Neutron star cooling: Theoretical aspects and observational constraints

The cooling theory of isolated neutron stars is reviewed. The main cooling regulators are discussed, first of all, operation of direct Urca process (or similar processes in exotic phases of dense matter) and superfluidity in stellar interiors. The prospects to constrain gross parameters of supranuclear matter in neutron-star interiors by confronting cooling theory with observations of isolated neutron stars are outlined. A related problem of thermal states of transiently accreting neutron stars with deep crustal heating of accreted matter is discussed in application to soft X-ray transients.Comment: 10 pages, 3 figures, Proceedings of the 34th COSPAR Scientific Assembly (Adv. Sp. Res., accepted

Cooling of Neutron Stars with Strong Toroidal Magnetic Fields

We present models of temperature distribution in the crust of a neutron star in the presence of a strong toroidal component superposed to the poloidal component of the magnetic field. The presence of such a toroidal field hinders heat flow toward the surface in a large part of the crust. As a result, the neutron star surface presents two warm regions surrounded by extended cold regions and has a thermal luminosity much lower than in the case the magnetic field is purely poloidal. We apply these models to calculate the thermal evolution of such neutron stars and show that the lowered photon luminosity naturally extends their life-time as detectable thermal X-ray sources

Electron Conduction along Quantizing Magnetic Fields in Neutron Star Crusts - II. Practical formulae

. We derive practical expressions for a rapid and accurate evaluation of electric and thermal conductivities and thermopower of degenerate relativistic electrons along quantizing magnetic fields in outer neutron star crusts. We consider the electron Coulomb scattering on ions in liquid matter, as well as on high-temperature phonons or charged impurities in solid matter. We propose also a reasonable semi-quantitative treatment of low-temperature phonons. The transport properties are expressed through the energy dependent effective electron relaxation time averaged over electron energies. We calculate this relaxation time, using the theoretical formalism of the previous work, obtain accurate fitting expressions, and propose an efficient energy averaging procedure. We create a computer code which calculates the longitudinal transport properties of degenerate electrons in strong magnetic fields for any parameters of dense stellar matter of practical interest. We analyse quantum oscillation..

Strongly Coupled Coulomb and Nuclear Plasma in Inner Crusts of Neutron Stars

Matter of subnuclear density in the inner crusts of neutron stars consists of neutron-rich atomic nuclei immersed in strongly degenerate relativistic gas of electrons and strongly nonideal liquid of neutrons. Thermodynamic and kinetic properties of this matter are greatly aected by Coulomb and nuclear interactions and can be studied, in principle, from observations of thermal radiation of young (age 100 yr) neutron stars. 1 Introduction Neutron stars (NSs) are the most fascinating stars in the Universe. Their masses are M 1:4 M , and their radii R 10 km. Accordingly, their mean mass density is about (2-3) 0 , where 0 = 2:8 10 14 g cm 3 is the mass density of matter in atomic nuclei. Thus, NSs contain matter of supranuclear density compressed by huge gravitational forces. Accordingly, they are treated as unique astrophysical laboratories of such matter. We show that young NSs are also laboratories of strongly coupled Coulomb{nuclear plasmas of subnuclear density. ..

Vibrational coherence in bacterial reaction centers with genetically modified B-branch pigment composition

Femtosecond absorption difference spectroscopy was applied to study the time and spectral evolution of low-temperature (90 K) absorbance changes in isolated reaction centers (RCs) of the HM182L mutant of Rhodobacter (Rb.) sphaeroides. In this mutant, the composition of the B-branch RC cofactors is modified with respect to that of wild-type RCs by replacing the photochemically inactive B-B accessory bacteriochlorophyll (BChl) by a photoreducible bacteriopheophytin molecule (referred to as Phi(B)). We have examined vibrational coherence within the first 400 fs after excitation of the primary electron donor P with 20-fs pulses at 870 nm by studying the kinetics of absorbance changes at 785 nm (Phi(B) absorption band), 940 nm (P*-stimulated emission), and 1020 nm (B-A(-) absorption band). The results of the femtosecond measurements are compared with those recently reported for native Rb. sphaeroides R-26 RCs containing an intact B-B BChl. At delay times longer than similar to 50 fs (maximum at 120 fs), the mutant RCs exhibit a pronounced BChl radical anion (B-A(-)) absorption band at 1020 nm, which is similar to that observed for Rb. sphaeroides R-26 RCs and represents the fort-nation of the intermediate charge-separated state P+BA-. Femtosecond oscillations are revealed in the kinetics of the absorption development at 1020 nm and of decay, of the P*-stimulated emission at 940 nm, with the oscillatory components of both kinetics displaying a generally synchronous behavior. These data are interpreted in terms of coupling of wave packet-like nuclear motions on the potential energy surface of the P* excited state to the primary electron-transfer reaction P* -> P+BA- in the A-branch of the RC cofactors. At very early delay times (up to 80 fs), the mutant RCs exhibit a weak absorption decrease around 785 nm that is not observed for Rb. sphaeroides R-26 RCs and can be assigned to a transient bleaching of the Q(y) ground-state absorption band of the Phi(B) molecule. In the range of 740-795 nm, encompassing the Qy optical transitions of bacteriopheophytins H-A, H-B, and Phi(B), the absorption difference spectra collected for mutant RCs at 30-50 fs resemble the difference spectrum of the P+Phi(-)(B) charge-separated state previously detected for this mutant in the picosecond time domain (E. Katilius, Z. Katiliene, S. Lin, A.K.W. Taguchi, N.W. Woodbury, J. Phys. Chem., B 106 (2002) 1471-1475). The dynamics of bleaching at 785 nm has a non-monotonous character, showing a single peak with a maximum at 40 fs. Based on these observations, the 785-nm bleaching is speculated to reflect reduction of 1% of Phi(B) in the B-branch within about 40 fs, which is earlier by similar to 80 fs than the reduction process in the A-branch, both being possibly linked to nuclear wave packet motion in the P* state. (c) 2006 Elsevier B.V. All rights reserved