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The High Angular Resolution Multiplicity of Massive Stars
Brian D. Mason, William I. Hartkopf, Douglas R. Gies +2
We present the results of a speckle interferometric survey of Galactic massive stars that complements and expands upon a similar survey made over a decade ago. The speckle observat…
First Resolved Images of the Eclipsing and Interacting Binary Beta Lyrae
M. Zhao, D. Gies, J. D. Monnier +12
We present the first resolved images of the eclipsing binary Beta Lyrae, obtained with the CHARA Array interferometer and the MIRC combiner in the H band. The images clearly show t…
A Spectroscopic Orbit for Regulus
D. R. Gies, S. Dieterich, N. D. Richardson +8
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 d) and probable…
Detection of a Hot Subdwarf Companion to the Be Star FY Canis Majoris
Geraldine J. Peters, Douglas R. Gies, Erika D. Grundstrom +1
The rapid rotation of Be stars may be caused in some cases by past mass and angular momentum accretion in an interacting binary in which the mass donor is currently viewed as a sma…
Angular Diameters of the G Subdwarf Cassiopeiae A and the K Dwarfs Draconis and HR 511 from Interferometric Measurements with the CHARA Array
Tabetha S. Boyajian, Harold A. McAlister, Ellyn K. Baines +13
Using the longest baselines of the CHARA Array, we have measured the angular diameter of the G5 V subdwarf Cas A, the first such determination for a halo population star. We co…
Dynamical Masses for the Large Magellanic Cloud Massive Binary System [L72] LH 54-425
S. J. Williams, D. R. Gies, T. J. Henry +8
We present results from an optical spectroscopic investigation of the massive binary system [L72] LH~54-425 in the LH 54 OB association in the Large Magellanic Cloud. We revise the…
Stellar Wind Variations During the X-ray High and Low States of Cygnus X-1
D. R. Gies, C. T. Bolton, R. M. Blake +10
We present results from Hubble Space Telescope UV spectroscopy of the massive X-ray binary system, HD226868 = Cyg X-1. The spectra were obtained at both orbital conjunction phases…
Spectroscopic Observations of the Mass Donor Star in SS 433
Todd C. Hillwig, Douglas R. Gies
The microquasar SS 433 is an interacting massive binary consisting of an evolved mass donor and a compact companion that ejects relativistic jets. The mass donor was previously ide…
Ultraviolet observations of the X-ray photoionized wind of Cygnus X-1 during X-ray soft/high state
S. D. Vrtilek, B. Boroson, A. Hunacek +2
(Shortened) Ultraviolet observations of the black hole X-ray binary Cygnus X-1 were obtained using the STIS on HSTubble. We detect P Cygni line features show strong, broad absorpti…
The B and Be Star Population of NGC 3766
M. Virginia McSwain, Wenjin Huang, Douglas R. Gies +2
We present multiple epochs of H-alpha spectroscopy for 47 members of the open cluster NGC 3766 to investigate the long term variability of its Be stars. Sixteen of the stars in thi…
Towards an understanding of the Of?p star HD 191612: optical spectroscopy
Ian D. Howarth, Nolan R. Walborn, Danny J. Lennon +17
We present extensive optical spectroscopy of the early-type magnetic star HD 191612 (O6.5f?pe-O8fp). The Balmer and HeI lines show strongly variable emission which is highly reprod…
A Spectroscopic Study of Mass Outflows in the Interacting Binary RY Scuti
E. D. Grundstrom, D. R. Gies, T. C. Hillwig +5
The massive interacting binary RY Scuti is an important representative of an active mass-transferring system that is changing before our eyes and which may be an example of the for…
Radial Velocities of Six OB Stars
T. S. Boyajian, D. R. Gies, E. K. Baines +7
We present new results from a radial velocity study of six bright OB stars with little or no prior measurements. One of these, HD 45314, may be a long-period binary, but the veloci…
Joint H-alpha and X-Ray Observations of Massive X-Ray Binaries. III. The Be X-ray Binaries HDE 245770 = A 0535+26 and X Persei
E. D. Grundstrom, T. S. Boyajian, C. Finch +9
We present results from an H-alpha monitoring campaign of the Be X-ray binary systems HDE 245770 = A 0535+26 and X Per. We use the H-alpha equivalent widths together with adopted v…
Joint H-alpha and X-ray Observations of Massive X-ray Binaries. I. The B-Supergiant System LS I +65 010 = 2S 0114+650
E. D. Grundstrom, J. L. Blair, D. R. Gies +8
We report on a three year spectroscopic monitoring program of the H-alpha emission in the massive X-ray binary LS I +65 010 = 2S 0114+650, which consists of a B-supergiant and a sl…
Joint H-alpha and X-Ray Observations of Massive X-Ray Binaries. II. The Be X-ray Binary and Microquasar LS I +61 303
E. D. Grundstrom, S. M. Caballero-Nieves, D. R. Gies +6
We present the results of an H-alpha monitoring campaign on the BeXRB and microquasar system LS I +61 303. We use radial velocity measurements of HeI lines in our spectra to re-eva…
Estimating Be Star Disk Radii using H-alpha Emission Equivalent Widths
Erika D. Grundstrom, Douglas R. Gies
We present numerical models of the circumstellar disks of Be stars, and we describe the resulting synthetic H-alpha emission lines and maps of the wavelength-integrated emission fl…
CHARA Array K'-band Measurements of the Angular Dimensions of Be Star Disks
D. R. Gies, W. G. Bagnuolo, E. K. Baines +22
We present the first K'-band, long-baseline interferometric observations of the northern Be stars gamma Cas, phi Per, zeta Tau, and kappa Dra. The measurements were made with multi…
A Spectroscopic Study of Field and Runaway OB Stars
M. Virginia McSwain, Tabetha S. Boyajian, Erika D. Grundstrom +1
Identifying binaries among runaway O- and B-type stars offers valuable insight into the evolution of open clusters and close binary stars. Here we present a spectroscopic investiga…
The B-Supergiant Components of the Double-Lined Binary HD1383
T. S. Boyajian, D. R. Gies, M. E. Helsel +4
We present new results from a study of high quality, red spectra of the massive binary star system HD 1383 (B0.5 Ib + B0.5 Ib). We determined radial velocities and revised orbital…
First Results from the CHARA Array. IV. The Interferometric Radii of Low-Mass Stars
D. H. Berger, D. R. Gies, H. A. McAlister +8
We have measured the angular diameters of six M dwarfs with the CHARA Array, a long-baseline optical interferometer located at Mount Wilson Observatory. Spectral types range from M…
Stellar Rotation in Young Clusters. II. Evolution of Stellar Rotation and Surface Helium Abundance
W. Huang, D. R. Gies
We derive the effective temperatures and gravities of 461 OB stars in 19 young clusters by fitting the H-gamma profile in their spectra. We use synthetic model profiles for rotatin…
Stellar Rotation in Young Clusters. I. Evolution of Projected Rotational Velocity Distributions
Wenjin Huang, Douglas R. Gies
Open clusters offer us the means to study stellar properties in samples with well-defined ages and initial chemical composition. Here we present a survey of projected rotational ve…
The Evolutionary Status of Be Stars: Results from a Photometric Study of Southern Open Clusters
M. Virginia McSwain, Douglas R. Gies
Be stars are a class of rapidly rotating B stars with circumstellar disks that cause Balmer and other line emission. There are three possible reasons for the rapid rotation of Be s…