J/ApJ/873/69 Radial velocities of the EB M-dwarf YYGem (Kochukhov+, 2019)
Magnetic field of the eclipsing M-dwarf binary YY Gem.
Kochukhov O., Shulyak D.
<Astrophys. J., 873, 69 (2019)>
=2019ApJ...873...69K 2019ApJ...873...69K
ADC_Keywords: Binaries, eclipsing; Radial velocities; Spectra, optical
Keywords: binaries: eclipsing; stars: activity; stars: fundamental parameters;
stars: individual (YY Gem); stars: magnetic field
Abstract:
YY Gem is a short-period eclipsing binary system containing two nearly
identical, rapidly rotating, very active early M dwarfs. This binary
represents an important benchmark system for calibrating empirical
relations between fundamental properties of low-mass stars and for
testing theories of interior structure and evolution of these objects.
Both components of YY Gem exhibit inflated radii, which has been
attributed to poorly understood magnetic activity effects. Despite a
long history of magnetic activity studies of this system, no direct
magnetic field measurements have been made for it. Here we present a
comprehensive characterization of the surface magnetic field in both
components of YY Gem. We reconstructed the global field topologies
with the help of a tomographic inversion technique applied to
high-resolution spectropolarimetric data. This analysis revealed
moderately complex global fields with a typical strength of 200-300G
and anti-aligned dipolar components. A complementary Zeeman
intensification analysis of the disentangled intensity spectra showed
that the total mean field strength reaches 3.2-3.4kG in both
components of YY Gem. We used these results together with other recent
magnetic field measurements of M dwarfs to investigate the relation
between the global and small-scale fields in these stars. We also
assessed predictions of competing magnetoconvection interior structure
models developed for YY Gem, finding that only one of them anticipated
the surface field strength compatible with our observations. Results
of our starspot mapping of YY Gem do not support the alternative
family of theoretical stellar models, which attempts to explain the
radius inflation by postulating a large spot filling factor.
Description:
Our investigation of YY Gem is based on a set of archival
high-resolution spectropolarimetric observations obtained with the
ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope
(CFHT). This instrument provides simultaneous coverage of the
370-1050nm wavelength interval at the resolving power of R=65000.
YY Gem was observed in the circular polarization mode, in the period
from 2012 January 4 to 17.
We have used the CFHT Science Archive interface to retrieve 36 Stokes
V observations and 144 Stokes I spectra corresponding to individual
polarimetric subexposures. These data were reprocessed.
Objects:
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RA (ICRS) DE Designation(s) (Per)
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07 34 37.45 +31 52 10.2 YY Gem = V* YY Gem (P=0.814282212)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 38 144 Radial velocity measurements of the YY Gem components
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See also:
B/cfht : Log of CFHT Exposures (CADC, 1979-)
IX/10 : ROSAT All-Sky Bright Source Catalogue (1RXS) (Voges+ 1999)
J/MNRAS/390/545 : Magnetic field & velocity of early M dwarfs (Donati+, 2008)
J/A+A/478/507 : Distances & atmospheric data of MSU stars (Morales+, 2008)
J/MNRAS/390/567 : Magnetic field and velocity of mid M dwarfs (Morin+, 2008)
J/ApJ/691/1400 : Absolute properties of CM Dra (Morales+, 2009)
J/ApJ/707/671 : IM Vir BVRI photometry & radial velocities (Morales+, 2009)
J/MNRAS/407/2269 : Polarisation of a sample of late M dwarfs (Morin+, 2010)
J/other/A+ARV/18.67 : Accurate masses and radii of normal stars (Torres+, 2010)
J/ApJ/765/126 : Star spot models for M-dwarfs in NGC 2516 (MacDonald+, 2013)
J/MNRAS/444/3517 : BCool survey of solar-type stars (Marsden+ 2014)
J/MNRAS/441/2361 : Stellar magnetism, age and rotation (Vidotto+, 2014)
J/AJ/149/131 : Galactic nearby main-sequence star parameters (Eker+, 2015)
J/AJ/152/180 : Bolometric fluxes of EBs in Tycho-2 (Stassun+, 2016)
J/A+A/600/A30 : Limb-darkening for TESS satellite (Claret, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 F10.4 d HJD [55930.8/55944.1] Reduced Heliocentric Julian
Date of mid-exposure; HJD-2400000
12- 16 F5.3 --- Phase [0/1] Orbital phase
18- 20 I3 --- SNR [22/318] Signal-to-noise ratio of spectrum
22- 28 F7.2 km/s HRV-A [-119.05/124.05] Heliocentric radial velocity,
component A
30- 36 F7.2 km/s HRV-B [-118.92/123.22] Heliocentric radial velocity,
component B
38- 38 A1 --- ofit [yn] Used for the orbital fit
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Aug-2020