Jeffrey A. Sabby

Absolute Dimensions of the Unevolved B-Type Eclipsing Binary GG Orionis

We present photometric observations in B and V, as well as spectroscopic observations of the detached, eccentric 6.6 day double-lined eclipsing binary GG Ori, a member of the Orion OB1 association. Absolute dimensions of the components, which are virtually identical, are determined to high accuracy (better than 1% in the masses and better than 2% in the radii) for the purpose of testing various aspects of theoretical modeling. We obtain MA = 2.342 ± 0.016 M⊙ and RA = 1.852 ± 0.025 R⊙ for the primary, and MB = 2.338 ± 0.017 M⊙ and RB = 1.830 ± 0.025 R⊙ for the secondary. The effective temperature of both stars is 9950 ± 200 K, corresponding to a spectral type of B9.5. GG Ori is very close to the zero-age main sequence, and comparison with current stellar evolution models gives ages of 65–82 Myr or 7.7 Myr, depending on whether the system is considered to be burning hydrogen on the main sequence or still in the final stages of pre–main-sequence contraction. Good agreement is found in both scenarios for a composition close to solar. We have detected apsidal motion in the binary at a rate of = 000061 ± 000025 cycle-1, corresponding to an apsidal period of U = 10,700 ± 4500 yr. A substantial fraction of this (~70%) is due to the contribution from general relativity, and our measurement is entirely consistent with theory. The eccentric orbit of GG Ori is well explained by tidal evolution models, but both theory and our measurements of the rotational velocity of the components are as yet inconclusive as to whether the stars are synchronized with the orbital motion.

Absolute Properties of the Main-Sequence Eclipsing Binary Star WW Camelopardalis*

We present absolute photometric observations in uvby? and 5759 differential observations in the V filter (the most complete light curve ever obtained) measured by a robotic telescope, as well as radial velocities from spectroscopic observations of the detached, eccentric, 2.3 day, double-lined, eclipsing binary star WW Camelopardalis. Absolute dimensions of the components are determined with high precision (better than 1% in the masses and radii) for the purpose of testing various aspects of theoretical modeling. We obtain 1.920 ? 0.013 M? and 1.911 ? 0.016 R? for the primary, and 1.873 ? 0.018 M? and 1.808 ? 0.014 R? for the secondary. The effective temperatures and interstellar reddening of the stars are accurately determined from new uvby? photometry: 8350 ? 135 K for the primary and 8240 ? 135 K for the secondary, corresponding to a spectral type of A4m for both, and 0.294 mag for Eb-y. The metallic-lined character of the stars is revealed by high-resolution spectroscopy and uvby? photometry. Spectral line widths give rotational velocities that are synchronous with the orbital motion in a slightly eccentric orbit (e = 0.0098). The components of WW Cam are main-sequence stars with an age of about 490 Myr according to models.

Absolute Dimensions of the A-Type Eclipsing Binary V364 Lacertae

We present photoelectric observations in B and V, as well as spectroscopic observations of the 7.3 day period double-lined eclipsing binary V364 Lacertae. From the analysis of the light curves and the radial velocity curves we have determined the absolute dimensions of the components with high precision (1%). The masses for the primary and secondary are MA = 2.333 ± 0.015 M⊙ and MB = 2.296 ± 0.025 M⊙, respectively, and the radii are RA = 3.307 ± 0.038 R⊙ and RB = 2.985 ± 0.035 R⊙. We derive also effective temperatures of T = 8250 ± 150 K and T = 8500 ± 150 K, and projected rotational velocities of vA sin i = 45 ± 1 km s-1 and vB sin i = 15 ± 1 km s-1. Evolutionary tracks from current stellar evolution models are in good agreement with the observations for a system age of log t = 8.792 (6.2 × 108 yr) and for solar metallicity. Hints of a lower metallicity from spectroscopy and photometry appear to be ruled out by these models, but a definitive comparison must await a more accurate spectroscopic abundance determination. Analysis of all available eclipse timings along with our radial velocities of this moderately eccentric system (e = 0.2873 ± 0.0014) has revealed a small but significant motion of the line of apsides of = 0.00258 ± 0.00033 deg cycle-1, corresponding to an apsidal period of U = 2810 ± 360 yr. The contribution from general relativity effects is significant (~17%). A comparison with predictions from interior structure models shows the real stars to be less concentrated in mass than expected. Our measurements of the projected rotational velocities indicate that the primary star is essentially pseudosynchronized (synchronized at periastron), while the secondary is spinning 3 times more slowly and is not yet synchronized. Both the rotational status of the stars and the nonzero eccentricity of the orbit are consistent with the predictions from tidal theory, specifically for the radiative damping mechanism.

ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR V459 CASSIOPEIAE

We present 5064 differential observations in the V filter measured by a robotic telescope, as well as 30 pairs of radial velocities from high-resolution spectroscopic observations, of the detached, EA-type, 8.46 day period double-lined eclipsing binary star V459 Cas. Absolute dimensions of the components are determined with good precision (better than 1.6% in the masses and radii) for the purpose of testing various aspects of theoretical modeling. We obtain 2.02 ± 0.03 M⊙ and 2.009 ± 0.013 R⊙ for the hotter, larger, more massive and more luminous photometric primary (star A), and 1.96 ± 0.03 M⊙ and 1.965 ± 0.013 R⊙ for the cooler, smaller, less massive and less luminous photometric secondary (star B). The effective temperatures and interstellar reddening of the stars are accurately determined from uvbyβ photometry: 9140 ± 300 K for the primary, 9100 ± 300 K for the secondary—corresponding to spectral types of A1—and 0.186 mag for Eb-y. The orbits are eccentric, and spectral line widths give observed rotational velocities that are much faster than synchronous for both components. The components of V459 Cas are main-sequence stars with an age of about 525 Myr according to models.

ABSOLUTE PROPERTIES OF THE MAIN-SEQUENCE ECLIPSING BINARY STAR BP VULPECULAE

We present 5236 differential observations in the V filter measured by a robotic telescope, as well as radial velocities from spectroscopic observations, of the detached, eccentric 1.9 day double-lined eclipsing binary star BP Vul. Absolute dimensions of the components are determined with high precision (better than 1% in the masses and radii) for the purpose of testing various aspects of theoretical modeling. We obtain 1.737 ± 0.015 M⊙ and 1.852 ± 0.014 R⊙ for the primary, and 1.408 ± 0.009 M⊙ and 1.489 ± 0.014 R⊙ for the secondary. The effective temperatures and interstellar reddening of the stars are accurately determined from uvbyβ photometry: 7700 ± 150 K for the primary, 6800 ± 150 K for the secondary—corresponding to spectral types of A7m and F2m—and 0.022 mag for Eb-y. The metallic-lined character of the stars is revealed by high-resolution spectroscopy and uvbyβ photometry. Spectral line widths give rotational velocities that are synchronous with the orbital motion for the secondary component, but subsynchronous for the primary component, in a slightly eccentric orbit (e = 0.0345). Apsidal motion based on times of minimum light appears to be negative with a period of about 75 years based on recent observations of minima, but this result is not confirmed by the radial velocity measurements, and it is indeterminate when older photographic and visual data are included. The components of BP Vul are main-sequence stars with an age of about 1 Gyr according to models.

Absolute Properties of the Eclipsing Binary Star FS Monocerotis

We present photometric observations in B and V as well as spectroscopic observations of the 1.9 day¨ period, double-lined main-sequence eclipsing binary FS Mon. From the analysis of the light curves and radial velocity curves, we have determined the masses and radii of the components: 1.631 ^ 0.012 M _ and 2.051 ^ 0.012 for the primary component; 1.461 ^ 0.010 and 1.629 ^ 0.012 for the sec- R _ M _ R _ ondary component. The formal uncertainties are all less than 1%. Based on our light curves as well as on the combined-light photometry of the system, we estimate eUective temperatures of 6715 ^ 100 K for the primary and 6550 ^ 100 K for the secondary component, corresponding to spectral types of F2 and F4, respectively. Projected rotational velocities (v sin i) from the spectograms are measured as 52 ^ 2k m s~1 and 43 ^ 3k m s~1, respectively, from the spectrograms and are consistent with rotation that is synchronous with the orbital motion. Evolutionary tracks from current models are in good agreement with the observations for a system age of about 1.6 ) 109 yr with slightly nonsolar chemical composi- tion. We —nd the best match for models with a slightly lower helium abundance and a higher metal abundance than the Sun. An accurate metallicity determination for FS Mon is needed to constrain the models further.

