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Could an X-ray flare after GRB 170817A originate from a post-merger slim accretion disc?
- Source :
-
Monthly Notices of the Royal Astronomical Society . Jun2019, Vol. 485 Issue 4, p5773-5776. 4p. - Publication Year :
- 2019
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Abstract
- GRB 170817A, detected by Fermi Gamma-ray Burst Monitor 1.7 s after the merger of a neutron star (NS) binary, provides the first direct evidence for a link between such a merger and a short-duration gamma-ray burst. The X-ray observations after GRB 170817A indicate a possible X-ray flare with a peak luminosity |$L_{\rm peak} \sim 2\times 10^{39}\, {\rm erg\, s}^{-1}$| near day 156. Here we show that this X-ray flare may be understood based on a slim disc around a compact object. On the one hand, there exists the maximal accretion rate |$\dot{M}_{\rm max}$| for the slim disc, above which an optically thick outflow is significant and radiation from the disc is obscured. Based on the energy balance analysis, we find that |$\dot{M}_{\rm max}$| is in the range of |${\sim } 4\dot{M}_{\rm Edd}$| and |${\sim } 21\dot{M}_{\rm Edd}$| when the angular velocity of the slim disc is between |$\rm (1/5)^{1/2}\Omega _K$| and |$\rm \Omega _K$| (where |$\dot{M}_{\rm Edd}$| is the Eddington accretion rate and ΩK is the Keplerian angular velocity). With |$\dot{M}_{\rm max}$|, the slim disc can provide a luminosity ∼ L peak for a compact object of |$2.5 \, \mathrm{M}_{\odot }$|. On the other hand, if the merger of two NSs forms a typical neutrino-dominated accretion disc whose accretion rate |$\dot{M}$| follows a power-law decline with an index −1.8, then the system must pass through the outflow regime and enter the slim disc in ∼11–355 d. These results imply that a post-merger slim accretion disc could account for the observed late-time L peak. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00358711
- Volume :
- 485
- Issue :
- 4
- Database :
- Academic Search Index
- Journal :
- Monthly Notices of the Royal Astronomical Society
- Publication Type :
- Academic Journal
- Accession number :
- 136160913
- Full Text :
- https://doi.org/10.1093/mnras/stz840