IUE AND OPTICAL OBSERVATIONS OF AM HERCULIS IN ITS LOW STATE

Ten spectra of AM Herculis were obtained with the SWP instrument of th e IUE over 2.5 orbital periods during a faint state in 1992 June. Sign ificant periodic variability was seen in the UV flux and spectra. On t he same day, UBVRI photometry was obtained at the 1.25 m optical teles cope of the Crimean Astrophysical Observatory. A periodic brightening was seen in the UV. The UV spectra and optical photometry at the same orbital phase were fitted to synthetic spectra derived from the stella r atmosphere models of Hubeny (1988) to determine the temperature and log (g). When AM Her was faint, a single cool (T = 20,000 K) model fit the data, while at phases when AM Her was bright, a second component with T = 35,000 +/- 5,000 K covering less than or equal to 8% of the w hite dwarf surface significantly improved the fit. The value of log (g ) determined from the fits is 8.0 +/- 0.2. A significant excess is see n in the R-band data, probably due to emission from the secondary. The next day we obtained 16 spectra with the Russian 6 m telescope. We di scuss the possibility that the white dwarf cools with a timescale simi lar to that of dwarf novae, but moderate and variable emission-line in tensities suggest highly variable accretion at a moderate level. The o bserved Zeeman features lead to a magnetic field strength of similar t o 13 MG.