Our work on HD 27130 (in the Hyades) and DS And and H235 (in NGC 752) (Schiller & Milone 1987, 1988; Milone et al. 1995) illustrates the value of studying eclipsing, double-lined spectroscopic binaries in stellar clusters and associations.
The age of DS And and H235 have been found to be 2.0+/- 0.2 x 10^9 y, with E(B-V) = 0.03 and [Fe/H] = 0.0. Heineman 235 is one of only a relatively small number of contact systems in open clusters for which a detailed light curve analysis has been carried out (Kaluzny and Rucinski 1993). H235 provides a fiducial point for understanding the evolution of contact systems and with a contact parameter of only 0.4, gives modest support for the merger hypothesis of their origins.
Analyses are planned for the following open cluster member candidates for which photometric observations are complete: QX Cas (NGC 7790), V448 Cyg (NGC 6871), and BS Sct (NGC 6705). These and younger systems are members of stellar ensembles; very young stars, such as the Wolf-Rayet binaries V444 Cygni (Berkeley 86) and DH Cephei (NGC 7380) are members of stellar associations, providing the boot-strap advantage to studies of both the binaries and the ensembles. Open clusters which contain variables which we (principally McVean, Milone, Steve Schiller (SDSU), Shadbolt, Frank Younger and Doug Bond at DAO) observed are: NGC 6791 (at least 8 systems), NGC 7142 (1), NGC 7209 (SS Lac), and IC 1848 (V497 and V498 Cas). The latter cluster has been observed by Mamnun Zakirov (Uzbekistan) and Young Woon Kang (Korea) as well as by McVean, Milone, & Schiller (see Milone et al 2000 re the properties of this currently non-eclipsing system and subsequent work by Torres 2000). We are searching for variable stars in other stellar ensembles also. One of these is NGC 752 which the work of Daniel et al. (1994) showed to be a potential mine of variables of various kinds; recent work on this system is described below.
The old but rich open cluster NGC 6791 has been observed: (U)BVRI images have been secured at Mt. Laguna, Mt. Wilson, and DAO This ancient yet metal-rich cluster has 17 variables (one a CV) in the field, as noted by Kaluzny & Rucinski (1993). The ascertainment of membership status of all of these objects is one of our goals. An important element in further progress is the acquisition of radial velocities to assist in light curve & system modeling as well as helping to decide the membership question.
As his MSc thesis, Jason R. McVean analyzed the light curves obtained by Mateo and Yan (1995) at Mt. Wilson. The results are available are in (McVean et al 1996).
I was invited to join a very capable team led by R. Gilliland in Sept., 1998, to to look for planets orbiting the stars of the bright globular cluster 47 Tucanae with HST. This program sought and obtained 8 days of HST time on two imaging instruments. The observations were obtained between July 3 and July 12 1999, and currently are being processed. We anticipate an abundance of events to analyze -- both planetary and stellar! Astrophysics majors Mr. Byron Desnoyers Winmill and Ms. Megan McClure have been involved in simulating events on our light curve analysis tools (see Light Curve Modeling)
and graduate student Michael Williams completed an MSc, in part on the analysis of the one planetary transit candidate we had, as well as the planetary transit in the HD 209458 system (Williams 2001; see Williams & Milone 2003 and Milone et al. 2004).
Because binaries are expected to concentrate at the cores of dense clusters and ground-based photometry of these clusters is limited by seeing, we would be very happy to be able to collaborate with groups with access to cluster photometry from the HST. Our interest is the light curve analysis of any light curves which may be obtained.
we have developed a method to make use of the isochrones of
well studied globular clusters when the photometric data base
consists of only 2-colour photometry. This method of yielding
fundamental parameters is described in the Merida proceedings by
Milone, et al. (2004).
We have been awaiting a renewed examination of the 47 Tuc photometry, and this has now been compketed by a team headed by Raja Guhathakurta (UC Berkeley), accordingly, we are now completing work on the eclipsing systems of this cluster.
