astro-grb

Jing Wang, Jing-song Deng, Yu-lei Qiu

In order to test systematic of the Amati relation, the 24 long-duration GRBs
with firmly determined $E_{\gamma,\mathrm{iso}}$ and $E_{\mathrm p}$ are
separated into two sub-groups according to B-band luminosity of their host
galaxies. The Amati relations in the two subgroups are found to be in agreement
with each other within uncertainties. Taking into account of the well
established luminosity - metallicity relation of galaxies, no strong evolution
of the Amati relation with GRB's environment metallicity is implied in this
study.

http://arxiv.org/abs/0710.5302

P.A. Curran (1), A.J. van der Horst (1,2), R.A.M.J. Wijers (1) ((1) University of Amsterdam, The Netherlands, (2)University of Alabama, Huntsville, USA)

Gamma-ray burst afterglow observations in the Swift era have a perceived lack
of achromatic jet breaks compared to the BeppoSAX, or pre-Swift era.
Specifically, relatively few breaks, consistent with jet breaks, are observed
in the X-ray light curves of these bursts. If these breaks are truly missing,
it has serious consequences for the interpretation of GRB jet collimation and
energy requirements, and the use of GRBs as cosmological tools. Here we address
the issue of X-ray breaks that are possibly `hidden' and hence the light curves
are misinterpreted as being single power laws. We do so by synthesising XRT
light curves and fitting both single and broken power laws, and comparing the
relative goodness of each fit via Monte Carlo analysis. Even with the well
sampled light curves of the Swift era, these breaks may be left misidentified,
hence caution is required when making definite statements on the absence of
achromatic breaks.

http://arxiv.org/abs/0710.5285

S. Valenti, S. Benetti, E. Cappellaro, F. Patat, P. Mazzali, M. Turatto, K. Hurley, K. Maeda, A. Gal-Yam, R. J. Foley, A. V. Filippenko, A. Pastorello, P. Challis, F. Frontera, A. Harutyunyan, M. Iye, K. Kawabata, R. P. Kirshner, W. Li, Y. M. Lipkin, T. Matheson, K. Nomoto, E. O. Ofek, Y. Ohyama, E. Pian, M. Salvo, D. N. Sauer, B. P. Schmidt, A. Soderberg, L. Zampieri

The results of a world-wide coordinated observational campaign on the
broad-lined Type Ic SN 2003jd are presented. In total, 74 photometric data
points and 26 spectra were collected using 11 different telescopes. SN 2003jd
is one of the most luminous SN Ic ever observed. A comparison with other Type
Ic supernovae (SNe Ic) confirms that SN 2003jd represents an intermediate case
between broad-line events (2002ap, 2006aj), and highly energetic SNe (1997ef,
1998bw, 2003dh, 2003lw), with an ejected mass of M_{ej} = 3.0 +/- 1 Mo and a
kinetic energy of E_{k}(tot) = 7_{-2}^{+3} 10^{51} erg. SN 2003jd is similar to
SN 1998bw in terms of overall luminosity, but it is closer to SNe 2006aj and
2002ap in terms of light-curve shape and spectral evolution. The comparison
with other SNe Ic, suggests that the V-band light curves of SNe Ic can be
partially homogenized by introducing a time stretch factor. Finally, due to the
similarity of SN 2003jd to the SN 2006aj/XRF 060218 event, we discuss the
possible connection of SN 2003jd with a GRB.

http://arxiv.org/abs/0710.5173

G. E. Brown, C. -H. Lee, E. Moreno Mendez

Knowing the Kerr parameters we can make quantitative calculations of the
rotational energy of black holes. We show that Nova Sco (GRO J1655 - 40), Il
Lupi (4U 1543 - 47), XTE J1550 - 564 and GS 2023 + 338 are relics of gamma-ray
burst (GRB) and Hypernova explosions. They had more than enough rotational
energy to power themselves. In fact, they had so much energy that they would
have disrupted the accretion disk of the black hole that powered them by the
communicated rotational energy, so that the energy delivery was self limiting.
The most important feature in producing high rotational energy in the binary is
low donor (secondary star) mass.

We suggest that V4641 Sgr (XTE J1819 - 254) and GRS 1915 + 105 underwent less
energetic explosions; because of their large donor masses. These explosions
were one or two orders of magnitude lower in energy than that of Nova Sco. Cyg
X - 1 (1956 + 350) had an even less energetic explosion, because of an even
larger donor mass.

We find that in the evolution of the soft X-ray transient sources the donor
(secondary star) is tidally locked with the helium star, which evolved from the
giant, as the hydrogen envelope is stripped off in common envelope evolution.
The tidal locking is transferred from the helium star to the black hole into
which it falls. Depending on the mass of the donor, the black hole can be spun
up to the angular momentum necessary to power the GRB and Hypernova explosion.
The donor decouples, acting as a passive witness to the explosion which, for
the given angular momentum, then proceeds as in the Woosley Collapsar model.

