Photometric study of the variable star population in the globular cluster NGC 6397

Abstract

We present the results of a photometric survey for variable stars in the central region of the nearby globular cluster NGC 6397.Time series photometry was obtained for 30 variable objects. The sample includes 12 new objects, of which 6 show periodic lightcurves and 2 are eclipsing binaries of unknown period. Six variables possess certain and three possess likely X-ray counterparts detected with the Chandra observatory. Among them four are cataclysmic variables and one is a foreground eclipsing binary. The cataclysmic variable CV2 exhibited a likely dwarf nova type outburst in May 2003. The cataclysmic variable CV3 was observed at 18.5<V<20.0 during 5 observing runs, but went into a low state in May 2003 when it reached V>22. We have found that thelight curve of the optical companion to the millisecond pulsar PSRJ1740-5340 exhibits noticeable changes of its amplitude on a time scale of a few months. A shallow eclipse with Delta_V=0.03 mag was detected in one of the cluster turnoff stars suggesting the presence of a large planet or brown dwarf in orbit.

8 pages, 9 figures, submitted to MNRAS on 21 April 2005

References in corpus (6)

• HST color-magnitude diagrams of 74 galactic globular clusters in the HST F439W and F555W bands
• Testing blend scenarios for extrasolar transiting planet candidates. I. -- OGLE-TR-33: a false positive
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• Accurate mass ratio and heating effects in the dual-line millisecond binary pulsar in NGC 6397
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• Time Series Photometry of Variable Stars in the Globular Cluster NGC 6397

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• On the Origin of Sub-subgiant Stars. I. Demographics
• Identification of Faint Chandra X-ray Sources in the Core-Collapsed Globular Cluster NGC 6397: Evidence for a Bimodal Cataclysmic Variable Population
• New Periodic 6.7 GHz Class II Methanol Maser Associated with G358.460-0.391
• Contribution of primordial binary evolution to the two blue-straggler sequences in globular cluster M30
• Cluster AgeS Experiment (CASE): Deficiency of observed dwarf novae in globular clusters
• A complete census of $H\alpha$ emitters in NGC 6397
• The Clusters AgeS Experiment (CASE). III. Analysis of the Eccentric Eclipsing Binary V32 in the Globular Cluster NGC 6397
• A time-series VI study of the variable stars of the globular cluster NGC 6397
• Compact X-ray Binaries in and out of Core Collapsed Globulars
• A 2 day orbital period for a redback millisecond pulsar candidate in the globular cluster NGC 6397
• A search for dormant binaries with degenerate components in omega Centauri and NGC 6397
• Low mass variable stars in the globular cluster NGC 6397