A photometric investigation of the fields of two short-period Cepheids in Cygnus

Abstract

Photoelectric, photographic and CCD photometry, as well as spectroscopic observations and proper motion data for stars in the fields of the short-period galactic Cepheids V1726 Cygni and SU Cygni are presented and analyzed. The existence of a sparsely populated cluster associated with V1726 Cyg has been confirmed, and a new, loose stellar group has been found in the vicinity of SU Cyg.

The newly obtained distance modulus for C2128+488 (Anon. Platais), the cluster associated with V1726 Cyg, is V[subscript 0] - M[subscript V] = 10.98 [plus or minus] 0.02, corresponding to a distance of 1568 [plus or minus] 13 pc. The spatial coincidence and the close match of the radial velocity, proper motion and age of V1726 Cyg with those of the cluster indicate a high probability of cluster membership for the Cepheid. The space reddening of V1726 Cyg, found from two neighbouring stars, is E[subscript B-V] = 0.43 [plus or minus] 0.02 and its luminosity as a cluster member is <M[subscript V]> = -3.42 [plus or minus] 0.07.

The newly found group of stars in the vicinity of SU Cyg has a distance modulus of V[subscript 0] - M[subscript V] = 10.98 [plus or minus] 0.02 (d = 1040 pc). It contains mostly early A to late F-type stars, with a few early B-type stars whose membership is more uncertain.

A reddening of E [subscript B-V] = 0.16 has been determined for SU Cyg from a nearby (20") star having an accurate MK spectral type.

The probable discovery of a new planetary nebula, located about 3' south of SU Cyg, and a possible new cluster 17' west of SU Cyg, are also reported. (Abstract shortened by UMI.)