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Neutron star crust cooling in the Terzan 5 X-ray transient Swift J174805.3–244637

Neutron star crust cooling in the Terzan 5 X-ray transient Swift J174805.3–244637
Neutron star crust cooling in the Terzan 5 X-ray transient Swift J174805.3–244637
When neutron stars reside in transient X-ray binaries, their crustal layers become heated during accretion outbursts and subsequently cool in quiescence. Observing and modelling this thermal response has yielded valuable insight into the physics of neutron star crusts. However, one unresolved problem is the evidence in several neutron stars for an extra energy source, located at shallow depth in the crust, that is not accounted for by standard heating models. Its origin remains puzzling, and it is currently unclear whether this additional heating occurs in all neutron stars, and if the magnitude is always the same. Here, we report on Chandra observations that cover two years after the 2012 outburst of the transient neutron star X-ray binary Swift J174805.3–244637 in the globular cluster Terzan 5. The temperature of the neutron star was elevated during the first two months following its ?8 week accretion episode, but had decayed to the pre-outburst level within ?100 d. Interpreting this as rapid cooling of the accretion-heated crust, we model the observed temperature curve with a thermal evolution code. We find that there is no need to invoke shallow heating for this neutron star, although an extra energy release up to ?1.4 MeV nucleon?1 is allowed by the current data (2? confidence). We also present two new data points on the crust-cooling curve of the 11-Hz X-ray pulsar IGR J17480–2446 in Terzan 5, which was active in 2010. The temperature of this neutron star remains significantly above the pre-outburst level, but we detect no change in the thermal emission since the previous measurements of 2013 February. This is consistent with the slow crust cooling expected several years post-outburst.
0035-8711
2071-2081
Degenaar, N.
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Wijnands, R.
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Bahramian, A.
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Sivakoff, G.R.
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Heinke, C.O.
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Brown, E.F.
357f29dd-cc4e-4a6e-9fea-4aad75253aa4
Fridreksson, J.K.
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Homan, J.
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Cackett, E.M.
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Cumming, A.
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Miller, J.M.
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Altamirano, D.
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Pooley, D.
a5ace8d5-12a1-442a-997e-c6fdbd35661c
Degenaar, N.
54149051-d74e-4e43-a7cd-501ec4023511
Wijnands, R.
382893ee-0e03-45e3-9321-db8b9fc74914
Bahramian, A.
1f016b89-98b9-4fa9-8df0-9390fbb5eeda
Sivakoff, G.R.
d3dd17f7-f61d-4139-acb4-e97e13c7d3b8
Heinke, C.O.
81e86af6-563d-4efc-ba4f-8e2902b2c9da
Brown, E.F.
357f29dd-cc4e-4a6e-9fea-4aad75253aa4
Fridreksson, J.K.
85bf992f-9947-40ec-b792-09a2e39f4ffd
Homan, J.
549baf32-2442-4247-824e-21bb018b05f5
Cackett, E.M.
2cd7b6af-a0e0-4265-94f6-092d68d1ba74
Cumming, A.
533b7dad-e34c-492f-a284-5b69a9c362be
Miller, J.M.
078305f0-03c7-4982-95ff-a92bc2f75b54
Altamirano, D.
d5ccdb09-0b71-4303-9538-05b467be075b
Pooley, D.
a5ace8d5-12a1-442a-997e-c6fdbd35661c

Degenaar, N., Wijnands, R., Bahramian, A., Sivakoff, G.R., Heinke, C.O., Brown, E.F., Fridreksson, J.K., Homan, J., Cackett, E.M., Cumming, A., Miller, J.M., Altamirano, D. and Pooley, D. (2015) Neutron star crust cooling in the Terzan 5 X-ray transient Swift J174805.3–244637. Monthly Notices of the Royal Astronomical Society, 451 (2), 2071-2081. (doi:10.1093/mnras/stv1054).

Record type: Article

Abstract

When neutron stars reside in transient X-ray binaries, their crustal layers become heated during accretion outbursts and subsequently cool in quiescence. Observing and modelling this thermal response has yielded valuable insight into the physics of neutron star crusts. However, one unresolved problem is the evidence in several neutron stars for an extra energy source, located at shallow depth in the crust, that is not accounted for by standard heating models. Its origin remains puzzling, and it is currently unclear whether this additional heating occurs in all neutron stars, and if the magnitude is always the same. Here, we report on Chandra observations that cover two years after the 2012 outburst of the transient neutron star X-ray binary Swift J174805.3–244637 in the globular cluster Terzan 5. The temperature of the neutron star was elevated during the first two months following its ?8 week accretion episode, but had decayed to the pre-outburst level within ?100 d. Interpreting this as rapid cooling of the accretion-heated crust, we model the observed temperature curve with a thermal evolution code. We find that there is no need to invoke shallow heating for this neutron star, although an extra energy release up to ?1.4 MeV nucleon?1 is allowed by the current data (2? confidence). We also present two new data points on the crust-cooling curve of the 11-Hz X-ray pulsar IGR J17480–2446 in Terzan 5, which was active in 2010. The temperature of this neutron star remains significantly above the pre-outburst level, but we detect no change in the thermal emission since the previous measurements of 2013 February. This is consistent with the slow crust cooling expected several years post-outburst.

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Accepted/In Press date: 6 May 2015
e-pub ahead of print date: 10 June 2015
Published date: 1 August 2015
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 396175
URI: http://eprints.soton.ac.uk/id/eprint/396175
ISSN: 0035-8711
PURE UUID: acaff114-00b7-4c15-8b07-96815ed5a7bc
ORCID for D. Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

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Date deposited: 07 Jun 2016 10:28
Last modified: 21 Nov 2021 03:10

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Contributors

Author: N. Degenaar
Author: R. Wijnands
Author: A. Bahramian
Author: G.R. Sivakoff
Author: C.O. Heinke
Author: E.F. Brown
Author: J.K. Fridreksson
Author: J. Homan
Author: E.M. Cackett
Author: A. Cumming
Author: J.M. Miller
Author: D. Altamirano ORCID iD
Author: D. Pooley

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