THE EFFECTS OF CLOSE COMPANIONS (AND ROTATION) ON THE MAGNETIC ACTIVITY OF M DWARFS

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.

[1]  Sloan/Johnson‐Cousins/2MASS Color Transformations for Cool Stars , 2006, astro-ph/0611087.

[2]  E. Parker.  Hydromagnetic Dynamo Models , 1955 .

[3]  J. Bochanski,et al.  Using the Galactic Dynamics of M7 Dwarfs to Infer the Evolution of Their Magnetic Activity , 2006, astro-ph/0609001.

[4]  New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence , 2000, astro-ph/0004361.

[5]  D. Lin,et al.  On the nonaxisymmetric convective instabilities in accretion disks , 1993 .

[6]  Cambridge,et al.  The UKIRT Infrared Deep Sky Survey ZY JHK photometric system: passbands and synthetic colours , 2006, astro-ph/0601592.

[7]  L. Hillenbrand,et al.  Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics , 2008, 0807.1686.

[8]  A. Koenigl.  Disk accretion onto magnetic T Tauri stars , 1991 .

[9]  G. Skinner,et al.  The main-sequence rotation-colour relation in the Coma Berenices open cluster , 2009, 0908.0189.

[10]  N. O. Weiss,et al.  The relation between stellar rotation rate and activity cycle periods , 1984 .

[11]  J. Davenport,et al.  Hα Emission Variability in Active M Dwarfs , 2011, 1112.1411.

[12]  Ž. Ivezić,et al.  PERIODIC VARIABILITY OF LOW-MASS STARS IN SLOAN DIGITAL SKY SURVEY STRIPE 82 , 2011, 1102.1387.

[13]  G. Basri,et al.  Rotation and Activity in Mid-M to L Field Dwarfs , 2002, astro-ph/0201455.

[14]  E. Parker.  A solar dynamo surface wave at the interface between convection and nonuniform rotation , 1993 .

[15]  Andrew A. West,et al.  A First Look at White Dwarf-M Dwarf Pairs in the Sloan Digital Sky Survey , 2003, astro-ph/0302405.

[16]  M. Browning.  Simulations of Dynamo Action in Fully Convective Stars , 2007, 0712.1603.

[17]  F. D’Antona,et al.  Evolution of very low mass stars and brown dwarfs. I. The minimum main-sequence mass and luminosity. , 1985 .

[18]  Suzanne L. Hawley,et al.  New light on dark stars : red dwarfs, low-mass stars, brown dwarfs , 2000 .

[19]  et al,et al.  The Sloan Digital Sky Survey Photometric Camera , 1998, astro-ph/9809085.

[20]  S. Hawley,et al.  The Palomar/MSU Nearby Star Spectroscopic Survey.II.The Southern M Dwarfs and Investigation of Magnetic Activity , 1996 .

[21]  L. Althaus,et al.  White dwarf mass distribution in the SDSS , 2006 .

[22]  X. Delfosse,et al.  Large-scale magnetic topologies of late M dwarfs★: Magnetic topologies of late M dwarfs , 2010, 1005.5552.

[23]  P. Hartigan,et al.  Disk Accretion and Mass Loss from Young Stars , 1995 .

[24]  O. C. Wilson,et al.  Calcium Emission Intensities as Indicators of Stellar Age , 1970 .

[25]  J. Bochanski,et al.  M DWARFS IN SLOAN DIGITAL SKY SURVEY STRIPE 82: PHOTOMETRIC LIGHT CURVES AND FLARE RATE ANALYSIS , 2009, 0906.2030.

[26]  S. Dye,et al.  The WFCAM Science Archive , 2006, 0711.3593.

[27]  A. Skumanich,et al.  TIME SCALES FOR Ca II EMISSION DECAY, ROTATIONAL BRAKING, AND LITHIUM DEPLETION. , 1971 .

[28]  L. Schmidtobreick,et al.  Multiple emission line components in detached post-common-envelope binaries , 2011, 1106.1929.

[29]  J. Papaloizou,et al.  The response of a gaseous disc to a binary encounter , 1995 .

[30]  M. Giampapa,et al.  High-Resolution H alpha Observations of M Dwarf Stars: Implications for Stellar Dynamo Models and Stellar Kinematic Properties at Faint Magnitudes , 1986 .

[31]  C. Clarke,et al.  Magnetic braking of T Tauri stars , 1995, astro-ph/9512018.

[32]  A. Schwope,et al.  Post-common envelope binaries from SDSS – XIV. The DR7 white dwarf–main-sequence binary catalogue , 2011, 1110.1000.

[33]  William H. Press,et al.  Book-Review - Numerical Recipes in Pascal - the Art of Scientific Computing , 1989 .

[34]  Leon Golub,et al.  Relations among stellar X-ray emission observed from Einstein, stellar rotation and bolometric luminosity , 1981 .

[35]  J. Bochanski,et al.  CONSTRAINING THE AGE–ACTIVITY RELATION FOR COOL STARS: THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 5 LOW-MASS STAR SPECTROSCOPIC SAMPLE , 2007, 0712.1590.

[36]  S. Hawley,et al.  Updated Colors for Cool Stars in the Sloan Digital Sky Survey , 2005 .

[37]  James Liebert,et al.  A Catalog of Spectroscopically Selected Close Binary Systems from the Sloan Digital Sky Survey Data Release Four , 2006 .

[38]  D. C. Barry.  The Chromospheric Age Dependence of the Birthrate, Composition, Motions, and Rotation of Late F and G Dwarfs within 25 Parsecs of the Sun , 1988 .

[39]  V. University,et al.  The Ages of Very Cool Hydrogen-rich White Dwarfs , 2000, astro-ph/0007031.

[40]  UK,et al.  The photometric structure of the inner Galaxy , 1997 .

[41]  J. Gunn,et al.  CHROMOSPHERIC VARIABILITY IN SLOAN DIGITAL SKY SURVEY M DWARFS. II. SHORT-TIMESCALE Hα VARIABILITY , 2009, 0911.2712.

[42]  M. Pinsonneault,et al.  Angular Momentum Evolution of Stars in the Orion Nebula Cluster , 2001, astro-ph/0107061.

[43]  S. Hawley,et al.  The Palomar/MSU Nearby Star Spectroscopic Survey. III. Chromospheric Activity, M Dwarf Ages, and the Local Star Formation History , 2002, astro-ph/0203499.

[44]  J. Papaloizou,et al.  On the stability of an accretion disc containing a toroidal magnetic field: the effect of resistivity , 1997 .

[45]  N. Pizzolato,et al.  The stellar activity-rotation relationship revisited: Dependence of saturated and non-saturated X-ray emission regimes on stellar mass for late-type dwarfs ? , 2003 .

[46]  I. Ribas,et al.  THE EFFECT OF MAGNETIC ACTIVITY ON LOW-MASS STARS IN ECLIPSING BINARIES , 2010, 1005.5720.

[47]  Andrew A. West,et al.  M DWARF FLARES FROM TIME-RESOLVED SLOAN DIGITAL SKY SURVEY SPECTRA , 2010 .

[48]  S. Hawley,et al.  χ Values for Blue Emission Lines in M Dwarfs , 2008, 0812.1221.

[49]  K. Stassun,et al.  The Effect of Binarity on Stellar Rotation: Beyond the Reach of Tides , 2007, 0707.1087.

[50]  The First Direct Measurements of Surface Magnetic Fields on Very Low Mass Stars , 2006, astro-ph/0610365.

[51]  David R. Soderblom,et al.  The Ages of Stars , 2007, 1003.6074.

[52]  I. Ribas,et al.  The initial–final mass relationship of white dwarfs revisited: effect on the luminosity function and mass distribution , 2008, 0804.3034.

[53]  A. Schwope,et al.  Post common envelope binaries from SDSS. XII : the orbital period distribution , 2011, 1109.6662.

[54]  S. Meibom,et al.  A Robust Measure of Tidal Circularization in Coeval Binary Populations: The Solar-Type Spectroscopic Binary Population in the Open Cluster M35 , 2004, astro-ph/0412147.

