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  • 1
    Digitale Medien
    Digitale Medien
    Constraints on the luminosities of gamma-ray bursts (1995)
    Springer
    Astrophysics and space science 231 (1995), S. 369-372 
    Details
    ISSN: 1572-946X
    Schlagwort(e): gamma-ray bursts ; luminosities ; origins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Constraints are found on the gamma-ray burst luminosity function from an analysis of the combined BATSE/PVO intensity distribution. If bursts originate in an extended Galactic halo, then the intrinsic luminosity range is narrow, with bursts spanning only a factor of five or less in luminosity. If bursts originate in a simple Friedmann cosmology with Ω = 1 and Λ = 0, then very few luminosity constraints exist.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00658652
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  • 2
    Digitale Medien
    Digitale Medien
    Selection effects and tests of repetition (clustering) in the BATSE 1B catalog (1995)
    Springer
    Astrophysics and space science 231 (1995), S. 23-26 
    Details
    ISSN: 1572-946X
    Schlagwort(e): gamma-ray bursts ; repetition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A “repeater statistic” (derived from the two-point angular correlation function and accounting for location errors) is used to identify constraints on the rate of burst repetition from the BATSE 1B catalog. Because of the anisotropic sky exposure, repeating sources should create additional effects in the large-scale distribution of close burst pairs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00658581
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  • 3
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    GBM Observations of Terrestrial Gamma-Ray Flashes (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-19
    Beschreibung: The TGF detection rate of Gamma-ray Burst Monitor (GBM) has been increased twice since launch. The most recent improvement is from a new operating mode in which data for individual photons are down-linked for selected portions of the orbit, enabling a more sensitive ground-based search for TGFs. The new search has increased the TGF detection rate and is finding TGFs more than five times fainter than the TGFs of the previous GBM sample. We summarize the properties of the original GBM TGF sample and compare to the less intense TGFs now being detected. In addition to gamma-ray TGFs, GBM is observing distant TGFs from the propagation of charged particles along geomagnetic field lines. Strong 511 keV annihilation lines have been observed, demonstrating that both electrons and positrons are present in the particle beams. Spectral fits to these electron/positron TGFs will be shown.
    Schlagwort(e): Astronomy
    Materialart: M11-0072 , 2010 American Geophysical Union (AGU) Fall Meeting; Dec 13, 2010 - Dec 17, 2010; San Francisco, CA; United States
    Format: application/pdf
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  • 4
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    SGR J1550-5418 Bursts Detected with the Fermi Gamma-Ray Burst Monitor during Its Most Prolific Activity (2012)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We have performed detailed temporal and time-integrated spectral analysis of 286 bursts from SGR J1550-5418 detected with the Fermi Gamma-ray Burst Monitor (GBM) in 2009 January, resulting in the largest uniform sample of temporal and spectral properties of SGR J1550-5418 bursts. We have used the combination of broadband and high time-resolution data provided with GBM to perform statistical studies for the source properties.We determine the durations, emission times, duty cycles, and rise times for all bursts, and find that they are typical of SGR bursts. We explore various models in our spectral analysis, and conclude that the spectra of SGR J15505418 bursts in the 8-200 keV band are equally well described by optically thin thermal bremsstrahlung (OTTB), a power law (PL) with an exponential cutoff (Comptonized model), and two blackbody (BB) functions (BB+BB). In the spectral fits with the Comptonized model, we find a mean PL index of -0.92, close to the OTTB index of -1. We show that there is an anti-correlation between the Comptonized E(sub peak) and the burst fluence and average flux. For the BB+BBfits, we find that the fluences and emission areas of the two BB functions are correlated. The low-temperature BB has an emission area comparable to the neutron star surface area, independent of the temperature, while the high temperature BB has a much smaller area and shows an anti-correlation between emission area and temperature.We compare the properties of these bursts with bursts observed from other SGR sources during extreme activations, and discuss the implications of our results in the context of magnetar burst models.
    Schlagwort(e): Astronomy
    Materialart: GSFC-E-DAA-TN9469 , Astrophysical Journal; 749; 2; 122
    Format: application/pdf
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  • 5
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    When a Standard Candle Flickers: Crab Nebula Variations in Hard X-rays (2011)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-19
    Beschreibung: In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM) since August 2008, a ~7% (70 mcrab) decline was observed in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline is independently confirmed in the ~15-50 keV band with four other instruments: Swift/BAT, the RXTE/PCA, INTEGRAL/IBIS, and INTEGRAL/SPI. A similar decline is also observed in the ~3-15 keV data from the RXTE/PCA and in the 50-100 keV band with GBM, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA since 1999 is consistent with the pulsar spin-down, indicating that the observed changes are nebular. Correlated variations in the Crab Nebula flux on a ~3 year timescale are also seen independently with the PCA, BAT, IBIS, and SPI from 2005 to 2008, with a flux minimum in April 2007. As of April 2011, the Crab nebula flux has stopped declining and may be beginning to increase. We will present updated results on our multi-instrument study of long-term Crab nebula variations.
