The X-ray transient 080109 in NGC 2770: an X-ray flash associated with a normal core-collapse supernova
Abstract
Although it is generally thought that long-duration gamma-ray bursts (LGRBs) are associated with core-collapse supernovae (SNe), so far only four pairs of GRBs and SNe with firmly established connection have been found. All the four GRB-SNe belong to special class of Type Ic - called the broad-lined SNe indicative of a large explosion energy, suggesting that only a small fraction of SNe Ibc have GRBs associated with them. This scheme has been refreshed by the discovery of a bright X-ray transient in NGC 2770 on 2008 January 9, which was followed by a rather normal Type Ib SN 2008D. In this paper, I argue that the transient 080109 is an X-ray flash (XRF, the soft version of a GRB) because of the following evidence. (1) The transient cannot be interpreted as a SN shock breakout event. (2) The GRB X-ray flare interpretation is not supported by the high-energy observation. I then show that XRF 080109 satisfies the well-known relation between the isotropic-equivalent energy and the peak spectral energy for LGRBs, which highly strengthens the XRF interpretation. Finally, I point out that the peak spectral energy of XRF 080109 and the maximum bolometric luminosity of SN 2008D agree with the Eγ,peak-LSN,max relationship of Li, strengthening the validity of the relationship. I speculate that events like XRF 080109 may occur at a rate comparable to SNe Ibc, and a soft X-ray telescope devoted to surveying for nearby X-ray flares will be very fruitful in discovering them.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 2008
- DOI:
- 10.1111/j.1365-2966.2008.13461.x
- arXiv:
- arXiv:0803.0079
- Bibcode:
- 2008MNRAS.388..603L
- Keywords:
-
- supernovae: general;
- supernovae: individual: SN 2008D;
- gamma-rays: bursts;
- Astrophysics
- E-Print:
- 8 pages, 6 figures. Final version for publication in MNRAS