J/A+A/678/A1 Paschen lines in M dwarfs chromospheres (Fuhrmeister+, 2023)
The CARMENES search for exoplanets around M dwarfs.
Behaviour of the Paschen lines during flares and quiescence.
Fuhrmeister B., Czesla S., Schmitt J.H.M.M., Schneider P.C., Caballero J.A.,
Jeffers S.V., Nagel E., Montes D., Galvez Ortiz M.C., Reiners A., Ribas I.,
Quirrenbach A., Amado P.J., Henning T., Lodieu N., Martin-Fernandez P.,
Morales J.C., Schoefer P., Seifert W., Zechmeister M.
<Astron. Astrophys. 678, A1 (2023)>
=2023A&A...678A...1F 2023A&A...678A...1F (SIMBAD/NED BibCode)
ADC_Keywords: Stars, M-type ; Spectra, infrared
Keywords: stars: activity - stars: chromospheres - stars: late-type
Abstract:
The hydrogen Paschen lines are known activity indicators, but studies
of them in M dwarfs during quiescence are as rare as their reports in
flare studies. This situation is mostly caused by a lack of
observations, owing to their location in the near-infrared regime,
which is covered by few high-resolution spectrographs. We study the
Paβ line, using a sample of 360 M dwarfs observed by the CARMENES
spectrograph. Descending the spectral sequence of inactive M stars in
quiescence, we find the Paβ line to get shallower until about
spectral type M3.5 V, after which a slight re-deepening is observed.
Looking at the whole sample, for stars with Hα in absorption, we
find a loose anti-correlation between the (median) pseudo-equivalent
widths (pEWs) of Hα and Paβ for stars of similar effective
temperature. Looking instead at time series of individual stars, we
often find correlation between pEW(Hα) and pEW(Paβ) for
stars with Hα in emission and an anti-correlation for stars with
Hα in absorption. Regarding flaring activity, we report the
automatic detection of 35 Paschen line flares in 20 stars.
Additionally we found visually six faint Paschen line flares in these
stars plus 16 faint Paschen line flares in another 12 stars. In strong
flares, Paschen lines can be observed up to Pa 14. Moreover, we find
that Paschen line emission is almost always coupled to symmetric
Hα line broadening, which we ascribe to Stark broadening,
indicating high pressure in the chromosphere. Finally we report a few
Paβ line asymmetries for flares that also exhibit strong Hα
line asymmetries.
Description:
The hydrogen Paschen beta, gamma, and delta lines are studied in a
sample of 360 M dwarfs using CARMENES spectra by using pseudo
equivalent width (pEW) measurements for a flare search. The Paschen
lines are purely of chromospheric origin. We identified Paβ in
all stellar spectra and found, that the line gets more shallow for
later spectral types with a slight re-deepening for types later than
M3.5. For similar effective temperature and Hα in absorption,
pEW(Hα) anti-correlates with pEW(Paβ). We report the
detection of 35 Paschen line flares in 20 stars following the
thresholds for flares listed in the paper.
We measure the pseudo-equivalent width (pEW) of the Pa lines in each
stellar spectrum. The integration ranges for the lines and the
reference bands are found in Table 1 of the paper. For comparison
purposes we also measure pEW values of Hα.
From these measurements we compute the median pEW and the median
absolute deviation (MAD) for the lines.
We also list some basic stellar parameters.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 193 360 Pa line measurements
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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
15- 44 A30 --- Name Common name of object
48- 51 F4.1 --- SpType Spectral type
56- 61 F6.1 K Teff Effective temperature
68- 71 F4.2 [cm/s2] logg Surface gravity
75- 81 F7.3 0.1nm pEWHal Median Hα pseudo equivalent width (1)
88- 93 F6.3 0.1nm pEWPab Median Paβ pseudo equivalent width (1)
100-105 F6.3 0.1nm pEWPag Median Paγ pseudo equivalent width (1)
112-117 F6.3 0.1nm pEWPad Median Paδ pseudo equivalent width (1)
125-129 F5.3 0.1nm MAD(pEWHa) Median average deviation about the median
(MAD) of pEW(Halpha)
137-141 F5.3 0.1nm MAD(pEWPab) Median average deviation about the median
(MAD) of pEWPab
149-153 F5.3 0.1nm MAD(pEWPag) Median average deviation about the median
(MAD) of pEWPag
161-165 F5.3 0.1nm MAD(pEWPad) Median average deviation about the median
(MAD) of pEWPad
174-179 F6.2 d Prot Rotation period
190-193 F4.1 km/s vsini Rotational velocity
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Note (1): Table 1: Parameters (vacuum wavelength) of the pEW calculation.
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Line Wavelength Width Reference band 1 Reference band 2
(Å) (Å) (Å) (Å)
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Hα 6564.60 1.6 6537.4- 6547.9 6577.9- 6586.4
CaII IRT1 8500.35 0.5 8476.3- 8486.3 8552.4- 8554.4
CaII IRT2 8544.44 0.5 8576.3- 8486.3 8552.4- 8554.4
Paβ (Pa 5) 12821.58 0.6 12812.0-12814.0 12789.0-12792.0
Paγ (Pa 6) 10941.17 1.5 10902.0-10904.0 10964.7-10966.7
Paδ (Pa 7) 10052.60 1.5 10045.0-10047.0 10076.0-10078.0
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Acknowledgements:
Birgit Fuhrmeister, bfuhrmeister(at)hs.uni-hamburg.de
(End) B. Fuhrmeister [Hamburg Univ., Germany], P. Vannier [CDS] 16-Aug-2023