EXTraS discovery of an 1.2-s X-ray pulsar in M 31
Date Issued
2016
Author(s)
Esposito, P.
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Belfiore, A.
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Novara, G.
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Tiengo, A.
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Haberl, F.
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Read, A. M.
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Salvetti, D.
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Wilms, J.
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D'Agostino, D.
Abstract
During a search for coherent signals in the X-ray archival data of XMM-Newton, we discovered a modulation at 1.2 s in 3XMM J004301.4+413017 (3X J0043), a source lying in the direction of an external arm of M 31. This short period indicates a neutron star (NS). Between 2000 and 2013, the position of 3X J0043 was imaged by public XMM-Newton observations 35 times. The analysis of these data allowed us to detect an orbital modulation at 1.27 d and study the long-term properties of the source. The emission of the pulsar was rather hard (most spectra are described by a power law with Γ < 1) and, assuming the distance to M 31, the 0.3-10 keV luminosity was variable, from ̃3 × 1037 to 2 × 1038 erg s-1. The analysis of optical data shows that, while 3X J0043 is likely associated to a globular cluster in M 31, a counterpart with V ≳ 22 outside the cluster cannot be excluded. Considering our findings, there are two main viable scenarios for 3X J0043: a peculiar low-mass X-ray binary, similar to 4U 1822-37 or 4U 1626-67, or an intermediate-mass X-ray binary resembling Her X-1. Regardless of the exact nature of the system, 3X J0043 is the first accreting NS in M 31 in which the spin period has been detected....
Volume
457
Issue
1
Start page
L5
Issn Identifier
1745-3925
Ads BibCode
2016MNRAS.457L...5E
Rights
open.access
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