Search for High-energy Gamma-ray Emission from Tidal Disruption Events with the Fermi Large Area Telescope
Abstract
Massive black holes at galaxy center may tear apart a star when the star passes occasionally within the disruption radius, which is the so-called tidal disruption event (TDE). Most TDEs radiate with thermal emission resulting from the acceleration disk, but three TDEs have been detected in bright nonthermal X-ray emission, which is interpreted as arising from the relativistic jets. A search for high-energy gamma-ray emission from one relativistic TDE (Swift J164449.3+573451) with the Fermi Large Area Telescope (LAT) has yielded nondetection. In this paper, we report the search for high-energy emission from the other two relativistic TDEs (Swift J2058.4+0516 and Swift J1112.2-8238) during the flare period. No significant GeV emission is found, with an upper limit fluence in the LAT energy range being less than 1% of that in X-rays. Compared with gamma-ray bursts and blazars, these TDEs have the lowest flux ratio between GeV emission and X-ray emission. The nondetection of high-energy emission from relativistic TDEs could be due to the fact that the high-energy emission is absorbed by soft photons in the source. Based on this hypothesis, upper limits on the bulk Lorentz factors, {{Γ }}≲ 30, are then obtained for the jets in these TDEs. We also search for high-energy gamma-ray emission from the nearest TDE discovered to date, ASASSN-14li. No significant GeV emission is found, and an upper limit of L(0.1{--}10 {GeV})≤slant 4.4× {10}42 erg s-1 (at 95% confidence level) is obtained for the first 107 s after the disruption.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2016
- DOI:
- 10.3847/0004-637X/825/1/47
- arXiv:
- arXiv:1601.02734
- Bibcode:
- 2016ApJ...825...47P
- Keywords:
-
- galaxies: nuclei;
- gamma rays: galaxies;
- radiation mechanisms:non-thermal;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Accepted by ApJ, 6 pages, 3 figures