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Rapid Neutrino Cooling in the Neutron Star MXB 1659-29

Edward F. Brown, Andrew Cumming, Farrukh J. Fattoyev, C. J. Horowitz, Dany Page, and Sanjay Reddy
Phys. Rev. Lett. 120, 182701 – Published 30 April 2018
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Abstract

We show that the neutron star in the transient system MXB 1659-29 has a core neutrino luminosity that substantially exceeds that of the modified Urca reactions (i.e., n+nn+p+e+ν¯e and inverse) and is consistent with the direct Urca (np+e+ν¯e and inverse) reaction occurring in a small fraction of the core. Observations of the thermal relaxation of the neutron star crust following 2.5 yr of accretion allow us to measure the energy deposited into the core during accretion, which is then reradiated as neutrinos, and infer the core temperature. For a nucleonic core, this requires that the nucleons are unpaired and that the proton fraction exceeds a critical value to allow the direct Urca reaction to proceed. The neutron star in MXB 1659-29 is the first with a firmly detected thermal component in its x-ray spectrum that needs a fast neutrino-cooling process. Measurements of the temperature variation of the neutron star core during quiescence would place an upper limit on the core specific heat and serve as a check on the fraction of the neutron star core in which nucleons are unpaired.

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  • Received 20 July 2017
  • Revised 20 December 2017

DOI:https://doi.org/10.1103/PhysRevLett.120.182701

© 2018 American Physical Society

Physics Subject Headings (PhySH)

Nuclear PhysicsGravitation, Cosmology & Astrophysics

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A Rapidly Cooling Neutron Star

Published 30 April 2018

Astrophysicists have found the first direct evidence for the fastest neutrino-emission mechanism by which neutron stars can cool.

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Authors & Affiliations

Edward F. Brown1,*, Andrew Cumming2,†, Farrukh J. Fattoyev3,‡, C. J. Horowitz3,§, Dany Page4,∥, and Sanjay Reddy5,¶

  • 1Department of Physics and Astronomy, Michigan State University, 567 Wilson Road, East Lansing, Michigan 48864, USA
  • 2Department of Physics and McGill Space Institute, McGill University, 3600 rue University, Montreal, Quebec, Canada H3A 2T8
  • 3Center for Exploration of Energy and Matter and Department of Physics, Indiana University, Bloomington, Indiana 47405, USA
  • 4Instituto de Astronomía, Universidad Nacional Autónoma de México, México, CDMX 04510, Mexico
  • 5Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195, USA

  • *ebrown@pa.msu.edu
  • andrew.cumming@mcgill.ca
  • ffattoye@indiana.edu
  • §horowit@indiana.edu
  • page@astro.unam.mx
  • sareddy@uw.edu

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Issue

Vol. 120, Iss. 18 — 4 May 2018

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