Messenger, C. and Patruno, A. (2015) A semi-coherent search for weak pulsations in AQUILA X–1. Astrophysical Journal, 806(2), 261. (doi: 10.1088/0004-637X/806/2/261)
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Abstract
Non-pulsating neutron stars in low mass X-ray binaries largely outnumber those that show pulsations. The lack of detectable pulses represents a big open problem for two important reasons. The first is that the structure of the accretion flow in the region closest to the neutron star is not well understood and it is therefore unclear what is the mechanism that prevents the pulse formation. The second is that the detection of pulsations would immediately reveal the spin of the neutron star. AQUILA X–1 is a special source among low mass X-ray binaries because it has showed the unique property of pulsating for only ~150 s out of a total observing time of more than 1.5 million seconds. However, the existing upper limits on the pulsed fraction leave open two alternatives. Either AQUILA X–1 has very weak pulses which have been undetected, or it has genuinely pulsed only for a tiny amount of the observed time. Understanding which of the two scenarios is the correct one is fundamental to increase our knowledge about the pulse formation process and understand the chances we have to detect weak pulses in other low-mass X-ray binaries. In this paper we perform a semi-coherent search on the entire X-ray data available for AQUILA X–1. We find no evidence for (new) weak pulsations with the most stringent upper limits being of the order of 0.3% in the 7–25 keV energy band.
| Item Type: | Articles |
|---|---|
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Messenger, Dr Christopher |
| Authors: | Messenger, C., and Patruno, A. |
| College/School: | College of Science and Engineering > School of Physics and Astronomy |
| Research Centre: | College of Science and Engineering > School of Physics and Astronomy > Institute for Gravitational Research |
| Journal Name: | Astrophysical Journal |
| Publisher: | American Astronomical Society |
| ISSN: | 0004-637X |
| ISSN (Online): | 1538-4357 |
| Copyright Holders: | Copyright © 2015 American Astronomical Society |
| First Published: | First published in Astrophysical Journal 806(2):261 |
| Publisher Policy: | Reproduced in accordance with the copyright policy of the publisher |
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