Second RXTE Observation of RS Oph in Outburst
ATel #741; J. L. Sokoloski, G. J. M. Luna (SAO), K. Mukai (GSFC)
on 20 Feb 2006; 18:11 UT
Credential Certification: Jennifer L. Sokoloski (jsokolos@cfa.harvard.edu)
Subjects: X-ray, Binary, Cataclysmic Variable, Nova, Star, Transient, Variables
Referred to by ATel #: 747, 754
We report on the second Rossi X-Ray Timing Explorer (RXTE) observation
of the symbiotic recurrent nova RS Oph in outburst. This 2.3 ks
observation was performed roughly one week into the eruption, on Feb
18, 2006, beginning at 17:27:00 UT. A preliminary analysis indicates
that the source is still X-ray bright. We find a 2-10 keV flux of
(1.54+/-0.05) e-9 erg/cm/cm/s and a 2-20 keV flux of (1.80+/-0.05) e-9
erg/cm/cm/s. Taking a distance of 1.6 kpc (note the different assumed
distance compared to ATel #737; Snijders 1987, in "RS Oph (1985) and
the Recurrent Nova Phenomenon", ed. M. F. Bode), the absorbed 2-20 keV
luminosity is approximately (5.5+/-0.1) e35 erg/s (compared to
(6.0+/-0.1) e35 erg/s on Feb 15). The spectrum softened compared to
the first outburst X-ray observation three days earlier (see ATel
#737). An absorbed thermal bremsstrahlung model gives a plasma
temperature of approximately 5 to 6 keV, compared to approximately 10
keV on Feb 15. The X-ray spectral evolution is thus consistent with
shock heating by ejecta that is decelerating. A plasma temperature of
5-6 keV corresponds to a strong shock moving at around 2200 km/s. The
complex of Fe lines near 6.6 keV also significantly decreased in
strength. Finally, the absorbing column dropped to roughly 5e21
cm^-2, which is close to the interstellar value of 3-4 e21 cm^-2 given
by Mason et al. (1987, in "RS Oph (1985) and the Recurrent Nova
Phenomenon").
