387,428 research outputs found
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
Testing Gravity Theories In The Radiative Regime Using Pulsar Timing Arrays
General relativity has predicted the existence of gravitational waves (GW),
which are waves of the distortions of space-time with two degrees of
polarization and the propagation speed of light. Alternative theories predict
more polarizations, up to a maximum of six, and possible deviation of
propagation speed from the light speed. The present paper reviews recent
proposals to test the gravity theories in the radiation regime by observing GWs
using pulsar timing arrays.Comment: 4 pages, 2 figures, PULSAR CONFERENCE 2010, Chia Laguna Resort,
Sardinia, Italy, 10-15 October, 201
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
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