    Schlagwort(e): Astronomy
    Materialart: M11-0563 , 2011 meeting of the High Energy Astrophysics Division of the American Astronomical Society; Sep 07, 2011 - Sep 10, 2011; Providence, RI; United States
    Format: application/pdf
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  • 6
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    The GLAST Burst Monitor (2001)
    In:  Other Sources
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    Publikationsdatum: 2019-07-18
    Beschreibung: The GLAST Burst Monitor The Gamma Ray Large Area Space Telescope, scheduled for launch in 2006, comprises a Large Area Telescope (LAT) and a GLAST Burst Monitor (GBM). The LAT is a pair telescope with unprecedented sensitivity in the 20 Mev to 300 GeV energy range. The GLAST Burst Monitor (GBM) consists of an array of NaI and BGO scintillation detectors operating in the 10 kev to 30 MeV range and covering a wide field of view. The GBM will enhance LAT observations of GRBs by extending the spectral coverage into the range of current GRB databases, and will provide a trigger for re-orienting the spacecraft to observe delayed emission from bursts outside the LAT field of view.
    Schlagwort(e): Astronomy
    Materialart: Gamma-Ray Burst and Afterglow Astronomy 2001 Workshop; Nov 05, 2001 - Nov 09, 2001; Woods Hole, MA; United States
    Format: text
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  • 7
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    GRB 970228 (1997)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-10
    Beschreibung: We made radio observations (5 GHz, 3".8 x 17" beamwidth) with the Westerbork array of the SAX/WFC error box of GRB 970228 (IAUC 6572) on Feb. 28 (19.9 hr after the onset of GRB 970228) for 1.2 hr, and on Mar. 1 and 2 for 12 hr each. The error box contains no radio sources above 0.7 mJy (4 sigma).
    Schlagwort(e): Astronomy
    Materialart: IAUC-6574 , International Astronomical Union Circular
    Format: text
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  • 8
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    A Maskless Gamma-Ray All-Sky Imager: BATSE/CGRO (1994)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The non-collimated detectors of BATSE (Burst And Transient Source Experiment) on the Compton Gamma Ray Observatory (CGRO) can be used as a high sensitivity hard X-ray and low energy gamma-ray all-sky imager in the energy range between 20 keV and 2 MeV. The fluxes from sources in the sky are modulated as the spacecraft orbits the Earth. The CGRO orbital precession further allows sampling of sky in strips corresponding to the limb of the earth at any given time. The modulation data are transformed into images by various reconstruction methods. High sensitivity images of location accuracy of about 0.1 deg and source seperation of about 1 deg are obtained.
    Schlagwort(e): Astronomy
    Materialart: NASA-CR-204027 , NAS 1.26:204027 , IEEE Transactions on Nuclear Science (ISSN 0018-9499); 41; 4; 1313-1320
    Format: text
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  • 9
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    When a Standard Candle Flickers (2010)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The Crab is the only bright steady source in the X-ray sky. The Crab consists of a pulsar wind nebula, a synchrotron nebula, and a cloud of expanding ejecta. On small scales, the Crab is extremely complex and turbulent. X-ray astronomers have often used the Crab as a standard candle to calibrate instruments, assuming its spectrum and overall flux remains constant over time. Four instruments (Fermi/GBM, RXTE/PCA, Swift/BAT, INTEGRAL/ISGRI) show a approx.5% (50 m Crab) decline in the Crab from 2008-2010. This decline appears to be larger with increasing energy and is not present in the pulsed flux, implying changes in the shock acceleration, electron population or magnetic field in the nebula. The Crab is known to be dynamic on small scales, so it is not too surprising that its total flux varies as well. Caution should be taken when using the Crab for in-orbit calibrations.
    Schlagwort(e): Astronomy
    Materialart: M10-1075 , 8th INTEGRAL Workshop: Restless Gamma-Ray Universe; Sep 27, 2010 - Sep 30, 2010; Dublin, Ireland; Ireland
    Format: application/pdf
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