Temperature Profiles of Accretion Disks around Rapidly Rotating Neutron Stars in General Relativity and Implications for Cygnus X-2

We calculate the temperature profiles of (thin) accretion disks around rapidly rotating neutron stars (with low surface magnetic fields), taking into account the full effects of general relativity. We then consider a model for the spectrum of the X-ray emission from the disk, parameterized by the mass accretion rate, the color temperature and the rotation rate of the neutron star. We derive constraints on these parameters for the X-ray source Cygnus X-2 using the estimates of the maximum temperature in the disk along with the disk and boundary layer luminosities, using the spectrum inferred from the EXOSAT data. Our calculations suggest that the neutron star in Cygnus X-2 rotates close to the centrifugal mass-shed limit. Possible constraints on the neutron star equation of state are also discussed.Comment: 18 pages, 9 figs., 2 tables, uses psbox.tex and emulateapj5.sty. Submitted to Ap

Energy Release During Disk Accretion onto a Rapidly Rotating Neutron Star

The energy release L_s on the surface of a neutron star (NS) with a weak magnetic field and the energy release L_d in the surrounding accretion disk depend on two independent parameters that determine its state (for example, mass M and cyclic rotation frequency f) and is proportional to the accretion rate. We derive simple approximation formulas illustrating the dependence of the efficiency of energy release in an extended disk and in a boundary layer near the NS surface on the frequency and sense of rotation for various NS equations of state. Such formulas are obtained for the quadrupole moment of a NS, for a gap between its surface and a marginally stable orbit, for the rotation frequency in an equatorial Keplerian orbit and in the marginally stable circular orbit, and for the rate of NS spinup via disk accretion. In the case of NS and disk counterrotation, the energy release during accretion can reach $0.67\dot{M}c^2$. The sense of NS rotation is a factor that strongly affects the observed ratio of nuclear energy release during bursts to gravitational energy release between bursts in X-ray bursters. The possible existence of binary systems with NS and disk counterrotation in the Galaxy is discussed. Based on the static criterion for stability, we present a method of constructing the dependence of gravitational mass M on Kerr rotation parameter j and on total baryon mass (rest mass) m for a rigidly rotating neutron star. We show that all global NS characteristics can be expressed in terms of the function M(j, m) and its derivatives.Comment: 42 pages, 12 figures, to appear in Astronomy Letters, 2000, v.26, p.69

High affinity binding of labeled androgens in the androgen-target tissues of the male rhesus monkey

High affinity testosterone (T)-specific and dihydrotestosterone (DHT)-specific binding sites exist in a 12 ratio in the cytosol fractions of the caput epididymidis, prostate, seminal vesicles and the ductus deferens of the rhesus monkey. The number of androgen-binding sites in the caput epididymidis is 3 times greater than that of the other 3 tissues

Anti-androgenic action of cyproterone acetate in the epididymis of the rhesus monkey

Cyproterone acetate (1 μM) inhibited the binding of labeled testosterone (T) and dihydrotestosterone (DHT) in the caput and cauda epididymides of the rhesus monkey. The same concentration of the anti-androgen failed to inhibit androgen binding in the ductus deferens, prostate and seminal vesicles