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- · arXiv e-print (arXiv:1105.2816)
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| Title: |
| GRB 110328A/Swift J164449.3+573451: The Tidal Obliteration of a Deeply Plunging Star? |
| Authors: |
| Cannizzo, J. K.; Troja, E.; Lodato, G. |
| Publication: |
| eprint arXiv:1105.2816 |
| Publication Date: |
| 05/2011 |
| Origin: |
| ARXIV |
| Keywords: |
| Astrophysics - High Energy Astrophysical Phenomena |
| Comment: |
| 6 pages, 1 figure, submitted to the Astrophysical Journal |
| Bibliographic Code: |
| 2011arXiv1105.2816C |
Abstract
We examine the tidal disruption event scenario to explain Sw 1644+57, a powerful and persistent X-ray source which suddenly became active as GRB 110328A. The precise localizations by HST and Chandra at the center of a z=0.354 galaxy argue for activity of the central engine as the underlying cause. We look at the suggestion by Bloom et al of the possibility of a tidal disruption event (TDE). We derive estimates for the accretion rate onto the expected massive black hole in the galactic center. We argue that Sw 1644+57 cannot be explained by the traditional TDE model in which the periastron distance is close to the tidal disruption radius - the orbit must be deeply plunging or else the powerful jet we are observing could not be produced, and the Swift/BAT rate would be too high. For nominal parameters without deep plunging, the disk accretion of the stellar remnants could only produce a disk accreting at ~0.01 Eddington. In addition, the predicted event rate in BAT for normal TDEs would be ~30/yr, taking into account beaming, compared to the observed rate of 1 in 7 years. For optimal parameters with deep plunging, the disk accretion rate is roughly Eddington, and the ratio of observed X-ray flux to accretion luminosity ~100 indicates that we are looking down a jet with a beaming factor ~0.01. We also estimate rates for detection of such events by Swift and X-ray all-sky monitors. Due to the extreme excess in the tidal force above that which would be required minimally to disrupt the star in a deeply plunging orbit at periastron, we suggest this scenario might be referred to more descriptively as a TOE (tidal obliteration event) rather than a TDE.
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