Lower limit on the heat capacity of the neutron star core

Cumming, Andrew; Brown, Edward F.; Fattoyev, F. J.; Horowitz, C. J.; Page, Dany; Reddy, Sanjay

doi:10.1103/physrevc.95.025806

Cited by 71 publications

(111 citation statements)

References 63 publications

(146 reference statements)

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“…As the present work was in progress, Cumming et al (2016) found that such an amount of energy can raise the core temperature and provides us with a lower limit on its heat capacity that depends on the tantalizing core composition. Comparing with their figure 7, ourT0 2 × 10 7 K provides the strongest constraint to date on the core heat capacity: it must be C > 10 37 (T0/10 8 K) erg K −1 , a value that is close to the minimum provided by the leptons in the core.…”

Section: Discussionmentioning

confidence: 99%

“…A shallow heat source, with a typical magnitude of Q sh 1 − 2 MeV and one extreme case of Q sh 6−16 MeV per accreted nucleon, has been inferred for several neutron stars although its origin remains unknown (e.g. Brown & Cumming 2009;Degenaar et al 2011a;Deibel et al 2015;Ootes et al 2016;Waterhouse et al 2016). We set ρ sh = 4 × 10 8 g cm…”

Section: Thermal Evolution Simulationsmentioning

confidence: 99%

“…The temperature evolution in quiescence of five quasi-persistent sources can be successfully explained as cooling of the strongly-heated neutron star crust and offers valuable insight into the structure and composition of these neutron stars (e.g. Rutledge et al 2002;Wijnands et al 2002Wijnands et al , 2004Shternin et al 2007;Brown & Cumming 2009;Page & Reddy 2013;Medin & Cumming 2014;Deibel et al 2015;Horowitz et al 2015;Turlione et al 2015;Cumming et al 2016). AMXPs distinguish themselves by displaying coherent X-ray pulsations when accreting (e.g.…”

Section: Introductionmentioning

confidence: 99%

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A cold neutron star in the transient low-mass X-ray binary HETE J1900.1–2455 after 10 yr of active accretion

Degenaar

Ootes

Reynolds

et al. 2016

Monthly Notices of the Royal Astronomical Society: Letters

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The neutron star low-mass X-ray binary and intermittent millisecond X-ray pulsar HETE J1900.1-2455 returned to quiescence in late 2015, after a prolonged accretion outburst of 10 yr. Using a Chandra observation taken 180 d into quiescence we detect the source at a luminosity of 4.5 × 10 31 (D/4.7 kpc) 2 erg s −1 (0.5-10 keV). The X-ray spectrum can be described by a neutron star atmosphere model with a temperature of 54 eV for an observer at infinity. We perform thermal evolution calculations based on the 2016 quiescent data and a 98 eV temperature upper limit inferred from a Swift observation taken during an unusually brief ( 2 weeks) quiescent episode in 2007. We find no evidence in the present data that the thermal properties of the crust, such as the heating rate and thermal conductivity, are different than those of non-pulsating neutron stars. Finding this neutron star so cold after its long outburst imposes interesting constraints on the heat capacity of the stellar core; these become even stronger if further cooling were to occur.

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Section: Discussionmentioning

confidence: 99%

Section: Thermal Evolution Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A cold neutron star in the transient low-mass X-ray binary HETE J1900.1–2455 after 10 yr of active accretion

Degenaar

Ootes

Reynolds

et al. 2016

Monthly Notices of the Royal Astronomical Society: Letters

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“…This balance is restored later, during subsequent quiescent states. Observations of the relaxation of such neutron stars combined with observations of an accretion outburst allow one to estimate a lower limit to the heat capacity of the neutron star core [13].…”

Section: Introductionmentioning

confidence: 99%

Neutrino luminosities and heat capacities of neutron stars in analytic form

et al. 2017

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We derive analytic approximations for the neutrino luminosities and the heat capacities of neutron stars with isothernal nucleon cores as functions of the mass and radius of stars. The neutrino luminosities are approximated for the three basic neutrino emission mechanisms, and the heat capacities for the five basic combinations of the partial heat capacities. The approximations are valid for for a wide class of equations of state of dense nucleonmatter. The results significantly simplify the theoretical interpretation of observations of cooling neutron stars as well as of quasistationary thermal states of neutron stars in X-ray transients. For illustration, we present an analysis of the neutrino cooling functions of nine isolated neutron stars taking into account the effects of their magnetic fields and of the presence of light elements in their heat blanketing envelopes. These results allow one to investigate the superfluid properties of neutron star cores.

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“…The origin of this shallow heat source is unknown and is important to resolve because the cooling curve can be used to constrain a number of different aspects of crust physics (such as conductivity of the crust and pasta, and the core specific heat; Brown & Cumming 2009;Horowitz et al 2015;Cumming et al 2017). Most systems need ∼1-2 MeV nucleon −1 of shallow heating to explain their cooling curves (e.g., Degenaar et al 2014;Parikh et al 2017;Wijnands et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Different Accretion Heating of the Neutron Star Crust during Multiple Outbursts in MAXI J0556–332

Parikh

Homan

Wijnands

et al. 2017

ApJL

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The transient neutron star (NS) low-mass X-ray binary MAXI J0556−332 provides a rare opportunity to study NS crust heating and subsequent cooling for multiple outbursts of the same source. We examine MAXI, Swift, Chandra, and XMM-Newton data of MAXI J0556−332 obtained during and after three accretion outbursts of different durations and brightnesses. We report on new data obtained after outburst III. The source has been tracked up to ∼1800 days after the end of outburst I. Outburst I heated the crust strongly, but no significant reheating was observed during outburst II. Cooling from ∼333 eV to ∼146 eV was observed during the first ∼1200 days. Outburst III reheated the crust up to ∼167 eV, after which the crust cooled again to ∼131 eV in ∼350 days. We model the thermal evolution of the crust and find that this source required a different strength and depth of shallow heating during each of the three outbursts. The shallow heating released during outburst I was ∼17 MeV nucleon −1 and outburst III required ∼0.3 MeV nucleon −1 . These cooling observations could not be explained without shallow heating. The shallow heating for outburst II was not well constrained and could vary from ∼0 to 2.2 MeV nucleon −1 , i.e., this outburst could in principle be explained without invoking shallow heating. We discuss the nature of the shallow heating and why it may occur at different strengths and depths during different outbursts.

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Lower limit on the heat capacity of the neutron star core

Cited by 71 publications

References 63 publications

A cold neutron star in the transient low-mass X-ray binary HETE J1900.1–2455 after 10 yr of active accretion

A cold neutron star in the transient low-mass X-ray binary HETE J1900.1–2455 after 10 yr of active accretion

Neutrino luminosities and heat capacities of neutron stars in analytic form

Different Accretion Heating of the Neutron Star Crust during Multiple Outbursts in MAXI J0556–332

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