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Up: Photoelectric photometry of

1. Introduction

Although the pulsation mechanism in intrinsic variable stars is well known, doubts still remain with respect to why some stars pulsate while others with the same age, chemical composition, and physical characteristics do not. In view of this, and as a part of a larger research project, the open cluster NGC 2422 was observed through Strömgren photometry to first identify member stars as well as to determine physical characteristics that could differentiate the causes that provoke pulsation in the stars. In the past, several papers reporting photoelectric photometry have been devoted to NGC 2422: Hoag et al. (1961) presents UBV photometric values for 20 stars and photographic photometry for 95 stars; Smyth & Nandy (1962) (hereinafter S & N) report photographic photometric values of 81 stars in three colours and a distance modulus of 8.4 mag considering both their data and that of Hoag et al. (1961). A thorough compilation of open clusters, including NGC 2422, was made by Mermilliod (1976). More recently, and with the advent of Strömgren photometry, Shobbrook (1984) reports measurements for 28 B and A stars and derives a distance modulus of 8.0 and a mean reddening value E(b- y) of 0.06. The most recent photometric study of NGC 2422 found is that of Nissen (1988) who reports Strömgren photometric values for several clusters including NGC 2422. With 19 stars of F spectral type, he derives a mean distance modulus of 8.14 mag and a mean reddening E(b-y) of 0.053.

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