J/A+A/636/A36 Absolute radial velocities of CARMENES M dwarfs (Lafarga+, 2020)
The CARMENES search for exoplanets around M dwarf: Radial velocities and
activity indicators from cross-correlation functions with weighted binary masks.
Lafarga M., Ribas I., Lovis C., Perger M., Zechmeister M., Bauer F.F.,
Kuerster M., Cortes-Contreras M., Morales J.C., Herrero E., Rosich A.,
Baroch D., Reiners A., Caballero J.A., Quirrenbach A., Amado P.J.,
Alacid J.M., Bejar V.J.S., Dreizler S., Hatzes A.P., Henning T.,
Jeffers S.V., Kaminski A., Montes D., Pedraz S., Rodriguez-Lopez C.,
Schmitt J.H.M.M.
<Astron. Astrophys. 636, A36 (2020)>
=2020A&A...636A..36L 2020A&A...636A..36L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Stars, M-type ; Radial velocities
Keywords: methods: data analysis - techniques: spectroscopic -
techniques: radial velocities - stars: late-type - stars: low-mass -
stars: activity
Abstract:
For years, the standard procedure to measure radial velocities (RVs)
of spectral observations consisted in cross-correlating the spectra
with a binary mask, that is, a simple stellar template that contains
information on the position and strength of stellar absorption lines.
The cross-correlation function (CCF) profiles also provide several
indicators of stellar activity.
We present a methodology to first build weighted binary masks and,
second, to compute the CCF of spectral observations with these masks
from which we derive radial velocities and activity indicators. These
methods are implemented in a python code that is publicly available.
To build the masks, we selected a large number of sharp absorption
lines based on the profile of the minima present in high
signal-to-noise ratio (S/N) spectrum templates built from observations
of reference stars. We computed the CCFs of observed spectra and
derived RVs and the following three standard activity indicators:
full-width-at-half-maximum as well as contrast and bisector inverse
slope.
We applied our methodology to CARMENES high-resolution spectra and
obtain RV and activity indicator time series of more than 300 M dwarf
stars observed for the main CARMENES survey. Compared with the
standard CARMENES template matching pipeline, in general we obtain
more precise RVs in the cases where the template used in the standard
pipeline did not have enough S/N. We also show the behaviour of the
three activity indicators for the active star YZ CMi and estimate the
absolute RV of the M dwarfs analysed using the CCF RVs.
Description:
Absolute radial velocities (RVs) of 323 M dwarf stars observed with
CARMENES. The RVs were computed using the cross-correlation function
(CCF) method with binary masks on CARMENES visual observations. The RV
values and uncertainties also take into account the gravitational
redshift and the convective blueshift of the stars. The gravitational
redshift is computed using mass and radius values from Schweitzer et
al., 2019A&A...625A..68S 2019A&A...625A..68S, Cat. J/A+A/625/A68. We consider the
convective blueshift to be 0±100m/s for all stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 53 323 Absolute radial velocities
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See also:
J/A+A/625/A68 : Radii and masses of the CARMENES targets (Schweitzer+, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Name of the star (Karmn), JHHMMm+DDMMA
13- 19 I7 m/s RVabs Absolute radial velocity
21- 23 I3 m/s e_RVabs Absolute radial velocity uncertainty (1)
25- 31 I7 m/s RVccf CCF RV weighted mean
33- 35 I3 m/s e_RVccf CCF RV weighted mean uncertainty (2)
37- 42 F6.2 m/s sigmaRVccf CCF RV scatter
44- 45 I2 m/s sigmamask Mask zero-point uncertainty
47- 49 I3 m/s RVgrav Gravitational redshift (3)
51- 53 I3 m/s e_RVgrav Gravitational redshift uncertainty
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Note (1): The RVabs uncertainty is the quadratic sum of the uncertainties from
the RV scatter (sigmaRVccf), the mask zero-point (sigmamask), the
gravitational redshift (e_RVgrav), and the convective blueshift, which we
assumed to be 100m/s for all stars.
Note (2): The uncertainty in RVccf is the quadratic sum of the scatter
(sigmaRVccf) and mask zero-points (sigmamask) uncertainties.
Note (3): RVgrav is computed using mass and radius values from
Schweitzer et al., 2019A&A...625A..68S 2019A&A...625A..68S, Cat. J/A+A/625/A68.
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Acknowledgements:
Marina Lafarga, lafarga(at)ice.cat
References:
Schweitzer et al., 2019A&A...625A..68S 2019A&A...625A..68S, Cat. J/A+A/625/A68
(End) Marina Lafarga [ICE, CSIC, IEEC Spain], Patricia Vannier [CDS] 03-Apr-2020