We have attempted to establish observational evidence for the presence of distant companions that may have acquired and/or absorbed angular momentum during the evolution of multiple systems, thus facilitating or enabling the formation of contact binaries. In this preliminary investigation we use several techniques (some of them distance- independent) and mostly disregard the detection biases of individual techniques in an attempt to establish a lower limit to the frequency of triple systems. While the whole sample of 151 contact binary stars brighter than V_max_=10mag gives a firm lower limit of 42%{+/-}5%, the corresponding number for the much better observed northern-sky subsample is 59%{+/-}8%. These estimates indicate that most contact binary stars exist in multiple systems.
The properties of the early-type binary Cyg OB2 #5 have been debated for many years and spectroscopic and photometric investigations yielded conflicting results. We have attempted to constrain the physical properties of the binary by collecting new optical and X-ray observations. The optical light curves obtained with narrow-band continuum and line-bearing filters are analysed and compared. Optical spectra are used to map the location of the He II 4686 and H-alpha line-emission regions in velocity space. New XMM-Newton as well as archive X-ray spectra are analysed to search for variability and constrain the properties of the hot plasma in this system.
We have conducted a deep (15~<r~<23 ), 20 night survey for transiting planets in the intermediate-age (~550Myr) open cluster M37 (NGC 2099) using the Megacam wide-field mosaic CCD camera on the 6.5m MMT. In this paper we present a catalog and light curves for 1445 variable stars; 1430 (99%) of these are new discoveries. We have discovered 20 new eclipsing binaries and 31 new short-period (P<1day) pulsating stars. The bulk of the variables are most likely rapidly rotating young low-mass stars, including a substantial number (>~500) that are members of the cluster. We identify and analyze five particularly interesting individual variables, including a previously identified variable that we suggest is probably a hybrid gamma Doradus/delta Scuti pulsator, two possible quiescent cataclysmic variables, a detached eclipsing binary (DEB) with at least one gamma Doradus pulsating component (only the second such variable found in an eclipsing binary), and a low-mass (M_P_~M_S~0.6M_{sun}_ DEB that is a possible cluster member. A preliminary determination of the physical parameters for the DEB+gamma Doradus system yields M_P_=1.58+/-0.04M_{sun}_, M_S_=1.58+/-0.04M_{sun}_, R_P_=1.39+/-0.07R_{sun}_, and R_S_=1.38+/-0.07R_{sun}_.
Differential UBV photoelectric photometry for the eclipsing binary MY Cyg is presented. The Wilson-Devinney program is used to simultaneously solve the three light curves together with previously published radial velocities. A comparison is made with the previous solution found with the Russell-Merrill method. We examine the long-term apsidal motion of this well-detached, slightly eccentric system. We determine absolute dimensions, discuss metallicity/Am-star issues, and estimate the evolutionary status of the stars.
The DIRECT Project aims to obtain direct distances to two Local Group galaxies, M31 and M33, which occupy a crucial position near the base of the cosmological distance ladder. The first step is to search for detached eclipsing binaries (DEBs) and Cepheids using 1m class telescopes to select good candidates, which will be followed up spectroscopically on 6.510m class telescopes. In this ninth paper, we present a catalog of variable stars discovered with image subtraction in field M31Y (RA=10.97{deg}, DE=41.69{deg}; J2000.0). The data were obtained with the Fred Lawrence Whipple Observatory 1.2m telescope on 25 nights, over a period of 6 months. In our search covering 22x22, we discovered 41 eclipsing binaries, 126 Cepheids, and 97 other periodic or nonperiodic variables, including a luminous blue variable candidate, a nova, and a Galactic cataclysmic variable. The catalog of variables, as well as their photometry and finding charts, is available electronically via anonymous ftp and the World Wide Web, at http://cfa-www.harvard.edu/~kstanek/DIRECT . The complete set of the CCD frames is available upon request.
The following Table 1 lists 550 timings of minima of eclipsing binaries secured both by photoelectrical as well as by visual means by BBSAG observers, primarily obtained between July 2003 and June 2004. The given O-C values generally refer to the linear elements of the GCVS (Kholopov et al., 1985), except for the cases stated in the remarks. All times given are heliocentric UTC.
The following Table 1 lists 508 timings of minima of eclipsing binaries secured both by photoelectric as well as by visual means by BBSAG observers, primarily obtained between September 2002 and June 2003. The given O-C values generally refer to the linear elements of the GC VS (Kholopov et al., 1985, see Cat. <II/214>), except for the cases stated in the remarks. All times given are heliocentric UTC.
We have calculated relative element abundances for a sample of 43 symbiotic stars. Helium abundances and the relative elemental abundances N/O, Ne/O, Ar/O were derived from new spectra collected in the optical range through low dispersion spectroscopy. The He ionic abundances were derived taking into account self-absorption effects in Balmer lines. We found that the symbiotic stars in the galactic bulge have heavy element abundances showing the same wide distribution as other bulge objects. In the galactic disk, the symbiotic stars follow the abundance gradient as derived from different kinds of objects.
New differential UBV photoelectric photometry for the eclipsing binary AY Cam is presented. The Wilson-Devinney program is used to simultaneously solve the three light curves together with previously published radial velocities.
We have classified 409 objects in the Northern Sky Variability Survey (NSVS) as new beta Lyrae or Algol-type eclipsing binaries. These candidates have outside of eclipse magnitudes of ~10-13. Through automated Fourier analysis routines and some manual inspection, we list the period, eclipse depths, coordinates, an estimate of the time of primary eclipse, and the 2MASS colors for these candidates. This list of new beta Lyrae type candidates greatly increases the number of known systems of this type. We have also identified 37 candidate low-mass, main-sequence pairs (M_1,2_<1M_{sun}_,T<5500K) in the NSVS database. If confirmed, these systems will greatly increase the number of such low-mass systems known as well as help constrain atmospheric models for these types of stars.
