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Chromospheric Activities and Kinematics for Solar Type Dwarfs and Subgiants: Analysis of the Activity Distribution and the AVR | | James S. Jenkins
; F. Murgas
; P. Rojo
; Hugh R.A. Jones
; Avril C. Day-Jones
; Matias I. Jones
; James R.A. Clarke
; Maria-Teresa Ruiz
; David J. Pinfield
; | | Date: |
3 Mar 2011 | | Abstract: | In this work we present chromospheric activity indices, kinematics,
radial-velocities and rotational velocities for more than 850 FGK-type dwarfs
and subgiant stars in the southern hemisphere and test how best to calibrate
and measure S-indices from echelle spectra. We confirm the bimodal distribution
of chromospheric activities for such stars and highlight the role that the more
active K-dwarfs play in biasing the number of active stars. We show that the
age-activity relationship does appear to continue to ages older than the Sun if
we simply compare main sequence stars and subgiant stars, with an offset of
around 2.5 Gyrs between the peaks of both distributions. Also we show evidence
for an increased spin-down timescale for cool K dwarfs compared with earlier F
and G type stars. In addition, we show how kinematics can be used to preselect
inactive stars for future planet search projects. We see the well known trend
between projected rotational velocity and activity, however we also find a
correlation between kinematic space velocity and chromospheric activity. It
appears that after the Vaughan-Preston gap there is a quick step function in
the kinematic space motion towards a significantly larger spread in velocities.
We speculate on reasons for this correlation and provide some model scenarios
to describe the bimodal activity distribution through magnetic saturation,
residual low level gas accretion or accretion by the star of planets or
planetesimals. Finally, we provide a new empirical measurement for the disk
heating law, using the latest age-activity relationships to reconstruct the
age-velocity distribution for local disk stars. We find a value of
0.337+/-0.045 for the exponent of this power law (i.e. sigma_tot proportional
to t^0.337), in excellent agreement with those found using isochrone fitting
methods and with theoretical disk heating models. [Abridged] | | Source: | arXiv, 1103.0584 | | Services: | Forum | Review | PDF | Favorites | |
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