data of several GRBs, with and without detected afterglows.

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Lamon 2008 GLAST 和Lorentz violation

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· arXiv e-print (arXiv:0805.1219)

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Title:		GLAST and Lorentz violation
Authors:		Lamon, Raphael
Publication:		eprint arXiv:0805.1219
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		11 pages, 7 figures and 2 tables
Bibliographic Code:		2008arXiv0805.1219L

Abstract

We study possible Lorentz violations by means of gamma-ray bursts (GRB) with special focus on the Large Array Telescope (LAT) of GLAST. We simulate bursts with gtobssim and introduce a Lorentz violating term in the arrival times of the photons. We further perturb these arrival times and energies with a Gaussian distribution corresponding to the time resp. energy resolution of GLAST. We then vary the photon flux in gtobssim in order to derive a relation between the photon number and the standard deviation of the Lorentz violating term. We conclude with the fact that our maximum likelihood method as first developed in [1] is able to make a statement whether Nature breaks the Lorentz symmetry if the number of bursts with known redshifts is of the order of 100.

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Malesani 2008 SN 2008D 的早期谱

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· arXiv e-print (arXiv:0805.1188)

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Title:		Early spectroscopic identification of SN 2008D
Authors:		Malesani, D.; Fynbo, J. P. U.; Hjorth, J.; Leloudas, G.; Sollerman, J.; Stritzinger, M. D.; Vreeswijk, P. M.; Watson, D. J.; Gorosabel, J.; Michałowski, M. J.; Thöne, C. C.; Augusteijn, T.; Bersier, D.; Jakobsson, P.; Jaunsen, A. O.; Ledoux, C.; Levan, A. J.; Milvang-Jensen, B.; Rol, E.; Tanvir, N. R.; Wiersema, K.; Xu, D.; Albert, L.; Bayliss, M.; Gall, C.; Grove, L. F.; Koester, B. P.; Leitet, E.; Pursimo, T.; Skillen, I.
Publication:		eprint arXiv:0805.1188
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		6 pages, 5 figures, 4 tables; submitted to ApJ Letters
Bibliographic Code:		2008arXiv0805.1188M

Abstract

SN 2008D was discovered while following up a luminous, unusual X-ray transient in the nearby spiral galaxy NGC 2770. We present early spectra of the optical counterpart (1.77 days after the X-ray transient) which first allowed to identify the object as a supernova at redshift z = 0.007. These spectra were acquired during the initial declining phase of the light curve, likely due to the shock breakout. They show a relatively flat continuum with broad undulations, and a strong, W-shaped feature with minima at 3980 and 4190 AA (rest frame). We also present extensive spectroscopic and photometric monitoring of the supernova covering the photospheric phase. Unlike supernovae associated with gamma-ray bursts, SN 2008D displayed prominent He features and is therefore of Type Ib.

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Updike 2008 GRB 070125 observations

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· arXiv e-print (arXiv:0805.1094)

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Title:		The Rapidly Flaring Afterglow of the Very Bright and Energetic GRB 070125
Authors:		Updike, Adria C.; Haislip, Joshua B.; Nysewander, Melissa C.; Fruchter, Andrew S.; Kann, D. Alexander; Klose, Sylvio; Milne, Peter A.; Williams, G. Grant; Zheng, Weikang; Hergenrother, Carl W.; Prochaska, Jason X.; Halpern, Jules P.; Mirabal, Nestor; Thorstensen, John R.; van der Horst, Alexander J.; Starling, Rhaana L. C.; Racusin, Judith L.; Burrows, David N.; Kuin, N. P. M.; Roming, Peter W. A.; Bellm, Eric; Hurley, Kevin; Li, Weidong; Filippenko, Alexei V.; Blake, Cullen; Starr, Dan; Falco, Emilio E.; Brown, Warren R.; Dai, Xinyu; Deng, Jinsong; Xin, Liping; Qiu, Yulei; Wei, Jianyan; Urata, Yuji; Nanni, Domenico; Maiorano, Elisabetta; Palazzi, Eliana; Greco, Giuseppe; Bartolini, Corrado; Guarnieri, Adriano; Piccioni, Adalberto; Pizzichini, Graziella; Terra, Federica; Misra, Kuntal; Bhatt, B. C.; Anupama, G. C.; Fan, X.; Jiang, L.; Wijers, Ralph A. M. J.; Reichart, Dan E.; Eid, Hala A.; Bryngelson, Ginger; Puls, Jason; Goldthwaite, R. C.; Hartmann, Dieter H.
Publication:		eprint arXiv:0805.1094
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		50 pages, 9 figures, 5 tables Accepted to the Astrophysical Journal
Bibliographic Code:		2008arXiv0805.1094U

