4,164 research outputs found
Synchrotron Emission as the Source of GRB Spectra, Part II: Observations
We test the models of synchrotron emission presented in Part I of this series
(Lloyd & Petrosian, these proceedings) against the distributions and evolution
of GRB spectral parameters (particularly the low energy index, ). With
knowledge of the distribution and the correlation between and
presented in Part I, we show how to derive the expected distribution of
from fits to optically thin synchrotron spectra, and compare this with
the observed distribution. We show that there is no difficulty explaining
bursts below the ``line of death'', , and that these bursts
indicate that the spectrum of accelerated electrons must flatten or decline at
low energies. Bursts with low energy spectral indices that fall above this
limit are explained by the synchrotron self-absorption frequency entering the
lower end of the BATSE window. Finally, we discuss a variety of spectral
evolution behavior seen in GRBs and explain this behavior in the context of
synchrotron emission from internal shocks.Comment: To appear in the proceedings of the 5th Huntsville Symposium on Gamma
Ray Burst
Proving Lost Profits Under Daubert: Five Questions Every Court Should Ask Before Admitting Expert Testimony
Cosmological versus Intrinsic: The Correlation between Intensity and the Peak of the nu F_nu Spectrum of Gamma Ray Bursts
We present results of correlation studies, examining the association between
the peak of the nu F_nu spectrum of gamma ray bursts, E_p, with the burst's
energy fluence and photon peak flux. We discuss methods to account for data
truncation in E_p and fluence or flux when performing the correlation analyses.
However, because bursts near the detector threshold are not usually able to
provide reliable spectral parameters, we focus on results for the brightest
bursts in which we can better understand the selection effects relevant to E_p
and burst strength.
We find that there is a strong correlation between total fluence and E_p. We
discuss these results in terms of both cosmological and intrinsic effects.
In particular, we show that for realistic distributions of the burst
parameters, cosmological expansion alone cannot account for the correlation
between E_p and total fluence; the observed correlation is likely a result of
an intrinsic relation between the burst rest-frame peak energy and the total
radiated energy. We investigate this latter scenario in the context of
synchrotron radiation from external and internal shock models of GRBs. We find
that the internal shock model is consistent with our interpretation of the
correlation, while the external shock model cannot easily explain this
intrinsic relation between peak energy and burst radiated energy.Comment: 23 pages, including 8 postscript figures. Submitted to Ap
A Middle Miocene Rhinoceros Quarry in Morrill County, Nebraska (with Notes on Hip Disease in Diceratherium)
Extensive deposits of fossil rhinoceros bones have been excavated from University of Nebraska State Museum collecting localities Mo-113, -114, -115, -116, and -118 some 8 1/2 to 9 1/2 miles north of Bridgeport, Morrill County, Nebraska. The fossils were associated with other faunal elements in the lower portion of the Marsland formation (middle Miocene) of the Hemingford group. The rhinoceros is considered to be Diceratherium niobrarensis Peterson, geologic variety. A pathologic right femur of D. niobrarensis provides evidence of hip disease in the medial Miocene rhinoceroses
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