J/A+A/686/A66 EV Lac, DS Leo, and CN Leo magnetic fields (Bellotti+, 2024)
Long-term monitoring of large-scale magnetic fields across optical and
near-infrared domains with ESPaDOnS, Narval and SPIRou.
The cases of EV Lac, DS Leo, and CN Leo.
Bellotti S., Morin J., Lehmann L.T., Petit P., Hussain G.A.J., Donati J-F.,
Folsom C.P., Carmona A., Martioli E., Klein B., Fouque P., Moutou C.,
Alencar S., Artigau E., Boisse I., Bouchy F., Bouvier J., Cook N.J.,
Delfosse X., Doyon R., Hebrard G.
<Astron. Astrophys. 686, A66 (2024)>
=2024A&A...686A..66B 2024A&A...686A..66B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Magnetic fields ; Optical ; Infrared
Keywords: techniques: polarimetric - stars: activity - stars: magnetic field -
stars: individual: EV Lac - stars: individual: DS Leo -
stars: individual: CN Leo
Abstract:
Dynamo models of stellar magnetic fields for partly and fully
convective stars are guided by observational constraints.
Zeeman-Doppler imaging has revealed a variety of magnetic field
geometries and, for fully convective stars in particular, a dichotomy:
either strong, mostly axisymmetric, and dipole- dominated or weak,
non-axisymmetric, and multipole-dominated. This dichotomy is explained
by dynamo bistability or by long-term magnetic cycles, but there is no
definite conclusion on the matter. We analysed optical
spectropolarimetric data sets collected with ESPaDOnS and Narval
between 2005 and 2016, and near-infrared SPIRou data obtained between
2019 and 2022 for three active M dwarfs with masses between 0.1 and
0.6M☉: EV Lac, DS Leo, and CN Leo. We looked for changes in time
series of longitudinal magnetic field, width of unpolarised mean-line
profiles, and large-scale field topology as retrieved with principal
component analysis and Zeeman-Doppler imaging. We retrieved pulsating
(EV Lac), stable (DS Leo), and sine-like (CN Leo) long-term trends in
longitudinal field. The width of near-infrared mean-line profiles
exhibits rotational modulation only for DS Leo, whereas in the optical
it is evident for both EV Lac and DS Leo. The line width variations
are not necessarily correlated to those of the longitudinal field,
suggesting complex relations between small- and large-scale field. We
also recorded topological changes: a reduced axisymmetry for EV Lac
and a transition from toroidal- to poloidal-dominated regime for DS
Leo. For CN Leo, the topology remained dipolar and axisymmetric, with
only an oscillation in field strength. Our results show a peculiar
evolution of the magnetic field for each M dwarf, confirming that M
dwarfs with distinct masses and rotation periods can undergo magnetic
long-term variations, and suggesting a variety of cyclic behaviours of
their magnetic fields.
Description:
SPIRou observations and longitudinal field from ESPaDOnS, Narval and
SPIRou for EV Lac, DS Leo and CN Leo.
Objects:
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RA (2000) DE Designation(s)
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22 46 49.73 +44 20 02.4 EV Lac = BD+43 4305
11 02 38.34 +21 58 01.7 DS Leo = HD 95650
10 56 28.92 +07 00 53.0 CN Leo = Wolf 359
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablee1.dat 53 162 SPIRou observations of EV Lac
tablee2.dat 53 130 SPIRou observations of DS Leo
tablee3.dat 53 164 SPIRou observations of CN Leo
tablee4.dat 31 204 Longitudinal field of EV Lac from ESPaDOnS,
Narval and SPIRou
tablee5.dat 31 223 Longitudinal field of DS Leo from ESPaDOnS,
Narval and SPIRou
tablee6.dat 31 168 Longitudinal field of CN Leo from ESPaDOnS,
Narval and SPIRou
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Byte-by-byte Description of file: tablee1.dat tablee2.dat tablee3.dat
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Bytes Format Units Label Explanations
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1- 10 A10 "date" Date Date of observation
12- 22 A11 "h:m:s" UT Universal time of observations
24- 32 F9.4 d HJD Heliocentric Julian date of the observation
(HJD-3450000)
34- 39 F6.2 --- Ncyc Cycle number as computed with Eq. 1
41- 45 A5 s texp Exposure time of polarimetric sequence
47- 49 I3 --- S/N Signal-to-noise ratio of polarimetric
sequence at 650nm
51- 53 F3.1 10-4 sigmaLSD RMS noise level of Stokes V
(in 1e-4 unpolarised continuum unit)
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Byte-by-byte Description of file: tablee4.dat tablee5.dat tablee6.dat
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Bytes Format Units Label Explanations
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1- 9 F9.4 d HJD Heliocentric Julian date of the observation
(HJD-2450000)
11- 16 F6.1 G Bl Longitudinal field
18- 22 F5.1 G e_Bl Formal error bar on longitudinal field
24- 31 A8 --- Inst Instrument
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Acknowledgements:
Stefano Bellotti, bellotti(at)strw.leidenuniv.nl
(End) Patricia Vannier [CDS] 15-Mar-2024