J/A+A/627/A97 Early disc dispersal in close binaries (Messina, 2019)
Evidence from stellar rotation for early disc dispersal owing to close
companions.
Messina S.
<Astron. Astrophys. 627, A97 (2019)>
=2019A&A...627A..97M 2019A&A...627A..97M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; Stars, double and multiple ; Stars, masses
Keywords: stars: low-mass - stars: rotation - binaries: close -
open clusters and associations: individual: Upper Scorpius -
stars: pre-main sequence - stars: variables: T Tauri, Herbig Ae/Be
Abstract:
Young (<600Myr) low-mass stars (M≲1M☉) of equal mass exhibit a
distribution of rotation periods. At the very early phases of stellar
evolution, this distribution is set by the star-disc locking
mechanism, which forces stars to rotate at the same rate as the inner
edge of the disc. The primordial disc lifetime and consequently the
duration of the disc-locking mechanism, can be significantly shortened
by the presence of a close companion, making the rotation period
distribution of close binaries different from that of either single
stars or wide binaries.
We use new data to investigate and better constrain the range of ages,
the components separation, and the mass ratio dependence at which the
rotation period distribution has been significantly affected by the
disc dispersal that is enhanced by close companions.
We select a sample of close binaries in the Upper Scorpius association
(age∼8Myr) whose components have measured the separation and the
rotation periods and compare their period distribution with that of
coeval stars that are single stars.
We find that components of close binaries have, on average, rotation
periods that are shorter than those of single stars. More precisely,
binaries with approximately equal-mass components (0.9≤M2/M1≤1.0)
have rotation periods that are shorter than those of single stars by
∼0.4d on average; the primary and secondary components of binaries
with smaller mass ratios (0.8<M2/M1<0.9) have rotation periods that
are shorter than those of single stars by ∼1.9d and ∼1.0d on average,
respectively. A comparison with the older 25-Myr β Pictoris
association shows that whereas in the latter, all close binaries with
projected separation ρ≤80AU rotate faster than single stars, in
the Upper Scorpius this is only the case for about 70% of stars.
We interpret the enhanced rotation in close binaries with respect to
single stars as the consequence of an early disc dispersal induced by
the presence of close companions. The enhanced rotation suggests that
disc dispersal timescales are longest for single stars and shorter for
close binaries.
Description:
We provide the basic parameters of the analysed close binaries. A few
quantities are taken from the paper by Tokovinin & Briceno
(2018AJ....156..138T 2018AJ....156..138T), that is the mass of primary components, I
magnitude, magnitude difference between the components, and projected
separation; other quantities are taken from Rebull et al. (2018, Cat.
J/AJ/155/196), that is (V-K)0 color of the system, rotation period
of the primary and secondary components. Finally, (V-K)0 colors of
primaries and secondaries, and the mass of secondary component are
computed in this study.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 104 49 Basic parameters of close binaries
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See also:
J/ApJS/224/2 : K2 EPIC stellar properties for 138600 targets (Huber+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [EPIC]
6- 14 I9 --- EPIC EPIC identification number
19- 22 F4.2 mag (V-K)0 De-reddened color of the integrated system
28- 31 F4.2 mag (V-K)0P De-reddened color of the primary component
37- 40 F4.2 mag (V-K)0S De-reddened color of the secondary component
46- 49 F4.2 Msun M1 Mass of primary component (solar unit)
55- 58 F4.2 Msun M2 Mass of secondary component (solar unit)
63- 67 F5.2 d P1 Rotation period of primary component
72- 76 F5.2 d P2 Rotation period of secondary component
81- 85 F5.2 mag Imag I magnitude of primary component
91- 94 F4.2 mag dImag I mag difference between components
99-104 F6.2 AU Sep Projected separation between the components
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Acknowledgements:
Sergio Messina, sergio.messina(at)inaf.it
(End) Sergio Messina [INAF, Italy], Patricia Vannier [CDS] 03-Jul-2019