DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. VIII. Additional Variables in the Field M33B 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 eighth paper we present a catalog of variable stars discovered in the data from the followup observations of DEB system D33J013337.0+303032.8 in field M33B [(RA,Dec)= (23.48, 30.57), 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 895 variable stars: 96 eclipsing binaries, 349 Cepheids, and 450 other periodic, possible long period or non-periodic variables. Of these variables 612 are newly discovered. Their light curves were extracted using the ISIS image subtraction package. For 77% of the variables we present light curves in standard V and B magnitudes, with the remaining 23% expressed in units of differential flux. We have discovered a population of first overtone Cepheid candidates and for six of them we present strong arguments in favor of this interpretation. The catalog of variables, as well as their photometry (about 9.2*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.

21 pages of text, 27 pages of tables, 14 figures; version with full resolution figures available through ftp at ftp://cfa-ftp.harvard.edu/pub/kstanek/DIRECT/papers/M33B2m

References in corpus (3)

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

Cited by in corpus (17)

• A Survey of Local Group Galaxies Currently Forming Stars: III. A Search for Luminous Blue Variables and Other H-alpha Emission-Lined Stars
• The First DIRECT Distance Determination to a Detached Eclipsing Binary in M33
• The Distances to Open Clusters from Main-Sequence Fitting. IV. Galactic Cepheids, the LMC, and the Local Distance Scale
• Deep CFHT Photometric Survey of the Entire M33 Galaxy I: Catalogue of 36000 Variable Point Sources
• The eclipsing massive X-ray binary M33 X-7: New X-ray observations and optical identification
• A comprehensive study of Cepheid variables in the Andromeda galaxy. Period distribution, blending and distance determination
• The UK Infrared Telescope M33 monitoring project. I. Variable red giant stars in the central square kiloparsec
• The UK Infrared Telescope M33 monitoring project. IV. Variable red giant stars across the galactic disc
• Chandra Observations of the Nucleus of M33
• A new Luminous Variable in M33
• Long-Term V-Band Monitoring of the Bright Stars of M33 at the Wise Observatory
• Re-analysis of VLT Data for M83 with Image Subtraction -- Nine-fold Increase in Number of Cepheids
• Photometric Analysis of the Optical Counterpart of the Black Hole HMXB M33 X-7
• Var C: Long-term photometric and spectral variability of an LBV in M33
• Eclipsing Binaries: Tools for Calibrating the Extragalactic Distance Scale
• Eclipsing Binaries in the Young LMC Cluster NGC 1850
• A large-scale survey for variable stars in M33