THE ROTATION
RATE AND SURFACE TEMPERATURE OF THE
HOT, ACCRETING WHITE DWARF IN THE DWARF
NOVA RX ANDROMEDAE
pdf ps
Edward
M. Sion
F.
H. Cheng
Department
of Astronomy and Astrophysics
Villanova
University
Villanova,
PA 19085
Paula
Szkody
Department
of Astronomy
University
of Washington
Seattle,
WA 98195
Boris
Gaensicke
Universitat-Sternwarte
Göttingen
37083
Germany
C.
La Dous
Webergasse
21
D-96450
Coburg
Germany
B.
Hassall
Dept.
of Physics, Astronomy and Mathematics
University
of Central Lancashire
Preston,
PR1 2HE
England
Presented
at the 89th Spring Meeting of the AAVSO, April 15, 2000
Abstract
We obtained Hubble GHRS
phase-resolved spectroscopic observations of the dwarf nova RX Andromedae at
three times in its outburst cycle: (1) near the end of an extraordinarily deep
and long dwarf nova quiescence, 3 months after the last previous outburst; (2)
during the rise to outburst; and (3) near the end of a decline from outburst.
The spectral wavelength range covered was 1149Å to 1435Å. All of the spectra
are dominated by absorption lines with weak to moderately strong emission wings
due to the continued presence of disk material. Uncertainities in line
velocities preclude a K1 determination or mass information. Our best fitting
model yielded Twd /1000 = 34.0 ±0.1K, log g = 8.0 ±0.1,
and Vrot = 600 km/s.
The Teff value is very similar to the Teff of
the white dwarf in U Gem, but the rotational velocity appears to be higher than
U Gem’s value. We report approximate subsolar chemical abundances of Carbon and
Silicon for RX And, with C being 0.05 x solar and Si = 0.1 x solar while other
elements are at essentially their solar values. However, accurate abundances
are complicated by line emission and we cannot exclude that the abundances of
all species are essentially at the solar values. We see no evidence of
thermonuclear-processed abundance ratios. If the white dwarf mass is 0.8
M (Ritter 1999), then the corresponding white dwarf cooling age,
4 x 106 years, is a lower limit to the age of this CV. If the
peculiar line features seen in the spectrum on the late decline from outburst
are inverse P Cygni in nature, then infall velocities of ~2000km/s are
indicated during the decline from outburst. We compare the surface properties
of the RX And white dwarf with the properties
of other CV degenerates studied to date with HST, HUT, and IUE.
Link to ADS abstract, article and citation information
