CDROM/AJ/V109/P1308 H-alpha Emission Variations (Olson & Etzel 1995) ================================================================================ Rapid H-Alpha Emission Variations in Accretion Disks in Long-Period Algols Edward C. Olson & Paul B. Etzel <1995, AJ, 109, 1308> =1995AJ....109.1308O ================================================================================ Abstract: We demonstrate the continuous presence of large variations in double-peaked H-alpha emission in nine long-period Algol-type binaries, using recently obtained CCD spectra. Most fluctuations occur on a time scale <= an orbital period, and a steady state in H-alpha emission is never reached. In AD Her (P = 10 d), H-alpha emission dropped in strength more than a factor of five in one seven-day interval. Contemporary O I lambda 7774 observations showed no significant changes in oxygen absorption strength or radial velocity during this time. We tentatively suggest that H-alpha variations arise from an inner-disk instability, possibly triggered by small modulations in the mass-transfer rate. This behavior is reminiscent of some cataclysmic variables. Description: Equivalent widths (EW; A) of violet (V) and red (R) H-alpha emission lobes. Clearly-resolved un-eclipsed V and R lobes are listed; in a few cases, combined EWs are given. Data deep in primary eclipses are not listed, because both lobes are partially eclipsed by cool losers. Note that in a few cases, EWs are measured from 0.9 of continuum level, because this level yields a better estimate of total hydrogen emission. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table.dat 61 385 Equivalent widths and radial velocities -------------------------------------------------------------------------------- Byte-by-byte Description of file: table.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 6 A6 --- Name Variable star name 7 1X --- --- Blank 8 A1 --- Flag [*] If emission measured from 0.9 of true continuum 9-10 2X --- --- Blank 11-30 A20 --- UT UT date and time of observation 31-41 F11.5 d HJD Heliocentric Julian Date of observation 42-49 F8.5 --- Phase Phase 50-55 A6 0.1nm EW_V Equivalent width of violet emission lobe 56-61 A6 0.1nm EW_R Equivalent width of red emission lobe -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 04-May-1995