The β Pictoris association low-mass members: Membership assessment, rotation period distribution, and dependence on multiplicity⋆
1 INAF−Catania Astrophysical Observatory, via S. Sofia 78, 95123 Catania, Italy
2 Universitá di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, via S. Sofia 78, 95123 Catania, Italy
3 Canada-France-Hawaii Telescope, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743, USA
4 INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
5 Instituto de Astronomía y Física del Espacio (IAFE-CONICET), 1053 Buenos Aires, Argentina
6 Departamento de Física, FCEN-Universidad de Buenos Aires, 1053 Buenos Aires, Argentina
7 Department of Physics, College of Science, Guizhou University, 550025 Guiyang, PR China
8 Research Institute Crimean Astrophysical Observatory, 298409 Nauchny, Crimea
9 York Creek Observatory, Georgetown, Tasmania, Australia
10 Remote Observatory Atacama Desert (ROAD), Vereniging Voor Sterrenkunde (VVS), Oude Bleken 12, 2400 Mol, Belgium
11 American Association of Variable Star Observers (AAVSO), Cambridge, MA 02138, USA
Received: 16 January 2017
Accepted: 5 July 2017
Context. Low-mass members of young loose stellar associations and open clusters exhibit a wide spread of rotation periods. Such a spread originates from the distributions of masses and initial rotation periods. However, multiplicity can also play a significant role.
Aims. We aim to investigate the role played by physical companions in multiple systems in shortening the primordial disk lifetime, anticipating the rotation spin up with respect to single stars.
Methods. We have compiled the most extensive list to date of low-mass bona fide and candidate members of the young 25-Myr β Pictoris association. We have measured from our own photometric time series or from archival time series the rotation periods of almost all members. In a few cases the rotation periods were retrieved from the literature. We used updated UVWXYZ components to assess the membership of the whole stellar sample. Thanks to the known basic properties of most members we built the rotation period distribution distinguishing between bona fide members and candidate members and according to their multiplicity status.
Results. We find that single stars and components of multiple systems in wide orbits (>80 AU) have rotation periods that exhibit a well defined sequence arising from mass distribution with some level of spread likely arising from initial rotation period distribution. All components of multiple systems in close orbits (<80 AU) have rotation periods that are significantly shorter than their equal-mass single counterparts. For these close components of multiple systems a linear dependence of rotation rate on separation is only barely detected. A comparison with the younger 13 Myr h Per cluster and with the older 40-Myr open clusters and stellar associations NGC 2547, IC 2391, Argus, and IC 2602 and the 130-Myr Pleiades shows that whereas the evolution of F-G stars is well reproduced by angular momentum evolution models, this is not the case for the slow K and early-M stars. Finally, we find that the amplitude of their light curves is correlated neither with rotation nor with mass.
Conclusions. Once single stars and wide components of multiple systems are separated from close components of multiple systems, the rotation period distributions exhibit a well defined dependence on mass that allows us to make a meaningful comparison with similar distributions of either younger or older associations and clusters. Such cleaned distributions allow us to use the stellar rotation period meaningfully as an age indicator for F and G type stars.
Key words: stars: activity / stars: late-type / starspots / binaries: close / open clusters and associations: individual: βPictoris / stars: rotation
Tables 2 and 3 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A3
© ESO, 2017