Thermal luminosities of cooling neutron stars

Abstract

Ages and thermal luminosities of neutron stars, inferred from observations, can be interpreted with the aid of the neutron star cooling theory to gain information on the properties of superdense matter in neutron-star interiors. We present a survey of estimated ages, surface temperatures, and thermal luminosities of middle-aged neutron stars with relatively weak or moderately strong magnetic fields, which can be useful for these purposes. The catalogue includes results selected from the literature, supplemented with new results of spectral analysis of a few cooling neutron stars. The data are compared with the theory. We show that overall agreement of theoretical cooling curves with observations improves substantially for models where neutron superfluidity in stellar core is weak.

Nuclear Pairing Gaps and Neutron Star Cooling

“…This problem also persists when allowing s y < 1 scale factors for this channel [8,9]. The same conclusions were drawn by References [12,13,71,73] and other authors.…”

“…In Figure 4 we show the cooling diagrams, luminosity vs age, for several sets (s x , s y ) of interest, containing also the currently known data points with large (estimated) error bars, see Reference [12]. (We do not yet utilize the very recent update of these data [13] in this work.) Theoretical results employing a Fe atmosphere (solid curves) and those with a light-elements atmosphere (dashed curves) are compared.…”

“…An accurate quantitative theoretical computation of such effects is however still very difficult or impossible, and therefore we investigate in this work empirically the effects of such modifications on the cooling evolution in order to identify possible constraints that may be obtained in this way. In particular, we concentrate in this article on the NS mass distribution that can be obtained by comparing theoretical cooling curves with the currently available set of cooling data [12] (We do not yet utilize the very recent update of these data [13] in this work), and which is therefore a functional of the pairing gaps.…”

“…V18 BCS 1S0 pairing gap as a function of particle number density with different scale factors s x and s y applied, see Equation(13).…”

Evolution of Neutron Star Magnetic Fields

“…Relatively large surface temperatures of the M7 NSs deserve additional comments in the context of discussion of their field evolution. Even low-mass solutions, which provide slower cooling, due to the absence of direct URCA processes [120], cannot explain thermal luminosities of the M7 sources for their estimated ages [121]. This supports the idea presented by [122] (see also [123]) that surface temperatures of magnetars, M7, and maybe some other highly magnetised NSs, are determined not just by residual heat, but by magnetic energy released in the process of field decay.…”