Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998aipc..431..463k&link_type=abstract
Accretion processes in astrophysical systems: Some like it hot! - eigth astrophysics conference. AIP Conference Proceedings, Vo
Astronomy and Astrophysics
Astrophysics
Cataclysmic Binaries, Symbiotic Stars, Stellar Characteristics And Properties, Astronomical Observations
Scientific paper
Low-amplitude (~=0.5%) 29-s oscillations have been detected in HST/FOS eclipse observations of the nova-like cataclysmic variable UX UMa. These are the same dwarf nova-type oscillations that were originally discovered in this system by Warner & Nather in 1972. The 29-s oscillations are seen in one pair of eclipse sequences obtained with the FOS/PRISM in November of 1994. The oscillations in the PRISM data are sinusoidal to within the small observational errors and undergo an approximately -360° phase shift during eclipses. Their amplitudes are highest at pre-eclipse orbital phases and exhibit a rather gradual eclipse whose shape is roughly similar to, though perhaps slightly narrower than, UX UMa's overall light curve in the PRISM bandpass (2000 Å-8000 Å). Oscillation spectra constructed from out-of-eclipse data segments are extremely blue. Blackbody and stellar atmosphere model fits to these data converge on effectively infinite temperatures. By contrast, oscillation spectra derived from mid-eclipse data segments are much redder. Model fits to these spectra yield temperature estimates in the range 20,000 K<=T<=30,000 K. Based on these observational constraints, we suggest that the ultimate source of the oscillations is a hot, compact region near disk center, but that a significant fraction of the observed, modulated flux is due to reprocessing of the light emitted by this source in the accretion disk atmosphere. The compact source is occulted at orbital phases near mid-eclipse, leaving only part of the more extended reprocessing region(s) to produce the weak oscillations that persist even at conjunction.
Baptista Raymundo
Drake Nick
Horne Keith
Knigge Christian
Long Knox S.
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