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Diffusive nuclear burning in cooling simulations and application to new temperature data of the Cassiopeia A neutron star

Diffusive nuclear burning in cooling simulations and application to new temperature data of the Cassiopeia A neutron star
Diffusive nuclear burning in cooling simulations and application to new temperature data of the Cassiopeia A neutron star
A critical relation in the study of neutron star cooling is the one between surface temperature and interior temperature. This relation is determined by the composition of the neutron star envelope and can be affected by the process of diffusive nuclear burning (DNB), which occurs when elements diffuse to depths where the density and temperature are sufficiently high to ignite nuclear burning. We calculate models of H-He and He-C envelopes that include DNB and obtain analytic temperature relations that can be used in neutron star cooling simulations. We find that DNB can lead to a rapidly changing envelope composition and prevents the build-up of thermally stable hydrogen columns yH ≳ 107 g cm-2, while DNB can make helium envelopes more transparent to heat flux for surface temperatures Ts ≳ 2x106 K. We perform neutron star cooling simulations in which we evolve temperature and envelope composition, with the latter due to DNB and accretion from the interstellar medium. We find that a time-dependent envelope composition can be relevant for understanding the long-term cooling behaviour of isolated neutron stars. We also report on the latest Chandra observations of the young neutron star in the Cassiopeia A supernova remnant; the resulting 13 temperature measurements over more than 18 years yield a ten-year cooling rate of ~2%. Finally, we fit the observed cooling trend of the Cassiopeia A neutron star with a model that includes DNB in the envelope.
0035-8711
974-988
Wijngaarden, Marcella J.P.
e6064827-8f6f-4fc4-b24d-140d11939237
Ho, Wynn C.G.
d78d4c52-8f92-4846-876f-e04a8f803a45
Chang, Philip
7f213428-5533-49c7-bd52-a5a2feee4792
Heinke, Craig O.
9497af53-26df-4701-8621-6752b0398161
Page, Dany
5f9c4edb-50e2-4d9d-bf5d-284293446739
Beznogov, Mikhail
50a96abd-1d56-4274-8d7f-ca6a0681b4d8
Patnaude, Daniel J.
603f4876-8fcc-46ee-9448-5d10e960be4c
Wijngaarden, Marcella J.P.
e6064827-8f6f-4fc4-b24d-140d11939237
Ho, Wynn C.G.
d78d4c52-8f92-4846-876f-e04a8f803a45
Chang, Philip
7f213428-5533-49c7-bd52-a5a2feee4792
Heinke, Craig O.
9497af53-26df-4701-8621-6752b0398161
Page, Dany
5f9c4edb-50e2-4d9d-bf5d-284293446739
Beznogov, Mikhail
50a96abd-1d56-4274-8d7f-ca6a0681b4d8
Patnaude, Daniel J.
603f4876-8fcc-46ee-9448-5d10e960be4c

Wijngaarden, Marcella J.P., Ho, Wynn C.G., Chang, Philip, Heinke, Craig O., Page, Dany, Beznogov, Mikhail and Patnaude, Daniel J. (2019) Diffusive nuclear burning in cooling simulations and application to new temperature data of the Cassiopeia A neutron star. Monthly Notices of the Royal Astronomical Society, 484 (1), 974-988. (doi:10.1093/mnras/stz042).

Record type: Article

Abstract

A critical relation in the study of neutron star cooling is the one between surface temperature and interior temperature. This relation is determined by the composition of the neutron star envelope and can be affected by the process of diffusive nuclear burning (DNB), which occurs when elements diffuse to depths where the density and temperature are sufficiently high to ignite nuclear burning. We calculate models of H-He and He-C envelopes that include DNB and obtain analytic temperature relations that can be used in neutron star cooling simulations. We find that DNB can lead to a rapidly changing envelope composition and prevents the build-up of thermally stable hydrogen columns yH ≳ 107 g cm-2, while DNB can make helium envelopes more transparent to heat flux for surface temperatures Ts ≳ 2x106 K. We perform neutron star cooling simulations in which we evolve temperature and envelope composition, with the latter due to DNB and accretion from the interstellar medium. We find that a time-dependent envelope composition can be relevant for understanding the long-term cooling behaviour of isolated neutron stars. We also report on the latest Chandra observations of the young neutron star in the Cassiopeia A supernova remnant; the resulting 13 temperature measurements over more than 18 years yield a ten-year cooling rate of ~2%. Finally, we fit the observed cooling trend of the Cassiopeia A neutron star with a model that includes DNB in the envelope.

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1901.01012 - Accepted Manuscript
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Accepted/In Press date: 29 December 2018
e-pub ahead of print date: 7 January 2019

Identifiers

Local EPrints ID: 427344
URI: http://eprints.soton.ac.uk/id/eprint/427344
ISSN: 0035-8711
PURE UUID: e60c1f69-fbaa-480e-b950-cbe803a16e90
ORCID for Wynn C.G. Ho: ORCID iD orcid.org/0000-0002-6089-6836

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Date deposited: 14 Jan 2019 17:30
Last modified: 17 Dec 2019 05:05

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Contributors

Author: Wynn C.G. Ho ORCID iD
Author: Philip Chang
Author: Craig O. Heinke
Author: Dany Page
Author: Mikhail Beznogov
Author: Daniel J. Patnaude

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