Abstract

We report on multi-wavelength observations, ranging from the X-ray to radio wave bands, of the IPN-localized gamma-ray burst GRB 070125. Spectroscopic observations reveal the presence of absorption lines due to O I, Si II, and C IV, implying a likely redshift of z = 1.547. The well-sampled light curves, in particular from 0.5 to 4 days after the burst, suggest a jet break at 3.7 days, corresponding to a jet opening angle of ~7.0 degrees, and implying an intrinsic GRB energy in the 1 - 10,000 keV band of around E = (6.3 - 6.9)x 10^(51) erg (based on the fluences measured by the gamma-ray detectors of the IPN network). GRB 070125 is among the brightest afterglows observed to date. The spectral energy distribution implies a host extinction of Av <> Bibtex entry for this abstract Preferred format for this abstract

Basilakos 2008 用伽玛暴做标准烛光

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统计了几种标准烛光关系$1:\epkk-E_\gamma$, $2:\epkk-L$, $3:\tlag-L$, $4:V-L$, $5:\trt-L$，结论基本上是否定结果。

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· arXiv e-print (arXiv:0805.0875)

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Title:		Testing GRBs as Standard Candles
Authors:		Basilakos, S.; Perivolaropoulos, L.
Publication:		eprint arXiv:0805.0875
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		10 two-column pages, 3 figures. The mathematica files used in the numerical analysis of the paper may be found at http://leandros.physics.uoi.gr/grb/grb.htm
Bibliographic Code:		2008arXiv0805.0875B

Abstract

Several correlations among Gamma Ray Burst (GRB) observables with available redshifts have been recently identified. Proper evaluation and calibration of these correlations may facilitate the use of GRBs as standard candles constraining the expansion history of the universe up to redshifts of $z>6$. Here we use the 69 GRB dataset recently compiled by Schaefer (astro-ph/0612285) and we test the calibration of five of the above correlations ($1:\epkk-E_\gamma$, $2:\epkk-L$, $3:\tlag-L$, $4:V-L$, $5:\trt-L$) with respect to two potential sources of systematics: Evolution with redshift and cosmological model used in the calibration. In examining the model dependence we assume flat \lcdm and vary $\omm$. Our approach avoids the circularity problem of previous studies since we do not fix $\omm$ to find the correlation parameters. Instead we simultaneously minimize $\chi^2$ with respect to both the log-linear correlation parameters $a$, $b$ and the cosmological parameter $\omm$. We find no statistically significant evidence for redshift dependence of $a$ and $b$ in any of the correlation relations tested. We also find that one of the five correlation relations tested ($\epkk-E_\gamma$) has a significantly lower intrinsic dispersion compared to the other correlations. For this correlation relation, the maximum likelihood method favors the existence of a cosmological constant while the other four correlation favor a flat matter dominated universe $\omm \simeq 1$. Finally, a cross-correlation analysis between the GRBs and SnIa data for various values of $\omm$ has shown that the $E_{peak}-E_\gamma$ relation traces well the SnIa redshift regime. However, even the tightest correlation relation ($E_{peak}-E_\gamma$) provides much weaker constraints on $\omm$ than current SnIa data.

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