J/A+A/696/A23 Chromospherically active stars (Bale+, 2025)
Chromospherically active stars:
Chemical composition of photospheres in 20 RS CVn stars.
Bale B., Tautvaisiene G., Minkeviciute R., Drazdauskas A., Mikolaitis S.,
Stonkute E., Ambrosch M.
<Astron. Astrophys. 696, A23 (2025)>
=2025A&A...696A..23B 2025A&A...696A..23B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Abundances ; Spectroscopy
Keywords: stars: abundances - stars: magnetic field - stars: variables: general
Abstract:
Various element transport processes modify the photospheric chemical
composition of low-mass stars during their evolution. The most
prominent one is the first dredge-up that occurs at the beginning of
the red giant branch. Then, various extra-mixing processes, e.g.
caused by thermohaline- or and rotation-induced mixing, come into
action. The extent of influence of stellar magnetic activity on
alterations of stellar chemical composition is among the least studied
questions.
To investigate how magnetic activity influences mixing in atmospheres
of magnetically active stars, we carried out a detailed study of C, N,
and up to ten other chemical element abundances, as well as carbon
isotope ratios in a sample of RS,CVn stars.
High-resolution spectra, observed with the VUES spectrograph on the
1.65m telescope at the Moletai Astronomical Observatory of Vilnius
University, were analyzed using a differential model atmosphere
method. Abundances of carbon were derived using the spectral synthesis
of the C_2 band heads at 5135 and 5635.5Å. The wavelength intervals
6470-6490Å and 7980-8005Å with CN features, was analyzed to
determine nitrogen abundances. The carbon isotope ratios were
determined from the 13 CN line at 8004.7Å. Oxygen abundances were
determined from the [OI] line at 6300Å. Abundances of other chemical
elements were determined from equivalent widths or spectral syntheses
of unblended spectral lines.
We determined the main atmospheric parameters and abundances of up to
12 chemical elements for a sample of 20 RS CVn giants representing
different evolutionary stages. We determined that *29 Dra, *b01 Cyg,
and V* V834 Her, which are in the evolutionary stage below the red
giant branch luminosity bump, already show the extra-mixing evidences
in their lowered carbon isotope ratios.
We provide observational evidence that in low-mass chromospherically
active RS CVn stars due to their magnetic activity the extra-mixing
processes may start acting below the luminosity bump of the red giant
branch.
Description:
High resolution spectroscopic analysis of 20 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. Stellar atmospheric
parameters along with C, N, O , MgI, SiI, CaI, ScI, ScII, TiI,
TiII, CrI, CrII, FeI, FeII, CoI, NiI along with CC and CN ratio
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 321 30 Stellar physical and chemical properties
--------------------------------------------------------------------------------
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 A15 --- TYC-2 Tycho-2 catalogue identification
17- 27 A11 --- Name Stellar star
29- 33 I5 --- Res Spectral resolution
35- 38 I4 K Teff Effective temperature
40- 41 I2 K e_Teff Uncertainty in effective temperature
43- 46 F4.2 [cm/s2] logg Stellar surface gravity
48- 51 F4.2 [cm/s2] e_logg Uncertainty in stellar surface gravity
53- 57 F5.2 [-] [Fe/H] Metallicity
59- 62 F4.2 [-] e_FeI Uncertainty in [FeI/H]
64- 66 I3 --- n_FeI Number of FeI lines
68- 71 F4.2 [-] e_FeII Uncertainty in [FeII/H]
73- 74 I2 --- n_FeII Number of FeII lines
76- 79 F4.2 [km/s] Vt Microturbulence velocity
81- 84 F4.2 [km/s] e_Vt Uncertainty in microturbulence velocity
86- 90 F5.2 [-] [C/H] Carbon abundance
92- 95 F4.2 [-] e_[C/H] Uncertainty in carbon abundance
97 I1 --- n_C Number of C2 lines
99-103 F5.2 [-] [N/H] Nitrogen abundance
105-108 F4.2 [-] e_[N/H] Uncertainty in nitrogen abundance
110-111 I2 --- n_N Number of CN lines
113-117 F5.2 [-] [O/H] Oxygen abundance
119-122 F4.2 [-] e_[O/H] Uncertainty in oxygen abundance
124 I1 - n_O Number of oxygen lines
126-130 F5.2 [-] [Mg/H] Magnesium abundance
132-135 F4.2 [-] e_[Mg/H] ?=- Uncertainty in magnesium abundance
137 I1 --- n_Mg Number of magnesium lines
139-143 F5.2 [-] [Si/H] Silicon abundance
145-148 F4.2 [-] e_[Si/H] Uncertainty in silicon abundance
150-151 I2 --- n_Si Number of silicon lines
153-157 F5.2 [-] [Ca/H] Calcium abundance
159-162 F4.2 [-] e_[Ca/H] Uncertainty in calcium abundance
164-165 I2 --- n_Ca Number of calcium lines
167-171 F5.2 [-] [ScI/H] Scandium abundance from neutral lines
173-176 F4.2 [-] e_[ScI/H] Uncertainty in [ScI/H] abundance
178 I1 - n_ScI Number of [ScI/H] lines
180-184 F5.2 [-] [ScII/H] Scandium abundance from ionized lines
186-189 F4.2 [-] e_[ScII/H] Uncertainty in [ScII/H] abundance
191-192 I2 --- n_ScII Number of [ScII/H] lines
194-198 F5.2 [-] [TiI/H] Titanium abundance from neutral lines
200-203 F4.2 [-] e_[TiI/H] Uncertainty in [TiI/H] abundance
205-206 I2 -- n_TiI Number of [TiI/H] lines
208-212 F5.2 [-] [TiII/H] Titanium abundance from ionized lines
214-217 F4.2 [-] e_[TiII/H] Uncertainty in [TiII/H] abundance
219-220 I2 -- n_TiII Number of [TiII/H] lines
222-226 F5.2 [-] [CrI/H] Chromium abundance from neutral lines
228-231 F4.2 [-] e_[CrI/H] Uncertainty in [CrI/H] abundance
233-234 I2 -- n_CrI Number of [CrI/H] lines
236-240 F5.2 [-] [CrII/H] ?=- Chromium abundance from ionized lines
242-245 F4.2 [-] e_[CrII/H] ?=- Uncertainty in [CrII/H] abundance
247-249 A3 -- n_CrII Number of [CrII/H] lines
251-255 F5.2 [-] [Co/H] Cobalt abundance
257-260 F4.2 [-] e_[Co/H] Uncertainty in cobalt abundance
262-263 I2 -- n_Co Number of cobalt lines
265-269 F5.2 [-] [Ni/H] Nickel abundance
271-274 F4.2 [-] e_[Ni/H] Uncertainty in nickel abundance
276-277 I2 -- n_Ni Number of nickel lines
279-281 I3 [-] 12C/13C ?=- Carbon isotope ratio
283-285 I3 [-] e_12C/13C ?=- Uncertainty in carbon isotope ratio
287-290 F4.2 [-] C/N Carbon-to-nitrogen abundance ratio
292-295 F4.2 Msun Mass Stellar mass
297-300 F4.2 Msun e_Mass Uncertainty of mass
302-306 F5.2 Gyr Age Stellar age
308-311 F4.2 Gyr e_Age Uncertainty of age
313-316 F4.2 kpc Rmean ?=- