J/AJ/144/93 Close white dwarf + M dwarf binaries (WD+dM) (Morgan+, 2012)
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.,
Silvestri N.M.
<Astron. J., 144, 93 (2012)>
=2012AJ....144...93M 2012AJ....144...93M
ADC_Keywords: Binaries, spectroscopic ; Stars, dwarfs ; Stars, white dwarf
Keywords: binaries: close - binaries: spectroscopic - stars: activity -
stars: low-mass - stars: rotation - white dwarfs
Abstract:
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.
Description:
Parameters for 1756 spectroscopic close white dwarf + M dwarf binary
pairs from SDSS.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table.dat 512 1756 Parameters for 1756 close WD+dM pairs
table.fits 2880 138 FITS version of the table
--------------------------------------------------------------------------------
See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/294 : SDSS Photometric Catalog, Release 7 (Adelman-McCarthy, 2009)
II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)
II/319 : UKIDSS-DR9 LAS, GCS and DXS Surveys (Lawrence+ 2012)
J/AJ/129/2428 : M dwarf-white dwarf binary systems (Silvestri+, 2005)
J/AJ/134/26 : Binaries with white dwarf in 2MASS (Hoard+, 2007)
J/MNRAS/382/1377 : SDSS WD main-sequence binaries (Rebassa-Mansergas+, 2007)
J/A+A/496/191 : Spectral analysis of 636 SDSS WD-M binaries (Heller+, 2009)
J/MNRAS/402/620 : SDSS WD main-sequence binaries (Rebassa-Mansergas+, 2010)
J/MNRAS/424/1841 : SDSS-UKIDSS white dwarf-main sequence binaries (Liu+, 2012)
Byte-by-byte Description of file: table.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Seq [0/1801] Catalog number
6- 24 I19 --- SDSS ?=- SDSS DR7/DR8 objid
26- 30 I5 --- MJD SDSS mjd number
32- 35 I4 --- Plate SDSS plate number
37- 39 I3 --- Fiber SDSS fiberID
41- 59 I19 --- GALEX ?=0 GALEX object ID
61- 72 I12 --- UKIDSS ?=0 UKIDSS object ID
74- 83 F10.6 deg RAdeg SDSS Right ascension (J2000.0)
85- 94 F10.6 deg DEdeg SDSS Declination (J2000.0)
96-104 F9.5 deg RAgdeg ?=- GALEX Right ascension (J2000.0)
106-114 F9.5 deg DEgdeg ?=- GALEX Declination (J2000.0)
116-124 F9.5 deg RAudeg ?=- UKIDSS Right ascension (J2000.0)
126-134 F9.5 deg DEudeg ?=- UKIDSS Declination (J2000.0)
136-144 F9.5 deg RA2deg ?=- 2MASS Right ascension (J2000.0)
146-154 F9.5 deg DE2deg ?=- 2MASS Declination (J2000.0)
156-158 F3.1 --- Mt [0/9.5] M dwarf spectral type
160-161 A2 --- WD White dwarf type: DA or DB
164-169 I6 K Twd [6000/100000] Effective temperature of
White Dwarf
171-174 F4.2 [cm/s2] logg [5/9] Surface gravity of White Dwarf
176 I1 --- Ha [0/2] Hα Magnetic activity flag (1)
178-185 F8.3 0.1nm EWHa [-330/163] Hα equivalent width
187-193 F7.3 0.1nm e_EWHa Error on EWHa (limited to 103 at CDS)
195-200 F6.1 --- HaS/N [-4/108] Hα equivalent width S/N
202-210 E9.3 --- LHa/bol [-1.e-2/0.08] Hα luminosity relative to
bolometric luminosity
212-219 E8.2 --- e_LHa/bol Error on LHa/bol
221-226 F6.1 km/s VdM [-992/609] M dwarf radial velocity
228-232 F5.1 km/s e_VdM [4/620]?=- Error on Vd
234-239 F6.1 km/s Vwd [-325/566] WD radial velocity
241-245 F5.1 km/s e_Vwd [3/800]?=- Error on Vwd
247-252 F6.1 km/s Vsys [-450/800] System radial velocity
254-258 F5.1 km/s e_Vsys [2/451]?=- Error on Vsys
260-268 F9.3 AU Sep [0.002/100000] System separation
270-278 F9.3 AU e_Sep [0.001/]?=- Error on Sep
(limited to 105AU ∼ 0.5pc at CDS)
280-288 F9.2 d Per [0.04/] System orbital period
(limited to 106yr at CDS)
290-296 F7.1 pc D [0/11261]?=- Spectroscopic distance (2)
298-305 F8.1 pc Z [-2407/10441]?=- Height above Galactic plane
307-312 I6 K Tc [6000/91000]?=- WD effective temperature (3)
314-318 I5 K e_Tc [181/6884]?=- Error on Tc (3)
320-323 F4.2 [cm/s2] loggc [7.4/9]?=- WD gravity surface (3)
325-328 F4.2 [cm/s2] e_loggc [0.02/0.9]?=- Error on loggc (3)
330-335 F6.3 Msun Mc [0.45/1.21]?=- Estimated WD mass (3)
337-342 F6.3 Msun e_Mc [0.008/0.5]?=- Error on Mc (3)
344-350 F7.2 Myr tc [2/2211]?=- Estimated WD cooling time (3)
352-358 F7.2 Myr e_tc [0.1/1609]?=- Error on tc (3)
360-364 F5.1 --- S/Nc [1.4/108]?=- Estimated signal-to-noise ratio
366 I1 --- fc [1]?=- Candidate for very close pair
--------------------------------------------------------------------------------
Note (1): Defined in West et al. 2011AJ....141...97W 2011AJ....141...97W,, Cat. J/AJ/141/97.
Note (2): Spectroscopic parallax distances using the method from Bochanski et
et al., 2010AJ....139.2679B 2010AJ....139.2679B.
Note (3): WD cooling analysis from Catalan et al. 2008a. More precise than
values reported in WDType, WDTeff, and WDlogg.
--------------------------------------------------------------------------------
Acknowledgements:
Dylan Morgan, dpmorg(at)bu.edu
(End) Dylan Morgan [BU, United States], Patricia Vannier [CDS] 15-May-2015