The Spectral Index Distribution of EGRET Blazars: Prospects for GLAST

Conference · Tue Nov 29 04:00:00 EST 2011 · AIP Conf.Proc.921:163-168,2007

OSTI ID:1030537

Venters, Tonia M; Pavlidou, Vasiliki

The intrinsic distribution of spectral indices in GeV energies of gamma-ray-loud blazars is a critical input in determining the spectral shape of the unresolved blazar contribution to the diffuse extragalactic gamma-ray background, as well as an important test of blazar emission theories. We present a maximum-likelihood method of determining the intrinsic spectral index distribution (ISID) of a population of {gamma}-ray emitters which accounts for error in measurement of individual spectral indices, and we apply it to EGRET blazars. We find that the most likely Gaussian ISID for EGRET blazars has a mean of 2.27 and a standard deviation of 0.20. We additionally find some indication that FSRQs and BL Lacs may have different ISIDs (with BL Lacs being harder). We also test for spectral index hardening associated with blazar variability for which we find no evidence. Finally, we produce simulated GLAST spectral index datasets and perform the same analyses. With improved statistics due to the much larger number of resolvable blazars, GLAST data will help us determine the ISIDs with much improved accuracy. Should any difference exist between the ISIDs of BL Lacs and FSRQs or between the ISIDs of blazars in the quiescent and flaring states, GLAST data will be adequate to separate these ISIDs at a significance better than 3{sigma}.

• Research Organization: SLAC National Accelerator Laboratory (SLAC)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 1030537
• Report Number(s): SLAC-PUB-14794; arXiv:0704.2417
• Conference Information: Journal Name: AIP Conf.Proc.921:163-168,2007
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCURACY
Astrophysics
ASTRO
DISTRIBUTION
FLARING
GALAXIES
HARDENING
SHAPE
STATISTICS