J/A+A/674/A61 Line-by-line sensitivity to activity in M dwarf (Lafarga+, 2023)
The CARMENES search for exoplanets around M dwarfs.
Line-by-line sensitivity to activity in M dwarfs.
Lafarga M., Ribas I., Zechmeister M., Reiners A., Lopez-Gallifa A.,
Montes D., Quirrenbach A., Amado P.J., Caballero J.A., Azzaro M.,
Bejar V.J.S., Hatzes A.P., Henning T., Jeffers S.V., Kaminski A.,
Kurster M., Schofer P., Schweitzer A., Tabernero H.M., Zapatero Osorio M.R.
<Astron. Astrophys. 674, A61 (2023)>
=2023A&A...674A..61L 2023A&A...674A..61L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Stars, M-type ; Spectroscopy
Keywords: techniques: spectroscopic - techniques: radial velocities -
stars: late-type - stars: low-mass - stars: activity - stars: rotation
Abstract:
Radial velocities (RVs) measured from high-resolution stellar spectra
are routinely used to detect and characterise orbiting exoplanet
companions. The different lines present in stellar spectra are created
by several species, which are non-uniformly affected by stellar
variability features such as spots or faculae. Stellar variability
distorts the shape of the spectral absorption lines from which precise
RVs are measured, posing one of the main problems in the study of
exoplanets. In this work we aim to study how the spectral lines
present in M dwarfs are independently impacted by stellar activity. We
use CARMENES optical spectra of six active early- and mid-type M
dwarfs to compute line-by-line RVs and study their correlation with
several well-studied proxies of stellar activity. We are able to
classify spectral lines based on their sensitivity to activity in five
M dwarfs displaying high levels of stellar activity. We further use
this line classification to compute RVs with activity-sensitive lines
and less sensitive lines, enhancing or mitigating stellar activity
effects in the RV time series. For specific sets of the least
activity-sensitive lines, the RV scatter decreases by ∼2 to 5 times
the initial one, depending on the star. Finally, we compare these
lines in the different stars analysed, finding the sensitivity to
activity to vary from star to star. Despite the high density of lines
and blends present in M dwarf stellar spectra, we find that a
line-by-line approach is able to deliver precise RVs. Line-by-line RVs
are also sensitive to stellar activity effects, and allow for an
accurate selection of activity- insensitive lines to mitigate activity
effects in RV. However, we find stellar activity effects to vary in
the same insensitive lines from star to star.
Description:
Tables containing information about the sensitivity to activity of the
different lines, one table for each of the six stars studied in this
work. Each table includes the central wavelength of the line as
measured in the spectral template used, the scatter of the line RV,
and the Pearson's correlation coefficient R obtained for the
correlation between the line RV and the three activity indicators
considered (i.e. three different R values, one per indicator). We note
that even though we use the term line, these 'lines' correspond to
minima in the spectrum and are the result of blends of true atomic
lines or features in molecular bands.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 49 6 List of studied stars
j05019.dat 53 2054 Line data for J05019+011
j07446.dat 53 2161 Line data for J07446+035
j10196.dat 53 2152 Line data for J10196+198
j11201.dat 53 1683 Line data for J11201-104
j15218.dat 53 1696 Line data for J15218+209
j22468.dat 53 2115 Line data for J22468+443
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See also:
J/A+A/636/A36 : CARMENES M dwarfs absolute radial velocities (Lafarga+, 2020)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Name
12- 13 I2 h RAh Right ascension (J2000)
15- 16 I2 min RAm Right ascension (J2000)
18- 24 F7.4 s RAs Right ascension (J2000)
26 A1 --- DE- Declination sign (J2000)
27- 28 I2 deg DEd Declination (J2000)
30- 31 I2 arcmin DEm Declination (J2000)
33- 38 F6.3 arcsec DEs Declination (J2000)
40- 49 A10 --- FileName File with line data
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Byte-by-byte Description of file: j*.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 A lambdac Line central wavelength in template
13- 23 F11.6 m/s sRV Line RV weighted standard deviation
25- 33 F9.6 --- Rccfbis ?=- Pearson's correlation coefficient R
between line RV and CCF BIS (1)
35- 43 F9.6 --- Rccfrvnzp ?=- Pearson's correlation coefficient R
between line RV and CCF RV
45- 53 F9.6 --- Rservalcrx ?=- Pearson's correlation coefficient R
between line RV and SERVAL CRX (2)
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Note (1): CCF BIS refers to the bisector inverse slope from the CCF computed as
described in Lafarga et al. (2020A&A...636A..36L 2020A&A...636A..36L, Cat. J/A+A/636/A36)
Note (2): SERVAL CRX refers to the chromatic index computed as described in
Zechmeister et al. (2018A&A...609A..12Z 2018A&A...609A..12Z).
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Acknowledgements:
Marina Lafarga, lafarga(at)ice.cat
References:
Lafarga, Ribas, Lovis, et al. 2020A&A...636A..36L 2020A&A...636A..36L, Cat. J/A+A/636/A36
The CARMENES search for exoplanets around M dwarfs. Radial velocities and
activity indicators from cross-correlation functions with weighted binary
masks
Zechmeister, Reiners, Amado, et al. 2018A&A...609A..12Z 2018A&A...609A..12Z
Spectrum radial velocity analyser (SERVAL). High-precision radial
velocities and two alternative spectral indicators
(End) Patricia Vannier [CDS] 13-Feb-2023