J/A+A/652/A28 Activity indicators across the M dwarf domain (Lafarga+, 2021)
The CARMENES search for exoplanets around M dwarfs:
Mapping stellar activity indicators across the M dwarf domain.
Lafarga M., Ribas I., Reiners A., Quirrenbach A., Amado P.J.,
Caballero J.A., Azzaro M., Bejar V.J.S., Cortes-Contreras M., Dreizler S.,
Hatzes A.P., Henning T., Jeffers S.V., Kaminski A., Kuerster M., Montes D.,
Morales J.C., Oshagh M., Rodriguez-Lopez C., Schoefer P., Schweitzer A.,
Zechmeister M.
<Astron. Astrophys. 652, A28 (2021)>
=2021A&A...652A..28L 2021A&A...652A..28L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, M-type ; Stars, masses ; Rotational velocities ;
Equivalent widths
Keywords: techniques: radial velocities - stars: late-type - stars: low-mass -
stars: activity - stars: rotation
Abstract:
Stellar activity poses one of the main obstacles for the detection and
characterisation of small exoplanets around cool stars, as it can
induce radial velocity (RV) signals that can hide or mimic the
presence of planetary companions. Several indicators of stellar
activity are routinely used to identify activity-related signals in
RVs, but not all indicators trace exactly the same activity effects,
nor are any of them always effective in all stars.
We evaluate the performance of a set of spectroscopic activity
indicators for M dwarf stars with different masses and activity levels
with the aim of finding a relation between the indicators and stellar
properties.
In a sample of 98 M dwarfs observed with CARMENES, we analyse the
temporal behaviour of RVs and nine spectroscopic activity indicators:
cross-correlation function (CCF) full-width-at-half-maximum (FWHM),
CCF contrast, CCF bisector inverse slope (BIS), RV chromatic index
(CRX), differential line width (dLW), and indices of the chromospheric
lines Hα and calcium infrared triplet.
A total of 56 stars of the initial sample show periodic signals
related to activity in at least one of these ten parameters. RV is the
parameter for which most of the targets show an activity-related
signal. CRX and BIS are effective activity tracers for the most active
stars in the sample, especially stars with a relatively high mass,
while for less active stars, chromospheric lines perform best. FWHM
and dLW show a similar behaviour in all mass and activity regimes,
with the highest number of activity detections in the low-mass,
high-activity regime. Most of the targets for which we cannot identify
any activity-related signals are stars at the low-mass end of the
sample (i.e. with the latest spectral types). These low-mass stars
also show the lowest RV scatter, which indicates that ultracool M
dwarfs could be better candidates for planet searches than earlier
types, which show larger RV jitter.
Our results show that the spectroscopic activity indicators analysed
behave differently, depending on the mass and activity level of the
target star.
This underlines the importance of considering different indicators of
stellar activity when studying the variability of RV measurements.
Therefore, when assessing the origin of an RV signal, it is critical
to take into account a large set of indicators, or at least the most
effective ones considering the characteristics of the star, as failing
to do so may lead to false planet claims.
Description:
Properties of the 98 sample stars. Values taken from the latest
version of the Carmencita database available at the time. We also show
the number of CARMENES VIS observations (before performing any
sigma-clipping or discarding any observations due to low S/N), the
number of different nights covered by the observations, their time
span, and their RV scatter, measured as the standard deviation (std)
of the corrected serval RVs (instrumental drift and nightly average
corrected, averaged same-night observations, and linear trend
removed).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 172 98 Properties of the stellar sample
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Karmn CARMENES identifier
13- 38 A26 --- Name Name(s) of the star
40- 46 A7 --- SpType Spectral type
48- 52 A5 --- r_SpType Spectral type reference (1)
54- 60 F7.5 Msun Mass Stellar mass (2)
62- 67 F6.4 Msun e_Mass Stellar mass uncertainty
69- 74 F6.3 mag Jmag J band magnitude (3)
76- 80 F5.3 mag e_Jmag J band magnitude uncertainty
82 A1 --- l_vsini Upper limit flag on vsini
83- 87 F5.2 km/s vsini Projected rotational velocity
89- 92 F4.2 km/s e_vsini ?=- Projected rotational velocity
uncertainty
94- 98 A5 --- r_vsini Projected rotational velocity
reference (4)
100-108 F9.5 d Prot ?=- Rotational period
109-116 F8.5 d e_Prot ?=- Rotational period uncertainty
118-122 A5 --- r_Prot Rotational period reference (5)
124-130 F7.4 0.1nm pEW'Ha Halpha pseudoequivalent width (6)
132-137 F6.4 0.1nm e_pEW'Ha ?=- Halpha pseudoequivalent width
uncertainty
139-145 F7.4 --- log(LHa/Lbol) ?=- Log ratio of Halpha and bolometric
luminosities (6)
147-152 F6.4 --- e_log(LHa/Lbol) ?=- Log ratio of Halpha and bolometric
luminosities uncertainty
154-156 A3 --- Planet Planetary companions
158-160 I3 --- Nobs Number of observations
162-165 I4 d Span Observations time span
167-172 F6.2 m/s s_RV Radial velocity standard deviation
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Note (1): Spectral type references as follows:
Haw96 = Hawley et al. (1996AJ....112.2799H 1996AJ....112.2799H, Cat. III/198)
Alo15 = Alonso-Floriano et al. (2015, Cat. J/A+A/577/A128)
Gra06 = Gray et al. (2006, Cat. J/AJ/132/161)
Gra03 = Gray et al. (2003, Cat. J/AJ/126/2048)
Lep13 = Lepine et al. (2013, Cat. J/AJ/145/102)
Ben17 = Benneke et al. (2017ApJ...834..187B 2017ApJ...834..187B)
New14 = Newton et al. (2014, Cat. J/ApJ/821/93)
Ria06 = Riaz et al. (2006, Cat. J/AJ/132/866)
Kir91 = Kirkpatrick et al. (ApJS, 77, 417).
Note (2): All values from Schweitzer et al. (2019, Cat. J/A+A/625/A68), except
J20451-313 computed using Mann et al. (2019, Cat. J/ApJ/871/63).
Note (3): All values from Skrutskie et al. (2006AJ....131.1163S 2006AJ....131.1163S, Cat. VII/233).
Note (4): Rotational velocity references as follows:
Rei18 = Reiners et al. (2018, Cat. J/A+A/612/A49)
Fou18 = Fouque et al. (2018, Cat. J/MNRAS/475/1960)
Del98 = Delfosse et al. (1998, Cat. J/A+A/331/581)
Mar14 = Martinez-Rodriguez (2014, MSc thesis, Universidad Complutense de
Madrid, Spain)
Lop10 = Lopez-Santiago et al. (2010, Cat. J/A+A/514/A97)
Tor06 = Torres et al. (2006, Cat. J/A+A/460/695)
Note (5): rotational period references as follows:
Die19 = Diez Alonso et al. (2019, Cat. J/A+A/621/A126)
Sua18 = Suarez Mascareno et al. (2018A&A...612A..89S 2018A&A...612A..89S)
New16 = Newton et al. (2016, Cat. J/ApJ/821/93)
Sua17 = Suarez Mascareno et al. (2017MNRAS.468.4772S 2017MNRAS.468.4772S)
Mor08 = Morin et al. (2008, Cat. J/MNRAS/390/567)
Mor10 = Morin et al. (2010, Cat. J/MNRAS/407/2269)
Sua15 = Suarez Mascareno et al. (2015MNRAS.452.2745S 2015MNRAS.452.2745S)
Mes11 = Messina et al. (2011, Cat. J/A+A/597/A52)
Wat06 = Watson et al. (2006, Society for Astronomical Sciences Annual
Symposium, 25, 47)
Note (6): All values form Schoefer et al. (2019, Cat. J/A+A/623/A44).
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Acknowledgements:
Marina Lafarga, marina.lafarga-magro(at)warwick.ac.uk
(End) Marina Lafarga [University of Warwick], Patricia Vannier [CDS] 03-Jun-2021