DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. VII. Additional Variables in the Field M33A Discovered with Image Subtraction

Abstract

DIRECT is a project to obtain directly the distances to two Local Group galaxies, M31 and M33, which occupy a crucial position near the bottom of the cosmological distance ladder. As the first step of the DIRECT project we have searched for detached eclipsing binaries (DEBs) and new Cepheids in the M31 and M33 galaxies with 1m-class telescopes. In this seventh paper we present a catalog of variable stars discovered in the data from the followup observations of DEB system D33J013346.2+304439.9 in field M33A [(RA,Dec)= (23.55, 30.72), J2000.0], collected with the Kitt Peak National Observatory 2.1m telescope. In our search covering an area of 108 sq. arcmin. we have found 434 variable stars: 63 eclipsing binaries, 305 Cepheids, and 66 other periodic, possible long period or non-periodic variables. Of these variables 280 are newly discovered, mainly short-period and/or faint Cepheids. Their light curves were extracted using the ISIS image subtraction package. For 85% of the variables we present light curves in standard V and B magnitudes, with the remaining 15% expressed in units of differential flux. We have discovered a population of first overtone Cepheid candidates and for eight of them we present strong arguments in favor of this interpretation. We also report on the detection of a non-linearity in the KPNO T2KA and T1KA cameras. The catalog of variables, as well as their photometry (about 7.8*10^4 BV measurements) and finding charts, is available electronically via anonymous ftp and the World Wide Web. The complete set of the CCD frames is available upon request.

40 pages LaTeX, 16 Postscript figures, to appear in the April 2001 issue of the Astronomical Journal

References in corpus (2)

• DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. VI. Variables in the Central Part of M33
• The DIRECT Project: Catalogs of Stellar Objects in Nearby Galaxies. I. The Central Part of M33

Cited by in corpus (24)

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• The RR Lyrae Distance to the Draco Dwarf Spheroidal Galaxy
• The Distances to Open Clusters from Main-Sequence Fitting. IV. Galactic Cepheids, the LMC, and the Local Distance Scale
• XMM-Newton survey of the Local Group galaxy M 33
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• Deep CFHT Photometric Survey of the Entire M33 Galaxy I: Catalogue of 36000 Variable Point Sources
• DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. IX. Variables in the Field M31Y Discovered with Image Subtraction
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• The UK Infrared Telescope M33 monitoring project. I. Variable red giant stars in the central square kiloparsec
• Time-Series Photometry of Globular Clusters: M62 (NGC 6266), the Most RR Lyrae-Rich Globular Cluster in the Galaxy?
• The UK Infrared Telescope M33 monitoring project. IV. Variable red giant stars across the galactic disc
• DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. VIII. Additional Variables in the Field M33B Discovered with Image Subtraction
• Long-term variability survey of the old open cluster NGC 6791
• Long-Term V-Band Monitoring of the Bright Stars of M33 at the Wise Observatory
• A 2.15 Hour Orbital Period for the Low Mass X-Ray Binary XB 1832-330 in the Globular Cluster NGC 6652
• Variable Stars in Large Magellanic Cloud Globular Clusters I: NGC 1466
• Variable stars in nearby galaxies. VI. Frequency-period distribution of Cepheids in IC 1613 and other galaxies of the Local Group
• Re-analysis of VLT Data for M83 with Image Subtraction -- Nine-fold Increase in Number of Cepheids
• The Masses Of The B-Stars In The High Galactic Latitude Eclipsing Binary IT Lib
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• Eclipsing Binaries in the Young LMC Cluster NGC 1850