J/A+A/672/A37 Activity indicators in M dwarfs (Ibanez Bustos+, 2023)
Correlation between activity indicators:
Halpha and Ca II lines in M-dwarf stars.
Ibanez Bustos R.V., Buccino A.P., Flores M., Martinez C.F., Mauas P.J.D.
<Astron. Astrophys. 672, A37 (2023)>
=2023A&A...672A..37I 2023A&A...672A..37I (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Stars, M-type ; Spectra, optical
Keywords: stars: activity - stars: late-type - techniques: spectroscopic
Abstract:
Different approaches have been adopted to study both short- and
long-term stellar magnetic activity, and although the mechanisms by
which low-mass stars generate large-scale magnetic fields are not well
understood, it is known that stellar rotation plays a key role.
There are stars that show a cyclical behaviour in their activity
studied on the blue side of the visible spectrum, which can be
explained by solar dynamo or αΩ dynamo models. However,
when studying late-type dwarf stars, they become redder and it is
necessary to implement other indicators to analyse their magnetic
activity. In the present work, we perform a comparative study between
the best-known activity indicators so far defined from the Ca II and
Hα lines to analyse M-dwarf stars.
We studied a sample of 29 M stars with different chromospheric
activity levels and spectral classes ranging from dM0 to dM6. To do
so, we employed 1796 spectra from different instruments with a median
time span of observations of 21 years. The spectra have a wide
spectral range that allowed us to compute the chrosmospheric activity
indicators based on CaII and Hα. In addition, we complemented
our data with photometric observations from the TESS space mission for
better stellar characterisation and short-term analysis.
We obtained a good and significant correlation (ρ=0.91) between
the indexes defined from the two lines for the whole set of stars in
the sample. However, we found that there is a deviation for faster
rotators (with Prot<4-days) and higher flare activity (at least one
flare per day). For the individual analysis, we found that the indexes
computed individually for each star correlate independently of the
level of chromospheric emission and the rotation period.
There is an overall positive correlation between CaII and Hα
emission in dM stars, except during flare events. In particular, we
found that low-energy high-frequency flares could be responsible for
the deviation in the linear trend in fast-rotator M dwarfs. This
implies that the rotation period could be a fundamental parameter to
study the stellar activity and that the rotation could drive the
magnetic dynamo in low-mass active stars.
Description:
We tabulate the chromospheric activity indicators defined from the
CaII and Hα lines to analyse M-dwarf stars.
The HKα Project has been operating since 1999 with the main
purpose being to study the long-term chromospheric activity of cool
main sequence stars observable from the southern hemisphere. In this
programme, we systematically observed latetype stars from dF5 to dM5.5
with the 2.15m Jorge Sahade telescope at the Complejo Astronomico El
Leoncito Observatory (CASLEO), which is located at 2552 m above sea
level in the Argentinian Andes.
We complemented our data with public observations obtained with
several spectrographs. We used 1061 echelle spectra observed by HARPS,
which is mounted at the3.6 m telescope (R∼115000) at La Silla
Observatory (LSO, Chile), and distributed during the interval
2003-2018.
In our study, 99 FEROS spectra were available. This spectrograph is
placed on the 2.2m telescope in LSO and has a resolution of R∼48000.
