A DISTINCT PEAK-FLUX DISTRIBUTION OF THE THIRD CLASS OF GAMMA-RAY BURSTS: A POSSIBLE SIGNATURE OF X-RAY FLASHES?

Journal Article · Mon Dec 20 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/725/2/1955· OSTI ID:21476654

Veres, P; Bagoly, Z ^[1]; Horvath, I ^[2]; Meszaros, A ^[3]

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1. Department of Physics of Complex Systems, Eoetvoes University, Pazmany P. s. 1/A, H-1117 Budapest (Hungary)
2. Department of Physics, Bolyai Military University, P.O. Box 15, H-1581 Budapest (Hungary)
3. Charles University, Faculty of Mathematics and Physics, Astronomical Institute, V Holesovickach 2, 180 00 Prague 8 (Czech Republic)

Gamma-ray bursts (GRBs) are the most luminous events in the universe. Going beyond the short-long classification scheme, we work in the context of three burst populations with the third group of intermediate duration and softest spectrum. We are looking for physical properties which discriminate the intermediate duration bursts from the other two classes. We use maximum likelihood fits to establish group memberships in the duration-hardness plane. To confirm these results we also use k-means and hierarchical clustering. We use Monte Carlo simulations to test the significance of the existence of the intermediate group and we find it with 99.8% probability. The intermediate duration population has a significantly lower peak flux (with 99.94% significance). Also, long bursts with measured redshift have higher peak fluxes (with 98.6% significance) than long bursts without measured redshifts. As the third group is the softest, we argue that we have related them with X-ray flashes among the GRBs. We give a new, probabilistic definition for this class of events.

• OSTI ID: 21476654
• Journal Information: Astrophysical Journal, Vol. 725, Issue 2; Other Information: DOI: 10.1088/0004-637X/725/2/1955; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COMPUTERIZED SIMULATION
COSMIC GAMMA BURSTS
MAXIMUM-LIKELIHOOD FIT
MONTE CARLO METHOD
PROBABILISTIC ESTIMATION
PROBABILITY
RED SHIFT
UNIVERSE
X RADIATION
CALCULATION METHODS
COSMIC RADIATION
ELECTROMAGNETIC RADIATION
IONIZING RADIATIONS
MATHEMATICAL SOLUTIONS
NUMERICAL SOLUTION
PRIMARY COSMIC RADIATION
RADIATIONS
SIMULATION