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MOST satellite photometry of stars in the M67 field: eclipsing binaries, blue stragglers and δ Scuti variables
We present two series of MOST (Microvariability and Oscillations ofSTars) space-based photometry, covering nearly continuously 10 d in 2004and 30 d in 2007, of selected variable stars in the upper main sequenceof the old open cluster M67. New high-precision light curves wereobtained for the blue straggler binary/triple systems AH Cnc, ES Cnc andEV Cnc. The precision and phase coverage of ES Cnc and EV Cnc is by farsuperior to any previous observations. The light curve of ES Cnc ismodelled in detail, assuming two dark photospheric spots and Rochegeometry. An analysis of the light curve of AH Cnc indicates a low massratio (q ~ 0.13) and a high inclination angle for this system. Two newlong-period eclipsing binaries, GSC 814-323 and HD 75638 (non-members ofM67) were discovered. We also present ground-based DDO spectroscopy ofES Cnc and of the newly found eclipsing binaries. Especially interestingis HD 75638, a member of a visual binary, which must itself be a tripleor a higher multiplicity system. New light curves of two δ Scutipulsators, EX Cnc and EW Cnc, have been analysed leading to detection of26 and eight pulsation frequencies of high temporal stability.Based on photometric data from MOST, a Canadian Space Agency mission(jointly operated by Dynacon Inc., the University of Toronto Institutefor Aerospace Studies and the University of British Columbia, with theassistance of the University of Vienna), and on spectroscopic data fromthe David Dunlap Observatory, University of Toronto.E-mail: pribulla@ta3.sk (TP); rucinski@astro.utoronto.ca (SR)
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
| A high relative precision colour-magnitude diagram of M67
We have calibrated and combined an extensive set of BVI observations ofM67 to produce a colour-magnitude diagram of stars measured with highrelative precision. We have selected stars that are most likely to besingle-star members of the cluster using proper motion, radial velocity,and variability information from the literature, and an examination ofthe most probable colour-magnitude diagram locations of unresolvedstellar blends. We have made detailed comparisons of our photometry ofthe selected stars with theoretical models, and discuss the most notablediscrepancies. Observations of M67 turn-off stars are a severe test ofalgorithms attempting to describe convective cores in the limit of smallextent, and we find strong evidence of a `hook' just fainter than theturn-off gap. The stars in M67 support assertions that the degree ofconvective core overshooting decreases to zero for stars with masses inthe range 1.0 < (M/Msolar) <= 1.5, but that the degreeof overshoot is smaller than currently used in published isochrones. Wealso verify that all current theoretical models for the lower mainsequence (with the exception of Baraffe et al. 1998) are too blue forMV>~ 6, even when the sequences are shifted to match M67near the MV of the Sun, probably due to a combination ofproblems with colour-Teff transformations and realisticsurface boundary conditions for models. Finally, we identify a subset ofcluster members with unusual photometry (candidate red giant binaries,blue straggler stars, and triple systems) deserving of further study.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| Study of proper motions in the region of the open cluster M67 and membership of stars
Relative proper motions and membership probabilities of 1046 stars inthe open cluster M67 area are determined from PDS measurements of nineplate pairs taken with the double astrograph at the Zo-Se station ofShanghai Observatory, which has an aperture of 40 cm, a focal length of6.9 m and a scale of 30 arcsec/mm. The number of stars with membershipprobabilities higher than 0.8 and at a distance less than 45 arcmin fromthe field center is 282. The average standard errors of proper motionsvary from +/- 0.0004 arcsec/yr for bright stars in the inner part of thefield to some +/- 0.00l5 arcsec/yr for faint stars in the outer part ofthe cluster. It is shown by a detailed discussion that the propermotions and membership probabilities of the stars determined in thispaper are in quite satisfactory agreement with those obtained by Sanders(1977) or Girard et al. (1989).
| Orbits of 22 spectroscopic binaries in the open cluster M67
Orbits are presented for 22 spectroscopic binaries in the field of theold open cluster M67. The binary frequency and the distribution oforbital eccentricity are discussed. The detected binary frequency is inthe range 9-15 percent, somewhat lower than that found among solar-massstars in the field. A transition from circular to eccentric orbits amongmain-sequence binaries at a period between 10.3 and 11.0 days is found,longer than similar transition periods found in younger binarypopulations. An increase of transition period with cluster age isconsistent with the interpretation that the shorter-period orbits havebeen tidally circularized. A circular orbit at a period of 43 days isfound for the cluster giant S1040, consistent with the theoreticalexpectation that more effective tidal circularization occurs withincreasing stellar radius and deepening convective zones.
| Precise radial velocities of late-type stars in the open clusters M11 and M67
Precise radial-velocity measurements of 39 stars and 170 stars areobtained in the fields of the open clusters M11 and M67, respectively;by the vast majority of the stars observed are cluster members. Allstars observed are of spectral type later than F5; the data set includesessentially all of the giants in both clusters and all main-sequencestars in M67 brighter than V = 12.8, plus an assortment of nonmembersand fainter members. Single-measurement precisions range from 0.3 to 0.8km/s. Almost all stars have been observed repeatedly, with clustermembers typically having 5-25 velocity measurements. Observations wereobtained over a span of 16 yr, although not all stars were observedthroughout that period. The time distribution of the observations is acombination of low-frequency coverage (less than 1/yr) over the first 11yr, and higher-frequency coverage (greater than 2/yr) over the final 5yr.
| Investigation of proper motions in the field of the cluster M 67 II,
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