2013A&A...550A.102T


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.14CEST19:20:57

2013A&A...550A.102T - Astronomy and Astrophysics, volume 550A, 102-102 (2013/2-1)

Anomalies in low-energy gamma-ray burst spectra with the Fermi gamma-ray burst monitor.

TIERNEY D., McBREEN S., PREECE R.D., FITZPATRICK G., FOLEY S., GUIRIEC S., BISSALDI E., BRIGGS M.S., BURGESS J.M., CONNAUGHTON V., GOLDSTEIN A., GREINER J., GRUBER D., KOUVELIOTOU C., McGLYNN S., PACIESAS W.S., PELASSA V. and VON KIENLIN A.

Abstract (from CDS):

A Band function has become the standard spectral function used to describe the prompt emission spectra of gamma-ray bursts (GRBs). However, deviations from this function have previously been observed in GRBs detected by BATSE and in individual GRBs from the Fermi era. We present a systematic and rigorous search for spectral deviations from a Band function at low energies in a sample of the first two years of high fluence, long bursts detected by the Fermi Gamma-ray Burst Monitor (GBM). The sample contains 45 bursts with a fluence greater than 2x10–5erg/cm2 (10-1000keV). An extrapolated fit method is used to search for low-energy spectral anomalies, whereby a Band function is fit above a variable low-energy threshold and then the best fit function is extrapolated to lower energy data. Deviations are quantified by examining residuals derived from the extrapolated function and the data and their significance is determined via comprehensive simulations which account for the instrument response. This method was employed for both time-integrated burst spectra and time-resolved bins defined by a signal-to-noise ratio of 25σ and 50σ. Significant deviations are evident in 3 bursts (GRB081215A, GRB090424 and GRB090902B) in the time-integrated sample (∼7%) and 5 bursts (GRB090323, GRB090424, GRB090820, GRB090902B and GRB090926A) in the time-resolved sample (∼11%). The advantage of the systematic, blind search analysis is that it can demonstrate the requirement for an additional spectral component without any prior knowledge of the nature of that extra component. Deviations are found in a large fraction of high fluence GRBs; fainter GRBs may not have sufficient statistics for deviations to be found using this method.

Abstract Copyright:

Journal keyword(s): gamma-ray burst: general - methods: data analysis - techniques: spectroscopic

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 M 1 SNR 05 34 31.94 +22 00 52.2           ~ 5596 4
2 GRB 090820 gB 05 51 +27.1           ~ 34 0
3 GRB 081215A gB 08 22 +54.0           ~ 46 0
4 GRB 090102 gB 08 32 59.50 +33 06 25.7           ~ 184 0
5 GRB 080817 gB 10 05 09.600 -19 15 36.00           ~ 22 0
6 GRB 090424 gB 12 38 07.40 +16 49 45.9           ~ 202 0
7 GRB 090323 gB 12 42 50.28 +17 03 11.9           ~ 183 1
8 GRB 090902B gB 17 39 45.26 +27 19 28.1           ~ 327 0
9 GRB 090618 gB 19 36 01.80 +78 21 07.1           ~ 269 0
10 GRB 091024 gB 22 37 +56.9           ~ 107 0
11 GRB 090926A gB 23 33 36.18 -66 19 25.9           ~ 250 0

    Equat.    Gal    SGal    Ecl

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2020.07.14-19:20:57

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