J/A+A/566/A66 Correlation of logR'HK with logIHα (Gomes da Silva+, 2014)
On the long-term correlation between the flux in the Ca II H & K and
Hα lines for FGK stars.
Gomes da Silva J., Santos N.C., Boisse I., Dumusque X., Lovis C.
<Astron. Astrophys., 566, A66-66 (2014)>
=2014A&A...566A..66G 2014A&A...566A..66G
ADC_Keywords: Stars, late-type ; Abundances
Keywords: stars: activity - stars: chromospheres - stars: solar-type -
planetary systems
Abstract:
The re-emission in the cores of the CaII H & K and Hα lines are
well known proxies of stellar activity. However, these activity
indices probe different activity phenomena: the first is more
sensitive to plage variation, while the other is more sensitive to
filaments. In this paper, we study the long-term correlation between
logR'HK and logIHα, two indices based on the CaII H & K and
Hα lines, respectively, for a sample of 271 FGK stars using
measurements obtained over a ∼9-year time span. Because stellar
activity is one of the main obstacles to the detection of low-mass and
long-period planets, understanding this activity index correlation
further can give us some hints about the optimal target to focus on
ways to correct for these activity effects. We found a great variety
of long-term correlations between logR'HK and logIHα. Around
20% of our sample has a strong positive correlation between the
indices while about 3% show strong negative correlation. These
fractions are compatible with those found for the case of early-M
dwarfs. Stars exhibiting a positive correlation have a tendency to be
more active when compared to the median of the sample, while stars
showing a negative correlation are more present among higher
metallicity stars. There is also a tendency for the positively
correlated stars to be more present among the coolest stars, a result
which is probably due to the activity level effect on the correlation.
Activity level and metallicity therefore seem to be playing a role on
the correlation between logR'HK and logIHα. Possible
explanations based on the influence of filaments for the diversity in
the correlations between these indices are discussed in this paper. As
a parallel result, we show a way to estimate the effective temperature
of FGK dwarfs that exhibit a low activity level by using the Hα
index.
Description:
The sample comes from ∼400 FGK stars High Accuracy Radial Velocity
Planet Searcher (HARPS, spectral resolution =115000) high-precision
sample that has been already used by Lovis et al. (2011, in prep.,
1107.5325) to study the long-term activity of FGK stars and its
effect on the measurement of precise radial velocities. A description
of the sample is presented in their paper. The spectra used in this
work were obtained between February 2003 and February 2012. We used
effective temperature, metallicity, and surface gravity that were
already calculated for this sample by Sousa et al.
(2008A&A...487..373S 2008A&A...487..373S, Cat. J/A+A/487/373). Absolute magnitude and
luminosity were both obtained from the Hipparcos catalogue.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 73 66 Parameters for the 66 stars with |ρ|≥0.5
from the nightly averaged 271-star sample
tableb2.dat 73 205 Parameters for the 205 stars with |ρ|≤0.5
from the nightly averaged 271-star sample
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See also:
J/ApJ/626/446 : Effective temperature scale of FGK stars (Ramirez+, 2005)
J/MNRAS/371/879 : Effective temperatures of 215 FGK giants (Kovtyukh+, 2006)
J/MNRAS/389/1336 : Reddenings of FGK supergiants + Cepheids (Kovtyukh+, 2008)
J/A+A/487/373 : 451 HARPS-GTO stars spectroscopic parameters (Sousa+, 2008)
J/A+A/520/A79 : Nearby FGK stars chromospheric activity
(Martinez-Arnaiz+, 2010)
J/A+A/533/A141 : Stellar parameters for 582 HARPS FGK stars (Sousa+, 2011)
J/A+A/545/A32 : Chemical abundances of 1111 FGK stars (Adibekyan+, 2012)
J/A+A/547/A106 : Li abundances in the FGK dwarfs (Mishenina+, 2012)
J/ApJ/735/41 : Carbon and oxygen abundances in FGK stars (Petigura+, 2011)
J/A+A/552/A27 : Stellar activity and kinematics of FGK stars (Murgas+, 2013)
J/A+A/556/A86 : FGK dwarf stars limb darkening coefficients (Neilson+, 2013)
J/ApJ/764/78 : Oxygen abundances in nearby FGK stars (Ramirez+, 2013)
J/A+A/564/A133 : Gaia FGK benchmark stars: metallicity (Jofre+, 2014)
Byte-by-byte Description of file: tableb1.dat tableb2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Star Star name
12- 14 I3 --- Nobs [10/279] Number of observations
16- 19 I4 d Tspan [340/3278] Span time
21- 25 F5.2 --- rho [-1/1] Correlation coefficient ρ between
logR'HK and logIHα indices
27- 31 F5.2 [Sun] [Fe/H] Metallicity
33- 36 F4.2 [Sun] e_[Fe/H] rms uncertainty on [Fe/H]
38- 41 I4 K Teff Effective temperature
43- 45 I3 K e_Teff rms uncertainty on Teff
47- 52 F6.3 --- <logR'HK> Mean logR'HK index
54- 58 F5.3 --- e_<logR'HK> rms uncertainty on <logR'HK>
60- 66 F7.4 --- <logIHa> Mean logIHα index
68- 73 F6.4 --- e_<logIHa> rms uncertainty on <logIHa>
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 09-Sep-2014