J/A+A/607/A124 K-G-F dwarfs stellar granulation variability (Meunier+, 2017)
Variability in stellar granulation and convective blueshift with spectral
type and magnetic activity.
II. From young to old main-sequence K-G-F stars.
Meunier N., Mignon L., Lagrange A.-M.
<Astron. Astrophys. 607, A124 (2017)>
=2017A&A...607A.124M 2017A&A...607A.124M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, dwarfs ; Magnetic fields
Keywords: convection - techniques: radial velocities - stars: magnetic field -
stars: activity - stars: solar-type - Sun: granulation
Abstract:
The inhibition of small-scale convection in the Sun dominates the
long-term radial velocity (RV) variability: it therefore has a
critical effect on light exoplanet detectability using RV techniques.
We here extend our previous analysis of stellar convective blueshift
and its dependence on magnetic activity to a larger sample of stars in
order to extend the Teff range, to study the impact of other stellar
properties, and finally to improve the comparison between observed RV
jitter and expected RV variations.
Methods. We estimate a differential velocity shift for Fe and Ti lines
of different depths and derive an absolute convective blueshift using
the Sun as a reference for a sample of 360 F7-K4 stars with different
properties (age, Teff, metallicity).
We confirm the strong variation in convective blueshift with Teff and
its dependence on (as shown in the line list in Paper I) activity
level. Although we do not observe a significant effect of age or
cyclic activity, stars with a higher metallicity tend to have a lower
convective blueshift, with a larger effect than expected from
numerical simulations. Finally, we estimate that for 71% of the stars
in our sample the RV and LogR'HK variations are compatible with the
effect of activity on convection, as observed in the solar case, while
for the other stars, other sources (such as binarity or companions)
must be invoked to explain the large RV variations. We also confirm a
relationship between LogR'HK and metallicity, which may affect
discussions of the possible relationship between metallicity and
exoplanets, as RV surveys are biased toward low LogR'HK and possibly
toward high-metallicity stars.
We conclude that activity and metallicity strongly affect the
small-scale convection levels in stars in the F7-K4 range, with a
lower amplitude for the lower mass stars and a larger amplitude for
low-metallicity stars.
Description:
List of stars studied in the paper (HARPS data from the ESO archive),
together with informations from various sources and outputs from our
analysis. The number of stars is 360.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 107 360 List of stars studied in the paper
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See also:
J/A+A/597/A52 : K and G dwarfs stellar granulation variability (Meunier+, 2017)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Star name
13- 16 I4 K Teff Teff
19 I1 --- r_Teff Reference for Teff (1)
22- 23 A2 --- SpType Spectral type from the CDS
26- 29 F4.2 --- B-V B-V from the CDS
33- 36 I4 --- Nsp Number of spectra used in the analysis
39- 45 F7.1 --- TSS Slope of the radial velocity versus line
intensity in m/s/(F/Fc) unit (2)
49- 53 F5.1 --- e_TSS 1-sigma uncertainty on TSS in m/s/(F/Fc)
56- 61 F6.3 --- logR'HK Averaged Mount Wilson logR'HK index
65- 69 F5.3 --- e_logR'HK 1-sigma uncertainty on logR'HK
73- 78 F6.1 m/s ConvBL Convective blueshift (3)
81- 85 F5.2 Gyr Age Age
87- 88 I2 --- r_Age ? Reference for the age (1)
90- 92 F3.1 km/s vsini ? Rotational velocity
94- 95 I2 --- r_vsini ? Reference for the vsini (1)
98-107 A10 --- Source Survey including the star (1)
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Note (1): References as follows:
1 = Sousa et al., 2008A&A...487..373S 2008A&A...487..373S
2 = Ramirez et al., 2014A&A...572A..48R 2014A&A...572A..48R
3 = Marsden et al., 2014MNRAS.444.3517M 2014MNRAS.444.3517M
4 = Datson et al., 2014MNRAS.439.1028D 2014MNRAS.439.1028D
5 = Borgniet et al., 2017, to be submitted
6 = Lagrange et al. 2013A&A...559A..83L 2013A&A...559A..83L
7 = Gray et al., 2015AJ....150..203G 2015AJ....150..203G
8 = Gray et al. 2006AJ....132..161G 2006AJ....132..161G
9 = Allende Prieto & Lambert, 1999A&A...352..555A 1999A&A...352..555A
10 = Holmberg et al., 2009A&A...501..941H 2009A&A...501..941H
11 = Delgado Mena et al., 2015A&A...576A..69D 2015A&A...576A..69D
12 = Borgniet et al., 2015, PhD Thesis
13 = Nordstrom et al., 2004A&A...418..989N 2004A&A...418..989N
14 = Jenkins et al. 2011A&A...531A...8J 2011A&A...531A...8J
15 = Valenti & Fischer, 2005ApJS..159..141V 2005ApJS..159..141V
16 = Dos Santos et al., 2016A&A...592A.156D 2016A&A...592A.156D
17 = Strassmeier et al., 2000A&AS..142..275S 2000A&AS..142..275S
18 = Lovis et al., 2005A&A...437.1121L 2005A&A...437.1121L
Note (2): Definition of the TSS: Slope of the radial velocity versus
line intensity, where the radial velocity and intensity are computed at
the bottom of each line. F/Fc represent the relative flux
(i.e. flux divided by the continuum flux)
Note (3): Convective blueshift is derived from the TSS in Section 4.1
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Acknowledgements:
Nadege Meunier, nadege.meunier(at)univ-grenoble-alpes.fr
References:
Meunier et al., Paper I 2017A&A...597A..52M 2017A&A...597A..52M, Cat. J/A+A/597/A52
(End) Patricia Vannier [CDS] 07-Sep-2017