5,838 research outputs found
Gravitationally Lensed Gamma-Ray Bursts as Probes of Dark Compact Objects
If dark matter in the form of compact objects comprises a large fraction of
the mass of the universe, then gravitational lensing effects on gamma-ray
bursts are expected. We utilize BATSE and Ulysses data to search for lenses of
different mass ranges, which cause lensing in the milli, pico, and femto
regimes. Null results are used to set weak limits on the cosmological abundance
of compact objects in mass ranges from 10 to 10 . A
stronger limit is found for a much discussed universe dominated
by black holes of masses , which is ruled out at the
90% confidence level.Comment: 14 pages, 4 figures, fixed minor corrections. Accepted for
publication in ApJ(L
No Evidence for Gamma-Ray Burst/Abell Cluster or Gamma- Ray Burst/Radio-Quiet Quasar Correlations
We examine the recent claims that cosmic gamma-ray bursts are associated with
either radio-quiet quasars or Abell clusters. These associations were based on
positional coincidences between cataloged quasars or Abell clusters, and
selected events from the BATSE 3B catalog of gamma-ray bursts. We use a larger
sample of gamma-ray bursts with more accurate positions, obtained by the 3rd
Interplanetary Network, to re-evaluate these possible associations. We find no
evidence for either.Comment: Accepted for publication in the Astrophysical Journa
Cooling of 2 kW H subscript 2-O subscript 2 fuel cell
An extensive research and development program has been carried out to devise an improved method of removing waste heat of reaction from a developmental 2 kW hydrogen-oxygen fuel cell
SGR 1806-20 Is a Set of Independent Relaxation Systems
The Soft Gamma Repeater 1806-20 produced patterns of bursts during its 1983
outburst that indicate multiple independent energy accumulation sites, each
driven by a continuous power source, with sudden, incomplete releases of the
accumulated energy. The strengths of the power sources and their durations of
activity vary over several orders of magnitude.Comment: Accepted ApJLett, 15 pages, 3 figure
Evidence for a Fast Decline in the Progenitor Population of Gamma Ray Bursts and the Nature of their Origin
We show that the source population of long gamma-ray bursts (GRBs) has
declined by at least a factor of 12 (at the 90% confidence level) since the
early stages of the Universe (). This result has been obtained
using the combined BATSE and \it Ulysses \rm GRB brightness distribution and
the detection of four GRBs with known redshifts brighter than 10 erg
s in the 50 - 300 keV range at their peak. The data indicate that the
decline of the GRB source population is as fast as, or even faster than, the
measured decline of the star formation rate. Models for the evolution of
neutron star binaries predict a significantly larger number of apparently
bright GRBs than observed. Thus our results give independent support to the
hypernova model, which naturally explains the fast decline in the progenitor
population.Comment: 7 pages, 6 figures, submitted to ApJ, added reference
Nature of fault planes in solid neutron star matter
The properties of tectonic earthquake sources are compared with those deduced
here for fault planes in solid neutron-star matter. The conclusion that
neutron-star matter cannot exhibit brittle fracture at any temperature or
magnetic field is significant for current theories of pulsar glitches, and of
the anomalous X-ray pulsars and soft-gamma repeaters.Comment: 5 AAS LaTeX pages 1 eps figur
Gamma Ray Burst Host Galaxies Have `Normal' Luminosities
The galactic environment of Gamma Ray Bursts can provide good evidence about
the nature of the progenitor system, with two old arguments implying that the
burst host galaxies are significantly subluminous. New data and new analysis
have now reversed this picture: (A) Even though the first two known host
galaxies are indeed greatly subluminous, the next eight hosts have absolute
magnitudes typical for a population of field galaxies. A detailed analysis of
the 16 known hosts (ten with red shifts) shows them to be consistent with a
Schechter luminosity function with as expected for
normal galaxies. (B) Bright bursts from the Interplanetary Network are
typically 18 times brighter than the faint bursts with red shifts, however the
bright bursts do not have galaxies inside their error boxes to limits deeper
than expected based on the luminosities for the two samples being identical. A
new solution to this dilemma is that a broad burst luminosity function along
with a burst number density varying as the star formation rate will require the
average luminosity of the bright sample (
or ) to be much greater than the
average luminosity of the faint sample ( or ). This places the bright bursts at distances
for which host galaxies with a normal luminosity will not violate the observed
limits. In conclusion, all current evidence points to GRB host galaxies being
normal in luminosity.Comment: 18 pages, 3 figures, Submitted to ApJLet
The Interplanetary Network Supplement to the BeppoSAX Gamma-Ray Burst Catalogs
Between 1996 July and 2002 April, one or more spacecraft of the
interplanetary network detected 787 cosmic gamma-ray bursts that were also
detected by the Gamma-Ray Burst Monitor and/or Wide-Field X-Ray Camera
experiments aboard the BeppoSAX spacecraft. During this period, the network
consisted of up to six spacecraft, and using triangulation, the localizations
of 475 bursts were obtained. We present the localization data for these events.Comment: 89 pages, 3 figures. Submitted to the Astrophysical Journal
Supplement Serie
Stereoscopic observations of hard x ray sources in solar flares made with GRO and other spacecraft
Since the launch of the Gamma Ray Observatory (GRO) in Apr. 1991, the Burst and Transient Source Experiment (BATSE) instrument on GRO has recorded a large number of solar flares. Some of these flares have also been observed by the Gamma-Ray Burst Detector on the Pioneer Venus Orbiter (PVO) and/or by the Solar X-Ray/Cosmic Gamma-Ray Burst Experiment on the Ulysses spacecraft. A preliminary list of common flares observed during the period May-Jun. 1991 is presented and the possible joint studies are indicated
The distances of short-hard GRBs and the SGR connection
We present a search for nearby (D<100 Mpc) galaxies in the error boxes of six
well-localized short-hard gamma-ray bursts (GRBs). None of the six error boxes
reveals the presence of a plausible nearby host galaxy. This allows us to set
lower limits on the distances and, hence, the isotropic-equivalent energy of
these GRBs. Our lower limits are around erg (at
confidence level); as a consequence, some of the short-hard GRBs we examine
would have been detected by BATSE out to distances greater than 1 Gpc and
therefore constitute a bona fide cosmological population. Our search is
partially motivated by the December 27, 2004 hypergiant flare from SGR 1806-20,
and the intriguing possibility that short-hard GRBs are extragalactic events of
a similar nature. Such events would be detectable with BATSE to a distance of
\~50 Mpc, and their detection rate should be comparable to the actual BATSE
detection rate of short-hard GRBs. The failure of our search, by contrast,
suggests that such flares constitute less than 15% of the short-hard GRBs (<40%
at 95% confidence). We discuss possible resolutions of this discrepancy.Comment: Enlarged sample of bursts; ApJ in pres
- âŠ