Spectra and Line Profiles of FU Orionis Objects: Comparisons between Boundary Layer Models and Observations

We present solutions for the accretion disks and boundary layers inpre-main-sequence stars undergoing FU Orionis outbursts. These solutions differfrom earlier disk solutions in that they include a self-consistent treatment ofthe boundary layer region. In a previous paper (Popham 1996), we showed thatthese stars should stop accreting angular momentum once they spin up to modestrotation rates. Here we show that for reasonable values of $\alpha$, these lowangular momentum accretion rate solutions fit the spectra and line profilesobserved in FU Orionis objects better than solutions with high rates of angularmomentum accretion. We find solutions which fit the observations of FU Orionisand V1057 Cygni. These solutions have mass accretion rates of 2 and $1 \times10^{-4} \msyr$, stellar masses of 0.7 and $0.5 \msun$, and stellar radii of5.75 and $5.03 \rsun$, respectively. They also have modest stellar rotationrates $8-9 \xss$, comparable to the observed rotation rates of T Tauri stars,and angular momentum accretion rates of zero. This supports our earliersuggestion that FU Orionis outbursts may regulate the rotation rates of T Tauristars.Comment: 29 pages, LaTeX, uses aaspp4.sty, with 7 Postscript figures, tarred, gzipped, uuencoded. To appear in the Astrophysical Journa