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A.P. Linnell (Mich.State)
Photometric evidence indicates that the massive gainer in the \beta~Lyrae system is hidden from the observer by a thick accretion disk (Linnell, Hubeny, & Harmanec, 1998, ApJ, 509, 379). It is believed that the gainer approximates a main sequence star of T\rm eff= 30000K. Spectroscopic analysis by Balachrandan et al. (1986, MNRAS, 219, 479) establishes a T\rm eff of 13,300K for the donor. System synthetic spectra, fitted via the BINSYN suite to spectrophotometric scan data and IUE spectra, establish a mean rim T\rm eff of 9000K.
Assuming conservative mass transfer, Harmanec & Scholz (1993, A&A, 279, 131) use the rate of period change to derive a mass transfer rate of 20{\times}10-6M\sun{\rm yr}-1. Connecting the rim T\rm eff to the accretion disk face T\rm eff with the Hubeny theory (Hubeny & Plavec 1991, AJ, 102, 1156) and using the standard accretion disk relations (Frank, King & Raine), the adopted mass transfer rate predicts a rim T\rm eff of 4500K. The BINSYN-derived 9000K rim T\rm eff would require a mass transfer rate 30 times larger than the adopted value. The observed rate of period change excludes such a large mass transfer rate.
The bolometric luminosity of the rim, from the BINSYN model, is 5.6{\times}1036{\rm erg~sec-1}. The bolometric luminosity of the gainer, on the adopted model, is 9.8{\times}1037{\rm erg~sec-1}. Thus, the luminosity of the rim is 6% of the luminosity of the gainer. On the BINSYN model, the accretion disk covers 26% of the sky, as seen by the gainer. Absorption of radiation from the gainer, and its reradiation by the accretion disk, could explain the derived T\rm eff of the rim. The conclusion is that the \beta~Lyrae accretion disk structure must be strongly affected by radiation from the hot gainer (unseen by the observer) at the center of the accretion disk.