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Cooling rates of neutron stars and the young neutron star in the Cassiopeia A supernova remnant

Cooling rates of neutron stars and the young neutron star in the Cassiopeia A supernova remnant
Cooling rates of neutron stars and the young neutron star in the Cassiopeia A supernova remnant
We explore the thermal state of the neutron star in the Cassiopeia A supernova remnant using the recent result of Ho & Heinke that the thermal radiation of this star is well described by a carbon atmosphere model and the emission comes from the entire stellar surface. Starting from neutron star cooling theory, we formulate a robust method to extract neutrino cooling rates of thermally relaxed stars at the neutrino cooling stage from observations of thermal surface radiation. We show how to compare these rates with the rates of standard candles – stars with non-superfluid nucleon cores cooling slowly via the modified Urca process. We find that the internal temperature of standard candles is a well-defined function of the stellar compactness parameter x=rg/R, irrespective of the equation of state of neutron star matter (R and rg are circumferential and gravitational radii, respectively). We demonstrate that the data on the Cassiopeia A neutron star can be explained in terms of three parameters: f?, the neutrino cooling efficiency with respect to the standard candle; the compactness x; and the amount of light elements in the heat-blanketing envelope. For an ordinary (iron) heat-blanketing envelope or a low-mass (? 10?13 M?) carbon envelope, we find the efficiency f?? 1 (standard cooling) for x? 0.5 and f?? 0.02 (slower cooling) for a maximum compactness x? 0.7. A heat blanket containing the maximum mass (?10?8 M?) of light elements increases f? by a factor of 50. We also examine the (unlikely) possibility that the star is still thermally non-relaxed
dense matter, equation of state, neutrinos, supernovae, cassiopeia a, x-rays, stars
0035-8711
1977-1988
Yakovlev, Dmitry G.
4d01543a-2614-4f42-a523-f393ef7e5fdc
Ho, Wynn C. G.
d78d4c52-8f92-4846-876f-e04a8f803a45
Shternin, Peter S.
be9ada72-0168-497a-9602-d5d18839749c
Heinke, Craig O.
d7382ed2-cb85-4e15-b2d9-296fc8b6221d
Potekhin, Alexander Y.
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Yakovlev, Dmitry G.
4d01543a-2614-4f42-a523-f393ef7e5fdc
Ho, Wynn C. G.
d78d4c52-8f92-4846-876f-e04a8f803a45
Shternin, Peter S.
be9ada72-0168-497a-9602-d5d18839749c
Heinke, Craig O.
d7382ed2-cb85-4e15-b2d9-296fc8b6221d
Potekhin, Alexander Y.
b9551650-f6ed-4c4f-b53c-d019cccc49fa

Yakovlev, Dmitry G., Ho, Wynn C. G., Shternin, Peter S., Heinke, Craig O. and Potekhin, Alexander Y. (2011) Cooling rates of neutron stars and the young neutron star in the Cassiopeia A supernova remnant. Monthly Notices of the Royal Astronomical Society, 411 (3), 1977-1988. (doi:10.1111/j.1365-2966.2010.17827.x).

Record type: Article

Abstract

We explore the thermal state of the neutron star in the Cassiopeia A supernova remnant using the recent result of Ho & Heinke that the thermal radiation of this star is well described by a carbon atmosphere model and the emission comes from the entire stellar surface. Starting from neutron star cooling theory, we formulate a robust method to extract neutrino cooling rates of thermally relaxed stars at the neutrino cooling stage from observations of thermal surface radiation. We show how to compare these rates with the rates of standard candles – stars with non-superfluid nucleon cores cooling slowly via the modified Urca process. We find that the internal temperature of standard candles is a well-defined function of the stellar compactness parameter x=rg/R, irrespective of the equation of state of neutron star matter (R and rg are circumferential and gravitational radii, respectively). We demonstrate that the data on the Cassiopeia A neutron star can be explained in terms of three parameters: f?, the neutrino cooling efficiency with respect to the standard candle; the compactness x; and the amount of light elements in the heat-blanketing envelope. For an ordinary (iron) heat-blanketing envelope or a low-mass (? 10?13 M?) carbon envelope, we find the efficiency f?? 1 (standard cooling) for x? 0.5 and f?? 0.02 (slower cooling) for a maximum compactness x? 0.7. A heat blanket containing the maximum mass (?10?8 M?) of light elements increases f? by a factor of 50. We also examine the (unlikely) possibility that the star is still thermally non-relaxed

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Published date: March 2011
Keywords: dense matter, equation of state, neutrinos, supernovae, cassiopeia a, x-rays, stars

Identifiers

Local EPrints ID: 175275
URI: http://eprints.soton.ac.uk/id/eprint/175275
ISSN: 0035-8711
PURE UUID: 532ee59e-8b7a-44b3-9bcb-a996e5da9eee
ORCID for Wynn C. G. Ho: ORCID iD orcid.org/0000-0002-6089-6836

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Date deposited: 23 Feb 2011 08:48
Last modified: 09 Jan 2022 03:30

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Contributors

Author: Dmitry G. Yakovlev
Author: Wynn C. G. Ho ORCID iD
Author: Peter S. Shternin
Author: Craig O. Heinke
Author: Alexander Y. Potekhin

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