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XMM-Newton observation of the highly magnetised accreting pulsar Swift J045106.8-694803: evidence of a hot thermal excess

XMM-Newton observation of the highly magnetised accreting pulsar Swift J045106.8-694803: evidence of a hot thermal excess
XMM-Newton observation of the highly magnetised accreting pulsar Swift J045106.8-694803: evidence of a hot thermal excess
Several persistent, low luminosity (LX ~ 1034 erg s-1), long spin period (P > 100 s) High Mass X-ray Binaries have been reported with blackbody components with temperatures > 1 keV. These hot thermal excesses have correspondingly small emitting regions (< 1 km2) and are attributed to the neutron star polar caps. We present a recent XMM-Newton target of opportunity observation of the newest member of this class, Swift J045106.8-694803. The period was determined to be 168.5 ± 0.2 s as of 17 July 2012 (MJD = 56125.0). At LX ~ 1036 erg s-1, Swift J045106.8-694803 is the brightest member of this new class, as well as the one with the shortest period. The spectral analysis reveals for the first time the presence of a blackbody with temperature kTBB = 1.8 +0.2-0.3 keV and radius RBB = 0.5 ± 0.2 km. The pulsed fraction decreases with increasing energy and the ratio between the hard (> 2 keV) and soft (< 2 keV) light curves is anticorrelated with the pulse profile. Simulations of the spectrum suggest that this is caused by the pulsations of the blackbody being ~ π out of phase with those of the power law component. Using a simple model for emission from hot spots on the neutron star surface, we fit the pulse profile of the blackbody component to obtain an indication of the geometry of the system.
0035-8711
2054-2062
Bartlett, Elizabeth
8a33af5a-5eb1-4888-b0b3-345d946860fe
Coe, Malcolm J.
04dfb23b-1456-46a3-9242-5cee983471d5
Ho, Wynn C.G.
d78d4c52-8f92-4846-876f-e04a8f803a45
Bartlett, Elizabeth
8a33af5a-5eb1-4888-b0b3-345d946860fe
Coe, Malcolm J.
04dfb23b-1456-46a3-9242-5cee983471d5
Ho, Wynn C.G.
d78d4c52-8f92-4846-876f-e04a8f803a45

Bartlett, Elizabeth, Coe, Malcolm J. and Ho, Wynn C.G. (2013) XMM-Newton observation of the highly magnetised accreting pulsar Swift J045106.8-694803: evidence of a hot thermal excess. Monthly Notices of the Royal Astronomical Society, 436 (3), 2054-2062. (doi:10.1093/mnras/stt1711).

Record type: Article

Abstract

Several persistent, low luminosity (LX ~ 1034 erg s-1), long spin period (P > 100 s) High Mass X-ray Binaries have been reported with blackbody components with temperatures > 1 keV. These hot thermal excesses have correspondingly small emitting regions (< 1 km2) and are attributed to the neutron star polar caps. We present a recent XMM-Newton target of opportunity observation of the newest member of this class, Swift J045106.8-694803. The period was determined to be 168.5 ± 0.2 s as of 17 July 2012 (MJD = 56125.0). At LX ~ 1036 erg s-1, Swift J045106.8-694803 is the brightest member of this new class, as well as the one with the shortest period. The spectral analysis reveals for the first time the presence of a blackbody with temperature kTBB = 1.8 +0.2-0.3 keV and radius RBB = 0.5 ± 0.2 km. The pulsed fraction decreases with increasing energy and the ratio between the hard (> 2 keV) and soft (< 2 keV) light curves is anticorrelated with the pulse profile. Simulations of the spectrum suggest that this is caused by the pulsations of the blackbody being ~ π out of phase with those of the power law component. Using a simple model for emission from hot spots on the neutron star surface, we fit the pulse profile of the blackbody component to obtain an indication of the geometry of the system.

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Published date: 16 November 2013
Organisations: Astronomy Group, Applied Mathematics

Identifiers

Local EPrints ID: 356621
URI: https://eprints.soton.ac.uk/id/eprint/356621
ISSN: 0035-8711
PURE UUID: 2e996819-cbbd-4344-b398-8eb6ffda5d49
ORCID for Malcolm J. Coe: ORCID iD orcid.org/0000-0002-0763-8547
ORCID for Wynn C.G. Ho: ORCID iD orcid.org/0000-0002-6089-6836

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Date deposited: 13 Sep 2013 13:13
Last modified: 20 Jul 2019 01:28

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