J/ApJ/746/36 RV standard deviation in the M2K survey (Gaidos+, 2012)
On the nature of small planets around the coolest Kepler stars.
Gaidos E., Fischer D.A., Mann A.W., Lepine S.
<Astrophys. J., 746, 36 (2012)>
=2012ApJ...746...36G 2012ApJ...746...36G
ADC_Keywords: Radial velocities ; Stars, nearby ; Planets
Keywords: astrobiology - planetary systems - techniques: radial velocities
Abstract:
We constrain the densities of Earth- to Neptune-size planets around
very cool (Te=3660-4660K) Kepler stars by comparing 1202 Keck/HIRES
radial velocity measurements of 150 nearby stars to a model based on
Kepler candidate planet radii and a power-law mass-radius relation.
Our analysis is based on the presumption that the planet populations
around the two sets of stars are the same. The model can reproduce the
observed distribution of radial velocity variation over a range of
parameter values, but, for the expected level of Doppler systematic
error, the highest Kolmogorov-Smirnov probabilities occur for a
power-law index α~4, indicating that rocky-metal planets
dominate the planet population in this size range. A single population
of gas-rich, low-density planets with α=2 is ruled out unless
our Doppler errors are ≥5m/s, i.e., much larger than expected based
on observations and stellar chromospheric emission. If small planets
are a mix of γ rocky planets (α=3.85) and 1-γ
gas-rich planets (α=2), then γ>0.5 unless Doppler errors
are ≥4m/s. Our comparison also suggests that Kepler's detection
efficiency relative to ideal calculations is less than unity. One
possible source of incompleteness is target stars that are
misclassified subgiants or giants, for which the transits of small
planets would be impossible to detect. Our results are robust to
systematic effects, and plausible errors in the estimated radii of
Kepler stars have only moderate impact.
Description:
The M2K survey has obtained 1406 RV measurements of 172 late K and
early M dwarfs, with at least three measurements for each star. Stars
were selected from the SUPERBLINK proper motion catalog (Lepine &
Shara 2005, Cat. I/298) based on V-J color and parallax - or
proper-motion-based absolute magnitudes (Lepine & Gaidos 2011,
Cat. J/AJ/142/138), and confirmed by moderate-resolution spectroscopy.
Targets have apparent magnitudes of V=8-12 and median R'HK=-4.70.
Doppler spectra are obtained with the red channel of the HIRES
spectrograph on the Keck I telescope. Exposure times are adjusted to
achieve S/N = 200.
The effective temperature Te of each star is estimated from the V-K
color and an empirical relation:
logTe∼3.9653-0.164(V-K)+0.0168(V-K)2
We use the Quarter 2 Kepler target list from the Multimission Archive
(STScI). Kepler candidate planets are taken from Borucki et al. (2011,
Cat. J/ApJ/736/19).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 20 150 Radial velocity statistics of 150 stars with
Te=3660-4660K in the M2K survey
--------------------------------------------------------------------------------
See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
I/298 : LSPM-North Catalog (Lepine+ 2005)
J/AJ/142/112 : KIC photometric calibration (Brown+, 2011)
J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
J/AJ/142/138 : All-sky catalog of bright M dwarfs (Lepine+, 2011)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/150] Stellar index number
5- 6 I2 --- Nm [3/68] Number of measurements
8- 15 F8.2 m/s StDeV [0.53/13331] Velocity standard deviation
17- 20 F4.2 m/s Err [0.1/8.41] Formal error
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Apps et al. M2K. I. HIP 79431 2010PASP..122..156A 2010PASP..122..156A
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 06-Aug-2013