Diagnostics for accretion disks around UX ori stars based on Balmer, Paschen, and Brackett lines

We have modeled the H-alpha, H-beta, and H-gamma (Balmer series), P-14 (Paschen series), and Br-gamma(Brackett series) hydrogen lines formed in the inner regions of the accretion disk around the Herbig Ae star UX Ori. Our calculations are based on spectra obtained with the Nordic Optical Telescope (NOT) and the IRTF. We computed a grid of non-LTE models for a radiating area in the accretion disk and determined the basic parameters of the lines using the method of Sobolev. Analyzing the theoretical and observed line profiles, equivalent widths, and luminosities, we have estimated the accretion rate and electron-temperature distribution in the inner parts of the accretion disk. The accretion rate of UX Ori is about M-a = (3-10) x 10(-9) M-circle dot/yr, and the temperature distribution is consistent with the power law T(r) = T(r(*))(r/r(*))(-1/n), where the electron temperature near the stellar surface T(r(*)) is 15000-20000 K and the power-law index n approximate to 2-3 is about two to three. The resulting value for M-a, eliminates problems connected with the application of magnetospheric accretion models to Herbig Ae/Be stars. Another important conclusion is that, at the estimated accretion rate, the energy release is substantially (about two orders of magnitude) lower than the stellar luminosity. Therefore, the optical radiation of UX Ori accretion disks cannot appreciably contribute to the observed variability of these stars, which must be determined mainly by variability in the circumstellar extinction. (C) 2001 MAIK Nauka/Interperiodica.