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Author: Publisher: ISBN: Category : Languages : en Pages : 8
Book Description
Motivated by the recent developments in the cyclotron resonance upscattering of soft photons or CUSP model of Gamma Ray Burst (GRB) continuum spectra, we revisit a select database of GRBs with credible cyclotron absorption features. We measure the break energy of the continuum, the slope below the break and deduce the soft photon energy or the electron beam Lorentz factor cutoff. We study the correlation (or lack of) between various parameters in the context of the CUSP model. One surprise result is that there appears to be marginal correlation between the break energy and the spectral index below the break. 20 refs., 8 figs., 2 tabs.
Author: Publisher: ISBN: Category : Languages : en Pages : 8
Book Description
Motivated by the recent developments in the cyclotron resonance upscattering of soft photons or CUSP model of Gamma Ray Burst (GRB) continuum spectra, we revisit a select database of GRBs with credible cyclotron absorption features. We measure the break energy of the continuum, the slope below the break and deduce the soft photon energy or the electron beam Lorentz factor cutoff. We study the correlation (or lack of) between various parameters in the context of the CUSP model. One surprise result is that there appears to be marginal correlation between the break energy and the spectral index below the break. 20 refs., 8 figs., 2 tabs.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Spectral measurements by the Solar Maximum Mission have been used to confirm the cyclotron lines in gamma-ray bursts reported from the Konus experiment. We present ISEE-3 data for the same burst (GB800419) during the same period of time which show no line. We discuss various problems in the analysis of scintillator spectra and point out that unfolded spectra are not necessarily unique and that the position of a data point in a deconvolved spectrum may vary depending on the assumed overall shape of the spectrum. As a result, if the analysis assumes a soft spectrum (such as optically thin thermal bremsstrahlung) an absorption feature might appear, whereas a harder spectrum (such as a Comptonized blackbody) would not require the feature. Since the continuum shape probably changes during the duration of a typical burst, the nonuniqueness of the spectral unfolding, combined with the assumption that the continuum is optically thin thermal bremsstrahlung, could give rise to spurious absorption features which vary on a time scale of seconds. Despite these problems, there is still some evidence for narrow spectral lines in the range 45 to 65 keV but not for the broad lines reported from the Konus experiment. Unfortunately, the range 45 to 65 keV is the most difficult spectral region to unfold.
Author: Cheng Ho Publisher: Cambridge University Press ISBN: 9780521414494 Category : Nature Languages : en Pages : 532
Book Description
Summarizes the current understanding of Astronomical gamma-ray bursts, short-lived flashes of high-energy radiation, which have eluded even a basic explanation for over twenty years, and describes directions for future research.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Gamma-ray bursts are observed to have very steep spectra below photon energy /approximately/100 keV; some have photon number spectra as steep as F /proportional to/ E/sup 0/. This property has been difficult to explain in terms of most radiation processes. The BATSE experiment on the Gamma Ray Observatory should be able to test how common this spectral property is and whether there are bursts with even steeper low-energy spectra. To explain this spectral steepness, we study a model in which the /gamma/ radiation is produced by inverse-Compton and cyclotron scattering of blackbody radiation from the surface of a neutron star by relativistic electrons. If the neutron star has negligible magnetic field, Compton scattering dominates in producing the observed gamma-ray burst spectra. If the field exceeds 10/sup 10/ G, cyclotron scattering is more important. In the low-magnetic-field case, steep spectra may be produced via the suppression of the low energy part of the ''cooling spectrum'' (the spectrum integrated over the radiation lifetime of an electron), as a result of the smaller and more collimated photon flux an electron sees as it moves away from the neutron star. In the high-magnetic-field case, low-energy suppression occurs because electrons with higher energies scatter the blackbody photons more efficiently due to the cyclotron resonance, preferentially producing high energy photons. 27 refs., 5 figs.
Author: Gerald J. Fishman Publisher: American Institute of Physics ISBN: 9781563963360 Category : Technology & Engineering Languages : en Pages : 776
Book Description
Annotation Proceedings of the Second Huntsville Gamma-Ray Burst Workshop, held in Huntsville, Alabama, October 1993. Papers are grouped in thematic sections, some with subsections: general observations and global studies (general burst observations/intensity distributions and isotropy measures/studies of and searches for burst repetition and clustering); temporal studies; spectral studies; burst localizations and searches for counterparts (burst localization/counterpartsgeneral/optical counterparts/x-ray counterparts/very high energy counterpart searches/soft gamma-ray repeaters--counterparts); burst origins and emission processes--theory (cosmological models/galactic models/soft gamma-ray repeaters--theory); instrumentation and new analysis techniques; and miscellaneous. No index. Annotation c. by Book News, Inc., Portland, Or.
Author: Publisher: ISBN: Category : Languages : en Pages : 17
Book Description
We review the theoretical framework of both line and continuum spectra formation in gamma ray bursts. These include the cyclotron features at 10's of keV, redshifted annihilation features at (approximately)400 keV, as well as other potentially detectable nuclear transition lines, atomic x-ray lines, proton cyclotron lines and plasma oscillation lines. By combining the parameters derived from line and continuum modeling we can try to reconstruct the location, geometry and physical conditions of the burst emission region, thereby constraining and discriminating the astrophysical models. Hence spectroscopy with current and future generations of detectors should provide powerful diagnostic tools for gamma ray bursters. 48 refs., 10 figs., 4 tabs.
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Author: Cheng Ho
Author: Jay Preston Norris
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Author: Gerald J. Fishman
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Author: Dieter H. B. Hartmann
Author: Lyle A. Ford
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