Evidence for very nearby hidden white dwarfs

We report the discovery of a tertiary component to the prominent and nearby (d = 14 pc) visual binary alpha Fornacis. The new invisible component is part of a 4-d short-period Ba-Bb subsystem, whose K-type alpha For Ba primary shows a striking [Ba/Fe] = +0.26 dex overabundance, at variance with a close to solar [Ba/Fe] = +0.04 dex abundance for its distant visual companion alpha For A. For the even nearer (d = 8 pc) multiple star xi Ursae Majoris and its alike 4-d Ba-Bb subsystem, we similarly find [Ba/Fe] = +0.37 dex for its G-type xi UMa Ba primary, compared to a significantly lower [Ba/Fe] = +0.12 dex for the visual companion xi UMa A. In both cases, the differential barium enrichment is direct evidence for short-period white dwarf systems and the creation of blue straggler stars through mass transfer and wind accretion, for their close and distant companions, respectively. These findings also imply that conventional stellar age datings for both alpha For and xi UMa are likely not reliable.

[1]  R. Chini,et al.  MULTIPLICITY AMONG F-TYPE STARS. II. , 2015 .

[2]  R. Chini,et al.  ON THE AGE OF GLIESE 86 , 2014 .

[3]  E. Sion,et al.  THE WHITE DWARFS WITHIN 25 pc OF THE SUN: KINEMATICS AND SPECTROSCOPIC SUBTYPES , 2014, 1401.4989.

[4]  M. Burleigh,et al.  Where are all the Sirius-like binary systems? , 2013, 1307.8047.

[5]  R. Chini,et al.  MULTIPLICITY AMONG F-TYPE STARS , 2012 .

[6]  L. Ferrario.  Constraints on the pairing properties of main-sequence stars from observations of white dwarfs in binary systems , 2012, 1209.1427.

[7]  C. Corbally,et al.  FIRST DIRECT EVIDENCE THAT BARIUM DWARFS HAVE WHITE DWARF COMPANIONS , 2011 .

[8]  E. Sion,et al.  THE WHITE DWARFS WITHIN 20 PARSECS OF THE SUN: KINEMATICS AND STATISTICS , 2009, 0910.1288.

[9]  S. Rappaport,et al.  THE PAST AND FUTURE HISTORY OF REGULUS , 2009, 0904.0395.

[10]  D. Baade,et al.  A Spectroscopic Orbit for Regulus , 2008, 0806.3473.

[11]  K. Fuhrmann.  Nearby stars of the Galactic disc and halo – IV , 2008 .

[12]  C. Pereira.  Spectroscopic Verification of Barium Dwarf Candidates: The Analysis of HD 8270, HD 13551, and HD 22589 , 2005 .

[13]  J. B. Laird,et al.  Metal-poor Field Blue Stragglers: More Evidence for Mass Transfer , 2004, astro-ph/0412110.

[14]  Bruce W. Carney,et al.  A Survey of Proper-Motion Stars. XVI. Orbital Solutions for 171 Single-lined Spectroscopic Binaries , 2002 .

[15]  B. Carney,et al.  A Survey of Proper-Motion Stars. XIV. Spectroscopic Binaries among Metal-poor Field Blue Stragglers , 2001 .

[16]  Peter P. Eggleton,et al.  Orbital Evolution in Binary and Triple Stars, with an Application to SS Lacertae , 2001, astro-ph/0104126.

[17]  Wolfgang Voges,et al.  THE ROSAT ALL-SKY SURVEY CATALOGUE OF THE NEARBY STARS , 1999 .

[18]  G. P. D. Mello,et al.  Copper and Barium Abundances in the Ursa Major Moving Group , 1999, astro-ph/9901209.

[19]  Thomas Gehren,et al.  FOCES - a fibre optics Cassegrain échelle spectrograph , 1998 .

[20]  N. Hambly,et al.  WD 0346+246: A Very Low Luminosity, Cool Degenerate in Taurus , 1997 .

[21]  R. Jeffries,et al.  Wind-accretion induced rapid rotation and a new class of active star , 1996 .

[22]  R. Di Stefano,et al.  The relation between white dwarf mass and orbital period in wide binary radio pulsars , 1995 .

[23]  R. Mcclure,et al.  The binary nature of the barium stars. , 1980 .

[24]  F. R. Harnden,et al.  X-ray spectra and the rotation-activity connection of RS Canum Venaticorum binaries , 1986 .