A Search for Variable Stars and Planetary Occultations in NGC 2301 II: Variability

Abstract

We performed R-band time series observations of the young, metal rich open cluster NGC 2301 for 12 nights in Feb. 2004. B images were also obtained and color magnitude diagrams, having limits of R=19.5 and B=21.5, were produced. Only asmall effort was made to determine cluster membership as our magnitude limits are far deeper than previously published values. Our photometric precision, for the brightest 5 magnitudes of sources, is 1-2 mmag. We determine that for the $\sim$4000 stars which have time-series data, 56% are variable and of these, approximately 13% are observed to exhibit periodic light curves ranging from tens of minutes to days. We present some examples of the light curves obtained and produce cuts in variability space based on parameters such as color and amplitude. The percentage of variability is approximately equal across all colors with the majority of variables having amplitudes of 0.15 magnitudes or less. In general, redder stars show larger variability amplitudes. We find a smooth decline in the number of periodic variables toward longer period. This decline is probably due to a transition from intrinsic to extrinsic variability and, in part, to our limited observing period of 12 nights. Essentially all the A and F main sequence stars in our sample are variable ($\sim$2 mmag and larger) and most present complex light curves containing multiple periods suggestive of their inclusion in the $\delta$Sct and $\gamma$Dor classes. A variable non-cluster member giant and two variable white dwarf candidates are discussed. Our equational description of variability is shown to be an excellent predictive tool for determining the cumulative fraction of variables that will be observed in a photometric survey. Our entire dataset is available electronically.

arXiv comment25 pages, 21 figures Accepted to PASP

References in corpus (5)

• The Orthogonal Transfer CCD
• Rotation periods for very low mass stars in the Pleiades
• A Search for Variable Stars and Planetary Occultations in NGC2301 I: Techniques
• WFPC2 Observations of the Ursa Minor Dwarf Spheroidal Galaxy
• Wind Circulation in Selected Rotating Magnetic Early-B Stars

Cited by in corpus (14)

• The NASA Exoplanet Archive: Data and Tools for Exoplanet Research
• K2 Discovers a Busy Bee: An Unusual Transiting Neptune Found in the Beehive Cluster
• Ensemble analysis of open cluster transit surveys: upper limits on the frequency of short-period planets consistent with the field
• KELT-10b: The First Transiting Exoplanet from the KELT-South Survey -- A Hot Sub-Jupiter Transiting a V = 10.7 Early G-Star
• Improved characterisation of intra-night optical variability of prominent AGN classes
• Ground-Based Submillimagnitude CCD Photometry of Bright Stars Using Snapshot Observations
• Multicolor Variability of Young Stars in the Lagoon Nebula: Driving Causes and Intrinsic Timescales
• On the photometric error calibration for the `differential light curves' of point-like Active Galactic Nuclei
• The Burrell-Optical-Kepler-Survey (BOKS) I: Survey Description and Initial Results
• Did a stellar fly-by shape the planetary system around Pr 0211 in the cluster M 44?
• Astrophysics in 2006
• The NStED Exoplanet Transit Survey Service
• High reddening patches in Gaia DR2. Possible artifacts or indication of star formation at the edge of the Galactic disk
• The LAEX and NASA portals for CoRoT public data