THE EFFECTS OF CLOSE COMPANIONS (AND ROTATION) ON THE MAGNETIC ACTIVITY OF M DWARFS
- Astronomy Department, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)
- Institut de Ciencies de l'Espai (IEEC-CSIC), Facultat de Ciencies, Campus UAB, E-08193 Bellaterra (Spain)
- Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 AB (United Kingdom)
We present a study of close white dwarf and M dwarf (WD+dM) binary systems and examine the effect that a close companion has on the magnetic field generation in M dwarfs. We use a base sample of 1602 white dwarf main-sequence binaries from Rebassa-Mansergas et al. to develop a set of color cuts in GALEX, SDSS, UKIDSS, and 2MASS color space. Then using the SDSS Data Release 8 spectroscopic database, we construct a sample of 1756 WD+dM high-quality pairs from our color cuts and previous catalogs. We separate the individual WD and dM from each spectrum using an iterative technique that compares the WD and dM components to best-fit templates. Using the absolute height above the Galactic plane as a proxy for age, and the H{alpha} emission line as an indicator for magnetic activity, we investigate the age-activity relation for our sample for spectral types {<=} M7. Our results show that early-type M dwarfs ({<=}M4) in close binary systems are more likely to be active and have longer activity lifetimes compared to their field counterparts. However, at a spectral type of M5 (just past the onset of full convection in M dwarfs), the activity fraction and lifetimes of WD+dM binary systems become more comparable to that of the field M dwarfs. One of the implications of having a close binary companion is presumed to be increased stellar rotation through disk disruption, tidal effects, or angular momentum exchange. Thus, we interpret the similarity in activity behavior between late-type dMs in WD+dM pairs and late-type field dMs to be due to a decrease in sensitivity in close binary companions (or stellar rotation), which has implications for the nature of magnetic activity in fully convective stars. Using the WD components of the pairs, we find WD cooling ages to use as an additional constraint on the age-activity relation for our sample. We find that, on average, active early-type dMs tend to be younger and that active late-type dMs span a much broader age regime making them indistinguishable from the inactive late-type population. We also show that magnetic strength, as measured by H{alpha}, is comparable between paired and field M dwarfs until a spectral type of M6/M7 where M dwarf activity for stars with close companions becomes much stronger. In addition, we present 37 very close candidate pairs with fast-moving orbits that display radial velocity changes over hour timescales.
- OSTI ID:
- 22089878
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 144, Issue 4; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
Similar Records
USING CLOSE WHITE DWARF + M DWARF STELLAR PAIRS TO CONSTRAIN THE FLARE RATES IN CLOSE STELLAR BINARIES
THE ELM SURVEY. I. A COMPLETE SAMPLE OF EXTREMELY LOW-MASS WHITE DWARFS