4 research outputs found
A Radial velocity survey of spatially resolved young, low-mass binaries
The identification and characterisation of low-mass binaries is of importance for a range of astrophysical investigations. Low-mass binaries in young (∼10–100 Myr) moving groups (YMGs) in the solar neighborhood are of particular significance as they provide unique opportunities to calibrate stellar models and evaluate the ages and coevality of the groups themselves. Low-mass M-dwarfs have pre-main sequence life times on the order of ∼100 Myr and therefore are continually evolving along a mass-luminosity track throughout the YMG phase, providing ideal laboratories for precise isochronal dating, if a model-independent dynamical mass can be measured. AstraLux lucky imaging multiplicity surveys have recently identified hundreds of new YMG low-mass binaries, where a subsample of M-dwarf multiples have estimated orbital periods less than 50 yr. We have conducted a radial velocity survey of a sample of 29 such targets to complement the astrometric data. This will allow enhanced orbital determinations and precise dynamical masses to be derived in a shorter timeframe than possible with astrometric monitoring alone, and allow for a more reliable isochronal analysis. Here we present radial velocity measurements derived for our sample over several epochs. We report the detection of the three-component spectroscopic multiple 2MASS J05301858-5358483, for which the C component is a new discovery, and forms a tight pair with the B component. Originally identified as a YMG member, we find that this system is a likely old field interloper, whose high chromospheric activity level is caused by tidal spin-up of the tight BC pair. Two other triple systems with a tight pair exist in the sample, 2MASS J04244260-0647313 (previously known) and 2MASS J20163382-0711456, but for the rest of the targets we find that additional tidally synchronized companions are highly unlikely, providing further evidence that their high chromospheric activity levels are generally signatures of youth
Radial velocity survey of spatially resolved young, low-mass binaries
The identification and characterisation of low-mass binaries is of importance
for a range of astrophysical investigations. Low-mass binaries in young
( Myr) moving groups (YMGs) are of particular significance as
they provide unique opportunities to calibrate stellar models and evaluate the
ages and coevality of the groups themselves. Low-mass M-dwarfs have pre-main
sequence life times on the order of Myr and therefore are continually
evolving along a mass-luminosity track throughout the YMG phase, providing
ideal laboratories for precise isochronal dating, if a model-independent
dynamical mass can be measured. AstraLux lucky imaging multiplicity surveys
have recently identified hundreds of new YMG low-mass binaries, where a
subsample of M-dwarf multiples have estimated orbital periods less than 50
years. We have conducted a radial velocity survey of a sample of 29 such
targets to complement the astrometric data. This will allow enhanced orbital
determinations and precise dynamical masses to be derived in a shorter
timeframe than possible with astrometric monitoring alone, and allow for a more
reliable isochronal analysis. Here we present radial velocity measurements for
our sample over several epochs. We report the detection of the three-component
spectroscopic multiple 2MASS J05301858-5358483, for which the C component is a
new discovery, and forms a tight pair with the B component. Originally
identified as a YMG member, we find that this system is a likely old field
interloper, whose high chromospheric activity level is caused by tidal spin-up
of the tight BC pair. Two other triple systems with a tight pair exist in the
sample, but for the rest of the targets we find that additional tidally
synchronized companions are highly unlikely, providing further evidence that
their high chromospheric activity levels are generally signatures of youth.Comment: 15 pages, 9 figure
HD 66051: the first eclipsing binary hosting an early-type magnetic star
International audienceEarly-type magnetic stars are rarely found in close binary systems. No such objects were known in eclipsing binaries prior to this study. Here we investigated the eclipsing, spectroscopic double-lined binary HD 66051, which exhibits out-of-eclipse photometric variations suggestive of surface brightness inhomogeneities typical of early-type magnetic stars. Using a new set of high-resolution spectropolarimetric observations, we discovered a weak magnetic field on the primary and found intrinsic, element-dependent variability in its spectral lines. The magnetic field structure of the primary is dominated by a nearly axisymmetric dipolar component with a polar field strength Bd ≈ 600 G and an inclination with respect to the rotation axis of βd = 13°. A weaker quadrupolar component is also likely to be present. We combined the radial velocity measurements derived from our spectra with archival optical photometry to determine fundamental masses (3.16 and 1.75 M⊙) and radii (2.78 and 1.39 R⊙) with a 1-3 per cent precision. We also obtained a refined estimate of the effective temperatures (13000 and 9000 K) and studied chemical abundances for both components with the help of disentangled spectra. We demonstrate that the primary component of HD 66051 is a typical late-B magnetic chemically peculiar star with a non-uniform surface chemical abundance distribution. It is not an HgMn-type star as suggested by recent studies. The secondary is a metallic-line star showing neither a strong, global magnetic field nor intrinsic spectral variability. Fundamental parameters provided by our work for this interesting system open unique possibilities for probing interior structure, studying atomic diffusion, and constraining binary star evolution