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1

The All Sky Automated Survey. The Catalog of Variable Stars in the Kepler Field of View

Pigulski A., Pojmański G., Pilecki B., Szczygieł D. M.

Acta Astronomica

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2009

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Vol. 59, No. 1

33--46

EN

We present the catalog of 947 variable stars located in the field of view of the Kepler satellite. The catalog is a result of the analysis of VI photometry obtained during the first 17-month observations in the ASAS3-North station. The variable stars we present are divided into eleven groups according to the presented variability; the groups are briefly discussed. The catalog is intended to be a source of information for target selection process and follow-up programs.

2

Photometric Study of Variable Stars in the Open Cluster NGC 6866

Molenda-Żakowicz J., Kopacki G., Stęślicki M., Narwid A.

Acta Astronomica

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2009

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Vol. 59, No. 2

193--211

EN

We report the discovery of 19 variable stars and two blue stragglers in the field of the open cluster NGC 6866. Three of the variable stars we classify as δ Sct, two as γ Dor, four as W UMa, two as ellipsoidal variables, and one as an eclipsing binary. Seven stars show irregular variability. Two of the pulsators, δ Sct star NGC 6866-29 and γ Dor star NGC 6866-21, are multiperiodic. From an analysis of proper motions, we conclude that the δ Sct stars, one of the γ Dor stars and both blue stragglers are very probable members of the cluster. The position on the color-magnitude diagram of seven other variables suggests that they also belong to the cluster. The eclipsing binary, which we discover to be a new high velocity star, and the seven irregular variables are non-members. We discuss in detail the age and metallicity of open clusters that host γ Dor stars and we show that none of these parameters is correlated with the number of γ Dor stars in cluster.

3

Finding the Brightest Galactic Bulge Microlensing Events with a Small Aperture Telescope and Image Subtraction

Nataf D. M., Stanek K. Z., Bakos G. A.

Acta Astronomica

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2009

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Vol. 59, No. 3

255--272

EN

Following the suggestion of Gould and Depoy (1998) we investigate the feasibility of studying the brightest microlensing events towards the Galactic bulge using a small aperture (≈10 cm) telescope. We used one of the HAT telescopes to obtain 151 exposures spanning 88 nights in 2005 of an 8°4×8°4 FOV centered on (l,b)=(2.85, -5.00). We reduced the data using image subtraction software. We find that such a search method can effectively contribute to monitoring bright microlensing events, as was advocated. Comparing this search method to the existing ones we find a dedicated bulge photometric survey of this nature would fulfill a significant niche at excellent performance and rather low cost. We obtain matches to 7 microlensing events listed in the 2005 OGLE archives. We find several other light curves whose fits closely resemble microlensing events. Unsurprisingly, many periodic variable stars and miscellaneous variable stars are also detected in our data, and we estimate approximately 50% of these are new discoveries. We conclude by briefly proposing Small Aperture Microlensing Survey, which would monitor the Galactic bulge around the clock to provide dense coverage of the highest magnification microlensing events.

4

Planets in Stellar Clusters Extensive Search. V. Search for Planets and Identification of 18 new Variable Stars in the Old Open Cluster NGC 188

Mochejska B. J., Stanek K. Z., Sasselov D. D., Szentgyorgyi A. H., Cooper R. L., Hickox R. C., Hradecky V., Marrone D., P., Winn J. N., Schwarzenberg-Czerny A.

Acta Astronomica

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2008

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Vol. 58, No. 3

263--278

EN

We have undertaken a long-term project, Planets in Stellar Clusters Extensive Search (PISCES), to search for transiting planets in open clusters. In this paper we present the results for NGC 188, an old, rather populous cluster. We have monitored the cluster for more than 87 hours, spread over 45 nights. We have not detected any good transiting planet candidates. We have discovered 18 new variable stars in the cluster, bringing the total number of identified variables to 28, and present for them high precision light curves, spanning 15 months.

5

New Variable Stars on Digitized Moscow Collection Plates. Field 66 Ophiuchi (Northern Half)

Kolesnikova D. M., Sat L. A., Sokolovsky K. V., Antipin S. V., Samus N. N.

Acta Astronomica

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2008

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Vol. 58, No. 3

279--292

EN

We initiated digitization of the Moscow collection of astronomical plates using flatbed scanners. Techniques of photographic photometry of the digital images were applied, enabling an effective search for new variable stars. Our search for new variables among 140 000 stars in the 10°×5° northern half of the field centered at 66 Oph, photographed with the Sternberg Institute's 40-cm astrograph in 1976-1995, gave 274 new discoveries, among them: 2 probable Population II Cepheids, 81 eclipsing variables, 5 high-amplitude δ Sct stars (HADSs), 82 RR Lyr stars, 62 red irregular variables and 41 red semiregular stars, 1 slow irregular variable not red in color. Ephemerides were determined for periodic variable stars. We detected about 30 variability suspects for follow-up CCD observations, confirmed 11 stars from the New Catalog of Suspected Variable Stars, and derived new ephemerides for 2 stars already contained in the General Catalog of Variable Stars.

6

Variable Star Census in CoRoT "Eyes"

Benkö J. M., Csubry Z.

Acta Astronomica

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2007

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Vol. 57, No. 1

73--85

EN

A complete catalog of variable stars in the possible observing areas ("eyes") of the CoRoT satellite is presented. All known data sources were cross-correlated and compiled confirming the variability of 81 stars formerly known as suspected variables. By means of the TiFrAn program package a comprehensive variability search was carried out on the NSVS (ROTSE-I) database for the first time in these regions. This search has demonstrated the effectiveness of TiFrAn as a tool for finding and analyzing variable stars in big databases. Our catalog contains 4925 variable stars of which 1396 stars are new discoveries. Also appended is a list of 198 suspected variable stars.

7

A Study of Stellar Photometric Variability Within the Central 4 pc of the Galactic Center with Infrared Image Subtraction

Peeples M. S., Stanek K. Z., DePoy D. L.

Acta Astronomica

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2007

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Vol. 57, No. 2

173--199

EN

We present a catalog of 110 variable stars within ≈1' of Sgr A* based on image subtraction of near-infrared (H and K) photometry. Our images were obtained over 133 nights from 2000 to 2002 in H-band and over 134 nights from 2001 to 2002 in K-band; the typical FWHM is 1".4. We match the catalog to other near-infrared, X-ray, and radio (i.e., maser) data, and we discuss some of the more interesting objects. The catalog includes 14 sources with measurable periods, several known long-period variables and three new LPV candidates. We associate IRS 10* with OH, SiO, and H2O masers and a bright X-ray point source; this analysis suggests IRS 10* is an AGB star with an accreting companion. Among the ≈90 newly discovered sources are a probable cataclysmic variable, a potential edge-on contact 84 day period eclipsing binary, and a possible 41 day period pulsating variable.