Two Confirmed Cataclysmic Variables in the Old Stellar Cluster NGC 6791

Abstract

Based on new CCD photometry and spectroscopy we confirm the presence of two cataclysmic variables (CVs) in the very old open cluster NGC 6791. One of these variables, known as B8, was observed by Rucinski, Kaluzny & Hilditch (1996) to undergo a large magnitude outburst in 1995. The spectrum of this star outside the outburst, obtained by us with MMT, shows clearly the emission lines characteristic for dwarf novae. We observed the second star, known as B7, to undergo large ($\sim 3mag$) drop in its brightness over $\sim 10days$. The spectrum of B7 obtained in the high state resembles spectra of nova-like CVs. This star a likely member of UX~UMa subtype of CVs. Variables B7 and B8 represent only the second and the third cataclysmic variables known in open clusters. Variable B7 has observational characteristics which would make it difficult to identify as a CV with some of the methods being currently used in surveys for CVs in globular clusters.

submitted to the ApJ Letters, 12 pages, 5 figures

Cited by in corpus (17)

• DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. I. Variables in the Field M31B
• An Extensive Census of HST Counterparts to Chandra X-ray Sources in the Globular Cluster 47 Tucanae. II. Time Series and Analysis
• Planets in Stellar Clusters Extensive Search. I. Discovery of 47 Low-amplitude Variables in the Metal-rich Cluster NGC 6791 with Millimagnitude Image Subtraction Photometry
• The Hot Stars of Old Open Clusters: M67, NGC 188 and NGC6791
• Cataclysmic Variables and a Candidate Helium White Dwarf in the Globular Cluster NGC 6397
• Planets in Stellar Clusters Extensive Search. II. Discovery of 57 Variables in the Cluster NGC 2158 with Millimagnitude Image Subtraction Photometry
• Planets in Stellar Clusters Extensive Search. IV. A detection of a possible transiting planet candidate in the open cluster NGC 2158
• Variable stars in the open cluster NGC 6791 and its surrounding field
• Analysis of Three SU UMa-Type Dwarf Novae in the Kepler Field
• A Chandra X-ray study of the interacting binaries in the old open cluster NGC6791
• Long-term variability survey of the old open cluster NGC 6791
• The X-ray Emissivity of Low-Density Stellar Populations
• Cluster AgeS Experiment (CASE): Detection of a dwarf nova in the globular cluster M55
• Time-resolved Spectroscopy of the Polar EU Cancri in the Open Cluster Messier 67
• The Kepler and Hale observations of V523 Lyr
• Flickering around the outburst cycle in Kepler dwarf novae
• Pulsating subdwarf B stars in the oldest open cluster NGC6791