The neutrino emission due to plasmon decay and neutrino luminosity of white dwarfs

One of the effective mechanisms of neutrino energy losses in red giants, pre-supernovae and in the cores of white dwarfs is the emission of neutrino–antineutrino pairs in the process of plasmon decay. In this paper, we numerically calculate the emissivity due to plasmon decay in a wide range of temperatures 10⁷–10¹¹ K and densities (2 × 10²–10¹⁴) g cm⁻³. Numerical results are approximated by convenient analytical expressions. We also calculate and approximate by analytical expressions the neutrino luminosity of white dwarfs due to plasmon decay, as a function of their mass and internal temperature. This neutrino luminosity depends on the chemical composition of white dwarfs only through the parameter μ_e (the net number of baryons per electron) and is the dominant neutrino luminosity in all white dwarfs at the neutrino cooling stage.     

Cooling of neutron stars: Two types of triplet neutron superfluidity

We consider the cooling of neutron stars with superfluid cores composed of neutrons, protons, and electrons (for singlet proton pairing and triplet neutron pairing). The emphasis is on triplet neutron pairing with the component of the total moment of neutron pairs along the quantization axis |m _J | = 2. This case stands out in that it leads to power-law rather than exponential suppression of the main neutrino processes by neutron superfluidity. For the chosen critical neutron temperatures T _cn, the cooling with |m _J | = 2 proceeds either almost in the same way as the commonly considered cooling with m _J =0 or appreciably faster. The cooling with variable (over the core) critical temperatures T _cn(ρ) and T _cp(ρ) can generally be described by the cooling with some effective constant temperatures T _cn and T _cp. The hypothesis of strong neutron superfluidity with |m _J | = 2 is in conflict with the observational data on the thermal radiation from isolated neutron stars; the hypothesis of weak neutron superfluidity of any type is consistent with the observations.     

Symmetry of the neutron and proton superfluidity effects in cooling neutron stars

We investigate the combined effect of neutron and proton superfluidities on the cooling of neutron stars whose cores consist of nucleons and electrons. We consider the singlet state paring of protons and the triplet pairing of neutrons in the cores of neutron stars. The critical superfluid temperatures T _c are assumed to depend on the matter density. We study two types of neutron pairing with different components of the total angular momentum of a Cooper pair along the quantization axis (|m _J |=0 or 2). Our calculations are compared with the observations of thermal emission from isolated neutron stars. We show that the observations can be interpreted by using two classes of superfluidity models: (1) strong proton superfluidity with a maximum critical temperature in the stellar core T _c ^max ?4×10⁹ K and weak neutron superfluidity of any type (T _c ^max ?2×10⁸ K); (2) strong neutron superfluidity (pairing with m _J =0) and weak proton superfluidity. The two types of models reflect an approximate symmetry with respect to an interchange of the critical neutron and proton pairing temperatures.     

Physicochemical Properties of Bottom Sediments in Water Bodies in the Central and Southern Vietnam

Water Resources - The physicochemical characteristics of bottom sediments in inland water bodies in the Central and Southern Vietnam are presented for the first time, including particle-size...     

Minimal models of cooling neutron stars with accreted envelopes

We study the 'minimal' cooling scenario of superfluid neutron stars with nucleon cores, where the direct Urca process is forbidden and enhanced cooling is produced by neutrino emission due to the Cooper pairing of neutrons. Extending our recent previous work, we include the effects of surface accreted envelopes of light elements. We employ the phenomenological density-dependent critical temperatures   T _cp(ρ)  and   T _cnt(ρ)  of singlet-state proton and triplet-state neutron pairing in a stellar core, as well as the critical temperature   T _cns(ρ)  of singlet-state neutron pairing in a stellar crust. We show that the presence of accreted envelopes simplifies the interpretation of observations of thermal radiation from isolated neutron stars in the scenario of our recent previous work and widens the class of models for nucleon superfluidity in neutron star interiors consistent with the observations.     

The Effect of the Hydrological Regime in the Rybinsk Reservoir on the Distribution and Dynamics of Benthic Cyclops

Data on the abundance, horizontal distribution, and the seasonal dynamics of the dominant species and the entire group Cyclopoida in the meiobenthos of the open littoral and profundal of the Rybinsk Reservoir are presented. The probability that the passive and active migrations of cyclops in the reservoir are controlled by the natural (transsedimentational activity of hydrodynamic processes) and human-induced factors (artificial water level control) is discussed.