J/A+A/696/A230 Magnetic activity of M dwarfs (Ibanez Bustos+, 2025)
Characterisation of magnetic activity of M dwarfs.
Possible impact on the surface brightness.
Ibanez Bustos R.V., Buccino A.P., Nardetto N., Mourard D., Flores M.,
Mauas P.J.D.
<Astron. Astrophys. 696, A230 (2025)>
=2025A&A...696A.230I 2025A&A...696A.230I (SIMBAD/NED BibCode)
ADC_Keywords: Stars, M-type ; Stars, late-type ; Spectroscopy
Keywords: techniques: spectroscopic - stars: activity - stars: late-type
Abstract:
M dwarfs are an ideal laboratory for hunting Earth-like planets, and
the study of chromospheric activity is an important part of this task.
On the one hand, according to the study of short-term activity their
high levels of magnetic activity can affect habitability and make it
difficult to detect exoplanets orbiting around them. On the other
hand, however, long-term activity studies can show whether or not
these stars exhibit cyclical behaviour in their activity, facilitating
the detection of planets in periods of low magnetic activity.
The long-term cyclical behaviour of magnetic activity can be detected
by studying several spectral lines and explained by different stellar
dynamo models (such as α{OMEGA} or α2 dynamos). In the
present work, we studied the Mount Wilson S index to search for
evidence of long-term activity possibly driven by a solar-type dynamo.
We studied a sample of 35 M dwarfs with different levels of
chromospheric activity and spectral classes ranging from dM0 to dM6.
To do this, we used 2965 spectra in the optical range from different
instruments installed in the southern and northern hemispheres to
construct time series with extensions of up to 21 years. We analysed
these time series with different time-domain techniques to detect
cyclical patterns. In addition, using 2MASS-KS and visible
photometry we also studied the potential impact of chromospheric
activity on surface brightness.
Using the colour index (V-KS), we calculated the chromospheric
emission levels and found that most of the stars in the sample have
low emission levels, indicating that most of them are inactive or very
inactive stars. For 31 stars of 35, we constructed time series using
the S indexes, and we detected 13 potential cycles of magnetic
activity. These cycles have an approximate duration of between three
and 19 years, with false alarm probabilities (FAPs) less than 0.1%.
For stars that do not show cyclic behaviour, we found that the mean
value of the S index varies between 0.350 and 1.765, and its mean
variability and chromospheric emission level are around 12% and
-5.110dex, respectively. We do not find any impact of chromospheric
activity on the surface brightness in the domain of -5.6<logR'HK←4.5.
Description:
We tabulate the chromospheric activity indicators defined from CaII
for each spectrum used in the present work for each of the stars in
the sample.
We show the information for each spectrum used:
- the modified Julian day,
- the Instrument,
- the ID of the program with which the target was observed and
- the S-index computed in this work.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 36 35 List of studied sources
tableb1.dat 98 2808 S-indexes
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Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Name
12- 13 I2 h RAh Right ascension (J2000)
15- 16 I2 min RAm Right ascension (J2000)
18- 22 F5.2 s RAs Right ascension (J2000)
24 A1 --- DE- Declination sign (J2000)
25- 26 I2 deg DEd Declination (J2000)
28- 29 I2 arcmin DEm Declination (J2000)
31- 34 F4.1 arcsec DEs Declination (J2000)
36 A1 --- Note [N] N when no data in file table B1
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Name
11- 26 F16.10 d MJD ? Modified Julian day
30- 37 A8 --- Inst Spectrograph
39- 52 A14 --- ProgID Program ID
56- 67 F12.7 --- S-Index ? Activity index
69- 98 A30 --- Com Comments
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History:
From Romina Ibanez Bustos, romina.ibanez(at)oca.eu
Acknowledgements:
This project has received funding from the European Research
Council (ERC) under the European Union's Horizon 2020 research and
innovation programme (Grant agreement No. 101019653).
(End) Patricia Vannier [CDS] 05-Mar-2025