Photometric Variability Among the Brightest Asymptotic Giant Branch Stars Near the Center of M32

Abstract

Deep K' images with 0.1 arcsec angular resolution, obtained with ALTAIR+NIRI on Gemini North, are used to investigate photometric variablity among the brightest asymptotic giant branch (AGB) stars in the central regions of M32. Based on a comparison with brightnesses obtained from the K-band data discussed by Davidge et al. (2000, ApJ, 545, L89), it is concluded that (1) at least 60% of bright AGB stars near the center of M32 are photometrically variable, and (2) the amplitudes of the light variations are similar to those of long period variables in the Galactic bulge. We do not find evidence for a population of large amplitude variables, like those detected by IRAS in the Galactic bulge. The technique discussed here may prove useful for conducting an initial reconnaisance of photometric variability among AGB stars in spheroids in the Virgo cluster and beyond, where the required long exposure times may restrict observations to only a few epochs.

arXiv comment8 pages of text, 3 postscript figures. ApJ (letters) in press

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• The Brightest Stars in M32: Comparing Predictions from Spectra with the Resolved Stellar Content
• Seeing Red in M32: Constraints on the Stellar Content from Near- and Mid-Infrared Observations and Applications for Studies of More Distant Galaxies
• Ubiquitous Time Variability of Integrated Stellar Populations
• Infrared variable stars in the compact elliptical galaxy M32