7 research outputs found
Gamma-Ray Burst Detection with INTEGRAL/SPI
The spectrometer SPI, one of the two main instruments of the INTEGRAL
spacecraft, has strong capabilities in the Field of Gamma-Ray Burst (GRB)
detections. In its 16 degree Field of view (FoV) SPI is able to trigger and to
localize GRBs. With its large anticoincidence shield (ACS) of 512 kg of BGO
crystals SPI is able to detect GRBs quasi omnidirectionally with a very high
sensitivity. The ACS GRB alerts will provide GRB arrival times with high
accuracy but with no or very rough positional information. The expected GRB
detection rate in SPI's FoV will be one per month and for the ACS around 300
per year. At MPE two SPI software contributions to the real-time INTEGRAL
burst-alert system (IBAS) at the INTEGRAL science data centre ISDC have been
developed. The SPI-ACS branch of IBAS will produce burst alerts and
light-curves with 50 ms resolution. It is planned to use ACS burst alerts in
the 3rd interplanetary network. The SPI-FoV branch of IBAS is currently under
development at MPE. The system is using the energy and timing information of
single and multiple events detected by the Germanium-camera of SPI. Using the
imaging algorithm developed at the University of Birmingham the system is
expected to locate strong bursts with an accuracy of better than 1 degree.Comment: 11 pages, 5 figure
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
Radioactive 26Al and massive stars in the Galaxy
Gamma-rays from radioactive 26Al (half life ~7.2 10^5 yr) provide a
'snapshot' view of ongoing nucleosynthesis in the Galaxy. The Galaxy is
relatively transparent to such gamma-rays, and emission has been found
concentrated along the plane of the Galaxy. This led to the conclusion1 that
massive stars throughout the Galaxy dominate the production of 26Al. On the
other hand, meteoritic data show locally-produced 26Al, perhaps from spallation
reactions in the protosolar disk. Furthermore, prominent gamma-ray emission
from the Cygnus region suggests that a substantial fraction of Galactic 26Al
could originate in localized star-forming regions. Here we report high spectral
resolution measurements of 26Al emission at 1808.65 keV, which demonstrate that
the 26Al source regions corotate with the Galaxy, supporting its Galaxy-wide
origin. We determine a present-day equilibrium mass of 2.8 (+/-0.8) M_sol of
26Al. We use this to estimate that the frequency of core collapse (i.e. type
Ib/c and type II) supernovae to be 1.9(+/- 1.1) events per century.Comment: accepted for publication in Nature, 24 pages including Online
Supplements, 11 figures, 1 tabl
The GLAST Burst Monitor
The next large NASA mission in the field of gamma-ray astronomy, GLAST, is
scheduled for launch in 2007. Aside from the main instrument LAT (Large-Area
Telescope), a gamma-ray telescope for the energy range between 20 MeV and > 100
GeV, a secondary instrument, the GLAST burst monitor (GBM), is foreseen. With
this monitor one of the key scientific objectives of the mission, the
determination of the high-energy behaviour of gamma-ray bursts and transients
can be ensured. Its task is to increase the detection rate of gamma-ray bursts
for the LAT and to extend the energy range to lower energies (from ~10 keV to
\~30 MeV). It will provide real-time burst locations over a wide FoV with
sufficient accuracy to allow repointing the GLAST spacecraft. Time-resolved
spectra of many bursts recorded with LAT and the burst monitor will allow the
investigation of the relation between the keV and the MeV-GeV emission from
GRBs over unprecedented seven decades of energy. This will help to advance our
understanding of the mechanisms by which gamma-rays are generated in gamma-ray
bursts.Comment: 8 pages, 7 figures, to appear in SPIE conference proceedings vol
5488, "UV-Gamma Ray Space Telescope Systems," Glasgow UK, 21-24 June 200
Ground-based calibration and characterization of the Fermi Gamma-Ray Burst Monitor Detectors
One of the scientific objectives of NASA's Fermi Gamma-ray Space Telescope is
the study of Gamma-Ray Bursts (GRBs). The Fermi Gamma-Ray Burst Monitor (GBM)
was designed to detect and localize bursts for the Fermi mission. By means of
an array of 12 NaI(Tl) (8 keV to 1 MeV) and two BGO (0.2 to 40 MeV)
scintillation detectors, GBM extends the energy range (20 MeV to > 300 GeV) of
Fermi's main instrument, the Large Area Telescope, into the traditional range
of current GRB databases. The physical detector response of the GBM instrument
to GRBs is determined with the help of Monte Carlo simulations, which are
supported and verified by on-ground individual detector calibration
measurements. We present the principal instrument properties, which have been
determined as a function of energy and angle, including the channel-energy
relation, the energy resolution, the effective area and the spatial
homogeneity.Comment: 36 pages, 28 figures, accepted for publication in Experimental
Astronom
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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