Measuring the cooling of the neutron star in Cassiopeia A with all Chandra X-ray Observatory detectors
Measuring the cooling of the neutron star in Cassiopeia A with all Chandra X-ray Observatory detectors
The thermal evolution of young neutron stars (NSs) reflects the neutrino emission properties of their cores. Heinke & Ho (2010) measured a 3.6+/-0.6% decay in the surface temperature of the Cassiopeia A (Cas A) NS between 2000 and 2009, using archival data from the Chandra X-ray Observatory ACIS-S detector in Graded mode. Page et al. (2011) and Shternin et al. (2011) attributed this decay to enhanced neutrino emission from a superfluid neutron transition in the core. Here we test this decline, combining analysis of the Cas A NS using all Chandra X-ray detectors and modes (HRC-S, HRC-I, ACIS-I, ACIS-S in Faint mode, and ACIS-S in Graded mode) and adding a 2012 May ACIS-S Graded mode observation, using the most current calibrations (CALDB 4.5.5.1). We measure the temperature changes from each detector separately and test for systematic effects due to the nearby filaments of the supernova remnant. We find a 0.92%-2.0% decay over 10 years in the effective temperature, inferred from HRC-S data, depending on the choice of source and background extraction regions, with a best-fit decay of 1.0+/-0.7%. In comparison, the ACIS-S Graded data indicate a temperature decay of 3.1%–5.0% over 10 years, with a best-fit decay of 3.5+/-0.4%. Shallower observations using the other detectors yield temperature decays of 2.6+/-1.9% (ACIS-I), 2.1+/-1.0%(HRC-I), and 2.1+/-1.9% (ACIS-S Faint mode) over 10 years. Our best estimate indicates a decline of 2.9+/-0.5stat+/-1.0sys% over 10 years. The complexity of the bright and varying supernova remnant background makes a definitive interpretation of archival Cas A Chandra observations difficult. A temperature decline of 1–3.5% over 10 years would indicate extraordinarily fast cooling of the NS that can be regulated by superfluidity of nucleons in the stellar core.
22-[10pp]
Elshamouty, K.G.
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Heinke, C.O.
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Sivakoff, G.R.
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Ho, Wynn C.G.
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Shternin, P.S.
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Yakovlev, D.G.
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Patnaude, D.J.
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David, L.
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10 October 2013
Elshamouty, K.G.
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Heinke, C.O.
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Sivakoff, G.R.
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Ho, Wynn C.G.
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Shternin, P.S.
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Yakovlev, D.G.
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Patnaude, D.J.
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David, L.
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Elshamouty, K.G., Heinke, C.O., Sivakoff, G.R., Ho, Wynn C.G., Shternin, P.S., Yakovlev, D.G., Patnaude, D.J. and David, L.
(2013)
Measuring the cooling of the neutron star in Cassiopeia A with all Chandra X-ray Observatory detectors.
Astrophysical Journal, 777 (1), .
(doi:10.1088/0004-637X/777/1/22).
Abstract
The thermal evolution of young neutron stars (NSs) reflects the neutrino emission properties of their cores. Heinke & Ho (2010) measured a 3.6+/-0.6% decay in the surface temperature of the Cassiopeia A (Cas A) NS between 2000 and 2009, using archival data from the Chandra X-ray Observatory ACIS-S detector in Graded mode. Page et al. (2011) and Shternin et al. (2011) attributed this decay to enhanced neutrino emission from a superfluid neutron transition in the core. Here we test this decline, combining analysis of the Cas A NS using all Chandra X-ray detectors and modes (HRC-S, HRC-I, ACIS-I, ACIS-S in Faint mode, and ACIS-S in Graded mode) and adding a 2012 May ACIS-S Graded mode observation, using the most current calibrations (CALDB 4.5.5.1). We measure the temperature changes from each detector separately and test for systematic effects due to the nearby filaments of the supernova remnant. We find a 0.92%-2.0% decay over 10 years in the effective temperature, inferred from HRC-S data, depending on the choice of source and background extraction regions, with a best-fit decay of 1.0+/-0.7%. In comparison, the ACIS-S Graded data indicate a temperature decay of 3.1%–5.0% over 10 years, with a best-fit decay of 3.5+/-0.4%. Shallower observations using the other detectors yield temperature decays of 2.6+/-1.9% (ACIS-I), 2.1+/-1.0%(HRC-I), and 2.1+/-1.9% (ACIS-S Faint mode) over 10 years. Our best estimate indicates a decline of 2.9+/-0.5stat+/-1.0sys% over 10 years. The complexity of the bright and varying supernova remnant background makes a definitive interpretation of archival Cas A Chandra observations difficult. A temperature decline of 1–3.5% over 10 years would indicate extraordinarily fast cooling of the NS that can be regulated by superfluidity of nucleons in the stellar core.
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e-pub ahead of print date: 25 August 2013
Published date: 10 October 2013
Organisations:
Applied Mathematics
Identifiers
Local EPrints ID: 356525
URI: http://eprints.soton.ac.uk/id/eprint/356525
ISSN: 0004-637X
PURE UUID: 2c3f5070-d4fc-4036-b4b1-57481866688e
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Date deposited: 18 Sep 2013 09:13
Last modified: 14 Mar 2024 14:50
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Contributors
Author:
K.G. Elshamouty
Author:
C.O. Heinke
Author:
G.R. Sivakoff
Author:
P.S. Shternin
Author:
D.G. Yakovlev
Author:
D.J. Patnaude
Author:
L. David
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