J/A+A/703/A128 Chromospherically active stars (Bale+, 2025)
Chromospherically active stars:
Lithium and CNO abundances in northern RS CVn stars.
Bale B., Tautvaisiene G., Minkeviciute R., Drazdauskas A., Mikolaitis S.,
Stonkute E., Ambrosch M.
<Astron. Astrophys. 703, A128 (2025)>
=2025A&A...703A.128B 2025A&A...703A.128B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Magnetic fields ; Abundances
Keywords: stars: abundances - stars: evolution - stars: magnetic field
Abstract:
We carried out a detailed investigation of Lthium and CNO abundances,
including carbon isotope ratios, in RS CVn stars to assess the role of
magnetic activity in the mixing of stellar atmospheres.
High-resolution spectra were observed at the Moletai Astronomical
Observatory to determine the lithium abundances by spectral synthesis
of the 6707Å line and the CNO abundances using the C2 band heads at
5135 and 5635.5Å, CN bands at 6470-6490Å and 7980-8005Å, and
the [O I] line at 6300Å. By fitting the 13CN band at 8004.7Å,
we determined the carbon isotope ratios.
We determined the main atmospheric parameters and investigated the
chemical composition for 32 RS CVn stars. Lithium NLTE abundances were
determined for 13 additional stars using archival spectra. We found
that iota Gem and HD 179094 have carbon isotope ratios already
affected by extra-mixing, even though being in the evolutionary stage
below the red giant branch luminosity bump. About half of the low-mass
giants, for which the lithium abundance was determined, follow the
first dredge-up predictions; however, other stars have Li abundances
reduced as predicted by the thermohaline-induced mixing. The
intermediate-mass stars have Li abundances reduced as predicted by the
rotation-induced mixing.
We found that in low-mass chromospherically active RS CVn stars extra
mixing of lithium along with carbon isotopes may begin earlier than in
normal giants. The Li-rich RS CVn giant V* OP And has quite large C/N
and carbon isotope ratios, and raises questions about the origin of
its lithium enhancement.
Description:
High resolution spectroscopic analysis of 32 RS CVn stars in the
northern hemisphere are presented. The observations are collected with
the 1.65m telescope and VUES spectrograph at the Moletai Astronomical
Observatory of Institute of Theoretical Physics and Astronomy, Vilnius
University. This spectrograph has a wavelength coverage from 400 to
900nm. For observations in this study, we used the spectral
resolutions R∼36000 and R∼68000. Lithium NLTE abundances were
determined for 13 additional stars using archival spectra.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 172 41 Atmospheric parameters
tablea2.dat 51 61 Lithium abundances
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- ID Tycho-2 catalogue identification
17- 28 A12 --- Name Stellar name
30- 34 I5 --- Res Spectral resolution
36- 39 I4 K Teff Effective temperature
41- 42 I2 K e_Teff Uncertainity in effective temperature
44- 47 F4.2 [cm/s2] logg Stellar surface gravity
49- 52 F4.2 [cm/s2] e_logg Uncertainity in stellar surface gravity
54- 58 F5.2 [-] [Fe/H] Metallicity
60- 63 F4.2 [-] e_[FeI/H] Uncertainity in [Fe I/H]
65- 66 I2 --- o_FeI Number of Fe I lines
68- 71 F4.2 [-] e_[FeII/H] Uncertainity in [Fe II/H]
73 I1 --- o_FeII Number of Fe II lines
75- 78 F4.2 km/s Vt Microturbulence velocity
80- 83 F4.2 km/s e_Vt Uncertainity in microturbulence velocity
85- 89 F5.2 [-] [C/H] ?=- Carbon abundance
91- 94 F4.2 [-] e_[C/H] ?=- Uncertainity in carbon abundance
96- 98 I3 --- o_C ?=- Number of C2 lines
100-104 F5.2 [-] [N/H] ?=- Nitrogen abundance
106-109 F4.2 [-] e_[N/H] ?=- Uncertainity in nitrogen abundance
111-113 I3 --- o_N ?=- Number of CN lines
115-119 F5.2 [-] [O/H] ?=- Oxygen abundance
121-124 F4.2 [-] e_[O/H] Uncertainity in oxygen abundance
126 I1 --- o_O Number of oxygen lines
128-132 F5.2 [-] [Mg/H] Magnesium abundance
134-137 F4.2 [-] e_[Mg/H] Uncertainity in magnesium abundance
139-142 F4.2 --- o_Mg Number of magnesium lines
144-146 I3 --- 12C/13C ?=- Carbon isotope ratio
148-150 I3 --- e_12C/13C ?=- Uncertainity in carbon isotope ratio
152-155 F4.2 --- C/N ?=- Carbon-to-nitrogen abundance ratio
157-160 F4.2 Msun Mass Stellar mass
162-165 F4.2 Msun e_Mass Uncertainity of mass
167-168 A2 --- Evol Evolutionary stage (1)
170-172 A3 --- Em [YES -] YES if emission is visible in the
CaII lines
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Note (1): Evolutionary stage as follows:
BB = stars below the RGB luminosity bump
AB = stars above the RGB luminosity bump
RC = Clump stars
SG = subgiant stars
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- ID Tycho-2 catalogue identification
17- 28 A12 --- Name Stellar name
30- 34 I5 --- Res Spectral resolution
36- 39 F4.2 [-] A(Li)LTE ?=- Lithium abundance in LTE
41- 44 F4.2 [-] A(Li)NLTE ?=- Lithium abundance in NLTE
46- 49 F4.2 [-] e_A(Li) ?=- Uncertainity in lithium abundance
51 I1 --- l_A(Li) [0/1]?=- Limit flag on A(Li)
(1 for upper limit)
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Acknowledgements:
From Barkha Bale, barkha.bale(at)ff.vu.lt
We acknowledge funding from the Research Council of Lithuania (LMTLT,
grant No. S-MIP-23-24). This work has made use of data from the
European Space Agency (ESA) mission Gaia
(https://www.cosmos.esa.int/gaia), processed by the Gaia Data
Processing and Analysis Consortium (DPAC,
https://www.cosmos.esa.int/web/gaia/dpac/ consortium). Funding for the
DPAC has been provided by national institutions, in particular, the
institutions participating in the Gaia Multilateral Agreement. We have
made extensive use of the NASA ADS and SIMBAD databases.
(End) Barkha Bale [ITPA, VU], Patricia Vannier [CDS] 29-Oct-2025