GeV Variability Properties of TeV Blazars Detected by Fermi-LAT
Abstract
Variability is a prominent observational feature of blazars. The high-energy radiation mechanism of jets has always been important but is still unclear. In this work, we performed a detailed analysis using Fermi-LAT data across 15 yr and obtained GeV light-curve information for 78 TeV blazars detected by Fermi. We provided annual GeV fluxes and corresponding spectral indices for the 78 TeV blazars and thorough monthly GeV fluxes for a subsample of 41 bright blazars. Our results suggest a strong correlation between the γ-ray photon index and $\mathrm{log}{L}_{\gamma }$ for the flat spectrum radio quasars (FSRQs) and high-energy peaked BL Lacs. Fourteen sources in our sample show significant GeV outbursts/flares above the relatively stable, low-flux light curve, with six of them showing a clear sharp peak profile in their 5 day binned light curves. We quantified the variability utilizing the fractional variability parameter F var, and found that the flux of the FSRQs showed significantly stronger variability than that of the BL Lacs. The 41 bright blazars in this work are best fit by a log-normal flux distribution. We checked the spectral behavior and found 11 out of the 14 sources show a bluer-when-brighter trend, suggesting this spectral behavior for these TeV blazars at the GeV band arises from the mechanism in which the synchrotron-self Compton process dominates the GeV emission. Our research offers a systematic analysis of the GeV variability properties of TeV blazars and serves as a helpful resource for further associated blazar studies.
- Publication:
-
The Astrophysical Journal Supplement Series
- Pub Date:
- February 2024
- DOI:
- 10.3847/1538-4365/ad0e08
- arXiv:
- arXiv:2312.01122
- Bibcode:
- 2024ApJS..270...22W
- Keywords:
-
- Relativistic jets;
- Active galactic nuclei;
- Gamma-ray observatories;
- 1390;
- 16;
- 632;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 22 pages, 9 figures, accepted for publication in ApJS