Systems which we have observed in the past include TY Boo, 44i Boo, AO CAM, RW Com, V1500 Cyg, OW Gem, V728 Her, UV Leo.
Observational work has been done on the variables of NGC 752, thanks to observing time on the 1-m telescope granted to us at Mount Laguna Observatory in November, 2004.
In recent years, we have been working with the Asiago group checking out the capability of the GAIA mission, a reconfirmed keystone mission of the European Space Agency, to provide fundamental data from eclipsing binary data. The mission will achieve 4 micro-arcsec astrometry, intermediate and broad passband photometry, and RV spectrophotometry, to accomplish a thorough exploration of the galaxy's kinematical and dynamical properties, and the fundamental parameters of its stars. The eclipsing binaries simulations work involves Hipparcos and Tycho photometry and echelle spectroscopy of the Ca triplet region. The four papers in this series published thus far (Munari, et al., 2001; Zwitter, et al. 2003; Marrese et al. 2003; and Milone 2005) have featured the systems: OO Peg, V505 Per, V570 Per, V781 Tau, UV Leo, GK Per, UW LMi, V432 Aur, CN Lyn, SV Cam, HP Dra, and BS Dra. The success of the analyses when the minima are well-covered and the both RV curves are visible can be seen with precision of parameters exceeding 2-3% in those cases. The cases where the light curve minima are sparse, or the light curves are variable, or where other complications exist (such as apsidal motion, or where only 1 RV curve is obtainable) provide limiting cases for GAIA also.
I have also been an associate member of the GAIA simulations group to explore further:
I am a member of the epsilon Aurigae team organized by Bob Stencil to observe that enormous and mysterious eclipsing binary prior to and during its coming eclipse in 2009. We will try to observe it with the 1.8-m ARCT equipped with the IRWG passband filters iz, iJ, iH, and iK.
Work on field delta Scuti stars has been carried out by Bill Wilson, David Fry,
Virginia Volk, and myself, aided by a number of hard-working colleagues -- see
groups -- on the systems EH Lib, DY Her, and DY Peg.
We have combined infrared photometry, carried out at KPNO, DAO, and the RAO,
with optical photometry obtained with RADS at the RAO, and radial
velocity data obtained at DAO, to obtain Wesselink radii and luminosities.
With an improved error determination technique, we have carefully assessed
the phase range of the colour indices to produce what we expect are more
reliable estimates of radii over previous attempts. Work has commenced on'
observations of several other variables, starting with the bright,
multi-periodic system, AI CVn. Mrs. Volk concentrated on the multi-periodic
V369 Sct, and Milone, Wilson and K. Volk completed a study of the
classical Cepheid SU Cas (P = 1.95d) pivotal to Period-Luminosity Relations.
J. Postma has completed a study of the 3-d Cepheid SZ Tau, despite the incomplete nature of the RAO telescope upgrades in recent years, because of the generosity of 26-in telescope time provided at the Mt. Laguna Observatory. Our work on this object is being prepared for publication.
A major development is the resurrection of a
Baker-Nunn satellite tracking camera made possible by partnership
funding. The resulting equatorially mounted Patrol Camera is
currently equipped with an FLI camera with a 4Kx4K chip, enabling
~19 square degrees of the sky to be imaged in a single exposure.
Mike Williams has been pursuing the limits of variable star detection
with this instrument since early 2004; hardware and other
problems held up the completion of this work for a while, but results
for this patrol camera are now in hand and are to be published shortly.
Mike has provided some details of the first fruits of this survey work at:
Finally, I am a member of the Canadian UVIT team to develop and make use of a UV instrument for a joint Indian and Canadian satellite project. If all goes according to plan, in 2006, my students and I selected optimal targets for this mission: the polars. With the help of Steve Howell, I presented the case for these objects in the CSA meeting in Montreal in Oct., 2007. The calibration of the detectors is to be carried out at the University of Calgary/s Space Science Laboratory. Joe Postma is heavily involved in this effort.