Furthermore, 55 spectra were taken between 2002 and 2016 with UVES,
which is attached to the Unit Telescope 2 (UT2) of the Very Large
Telescope (VLT) (R∼80000) at Paranal Observatory. In addition, 23
medium-resolution spectra (R∼8900) in the UVB wavelength range
(300-559.5nm) were obtained during the range 2010-2018 with the
X-SHOOTER spectrograph, mounted at the UT2 Cassegrain focus also at
the VLT. Finally, we employed 190 spectra from the HIRES spectrograph
mounted at the Keck-I telescope which were observed between 1996 and
2017.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 126 29 Activity indicators in M dwarfs
list.dat 80 368 List od fits spectra
sp/* . 368 Individual fits spectra
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/AcA/62/67 : ASAS photometry of ROSAT sources (Kiraga, 2012)
J/MNRAS/443/2561 : CONCH-SHELL catalog of nearby M dwarfs (Gaidos+, 2014)
J/A+A/597/A108 : GJ 536 HARPS and HARPS-N data (Suarez Mascareno+, 2017)
J/A+A/613/A25 : Radial velocity for Ross 128 (Bonfils+, 2018)
J/A+A/621/A126 : CARMENES input catalogue of M dwarfs IV. (Diez Alonso+ 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- Star Name of the star
15- 20 A6 --- SpType Spectral type
22- 26 F5.3 --- B-V (B-V) colour index
28- 31 I4 K Teff ?=- Effective temperature
33- 35 I3 K e_Teff ?=- Effective temperature error
37- 42 F6.4 Msun M* ?=- Stellar mass
44- 49 F6.4 Rsun R* ?=- Stellar radius
51- 56 F6.3 --- ?=- Mean value of the Mount Wilson index
58- 62 F5.3 --- ?=- Mean value of the A index
64- 68 F5.2 --- rhoS-A ?=- Correlation coefficient between indexes
70- 73 F4.2 --- e_rhoS-A ?=- Correlation coefficient standard error
75- 79 F5.2 --- B_rhoS-A ?=- Upper value of 95% confidence level
81- 85 F5.2 --- b_rhoS-A ? Lower value of 95% confidence level
87- 92 F6.3 [-] logR'HK Chromospheric emission level
94- 98 F5.3 [-] e_logR'HK Chromospheric emission level error
100-102 I3 --- Nobs Number of observations
105-113 F9.5 d Prot ?=- Rotation period
115-121 F7.5 d e_Prot ? Rotation period
123-126 A4 --- r_Prot Rotation period references (1)
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Note (1): References as follows:
* = This work
Gaia18 = Gaia Collaboration, 2018A&A...616A...1G 2018A&A...616A...1G, Cat. I/345
G14 = Gaidos et al. 2014, 2014MNRAS.443.2561G 2014MNRAS.443.2561G, Cat. J/MNRAS/443/2561
B18 = Bonfils et al., 2018A&A...613A..25B 2018A&A...613A..25B, Cat. J/A+A/613/A25
B89 = Byrne & Doyle, 1989A&A...208..159B 1989A&A...208..159B
DA19 = Diez Alonso et al., 2019, 2019A&A...621A.126D 2019A&A...621A.126D, Cat. J/A+A/621/A126
I19 = Ibanez Bustos et al., 2019MNRAS.483.1159I 2019MNRAS.483.1159I
I20 = Ibanez Bustos et al., 2020A&A...644A...2I 2020A&A...644A...2I
K12 = Kiraga, 2012AcA....62...67K 2012AcA....62...67K, Cat. J/AcA/62/67
K07 = Kiraga & Stepien, 2007AcA....57..149K 2007AcA....57..149K
L21 = Lafarga, arXiv e-prints, arXiv:2105.13467
SM17 = Suarez Mascareno, et al., 2017A&A...597A.108S 2017A&A...597A.108S, Cat. J/A+A/597/A108
SM16 = Suarez Mascareno et al., 2016A&A...595A..12S 2016A&A...595A..12S
SM15 = Suarez Mascareno et al., 2015MNRAS.452.2745S 2015MNRAS.452.2745S
TP19 = Toledo-Padron et al., 2019MNRAS.488.5145T 2019MNRAS.488.5145T
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Star Name of the star
15- 18 I4 --- Nx Number of pixels along X-axis
20- 23 I4 --- Ny Number of pixels along Y-axis
25- 34 A10 "datime" Obs.date Observation date
36- 40 I5 Kibyte size Size of FITS file
42- 62 A21 --- FileName Name of FITS file, in subdirectory sp
64- 80 A17 --- Title Title ofr the file
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Acknowledgements:
Romina Ibanez, ribanez(at)iafe.uba.ar
(End) Patricia Vannier [CDS] 03-Mar-2023