2,571 research outputs found
On the thermal and double episode emissions in GRB 970828
Following the recent theoretical interpretation of GRB 090618 and GRB 101023,
we here interpret GRB 970828 in terms of a double episode emission: the first
episode, observed in the first 40 s of the emission, is interpreted as the
proto-black-hole emission; the second episode, observed after t+50 s, as a
canonical gamma ray burst. The transition between the two episodes marks the
black hole formation. The characteristics of the real GRB, in the second
episode, are an energy of erg, a
baryon load of and a bulk Lorentz factor at transparency
of . The clear analogy with GRB 090618 would require also in
GRB 970828 the presence of a possible supernova. We also infer that the GRB
exploded in an environment with a large average particle density part/cm and dense clouds characterized by typical dimensions
of cm and . Such an environment
is in line with the observed large column density absorption, which might have
darkened both the supernova emission and the GRB optical afterglow.Comment: 7 pages, 10 figures, submitted to Ap
A common behavior in the late X-ray afterglow of energetic GRB-SN systems
The possibility to divide GRBs in different subclasses allow to understand
better the physics underlying their emission mechanisms and progenitors. The
induced gravitational collapse scenario proposes a binary progenitor to explain
the time-sequence in GRBs-SNe. We show the existence of a common behavior of
the late decay of the X-ray afterglow emission of this subclass of GRBs,
pointing to a common physical mechanism of their late emission, consistent with
the IGC picture.Comment: 3 pages, to appear in the proceedings of the Gamma-Ray Burst
Symposium 2012 - IAA-CSIC - Marbella, editors: Castro-Tirado, A. J.,
Gorosabel, J. and Park, I.
GRB 081024B and GRB 140402A: two additional short GRBs from binary neutron star mergers
Theoretical and observational evidences have been recently gained for a
two-fold classification of short bursts: 1) short gamma-ray flashes (S-GRFs),
with isotropic energy ~erg and no BH formation, and 2) the
authentic short gamma-ray bursts (S-GRBs), with isotropic energy
~erg evidencing a BH formation in the binary neutron star
merging process. The signature for the BH formation consists in the on-set of
the high energy (--~GeV) emission, coeval to the prompt emission, in
all S-GRBs. No GeV emission is expected nor observed in the S-GRFs. In this
paper we present two additional S-GRBs, GRB 081024B and GRB 140402A, following
the already identified S-GRBs, i.e., GRB 090227B, GRB 090510 and GRB 140619B.
We also return on the absence of the GeV emission of the S-GRB 090227B, at an
angle of from the \textit{Fermi}-LAT boresight. All the correctly
identified S-GRBs correlate to the high energy emission, implying no
significant presence of beaming in the GeV emission. The existence of a common
power-law behavior in the GeV luminosities, following the BH formation, when
measured in the source rest-frame, points to a commonality in the mass and spin
of the newly-formed BH in all S-GRBs.Comment: 16 pages, submitted to ApJ, second version addressing the comments by
the refere
GRB 170817A-GW170817-AT 2017gfo and the observations of NS-NS, NS-WD and WD-WD mergers
The LIGO-Virgo Collaboration has announced the detection of GW170817 and has
associated it with GRB 170817A. These signals have been followed after 11 hours
by the optical and infrared emission of AT 2017gfo. The origin of this complex
phenomenon has been attributed to a neutron star-neutron star (NS-NS) merger.
In order to probe this association we confront our current understanding of the
gravitational waves and associated electromagnetic radiation with four observed
GRBs originating in binaries composed of different combinations NSs and white
dwarfs (WDs). We consider 1) GRB 090510 the prototype of NS-NS merger leading
to a black hole (BH); 2) GRB 130603B the prototype of a NS-NS merger leading to
massive NS (MNS) with an associated kilonova; 3) GRB 060614 the prototype of a
NS-WD merger leading to a MNS with an associated kilonova candidate; 4) GRB
170817A the prototype of a WD-WD merger leading to massive WD with an
associated AT 2017gfo-like emission. None of these systems support the above
mentioned association. The clear association between GRB 170817A and AT 2017gfo
has led to introduce a new model based on on a new subfamily of GRBs
originating from WD-WD mergers. We show how this novel model is in agreement
with the exceptional observations in the optical, infrared, X- and gamma-rays
of GRB 170817A-AT 2017gfo.Comment: version accepted for publication in JCAP. Missing references adde
An evaporitic origin of the parent brines of Colombian emeralds : fluid inclusion and sulphur isotope evidence
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