HST eclipse maps of UX~UMa in the C\,IV~$\lambda 1550$ and He\,II~$\lambda 1640$ regions
Session 123 -- Intrinsic Variables and Active Stars
Oral presentation, Saturday, January 15, 2:15-3:45, Salon V Room (Crystal Gateway)

## [123.07] HST eclipse maps of UX~UMa in the C\,IV~$\lambda 1550$ and He\,II~$\lambda 1640$ regions

R.Baptista (STScI), K.Horne (Utrecht), R.Hilditch (St.\,Andrews), F.Cordova (PSU), J.E.Drew, T.R.Marsh (Oxford), K.O.Mason (Mullard), C.W.Mauche (Lawrence Livermore Nat. Lab.), J.C.Raymond (CfA)

We present spectrally-resolved eclipse maps of the accretion disk of the nova-like variable UX~UMa in the C\,IV $\lambda 1550$ and He\,II $\lambda 1640$ spectral regions. The analysis is based on time-resolved spectroscopy (wavelength range $\simeq 35$ \AA) during eclipse, obtained with the {\sl HST High Resolution Spectrograph} on 1993 Jan 19 - 22. The spectra were divided in a set of narrow passbands ($4-5$ \AA ~wide) and light curves were constructed for each one. The eclipse mapping method was used to obtain maps of the disk brightness distribution in each passband.

The continuum maps show a small disk with radius $\simeq 20$\% of the orbital separation. The radial temperature profile derived from these maps closely follows the radial dependence predicted by the stationary disk model ($T \propto R^{-3/4}$) at large disk radii, but becomes flatter than the theoretical model close to the disk center. The temperatures in the disk range from 30000\,K to 10000\,K and the inferred mass accretion rate is \.{M}$= 10^{-8.3\pm 0.2} \:{\rm M_{\odot} \,yr}^{-1}$. Eclipse maps from contemporary R-band photometry are shown for comparison. The He\,II map shows an extended brightness distribution which fills most of the primary lobe and whose temperature profile is much flatter than that of the continuum maps. The C\,IV doublet has a complex structure with absorption components superimposed on a broad emission profile. The line center does not eclipse and was not mapped.

The spatially-resolved spectra obtained by combining all maps show the He\,II line in absorption at the inner disk which progressively changes to broad emission with increasing disk radius. A similar but weaker effect is seen in the Si\,II $\lambda 1527, 1533$ absorption lines.