DISCOVERY AND CHARACTERIZATION OF A FAINT STELLAR COMPANION TO THE A3V STAR zeta VIRGINIS

Journal Article · Sat Mar 20 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/712/1/421· OSTI ID:21394265

Hinkley, Sasha; Hillenbrand, Lynne ^[1]; Oppenheimer, Ben R; Brenner, Douglas; Zimmerman, Neil; Sivaramakrishnan, Anand ^[2]; Roberts, Lewis C; Roberts, Jennifer E; Burruss, Rick; Shao, Michael; Vasisht, Gautam ^[3]; Parry, Ian R; King, David L ^[4]; Soummer, Remi ^[5]; Simon, Michal ^[6]; Perrin, Marshall D ^[7]; Lloyd, James P ^[8]; Bouchez, Antonin; Dekany, Richard ^[9]; Beichman, Charles ^[10]

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1. Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States)
2. Astrophysics Department, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024 (United States)
3. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States)
4. Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
5. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
6. Stony Brook University, NY (United States)
7. UCLA Department of Astronomy, CA (United States)
8. Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)
9. Caltech Optical Observatories, California Institute of Technology, Pasadena, CA 91125 (United States)
10. NASA Exoplanet Science Institute, California Institute of Technology, Pasadena, CA 91125 (United States)

Through the combination of high-order adaptive optics and coronagraphy, we report the discovery of a faint stellar companion to the A3V star zeta Virginis. This companion is {approx}7 mag fainter than its host star in the H band, and infrared imaging spanning 4.75 years over five epochs indicates this companion has common proper motion with its host star. Using evolutionary models, we estimate its mass to be 0.168{sup +0.012}{sub -0.016} M{sub sun}, giving a mass ratio for this system q = 0.082{sup +0.007}{sub -0.008}. Assuming the two objects are coeval, this mass suggests an M4V-M7V spectral type for the companion, which is confirmed through {integral} field spectroscopic measurements. We see clear evidence for orbital motion from this companion and are able to constrain the semimajor axis to be {approx}>24.9 AU, the period {approx}>124 yr, and eccentricity {approx}>0.16. Multiplicity studies of higher mass stars are relatively rare, and binary companions such as this one at the extreme low end of the mass ratio distribution are useful additions to surveys incomplete at such a low mass ratio. Moreover, the frequency of binary companions can help to discriminate between binary formation scenarios that predict an abundance of low-mass companions forming from the early fragmentation of a massive circumstellar disk. A system such as this may provide insight into the anomalous X-ray emission from A stars, hypothesized to be from unseen late-type stellar companions. Indeed, we calculate that the presence of this M-dwarf companion easily accounts for the X-ray emission from this star detected by ROSAT.

• OSTI ID: 21394265
• Journal Information: Astrophysical Journal, Vol. 712, Issue 1; Other Information: DOI: 10.1088/0004-637X/712/1/421; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
DATA ANALYSIS
EMISSION
IMAGE PROCESSING
MASS
MULTIPLICITY
PROPER MOTION
STARS
X RADIATION
ELECTROMAGNETIC RADIATION
IONIZING RADIATIONS
MOTION
PROCESSING
RADIATIONS