Variable stars in NGC 2169 from CCD photometry

G.Kopacki1, M.Jerzykiewicz1 J.Molenda-Zakowicz1 Z.Kolaczkowski1
1Wroclaw University Observatory, Kopernika 11, 51-622 Wroclaw, Poland

 

Continuing our search for B-type pulsators in young open clusters, we obtained time series photometry of NGC 2169. We used the same equipment as always, that is, a 6'x4' field-of-view CCD camera, mounted in the Cassegrain focus of a 60-cm reflecting telescope. The observations were carried out on 17 nights from January to April 2002.
The GCVS lists three variable stars in the field we observed, namely, two Cep variables, V916 Ori and V917 Ori, and an 2 CVn variable, V1356 Ori. We find V916 Ori to be constant in light. We confirm the variability of V917 Ori, but not the period given in GCVS. For this star we detect emission in H. Our tentative interpretation of somewhat irregular light-variation of the star is this: a Cep pulsation with a period equal to 0.267 d, distorted by Be-type variations. For V1356 Ori we definitely establish the period of 1.56 d, thus settling the uncertainty persisting in the literature since the star was discovered to be variable.
In addition, we find two other stars to be variable in light. Both show irregular variations. For one of them, Hoag No. 25, we detect emission in H.

 
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