High mass donors which tend to follow from low metallicity give long GRBs
because their lower energy can be accepted by the central engine.

http://arxiv.org/abs/0707.4008

Eric C. Bellm, Kevin Hurley, Valentin Pal'shin, Kazutaka Yamaoka, Mark E. Bandstra, Steven E. Boggs, Soojing Hong, Natsuki Kodaka, A. S. Kozyrev, M. L. Litvak, I. G. Mitrofanov, Yujin E. Nakagawa, Masanori Ohno, Kaori Onda, A. B. Sanin, Satoshi Sugita, Makoto Tashiro, V. I. Tretyakov, Yuji Urata, Claudia Wigger

The long, bright gamma-ray burst GRB 070125 was localized by the
Interplanetary Network. We present light curves of the prompt gamma-ray
emission as observed by Konus-WIND, RHESSI, Suzaku-WAM, and Swift-BAT. We
detail the results of joint spectral fits with Konus and RHESSI data. The burst
shows moderate hard-to-soft evolution in its multi-peaked emission over a
period of about one minute. The total burst fluence as observed by Konus is
$1.75 \times 10^{-4}$ erg/cm$^2$ (20 keV-10 MeV). Using the spectroscopic
redshift z = 1.547, we find that the burst is consistent with the Amati
$E_{peak,i}-E_{iso}$ and the Ghirlanda $E_{peak,i}-E_\gamma$ correlations.

http://arxiv.org/abs/0710.4590

Renyue Cen (Princeton), Taotao Fang (UCI)

Based on a simulation of galaxy formation in the standard cosmological model,
we suggest that a consistent picture for Gamma-Ray Bursts and star formation
may be found that is in broad agreement with observations: GRBs preferentially
form in low metallicity environments and in galaxies substantially less
luminous that L*. We find that the computed formation rate of stars with
metallicity less than 0.1Zsun agrees remarkably well with the rate evolution of
Gamma-Ray Bursts observed by Swift from z=0 to z=4, whereas the evolution of
total star formation rate is weaker by a factor of about 4. Given this finding,
we caution that any inference of star formation rate based on observed GRB rate
may require a more involved exercise than a simple proportionality.

http://arxiv.org/abs/0710.4370

STACEE Collaboration: A. Jarvis, J. Ball, J. E. Carson, C. E. Covault, D. D. Driscoll, P. Fortin, D. M. Gingrich, D. S. Hanna, J. Kildea, T. Lindner, R. Mukherjee, C. Mueller, R. A. Ong, K. Ragan, D. A. Williams, J. Zweerink

The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is an
atmospheric Cherenkov telescope (ACT) that uses a large mirror array to achieve
a relatively low energy threshold. For sources with Crab-like spectra, at high
elevations, the detector response peaks near 100 GeV. Gamma-ray burst (GRB)
observations have been a high priority for the STACEE collaboration since the
inception of the experiment. We present the results of 20 GRB follow-up
observations at times ranging from 3 minutes to 15 hours after the burst
triggers. Where redshift measurements are available, we place constraints on
the intrinsic high-energy spectra of the bursts.

http://arxiv.org/abs/0710.4149

R. Salvaterra, S. Campana, G. Chincarini, S. Covino, G. Tagliaferri

Long Gamma Ray Bursts (GRBs) constitute an important tool to study the
Universe near and beyond the epoch of reionization. We delineate here the
characteristics of an 'ideal' instrument for the search of GRBs at z>6-10. We
find that the detection of these objects requires soft band detectors with a
high sensitivity and moderately large FOV. In the light of these results, we
compare available and planned GRB missions, deriving conservative predictions
on the number of high-z GRBs detectable by these instruments along with the
maximum accessible redshift. We show that the Swift satellite will be able to
detect various GRBs at z>6, and likely at z>10 if the trigger threshold is
decreased by a factor of ~2. Furthermore, we find that INTEGRAL and GLAST are
not the best tool to detect bursts at z>6: the former being limited by the
small FOV, and the latter by its hard energy band and relatively low
sensitivity. Finally, future missions (SVOM, EDGE, but in particular EXIST)
will provide a good sample of GRBs at z>6 in a few years of operation.

http://arxiv.org/abs/0710.4280

Stephan Frank, Misty C. Bentz, Krzysztof Z. Stanek, Smita Mathur, Matthias Dietrich, Bradley M. Peterson, David W. Atlee (The Ohio State University)

We examine the recent report by Prochter et al. (2006) that gamma-ray burst
(GRB) sight lines have a much higher incidence of strong MgII absorption than
quasar sight lines. We propose that the discrepancy is due to the different
beam sizes of GRBs and quasars, and that the intervening MgII systems are
clumpy with the dense part of each cloudlet of a similar size as the quasars,
i.e. < 10^16 cm, but bigger than GRBs. We also discuss observational
predictions of our proposed model. Most notably, in some cases the intervening
MgII absorbers in GRB spectra should be seen varying, and quasars with smaller
sizes should show an increased rate of strong MgII absorbers. In fact, our
prediction of variable MgII lines in the GRB spectra has been now confirmed by
Hao et al. (2007), who observed intervening FeII and MgII lines at z=1.48 to be
strongly variable in the multi-epoch spectra of z=4.05 GRB060206.

http://arxiv.org/abs/astro-ph/0605676

Shlomo Dado, Arnon Dar, A. De Rujula

The mean iron abundance observed in the intergalactic medium (IGM) within
galaxy clusters and without galaxy clusters is consistent with the mean amount
of iron per unit volume in the Universe which has been produced by standard
supernova (SN) explosions with a rate proportional to the cosmic star-formation
rate. If most SNe took place inside galaxies, then the IGM could have been
enriched with their metals by galactic winds and jets that swept most of the
galactic gas with the SNe ejecta into the IGM. A significant fraction of the
early SNe, however, could have taken place outside galaxies or within dwarf
galaxies, which were later disrupted by tidal interactions, and/or mass loss
through fast winds, SN ejecta and jets. Little is known about such
intergalactic SNe at high red-shifts. They could have occurred primarily in
highly obscured environments, avoiding detection. Supporting evidence for
intergalactic SNe is provided by SNe associated with gamma ray bursts (GRBs)
without a host galaxy and from the ratio of well localized GRBs with and
without a host galaxy. A direct test of whether a significant contribution to
the iron abundance in the IGM came from intergalactic SNe would require the
measurement of their rate per comoving unit volume as function of red-shift.
This may be feasible with IR telescopes, such as the Spitzer Space Telescope.

http://arxiv.org/abs/astro-ph/0703293