Quasar proper motions and low-frequency gravitational waves
CR Gwinn, TM Eubanks, T Pyne…�- The Astrophysical�…, 1997 - iopscience.iop.org
We report observational upper limits on the mass-energy of the cosmological gravitational
wave background, from limits on proper motions of quasars. Gravitational waves with
periods longer than the time span of observations produce a simple pattern of apparent
proper motions over the sky, composed primarily of second-order transverse vector
spherical harmonics. A fit of such harmonics to measured motions yields a 95% confidence
limit on the mass-energy of gravitational waves with frequencies ν< 2� 10-9 Hz, of less than�…
wave background, from limits on proper motions of quasars. Gravitational waves with
periods longer than the time span of observations produce a simple pattern of apparent
proper motions over the sky, composed primarily of second-order transverse vector
spherical harmonics. A fit of such harmonics to measured motions yields a 95% confidence
limit on the mass-energy of gravitational waves with frequencies ν< 2� 10-9 Hz, of less than�…
ASCA observation of Cygnus X-1 in the soft state: mass of the compact object
T Dotani, H Inoue, K Mitsuda, F Nagase…�- The Astrophysical�…, 1997 - iopscience.iop.org
We describe the ASCA observation of the black hole candidate Cyg X-1 in the soft state of
1996 May and report the mass estimation of the central object from X-ray spectral analysis.
The energy spectrum in 0.7–10 keV can be described by the sum of a power law (&Ggr;=
2.3�0.1) and an ultrasoft component; the latter is most probably the emission from an
optically thick accretion disk. Through the spectral analysis of the ultrasoft component, we
estimated the size of the accretion disk, which is closely related to the Schwarzschild radius�…
1996 May and report the mass estimation of the central object from X-ray spectral analysis.
The energy spectrum in 0.7–10 keV can be described by the sum of a power law (&Ggr;=
2.3�0.1) and an ultrasoft component; the latter is most probably the emission from an
optically thick accretion disk. Through the spectral analysis of the ultrasoft component, we
estimated the size of the accretion disk, which is closely related to the Schwarzschild radius�…