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

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 candlesstars 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 = r g /R, irrespective of the equation of state of neutron star matter (R and r g 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.

Thermal Spectrum and Neutrino Cooling Rate of the Vela Pulsar

“…Testing different models of , one can limit those which are reasonably consistent with observations. All necessary formulae and caveats could be found in [17], Section 4.…”

“…We will employ the method similar to that discussed in [17,20,34] and in references therein. It is well described in the literature; we just outline the main points.…”

“…Older stars cool mostly through their thermal surface emission. The central black solid line shows the standard cooling [17] (of non-superfluid NSs with the modified Urca neutrino emission in the core and iron heat blanketing envelope). This curve is almost unaffected by the equation of state (EOS) of NS matter and NS mass (e.g., [18]).…”

Magnetar giant flare oscillations and the nuclear symmetry energy

“…Indeed, Gabler et al [53] found that for B 5 × 10 13 G torsional crust modes would be resonantly damped by coupling to the Alfvén continuum, with damping timescales ∼ 0.2 s. Their study did not, however, include the effects of proton pairing in the core nor did it include a re-alistic model of the neutron star crust. Observations of cooling of the young neutron star in the Cas A supernova remnant [54,55] suggest that the proton 1 S 0 pairing gap is large [56,57], so that the protons are in a superconducting state throughout the core. The crust-core coupling depends on the magnetic field configuration and the magnetic field strength near the crust-core interface [20], neither of which are well understood.…”

The double-dark portal

“…This introduces many subtleties into their cooling processes, which are not yet fully understood even in the Standard Model (see e.g. [50][51][52][53][54][55][56][57][58][59]). However, neutron stars are such powerful "φ-factories" in dmDM that we can still set very strong constraints despite these uncertainties.…”