A systematic study of soft X-ray pulse profiles of magnetars in quiescence
A systematic study of soft X-ray pulse profiles of magnetars in quiescence
Magnetars are neutron stars with extremely high surface magnetic fields. They show diverse X-ray pulse profiles in the quiescent state. We perform a systematic Fourier analysis of their soft X-ray pulse profiles. We find that most magnetars have a single-peaked profile and hence have low amplitudes of the second Fourier harmonic (A2). On the other hand, the pulsed fraction (PF) spreads over a wide range. We compared the results with theoretical profiles assuming various surface hotspot asymmetries, viewing geometries, and beaming functions. We found that a single value of the intensity ratio r between two antipodal hotspots is unable to reproduce the observed distribution of A2 and PF for all magnetars. The inferred r is probably anticorrelated with the thermal luminosity, implying that high-luminosity magnetars tend to have two symmetric hotspots. Our results are consistent with theoretical predictions, for which the existence of an evolving toroidal magnetic field breaks the symmetry of the surface temperature.
4274-4286
Hu, Chin-Ping
38ee07da-9735-4ef2-9662-35d9f0dc747b
Ng, C.-Y.
a7854a32-33ee-44c3-b58d-6654da468894
Ho, Wynn C.G.
d78d4c52-8f92-4846-876f-e04a8f803a45
May 2019
Hu, Chin-Ping
38ee07da-9735-4ef2-9662-35d9f0dc747b
Ng, C.-Y.
a7854a32-33ee-44c3-b58d-6654da468894
Ho, Wynn C.G.
d78d4c52-8f92-4846-876f-e04a8f803a45
Hu, Chin-Ping, Ng, C.-Y. and Ho, Wynn C.G.
(2019)
A systematic study of soft X-ray pulse profiles of magnetars in quiescence.
Monthly Notices of the Royal Astronomical Society, 485 (3), .
(doi:10.1093/mnras/stz513).
Abstract
Magnetars are neutron stars with extremely high surface magnetic fields. They show diverse X-ray pulse profiles in the quiescent state. We perform a systematic Fourier analysis of their soft X-ray pulse profiles. We find that most magnetars have a single-peaked profile and hence have low amplitudes of the second Fourier harmonic (A2). On the other hand, the pulsed fraction (PF) spreads over a wide range. We compared the results with theoretical profiles assuming various surface hotspot asymmetries, viewing geometries, and beaming functions. We found that a single value of the intensity ratio r between two antipodal hotspots is unable to reproduce the observed distribution of A2 and PF for all magnetars. The inferred r is probably anticorrelated with the thermal luminosity, implying that high-luminosity magnetars tend to have two symmetric hotspots. Our results are consistent with theoretical predictions, for which the existence of an evolving toroidal magnetic field breaks the symmetry of the surface temperature.
Text
1903.01091
- Accepted Manuscript
More information
Accepted/In Press date: 18 February 2019
e-pub ahead of print date: 27 March 2019
Published date: May 2019
Identifiers
Local EPrints ID: 429209
URI: http://eprints.soton.ac.uk/id/eprint/429209
ISSN: 1365-2966
PURE UUID: d2ec6901-0020-4765-9743-ba00de250ed8
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Date deposited: 22 Mar 2019 17:30
Last modified: 16 Mar 2024 07:39
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Author:
Chin-Ping Hu
Author:
C.-Y. Ng
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