Rowlinson, A., O'Brien, P. T., Tanvir, N. R., Zhang, B., Evans, P. A., Lyons, N., Levan, A. J., Willingale, R., Page, K. L., Onal, O., Burrows, D. N., Beardmore, A. P., Ukwatta, T. N., Berger, E., Hjorth, J., Fruchter, A. S., Tunnicliffe, R. L., Fox, D. B. and Cucchiara, A.. (2010) The unusual X-ray emission of the short Swift GRB 090515: evidence for the formation of a magnetar? Monthly Notices of the Royal Astronomical Society, Vol.409 (No.2). pp. 531-540. ISSN 0035-8711

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Abstract

The majority of short gamma-ray bursts (SGRBs) are thought to originate from the merger of compact binary systems collapsing directly to form a black hole. However, it has been proposed that both SGRBs and long gamma-ray bursts (LGRBs) may, on rare occasions, form an unstable millisecond pulsar (magnetar) prior to final collapse. GRB 090515, detected by the Swift satellite was extremely short, with a T-90 of 0.036 +/- 0.016 s, and had a very low fluence of 2 x 10(-8) erg cm(-2) and faint optical afterglow. Despite this, the 0.3-10 keV flux in the first 200 s was the highest observed for an SGRB by the Swift X-ray Telescope (XRT). The X-ray light curve showed an unusual plateau and steep decay, becoming undetectable after similar to 500 s. This behaviour is similar to that observed in some long bursts proposed to have magnetars contributing to their emission.

In this paper, we present the Swift observations of GRB 090515 and compare it to other gamma-ray bursts (GRBs) in the Swift sample. Additionally, we present optical observations from Gemini, which detected an afterglow of magnitude 26.4 +/- 0.1 at T+1.7 h after the burst. We discuss potential causes of the unusual 0.3-10 keV emission and suggest it might be energy injection from an unstable millisecond pulsar. Using the duration and flux of the plateau of GRB 090515, we place constraints on the millisecond pulsar spin period and magnetic field.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	Wiley
ISSN:	0035-8711
Official Date:	December 2010
Volume:	Vol.409
Number:	No.2
Number of Pages:	10
Page Range:	pp. 531-540
Identification Number:	10.1111/j.1365-2966.2010.17354.x
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Science and Technology Funding Council, NASA, DNRF
Grant number:	NAS5-00136
URI:	http://wrap.warwick.ac.uk/id/eprint/4788

Data sourced from Thomson Reuters' Web of Knowledge

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