Absolute Properties of the Upper Main-Sequence Eclipsing Binary Star MU Cassiopeiae

We present 6151 differential observations in the V filter measured by a robotic telescope, as well as 29 pairs of radial velocities from high-resolution spectroscopic observations, of the detached, EA-type, 9.65 day period double-lined eclipsing binary star MU Cas. Absolute dimensions of the components are determined with good precision (better than 2% in the masses and radii) for the purpose of testing various aspects of theoretical modeling. We obtain 4.57 ? 0.09 M? and 3.67 ? 0.04 R? for the hotter, but smaller, less massive and less luminous photometric primary (star A), and 4.66 ? 0.10 M? and 4.19 ? 0.05 R? for the cooler, larger, more massive and more luminous photometric secondary (star B). The effective temperatures and interstellar reddening of the stars are accurately determined from uvby? photometry: 15,100 ? 500 K for the primary, 14,750 ? 500 K for the secondary?corresponding to spectral types of B5 and B5?and 0.356 mag for Eb-y. The stars are located at a distance of about 1.7 kpc near the plane of the Galactic disk. The orbits of the stars are eccentric, and spectral line widths give observed rotational velocities that are synchronous with the mean orbital motion for both components. The components of MU Cas are upper main-sequence stars with an age of about 65 Myr according to models.

Absolute Properties of the Eclipsing Binary Star V396 Cassiopeiae

We present 6450 differential observations in the V filter measured by a robotic telescope, as well as 28 pairs of radial velocities from high-resolution spectroscopic observations of the detached EA-type, 5.505 day period, double-lined eclipsing binary star V396 Cas. Absolute dimensions of the components are determined with good precision (better than 1% in the masses and radii) for the purpose of testing various aspects of theoretical modeling. We obtain 2.398 ± 0.022 M⊙ and 2.592 ± 0.013 R⊙ for the hotter, larger, more massive and more luminous photometric primary (star A), and 1.901 ± 0.016 M⊙ and 1.779 ± 0.010 R⊙ for the cooler, smaller, less massive and less luminous photometric secondary (star B). The effective temperatures and interstellar reddening of the stars are accurately determined from uvbyβ photometry: 9225 ± 150 K for the primary and 8550 ± 120 K for the secondary, corresponding to spectral types of A1 and A3, and 0.119 mag for Eb-y. The metallicity of the stars appears to be significantly less than solar. The stars are located at a distance of about 560 pc near the plane of the Galactic disk. The orbits of the stars are apparently circular, and spectral line widths give observed rotational velocities that are not synchronous with the orbital motion for both components. The components of V396 Cas are main-sequence stars with an age of about 420 Myr according to models.

ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR RT CORONAE BOREALIS

We present an analysis of existing photometric observations in U, B, and V, and a new light curve in V, as well as spectroscopic observations, of the 5.1 day period, double-lined main-sequence eclipsing binary RT CrB. From the analysis of the light curves and radial velocity curves, we have determined the masses and radii of the components: 1.343 ± 0.010 M⊙ and 2.615 ± 0.04 R⊙ for the primary (hotter) component, 1.359 ± 0.009 M⊙ and 2.946 ± 0.05 R⊙ for the secondary (cooler) component. The formal uncertainties in the masses are both less than 1%, and the formal uncertainties in the radii are both less than 2%. Based on the analyzed light curves, as well as the combined absolute photometry of the system, we estimate effective temperatures of 5781 ± 100 K for the primary component and 5134 ± 100 K for the secondary component, corresponding to spectral types of G5 and K0, respectively. Projected rotational velocities (v sin i) from the spectrograms are measured as 25 ± 2 km s-1 for the primary component and 33 ± 3 km s-1 for the secondary component and are consistent with rotation that is synchronous with the orbital motion. Evolutionary tracks from the current models are in good agreement with the observations for a system of about age 3.5 × 109 yr with a slightly nonsolar chemical composition. We also report an approximate ΔP/P = 3.0 × 10-6 decrease in the orbital period over 37 years.