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Published July 10, 2008 | Published
Journal Article Open

GRB 070201: A possible soft gamma-ray repeater in M31

Abstract

GRB 070201 was a bright, short-duration, hard-spectrum gamma-ray burst detected by the Interplanetary Network. Its error quadrilateral, which has an area of 0.124 deg^2, intersects some prominent spiral arms of the nearby M31 (Andromeda) galaxy. Given the properties of this GRB, along with the fact that LIGO data argue against a compact binary merger origin in M31, it is an excellent candidate to have been an extragalactic soft gamma-ray repeater (SGR) giant flare, with an energy of 1.4 × 10^45 ergs. However, we cannot rule out the possibility that it was a short-duration GRB in the background. Analysis of ROTSE-IIIb visible-light observations of M31, taken 10.6 hr after the burst and covering 42% of the GRB error region, does not reveal any optical transient down to a limiting magnitude of 17.1. We inspected archival and proprietary XMM-Newton X-ray observations of the intersection of the GRB error region and M31, obtained about 4 weeks prior to the outburst, in order to look for periodic variable X-ray sources. No SGR or anomalous X-ray pulsar (AXP) candidates (periods in the range 1-20 s) were detected. We discuss the possibility of detecting extragalactic SGRs/AXPs by identifying their periodic X-ray light curves. Our simulations suggest that the probability of detecting the periodic X-ray signal of one of the known Galactic SGRs/AXPs, if placed in M31, is about 10% using a 50 ks XMM-Newton exposure, increasing to 50% for a 2 Ms observation.

Additional Information

© 2008 The American Astronomical Society. Received 2007 December 13; accepted 2008 February 18. This work is supported in part by grants from NSF and NASA. H. S. acknowledges support from the Bundesministerium fur Wirtschaft und Technologie/Deutsches Zentrum fur Luft- und Raumfahrt (BMWI/DLR, FKZ 50 OR 0405). M. M. K. acknowledges the Moore Foundation for the George Ellory Hale Fellowship.

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August 22, 2023
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