[55]  P. Bergeron,et al.  SPECTROSCOPIC ANALYSIS OF DA WHITE DWARFS: STARK BROADENING OF HYDROGEN LINES INCLUDING NONIDEAL EFFECTS , 2009, 0902.4182.

[56]  Ž. Ivezić,et al.  A Second Stellar Color Locus: a Bridge from White Dwarfs to M stars , 2004, astro-ph/0403218.

[57]  C. Copperwheat,et al.  Post Common Envelope Binaries from SDSS. XV: Accurate stellar parameters for a cool 0.4-solar mass white dwarf and a 0.16-solar mass M-dwarf in a 3 hour eclipsing binary , 2011, 1109.1171.

[58]  Pierre Bergeron,et al.  Calibration of Synthetic Photometry Using DA White Dwarfs , 2005 .

[59]  P. Kerry,et al.  A precision study of two eclipsing white dwarf plus M dwarf binaries , 2011, 1111.5694.

[60]  B. Goldman,et al.  A CATALOG OF ROTATION AND ACTIVITY IN EARLY-M STARS , 2012, 1201.5774.

[61]  G. Basri,et al.  On the magnetic topology of partially and fully convective stars , 2009, 0901.1659.

[62]  S. Barnes,et al.  ANGULAR MOMENTUM LOSS FROM COOL STARS: AN EMPIRICAL EXPRESSION AND CONNECTION TO STELLAR ACTIVITY , 2010, 1104.2350.

[63]  G. Fontaine,et al.  On the influence of the convective efficiency on the determination of the atmospheric parameters of DA white dwarfs , 1992 .

[64]  B. Gaensicke,et al.  The age, life expectancy, and space density of Post Common Envelope Binaries , 2003, astro-ph/0305531.

[65]  G. Marcy,et al.  ROTATION AND MAGNETIC ACTIVITY IN A SAMPLE OF M-DWARFS , 2010 .

[66]  C. Prieto,et al.  The initial-final mass relationship from white dwarfs in common proper motion pairs , 2007, 0710.1542.

[67]  M. Ossendrijver,et al.  The solar dynamo , 2003 .

[68]  M. G. Rawlings,et al.  The United Kingdom Infrared Telescope Infrared Deep Sky Survey First Data Release , 2007 .

[69]  W. Y. Chau,et al.  Theoretical models of low-mass stars and brown dwarfs. I. The lower main sequence , 1989 .

[70]  K. Abazajian,et al.  THE SEVENTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY , 2008, 0812.0649.

[71]  J. Najita,et al.  Magnetocentrifugally driven flows from young stars and disks. 2: Formulation of the dynamical problem , 1994 .

[72]  J. Bochanski,et al.  THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 7 SPECTROSCOPIC M DWARF CATALOG. II. STATISTICAL PARALLAX ANALYSIS , 2011 .

[73]  M. Fukugita,et al.  The Sloan Digital Sky Survey Photometric System , 1996 .

[74]  Martin Cohen,et al.  The displacement of the sun from the galactic plane using IRAS and faust source counts , 1995 .

[75]  A. Szalay,et al.  The Galaxy Evolution Explorer: A Space Ultraviolet Survey Mission , 2004, astro-ph/0411302.

[76]  Norbert Christlieb,et al.  High-resolution UVES/VLT spectra of white dwarfs observed for the ESO SN Ia progenitor survey (SPY). I. ?;?? , 2001 .

[77]  Andrew A. West,et al.  The χ Factor: Determining the Strength of Activity in Low‐Mass Dwarfs , 2004, astro-ph/0410422.

[78]  T. Marsh,et al.  Post-common-envelope binaries from SDSS – V. Four eclipsing white dwarf main-sequence binaries , 2008, 0812.2510.

[79]  B. Gaensicke,et al.  Observations of three pre-cataclysmic variables from the Edinburgh-Cape blue object survey , 2009, 0908.1078.

[80]  Ansgar Reiners,et al.  Chromospheric Activity, Rotation, and Rotational Braking in M and L Dwarfs , 2008, 0805.1059.

[81]  A. Rebassa-Mansergas,et al.  Post-common envelope binaries from SDSS - VII. A catalogue of white dwarf-main sequence binaries , 2009, 0910.4406.

