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TESS Light Curve of the Interacting Binary W Serpentis
Douglas R. Gies, Katherine A. Shepard, Aman Kar +1
The unusual light curve of the massive eclipsing binary W Ser was recently observed with high S/N and fast cadence by the NASA TESS mission. The TESS light curve records two eclips…
A Spectroscopic and Interferometric Study of W Serpentis Stars. I. Circumbinary Outflow in the Interacting Binary W Serpentis
Katherine Shepard, Douglas R. Gies, Gail H. Schaefer +6
W Serpentis is an eclipsing binary system and the prototype of the Serpentid class of variable stars. These are interacting binaries experiencing intense mass transfer and mass los…
Time-Evolution Images of the Hypergiant RW Cephei During the Re-brightening Phase Following the Great Dimming
Narsireddy Anugu, Douglas R. Gies, Rachael M. Roettenbacher +17
Stars with initial masses larger than 8 solar masses undergo substantial mass loss through mechanisms that remain elusive. Unraveling the origins of this mass loss is important for…
CHARA Near-Infrared Imaging of the Yellow Hypergiant Star Cassiopeiae: Convection Cells and Circumstellar Envelope
Narsireddy Anugu, Fabien Baron, John D. Monnier +18
Massive evolved stars such as red supergiants and hypergiants are potential progenitors of Type II supernovae, and they are known for ejecting substantial amounts of matter, up to…
The CHARA Array interferometric program on the multiplicity of classical Be stars: new detections and orbits of stripped subdwarf companions
Robert Klement, Thomas Rivinius, Douglas R. Gies +8
Rapid rotation and nonradial pulsations enable Be stars to build decretion disks, where the characteristic line emission forms. A major but unconstrained fraction of Be stars owe t…
The Great Dimming of the hypergiant star RW Cephei: CHARA Array images and spectral analysis
N. Anugu, F. Baron, D. R. Gies +15
The cool hypergiant star RW Cephei is currently in a deep photometric minimum that began several years ago. This event bears a strong similarity to the Great Dimming of the red sup…
The orbital and physical properties of five southern Be+sdO binary systems
Luqian Wang, Douglas R. Gies, Geraldine J. Peters +1
Close binary interactions may play a critical role in the formation of the rapidly rotating Be stars. Mass transfer can result in a mass gainer star spun up by the accretion of mas…
Gamma Cas Stars as Be + White Dwarf Binary Systems
Douglas Gies, Luqian Wang, Robert Klement
The origin of the bright and hard X-ray emission flux among the gamma Cas subgroup of B-emission line (Be) stars may be caused by gas accretion onto an orbiting white dwarf (WD) co…
Dynamical masses of the primary Be star and the secondary sdB star in the single-lined binary kappa Dra (B6 IIIe)
R. Klement, D. Baade, Th. Rivinius +16
Because many classical Be stars may owe their nature to mass and angular-momentum transfer in a close binary, the present masses, temperatures, and radii of their components are of…
Visual Orbits of Spectroscopic Binaries with the CHARA Array. IV. HD 61859, HD 89822, HD 109510, and HD 191692
Kathryn V. Lester, Gail H. Schaefer, Francis C. Fekel +18
We present the visual orbits of four spectroscopic binary stars, HD 61859, HD 89822, HD 109510, and HD 191692, using long baseline interferometry with the CHARA Array. We also obta…
ARMADA II: Further Detections of Inner Companions to Intermediate Mass Binaries with Micro-Arcsecond Astrometry at CHARA and VLTI
Tyler Gardner, John D. Monnier, Francis C. Fekel +18
We started a survey with CHARA/MIRC-X and VLTI/GRAVITY to search for low mass companions orbiting individual components of intermediate mass binary systems. With the incredible pre…
Spectroscopic Line Modeling of the Fastest Rotating O-type Stars
Katherine Shepard, Douglas R. Gies, Lex Kaper +1
We present a spectroscopic analysis of the most rapidly rotating stars currently known, VFTS 102 ( km s; O9: Vnnne+) and VFTS 285 ($v_{e} \sin i =…
Identification of new classical Be stars from the LAMOST MRS survey
Luqian Wang, Jiao Li, You Wu +6
Be stars are B-type main-sequence stars that display broad Balmer emission lines in their spectra. Identification of Be population is essential to further examine the formation and…
Mass Transfer as an Explanation for the Lifetime-Travel Time Discrepancy in IT Librae
Peter Wysocki, Douglas Gies, Katherine Shepard +2
The eclipsing binary IT Librae is an unusual system of two B-type stars that is situated about 1 kpc above the galactic plane. The binary was probably ejected from its birthplace i…
The Transformative Journey of HD 93521
Douglas R. Gies, Katherine Shepard, Peter Wysocki +1
HD 93521 is a massive, rapidly rotating star that is located about 1 kpc above the Galactic disk, and the evolutionary age for its estimated mass is much less than the time-of-flig…
Outbursts and stellar properties of the classical Be star HD 6226
Noel D. Richardson, Olivier Thizy, Jon E. Bjorkman +58
The bright and understudied classical Be star HD 6226 has exhibited multiple outbursts in the last several years during which the star grew a viscous decretion disk. We analyze 659…
Long Term Evolution of Surface Features on the Red Supergiant AZ Cyg
Ryan P. Norris, Fabien R. Baron, John D. Monnier +23
We present H-band interferometric observations of the red supergiant (RSG) AZ Cyg made with the Michigan Infra-Red Combiner (MIRC) at the six-telescope Center for High Angular Reso…
Gem: a hierarchical triple system with an outer Be star
Robert Klement, Petr Hadrava, Thomas Rivinius +17
Time series of spectroscopic, speckle-interferometric, and optical long-baseline-interferometric observations confirm that Gem is a hierarchical triple system. It consists of a…
The Detection and Characterization of Be+sdO Binaries from HST/STIS FUV Spectroscopy
Luqian Wang, Douglas R. Gies, Geraldine J. Peters +4
The B-emission line stars are rapid rotators that were probably spun up by mass and angular momentum accretion through mass transfer in an interacting binary. Mass transfer will st…
ARMADA I: Triple Companions Detected in B-Type Binaries alpha Del and nu Gem
Tyler Gardner, John D. Monnier, Francis C. Fekel +19
Ground-based optical long-baseline interferometry has the power to measure the orbits of close binary systems at ~10 micro-arcsecond precision. This precision makes it possible to…
Optically thin circumstellar medium in Lyr A system
M. Brož, D. Mourard, J. Budaj +7
beta Lyr A is a complex binary system with an extensive observational dataset: light curves (from FUV to FIR), interferometric squared visibility, closure phase, triple product mea…
Spectroscopic Detection of the Pre-White Dwarf Companion of Regulus
Douglas R. Gies, Kathryn V. Lester, Luqian Wang +6
Mass transfer in an interacting binary will often strip the mass donor of its entire envelope and spin up the mass gainer to near critical rotation. The nearby B-type star Regulus…
A High Angular Resolution Survey of Massive Stars in Cygnus OB2: Adaptive Optics Results from the Gemini Near-InfraRed Imager
S. M. Caballero-Nieves, D. R. Gies, E. K. Baines +8
We present results of a high angular resolution survey of massive OB stars in the Cygnus OB2 association that we conducted with the NIRI camera and ALTAIR adaptive optics system of…
The H-alpha Emission Line Variations of HR 6819
Douglas Gies, Luqian Wang
The star system HR 6819 was recently proposed by Rivinius et al. as the site of the nearest example of a stellar mass black hole. Their spectra show evidence of two components: a B…