The CHARA Array is a six 1 m telescope optical/IR interferometric array located on Mount Wilson, California, designed and built by the Center for High Angular Resolution Astronomy of Georgia State ...University. In this paper we describe the main elements of the Array hardware and software control systems, as well as the data reduction methods currently being used. Our plans for upgrades in the near future are also described.
We report on K-band interferometric observations of the bright, rapidly rotating star Regulus (type B7 V) made with the CHARA Array on Mount Wilson, California. Through a combination of ...interferometric and spectroscopic measurements, we have determined for Regulus the equatorial and polar diameters and temperatures, the rotational velocity and period, the inclination and position angle of the spin axis, and the gravity darkening coefficient. These first results from the CHARA Array provide the first interferometric measurement of gravity darkening in a rapidly rotating star and represent the first detection of gravity darkening in a star that is not a member of an eclipsing binary system.
A Spectroscopic Orbit for Regulus Gies, D. R; Dieterich, S; Richardson, N. D ...
Astrophysical journal/The Astrophysical journal,
08/2008, Volume:
682, Issue:
2
Journal Article
Peer reviewed
Open access
We present a radial velocity study of the rapidly rotating B star Regulus that indicates the star is a single-lined spectroscopic binary. The orbital period (40.11 days) and probable semimajor axis ...(0.35 AU) are large enough that the system is not Interacting at present. However, the mass function suggests that the secondary has a low mass (M sub(2) > 0.30 M), and we argue that the companion may be a white dwarf. Such a star would be the remnant of a former mass donor that was the source of the large spin angular momentum of Regulus itself.
We present the first K'-band, long-baseline interferometric observations of the northern Be stars g Cas, h Per, Tau, and Dra. The measurements were made with multiple telescope pairs of the CHARA ...Array interferometer and in every case the observations indicate that the circumstellar disks of the targets are resolved. We fit the interferometric visibilities with predictions from a simple disk model that assumes an isothermal gas in Keplerian rotation. We derive fits of the four model parameters (disk base density, radial density exponent, disk normal inclination, and position angle) for each of the targets. The resulting densities are in broad agreement with prior studies of the IR excess flux, and the resulting orientations generally agree with those from interferometric Ha and continuum polarimetric observations. We find that the angular size of the K' disk emission is smaller than that determined for the Ha emission, and we argue that the difference is the result of a larger Ha opacity and the relatively larger neutral hydrogen fraction with increasing disk radius. All the targets are known binaries with faint companions, and we find that companions appear to influence the interferometric visibilities in the cases of h Per and Dra. We also present contemporaneous observations of the Ha, Hg, and Brg emission lines. Synthetic model profiles of these lines that are based on the same disk inclination and radial density exponent as derived from the CHARA Array observations match the observed emission line strength if the disk base density is reduced by -1.7 dex.
We present the results of time-resolved spectroscopy of 13 O-type stars in the Cas OB6 stellar association. We conducted a survey for radial velocity variability in search of binary systems, which ...are expected to be plentiful in young OB associations. Here we report the discovery of two new single-lined binaries, and we present new orbital elements for three double-lined binaries (including one in the multiple-star system HD 17505). One of the double-lined systems is the eclipsing binary system DN Cas, and we present a preliminary light-curve analysis that yields the system inclination, masses, and radii. We compare the spectra of the single stars and the individual components of the binary stars with model synthetic spectra to estimate the stellar effective temperatures, gravities, and projected rotational velocities. We also make fits of the spectral energy distributions to derive E(B -V), R=A sub(V)/E(B - V), and angular diameter. A distance of 1.9 kpc yields radii that are consistent with evolutionary models. We find that 7 of 14 systems with spectroscopic data are probable binaries, consistent with the high binary frequency found for other massive stars in clusters and associations.
We present the results of a speckle interferometric survey made with the CHARA speckle camera and 4 m class telescopes of Galactic O-type stars with V less than 8. We can detect with the speckle ...camera binaries in the angular separation range 0.035-1.5 arcsec with delta M less than 3, and we have discovered 15 binaries among 227 O-type systems. We combined our results on visual binaries with measurements of wider pairs from the Washington Double Star Catalog and fainter pairs from the Hipparcos Catalog, and we made a literature survey of the spectroscopic binaries among the sample. We then investigated the overall binary frequency of the sample and the orbital characteristics of the known binaries. Binaries are common among O stars in clusters and associations but less so among field and especially runaway stars. There are many triple systems among the speckle binaries, and we discuss their possible role in the ejection of stars from clusters. The period distribution of the binaries is bimodal in log P, but we suggest that binaries with periods of years and decades may eventually be found to fill the gap. The mass ratio distribution of the visual binaries increases toward lower mass ratios, but low mass ratio companions are rare among close, spectroscopic binaries. We present distributions of the eccentricity and longitude of periastron for spectroscopic binaries with elliptical orbits, and we find strong evidence of a bias in the longitude of periastron distribution. (Author)
The Angular Diameter of λ Boötis Ciardi, David R; van Belle, Gerard T; Boden, Andrew F ...
Astrophysical journal/The Astrophysical journal,
04/2007, Volume:
659, Issue:
2
Journal Article
We have obtained high-resolution orbital data with the CHARA Array for the bright star 12 Persei, a resolved double-lined spectroscopic binary. We describe the data reduction process, which can give ...precision in separation of up to 25 mas along a given baseline. For this object we find a semimajor axis of a = 53.18 ± 0.15 mas, which is 0.3% smaller than that of Barlow and coworkers, but with much improved precision. The inclination angle i increases to 12817 ± 014, compared to 12677 ± 056 of Barlow and coworkers, again with better precision. We also found an intensity ratio for the components in the K' band (l = 2.13 mm) of r = 0.72 ± 0.01, or K' = 0.409 ± 0.013, after allowing for the partial resolution of the components. Assuming the spectral types of the components, we find that Pub Lclchangemark='ins'>V = 0.51, as compared to 0.57 by Barlow and coworkers. The revised masses (Pub Lclchangemark='ins'>Mp = 1.382 ± 0.019 and Ms = 1.240 ± 0.017 M) are found to be 5.8% larger than those of Barlow and coworkers, and the components are thus even more overmassive. The overall accuracy in the masses is about 1.3%, now primarily limited by the spectroscopically determined radial velocities. The precision of the masses due to the interferometrically derived 'visual' orbit alone is only about 0.2%.
The UV photospheric lines of the short-period, double-lined O-star spectroscopic binary AO Cas are analyzed. Archival data from IUE (16 spectra uniformly distributed in orbital phase) were analyzed ...with a tomography algorithm to produce the separate spectra of the two stars in six spectral regions. The spectral classifications of the primary and secondary, O9.5 III and O8 V, respectively, were estimated through a comparison of UV line ratios with those in spectral standard stars. An intensity ratio of 0.5-0.7 (primary brighter) at 1600 A is compatible with the data.
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