[82]  The UKIRT Infrared Deep Sky Survey Second Data Release , 2007, astro-ph/0703037.

[83]  Large-scale alpha^2-dynamo in low-mass stars and brown dwarfs , 2005, astro-ph/0510075.

[84]  M. Marley,et al.  From Giant Planets to Cool Stars , 1999 .

[85]  S. Lubow,et al.  Dynamics of binary-disk interaction. 1: Resonances and disk gap sizes , 1994 .

[86]  G. Basri,et al.  A VOLUME-LIMITED SAMPLE OF 63 M7–M9.5 DWARFS. II. ACTIVITY, MAGNETISM, AND THE FADE OF THE ROTATION-DOMINATED DYNAMO , 2009, 0912.4259.

[87]  Roy Ostensen,et al.  Spectral analysis of 636 white dwarf-M star binaries from the sloan digital sky survey , 2009 .

[88]  Keivan G. Stassun,et al.  SLOAN LOW-MASS WIDE PAIRS OF KINEMATICALLY EQUIVALENT STARS (SLoWPoKES): A CATALOG OF VERY WIDE, LOW-MASS PAIRS , 2010, 1004.2755.

[89]  D. Soderblom,et al.  The chromospheric emission-age relation for stars of the lower main sequence and its implications for the star formation rate , 1991 .

[90]  A. West,et al.  A FIRST LOOK AT ROTATION IN INACTIVE LATE-TYPE M DWARFS , 2008, 0812.1220.

[91]  Saurav Dhital,et al.  THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 7 SPECTROSCOPIC M DWARF CATALOG. I. DATA , 2011, 1101.1082.

[92]  Andrew A. West,et al.  Low-Mass Dwarf Template Spectra from the Sloan Digital Sky Survey , 2006, astro-ph/0610639.

[93]  J. Brinkmann,et al.  Spectroscopic Properties of Cool Stars in the Sloan Digital Sky Survey: An Analysis of Magnetic Activity and a Search for Subdwarfs , 2004, astro-ph/0403486.

[94]  William H. Press,et al.  Numerical recipes in FORTRAN (2nd ed.): the art of scientific computing , 1992 .

[95]  David A. Golimowski,et al.  ERRATUM: “THE LUMINOSITY AND MASS FUNCTIONS OF LOW-MASS STARS IN THE GALACTIC DISK. II. THE FIELD” (2010, AJ, 139, 2679) , 2010, 1004.4002.

[96]  X. Delfosse,et al.  Large-scale magnetic topologies of late M dwarfs⋆ , 2008, 0808.1423.

[97]  J. Gizis,et al.  A Search for Variability in the Active T Dwarf 2MASS 1237+6526 , 2002, astro-ph/0201382.

[98]  T. Greene,et al.  SPIN EVOLUTION OF ACCRETING YOUNG STARS. II. EFFECT OF ACCRETION-POWERED STELLAR WINDS , 2011, 1111.6407.

[99]  S. Barnes.  Accepted for publication in The Astrophysical Journal Ages for illustrative field stars using gyrochronology: viability, limitations and errors , 2022 .

[100]  S. Sofia,et al.  On the Origin of the Ultrafast Rotators in Young Star Clusters , 1996 .

[101]  M. Skrutskie,et al.  The Two Micron All Sky Survey (2MASS) , 2006 .

[102]  C. Blake,et al.  THE CLOSE BINARY FRACTION OF DWARF M STARS , 2011, 1110.4016.

[103]  I. Ribas,et al.  Stellar chronology with white dwarfs in wide binaries , 2008, Proceedings of the International Astronomical Union.

[104]  Michael C. Liu,et al.  ON THE DISTRIBUTION OF ORBITAL ECCENTRICITIES FOR VERY LOW-MASS BINARIES , 2011, 1103.5744.

[105]  X. Delfosse,et al.  Large-scale magnetic topologies of early M dwarfs , 2008, 0809.0269.

[106]  M. Tamura,et al.  A near-infrared survey of Miras and the distance to the Galactic Centre , 2009, 0907.2761.

[107]  M. Irwin,et al.  The UKIRT Infrared Deep Sky Survey (UKIDSS) , 2006, astro-ph/0604426.