J/A+A/701/A17 Activity clusters list of lines isolated (Charpentier+, 2025)
A reliable activity proxy in SPIRou spectra of M dwarfs using machine learning.
Charpentier P., Moutou C., Donati J.-F., Cristofari P.I., Larue P.,
Marion S., Hood T., Ould-Elhkim M., Artigau E., Cadieux C., Boisse I.,
Carmona A., Cook N.J., Delfosse X., Doyon R., Morin J., the SLS Consortium
<Astron. Astrophys. 701, A17 (2025)>
=2025A&A...701A..17C 2025A&A...701A..17C (SIMBAD/NED BibCode)
ADC_Keywords: Atomic physics ; Spectroscopy ; Optical
Keywords: techniques: radial velocities - techniques: spectroscopy -
stars: magnetic field
Abstract:
Recent instruments have extended radial velocity observations from the
optical domain to the near-infrared range. In particular, this has
allowed to study M dwarfs more extensively, which are known to host
rocky planets more frequently. However, these stars also have on
average stronger magnetic activity than solar-type stars. Therefore,
investigating this magnetic activity is key to uncovering planets
around such stars.
This paper aims to extensively test a new reliable magnetic activity
indicator, named W1, and confirm it as a proxy for the small-scale
magnetic field for M dwarf stars.
W1 is derived from a Principal Component Analysis (PCA) applied on
the per-line differential Line Width (dLW). However, the PCA is highly
sensitive to contamination from telluric residuals in the spectra.
Therefore, we employ a filtering technique based on machine learning
tools such as unsupervised Dimensional Reduction (DR) algorithm and
Support Vector Machine (SVM) to remove faulty lines. We assess the
performances of this filtering method using a simulation of
observations of the per-line $dLW$ variations before applying it on
near-infrared (nIR) high resolution spectroscopic observations using
SPIRou at the Canada-France-Hawaii Telescope (CFHT) on five targets,
with various levels of stellar magnetic activity, spectral types and
rotation periods, from the SPIRou Legacy Survey, namely AU Mic,
EV Lac, GJ1286, GJ1289 and Gl 410.
The filtered W1 signal is modulated with a period consistent with
the rotation period retrieved from activity indicators, corresponding
to the magnetic activity for all the stars studied. It also correlates
with the small- scale magnetic field for all the five stars, with a
direct Pearson correlation coefficient greater than 0.80.
Additionally, we identified 201 stellar lines that are particularly
sensitive to magnetic activity that could be valuable for studying of
magnetic fields.
Description:
Complete list of lines isolated from the activity clusters of AU Mic,
EV Lac and GJ1289. The identification is based on a 3500K synthetic
stellar spectra mask calculated from VALD.
Objects:
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RA (2000) DE Designation(s)
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20 45 09.53 -31 20 27.2 AU Mic = 2MASS J20450949-3120266
22 46 49.73 +44 20 02.3 EV Lac = 2MASS J22464980+4420030
23 43 06.31 +36 32 13.1 GJ1289 = 2MASS J23430628+3632132
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
lines.dat 76 228 Complete list of lines isolated from the activity
clusters of AU Mic, EV Lac and GJ1289
guess.dat 30 111 Guess lines
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Byte-by-byte Description of file: lines.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- LineID Line ID
5- 13 F9.4 nm WaveStart Wavelenth Start of the line
15- 23 F9.4 nm WaveEnd Wavelenth End of the line
25- 30 F6.4 --- Depth Depth of the line
32- 38 F7.4 km/s dLWAmp Amplitude of the dLW variations for that line
40- 45 A6 --- Star Star from which this line is derived
47- 49 I3 --- LineID1 ? Line ID 1
51- 53 I3 --- LineID2 ? Line ID 2
55- 57 I3 --- LineID3 ? Line ID 3
59- 60 A2 --- Comment Comment on the identification (1)
62- 64 I3 --- Guess1 ? Possible Guess ID
66- 68 I3 --- Guess2 ? Possible Guess ID
70- 72 I3 --- Guess3 ? Possible Guess ID
74- 76 I3 --- Guess4 ? Possible Guess ID
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Note (1): Comments as follows:
E0 = No lines found in that wavelength range in the identification mask
E1 = Several lines found in that wavelength range in the identification mask
but only one with a significant depth (the one that as been guessed
E2 = Several lines found in that wavelength range in the identification mask
with multiple lines with a significant depth (all of them are displayed)
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Byte-by-byte Description of file: guess.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- GuessID Guess ID
5- 13 F9.4 nm WaveGuessed Wavelenth of the line in the mask
15- 19 A5 --- Species Species of the line
21- 24 F4.2 --- LandeG ? Lande Factor of the line
26- 30 F5.3 --- MaskDepth Depth of the line in the mask
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Acknowledgements:
Paul Charpentier, p.charpentier(at)irap.omp.eu
(End) Paul Charpentier [IRAP, France], Patricia Vannier [CDS] 24-Jun-2025