2012AJ....144...93M


Query : 2012AJ....144...93M

2012AJ....144...93M - Astron. J., 144, 93 (2012/October-0)

The effects of close companions (and rotation) on the magnetic activity of M dwarfs.

MORGAN D.P., WEST A.A., GARCES A., CATALAN S., DHITAL S., FUCHS M. and SILVESTRI N.M.

Abstract (from CDS):

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 Hα 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 Hα, 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.

Abstract Copyright:

Journal keyword(s): binaries: close - binaries: spectroscopic - stars: activity - stars: low-mass - stars: rotation - white dwarfs

VizieR on-line data: <Available at CDS (J/AJ/144/93): table.dat table.fits>

Simbad objects: 26

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Number of rows : 26
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 SDSS J000109.42+255459.6 ** 00 01 09.4247894400 +25 54 59.710804632           dM2.5+DA 6 0
2 SDSS J000152.08+000644.5 ** 00 01 52.0828654272 +00 06 44.615966184           dM0+DA 6 0
3 SDSS J000250.64-045041.5 ** 00 02 50.6566594752 -04 50 41.484986448           DB+dM4 2 0
4 SDSS J000356.93-050332.7 ** 00 03 56.9319298080 -05 03 32.815305108           dM4.5+DA 5 0
5 SDSS J000421.61+004341.5 ** 00 04 21.613 +00 43 41.60           dM5+DB 1 0
6 SDSS J000447.76+291141.1 WD* 00 04 47.7679528056 +29 11 41.010518616           DA 3 0
7 SDSS J000453.94+265420.3 ** 00 04 53.9388223536 +26 54 20.337629220           DA+dM4 5 0
8 SDSS J000504.91+243409.7 ** 00 05 04.9162074984 +24 34 09.753120948   18.5   18.1   DA+dM4.5 7 0
9 SDSS J000531.10-054343.3 ** 00 05 31.0608333744 -05 43 43.130759160           DA+dM5 6 0
10 SDSS J000559.87-054416.0 ** 00 05 59.8682204112 -05 44 16.003354272           DA+dM1.5 7 0
11 SDSS J000651.91+284647.1 * 00 06 51.9062697864 +28 46 46.815974760           M3 6 0
12 SDSS J000711.40+283848.4 ** 00 07 11.4084637584 +28 38 48.553738512           DA+M 2 0
13 SDSS J000829.91+273340.3 ** 00 08 29.9173061592 +27 33 40.495357584           DA+M2 4 0
14 SDSS J001247.18+001048.8 ** 00 12 47.1860599296 +00 10 48.822389868           DA+M 9 0
15 SDSS J001726.63-002451.2 ** 00 17 26.6348887072 -00 24 51.475678762           DA+dMe 15 0
16 SDSS J002157.91-110331.6 ** 00 21 57.9085845240 -11 03 31.611384504           DA+M4 11 0
17 SDSS J005245.11-005337.2 ** 00 52 45.1155098856 -00 53 37.527493848           DA+dMe 23 0
18 SDSS J015225.38-005808.5 ** 01 52 25.3847681856 -00 58 08.621196240           DA+M 15 0
19 SDSS J021849.98+005739.2 ** 02 18 49.9827391752 +00 57 39.317436072           DA+M 9 0
20 SDSS J023938.04+273654.0 ** 02 39 38.0408935920 +27 36 54.194673924           DA+M4 5 0
21 SDSS J030138.24+050218.9 ** 03 01 38.2315293504 +05 02 18.864882708           DA+M4 9 0
22 US 3566 WD* 03 03 08.3621593176 +00 54 43.921390896   18.9 18.06 18.1 16.00 DC+M4.5e 37 0
23 SDSS J073003.86+405450.0 ** 07 30 03.8672542584 +40 54 49.973613768           ~ 2 0
24 SDSS J073455.91+410537.4 ** 07 34 55.9211558736 +41 05 37.427916444           DA+M 5 0
25 SDSS J075919.41+321948.4 ** 07 59 19.4217759960 +32 19 48.491450328           DA+M 15 0
26 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 13204 0

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2022.10.06-20:49:24

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