J/A+A/640/A52 M dwarfs HeI infrared triplet variability (Fuhrmeister+, 2020)
The CARMENES search for exoplanets around M dwarfs.
Variability of the He I IR line at 10830 Å.
Fuhrmeister B., Czesla S., Hildebrandt L., Nagel E., Schmitt J.H.M.M.,
Jeffers S.V., Caballero J.A., Hintz D., Johnson E.N., Schoefer P.,
Zechmeister M., Reiners A., Ribas I., Amado P.J., Quirrenbach A.,
Nortmann L., Bauer F.F., Bejar V.J.S., Cortes-Contreras M., Dreizler S.,
Galadi-Enriquez D., Hatzes A.P., Kaminski A., Kuerster M., Lafarga M.,
Montes D.
<Astron. Astrophys. 640, A52 (2020)>
=2020A&A...640A..52F 2020A&A...640A..52F (SIMBAD/NED BibCode)
ADC_Keywords: Stars, M-type; Spectra, infrared
Keywords: stars: activity - stars: chromospheres - stars: late-type
Abstract:
The HeI infrared (IR) triplet at 10830Å is an important activity
indicator for the Sun and in solar-type stars, however, it has rarely
been studied in relation to M dwarfs to date. In this study, we use
the time-averaged spectra of 319 single stars with spectral types
ranging from M0.0 V to M9.0V obtained with the CARMENES high
resolution optical and near-infrared spectrograph at Calar Alto to
study the properties of the HeI IR triplet lines. In quiescence, we
find the triplet in absorption with a decrease of the measured pseudo
equivalent width (pEW) towards later sub-types. For stars later than
M5.0 V, the HeI triplet becomes undetectable in our study. This
dependence on effective temperature may be related to a change in
chromospheric conditions along the Mdwarf sequence. When an emission
in the triplet is observed, we attribute it to flaring. The absence of
emission during quiescence is consistent with line formation by
photo-ionisation and recombination, while flare emission may be caused
by collisions within dense material. The HeI triplet tends to increase
in depth according to increasing activity levels, ultimately becoming
filled in; however, we do not find a correlation between the pEW(He
IR) and X-ray properties. This behaviour may be attributed to the
absence of very inactive stars (LX/Lbol←5.5) in our sample or to the
complex behaviour with regard to increasing depth and filling in.
Description:
The HeI infrared (IR) triplet at 10830Å is known as an activity
indicator and has become a primary diagnostic in exoplanetary
transmission spectroscopy. The HeI IR lines are a tracer of the
stellar extreme-ultraviolet irradiation from the transition region and
corona. We study the variability of the HeI IR triplet lines in
spectral time series of 319 M dwarf stars, obtained with the CARMENES
spectrograph.
We measure the pseudo-equivalent width (pEW) in each stellar spectrum.
The integration ranges for the line and the reference bands are found
in Table 1 of the paper. For comparison purposes we also measure pEW
values of Hα, the bluest CaII IR triplet line, and the HeI D3
line. From these measurements we compute the mean pEW, the median
absolute deviation (MAD) and Pearson's correlation coefficients for
the lines.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 140 319 HeI infrared triplet variability measurements
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See also:
J/A+A/632/A24 : HeI IR triplet measurements for M dwarfs (Fuhrmeister+, 2019)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Karmn CARMENES identification number
17- 22 F6.3 --- corr(He-Ha) Correlation coefficient HeI IR and
Hα
25- 29 F5.3 --- p(He-Ha) p-value HeI IR and Halpha
32- 37 F6.3 --- corr(He-HeD3) Correlation coefficient He I IR and
HeI D_3
40- 44 F5.3 --- p(He-HeD3) p-value HeI IR and HeI D3
48- 53 F6.3 --- corr(He-Ca) Correlation coefficient HeI IR and
CaII IRT
56- 60 F5.3 --- p(He-Ca) p-value HeI IR and CaII IRT
63- 68 F6.3 --- corr(Ha-Ca) Correlation coefficient Halpha and
CaII IRT
72- 76 F5.3 --- p(Ha-Ca) p-value Hα and CaII IRT
79- 84 F6.3 0.1nm mean(pEW(He)) Mean pEW(HeI IR)
87- 92 F6.3 0.1nm mean(pEW(Ha)) Mean pEW(Hα)
96-101 F6.3 0.1nm mean(pEW(HeD3)) Mean pEW(HeI D3)
104-109 F6.3 0.1nm mean(pEW(Ca)) Mean pEW(CaII IRT)
113-117 F5.3 0.1nm MAD(pEW(He)) Median absolute deviation (MAD)
pEW(HeI IR)
120-124 F5.3 0.1nm MAD(pEW(Ha)) Median absolute deviation (MAD)
pEW(Hα)
128-132 F5.3 0.1nm MAD(pEW(HeD3)) Median absolute deviation (MAD)
pEW(HeI D3)
136-140 F5.3 0.1nm MAD(pEW(Ca)) Median absolute deviation (MAD)
pEW(CaII IRT)
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Acknowledgements:
Birgit Fuhrmeister, bfuhrmeister(at)hs.uni-hamburg.de
(End) B. Fuhrmeister [Hamburg Univ., Germany], P. Vannier [CDS] 04-Jun-2020