Semi-Competing Risks on A Trivariate Weibull Survival Model

A setting of a trivairate survival function using semi-competing risks concept is proposed. The Stanford Heart Transplant data is reanalyzed using a trivariate Weibull distribution model with the proposed survival function

On the Profiles and Polarization of Raman Scattered Emission Lines in Symbiotic Stars:II. Numerical Simulations

A Monte Carlo method is used to calculate the profiles and the polarization of the Raman scattered O VI lines(lambda lambda 6827,7088) in symbiotic stars. A point-like isotropic UV radiation source is assumed and a simple spherical wind model is adopted for the kinematics of the scattering material from the cool giant. We first investigate the case where the incident line photons are described by a Gaussian profile having a width of 10^4 K. We subsequently investigate the effects of the extended ionized region and non-spherical wind models including a disk-type wind and a bipolar wind. The cases where the emissin source is described by non-Gaussian profiles are briefly studied. Finally, as an additional component for the kinematics of symbiotic stars the orbital motion of the hot component around the cool giant is included and the effect on the spectropolarimetry is investigated. In this case the polarization direction changes around the red part of the Raman-scattered emission lines, when the observer's line of sight is perpendicular to the orbital plane, and no such effect is seen when the line of sight lies in the orbital plane. Furthermore, complex peak structures are seen in the degree of polarization and polarized flux, which have often been observed in several symbiotic systems including RR Tel. Brief observational consequences and preditions are discussed in relation to the present and future spectropolarimetry for symbiotic stars. It is concluded that spectropolarimetry may provide a powerful diagnostic of the physical conditions of symbiotic stars.Comment: 22 pages, Tex, 15 postscript figuer

Fermion Production in Strong Magnetic Field and its Astrophysical Implications

We calculate the effective potential of a strong magnetic field induced by fermions with anomalous magnetic moments which couple to the electromagnetic field in the form of the Pauli interaction. For a uniform magnetic field, we find the explicit form of the effective potential. It is found that the non-vanishing imaginary part develops for a magnetic field stronger than a critical field and has a quartic form which is quite different from the exponential form of the Schwinger process. We also consider a linear magnetic field configuration as an example of inhomogeneous magnetic fields. We find that the imaginary part of the effective potential is nonzero even below the critical field and shows an exponentially decreasing behavior with respect to the inverse of the magnetic field gradient, which is the non-perturbative characteristics analogous to the Schwinger process. These results imply the instability of the strong magnetic field to produce fermion pairs as a purely magnetic effect. The possible applications to the astrophysical phenomena with strong magnetic field are also discussed.Comment: 13 pages, 3 figure