Time-resolved Spectroscopy of AL Comae

Abstract

We present time-resolved spectroscopy for AL Corn, one of the faintest known tremendous outburst amplitude dwarf novae (TOADs). Using newly produced models for a white dwarf and red secondary, we show that the star AL Com has orbitally phase-resolved broad absorption features of yet unidentified origin and an optically thin accretion disk. Radial velocities measured from the few spectra available show essentially no motion of the white dwarf, leading to a strict upper limit on the secondary mass of ≤0.18 M⊙, with a likely value of 0.04-0.09 M⊙. This agrees well with recent theoretical arguments placing the TOADs as post-period minimum cataclysmic variables. © 1998. The American Astronomical Society. All rights reserved.