38 research outputs found
The Locations of Gamma-Ray Bursts Measured by COMPTEL
The COMPTEL instrument on the Compton Gamma Ray Observatory is used to
measure the locations of gamma-ray bursts through direct imaging of MeV
photons. In a comprehensive search, we have detected and localized 29 bursts
observed between 1991 April 19 and 1995 May 31. The average location accuracy
of these events is 1.25\arcdeg (1), including a systematic error of
\sim0.5\arcdeg, which is verified through comparison with Interplanetary
Network (IPN) timing annuli. The combination of COMPTEL and IPN measurements
results in locations for 26 of the bursts with an average ``error box'' area of
only 0.3 deg (1). We find that the angular distribution of
COMPTEL burst locations is consistent with large-scale isotropy and that there
is no statistically significant evidence of small-angle auto-correlations. We
conclude that there is no compelling evidence for burst repetition since no
more than two of the events (or 7% of the 29 bursts) could possibly have
come from the same source. We also find that there is no significant
correlation between the burst locations and either Abell clusters of galaxies
or radio-quiet quasars. Agreement between individual COMPTEL locations and IPN
annuli places a lower limit of 100~AU (95% confidence) on the distance to
the stronger bursts.Comment: Accepted for publication in the Astrophysical Journal, 1998 Jan. 1,
Vol. 492. 33 pages, 9 figures, 5 table
Discovery of a New Soft Gamma Repeater, SGR 1627-41
We report the discovery of a new soft gamma repeater (SGR), SGR 1627-41, and
present BATSE observations of the burst emission and BeppoSAX NFI observations
of the probable persistent X-ray counterpart to this SGR. All but one burst
spectrum are well fit by an optically thin thermal bremsstrahlung (OTTB) model
with kT values between 25 and 35 keV. The spectrum of the X-ray counterpart,
SAX J1635.8-4736, is similar to that of other persistent SGR X-ray
counterparts. We find weak evidence for a periodic signal at 6.41 s in the
light curve for this source. Like other SGRs, this source appears to be
associated with a young supernova remnant G337.0-0.1. Based upon the peak
luminosities of bursts observed from this SGR, we find a lower limit on the
dipole magnetic field of the neutron star B_dipole > 5 * 10^14 Gauss.Comment: 5 pages, 4 figures, submitted to ApJ Letter
INTEGRAL Spectrometer Analysis of GRB030227 & GRB030131
The spectrometer SPI on board INTEGRAL is capable of high-resolution
spectroscopic studies in the energy range 20keV to 8MeV for GRBs which occur
within the fully coded field of view (16 degrees corner to corner). Six GRBs
occurred within the SPI field of view between October 2002 and November 2003.
We present results of the analysis of the first two GRBs detected by SPI after
the payload performance and verification phase of INTEGRAL.Comment: 4 pages, to appear in proceedings of 2003 Gamma-Ray Burst Conference
(Santa Fe, New Mexico, September 8-12, 2003), to be published by AI
Preliminary INTEGRAL Analysis of GRB040106
On January 6th 2004, the IBAS burst alert system triggered the 8th gamma-ray
burst (GRB) to be detected by the INTEGRAL satellite. The position was
determined and publicly distributed within 12s, enabling ESA's XMM-Newton to
take advantage of a ToO observation just 5 hours later during which the x-ray
afterglow was detected. Observations at optical wavelengths also revealed the
existence of a fading optical source. The GRB is ~52s long with 2 distinct
peaks separated by ~24s. At gamma-ray energies the burst was the weakest
detected by INTEGRAL up to that time with a flux in the 20-200 keV band of 0.57
photons/cm^2/s. Nevertheless, it was possible to determine its position and
extract spectra and fluxes. Here we present light curves and the results of
imaging, spectral and temporal analyses of the prompt emission and the onset of
the afterglow from INTEGRAL data.Comment: 4 pages. To appear in proceedings of the 5th INTEGRAL Workshop, "The
INTEGRAL Universe", February 16-20, 2004, Munich. (Typos corrected in author
addresses, some refs added
CASTER - a concept for a Black Hole Finder Probe based on the use of new scintillator technologies
The primary scientific mission of the Black Hole Finder Probe (BHFP), part of
the NASA Beyond Einstein program, is to survey the local Universe for black
holes over a wide range of mass and accretion rate. One approach to such a
survey is a hard X-ray coded-aperture imaging mission operating in the 10--600
keV energy band, a spectral range that is considered to be especially useful in
the detection of black hole sources. The development of new inorganic
scintillator materials provides improved performance (for example, with regards
to energy resolution and timing) that is well suited to the BHFP science
requirements. Detection planes formed with these materials coupled with a new
generation of readout devices represent a major advancement in the performance
capabilities of scintillator-based gamma cameras. Here, we discuss the Coded
Aperture Survey Telescope for Energetic Radiation (CASTER), a concept that
represents a BHFP based on the use of the latest scintillator technology.Comment: 12 pages; conference paper presented at the SPIE conference "UV,
X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XIV." To be
published in SPIE Conference Proceedings, vol. 589
Calibration of the GLAST Burst Monitor detectors
The GLAST Burst Monitor (GBM) will augment the capabilities of GLAST for the
detection of cosmic gamma-ray bursts by extending the energy range (20 MeV to >
300 GeV) of the Large Area Telescope (LAT) towards lower energies by 2
BGO-detectors (150 keV to 30 MeV) and 12 NaI(Tl) detectors (10 keV to 1 MeV).
The physical detector response of the GBM instrument for GRBs is determined
with the help of Monte Carlo simulations, which are supported and verified by
on-ground calibration measurements, performed extensively with the individual
detectors at the MPE in 2005. All flight and spare detectors were irradiated
with calibrated radioactive sources in the laboratory (from 14 keV to 4.43
MeV). The energy/channel-relations, the dependences of energy resolution and
effective areas on the energy and the angular responses were measured. Due to
the low number of emission lines of radioactive sources below 100 keV,
calibration measurements in the energy range from 10 keV to 60 keV were
performed with the X-ray radiometry working group of the
Physikalisch-Technische Bundesanstalt (PTB) at the BESSY synchrotron radiation
facility, Berlin.Comment: 2 pages, 1 figure; to appear in the Proc. of the First Int. GLAST
Symp. (Stanford, Feb. 5-8, 2007), eds. S.Ritz, P.F.Michelson, and C.Meegan,
AIP Conf. Pro
CASTER: a scintillator-based black hole finder probe
The primary scientific mission of the Black Hole Finder Probe (BHFP), part of the NASA Beyond Einstein program, is to survey the local Universe for black holes over a wide range of mass and accretion rate. One approach to such a survey is a hard X-ray coded-aperture imaging mission operating in the 10-600 keV energy band, a spectral range that is considered to be especially useful in the detection of black hole sources. The development of new inorganic scintillator materials provides improved performance (for example, with regards to energy resolution and timing) that is well suited to the BHFP science requirements. Detection planes formed with these materials coupled with a new generation of readout devices represent a major advancement in the performance capabilities of scintillator-based gamma cameras. Here, we discuss the Coded Aperture Survey Telescope for Energetic Radiation (CASTER), a concept that represents a BHFP based on the use of the latest scintillator technology