Search for high-energy gamma-ray emission from tidal disruption events with the Fermi large area telescope
- School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China)
- School of Science, Nanchang University, Nanchang 330031 (China)
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)⩽4.4×10{sup 42} erg s{sup −1} (at 95% confidence level) is obtained for the first 10{sup 7} s after the disruption.
- OSTI ID:
- 22868955
- Journal Information:
- Astrophysical Journal, Vol. 825, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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