HST spectrally-resolved accretion disk maps of UX~UMa in the ultraviolet

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Session 116 -- Globular Clusters and Compact Objects
Oral presentation, Thursday, 12, 1995, 10:00am - 11:30am

[116.05] HST spectrally-resolved accretion disk maps of UX~UMa in the ultraviolet

R. Baptista, K. Long (STScI), K. Horne (St.\,Andrews), I. Hubeny (GSFC), C.W. Mauche (Lawrence Livermore Nat. Lab.), R.G.M. Rutten (RGO, Tenerife), R.A. Wade (PSU)

We present spectrally-resolved eclipse maps of the UX~UMa accretion disk in the spectral region 1170--2400 \AA. The analysis is based on low-dispersion time-resolved spectroscopy during eclipse, obtained with the HST {\sl Faint Object Spectrograph}.

The out-of-eclipse spectra show prominent emission lines (C\,III $\lambda 1176$, Ly$\alpha$, N\,V $\lambda 1240$, Si\,IV $\lambda 1400$, C\,IV $\lambda 1550$) as well as many absorption features and possibly a broad absorption band centered at about 1900~\AA. He\,II $\lambda 1640$ appears as a weak emission line. At mid-eclipse the continuum flux is reduced by a factor $\sim 3$, while the emission lines are much less affected by the eclipse and some of the lines that are seen in absorption in the out-of-eclipse spectra appear in emission. UV continuum light curves show significant flickering activity outside of eclipse, relatively much stronger than observed in the optical range. The eclipses are deep and steep in the continuum with an asymmetry in their egress portion, however no clear evidence of a compact bright spot is seen.

The spectra were divided into passbands ($\sim 40$~\AA ~in the continuum and $\sim 3000$ Km/s in the emission lines) and light curves were extracted for each one. Maximum-entropy eclipse mapping techniques were used to solve for a map of the disk brightness distribution and for the flux of an additional uneclipsed component in each band. Radial brightness temperature profiles and spatially-resolved disk spectra derived from these maps are presented and discussed.

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