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A study of the stellar population of the M31 spiral arm around OB associationA24 was carried out based on the photometric data obtained from deep V and JHKimaging. The luminosity function was obtained for -7 <~ Mbol <~ -3.5 byapplying the extinction correction corresponding to Av=1 and the bolometriccorrection BC(K) as an empirical function of (J-K)o. In comparing the observedcolor-luminosity diagrams with semitheoretical isochrones modified for thedust-shell effects, we found the young population of t <~ 30 Myr withsupergiants of Mbol <~ -5, the bulk of the intermediate-age population of t ~0.2 - 2.5 Gyr with bright asymptotic giant branch (AGB) stars of -5 <~ Mbol <~-4, and old populations of t ~> 3 Gyr with AGB and red giant branch (RGB) starsof Mbol ~> -4. The average star formation rate was estimated to be ~1.8x10^4M_o/Myr and ~0.7x10^4 M_o/Myr per deprojected disk area of 1 kpc^2 from thenumber density of B0 V stars around Mv=-4.0 (age ~10 Myr) and the numberdensity of bright AGB stars around Mbol = -4.3 (age ~1 Gyr), respectively. Astudy of the local variation in the V and the J and H luminosity functionsrevealed a kind of anticorrelation between the population of the youngcomponent and that of the intermediate-age component when subdomains of ~100 pcscales were concerned. This finding suggests that the disk domain around theA24 area experienced a series of star formation episodes alternatively amongdifferent subdomains with a timescale of a few spiral passage periods. Briefdiscussions are given about the interstellar extinction and about the lifetimesof bright AGB stars and the highly red objects (HROs) in the same area.Comment: 27 pages, 11 figures, accepted: ApJ, July 1, 199

The Stellar Population of the M31 Spiral Arm around OB Association A24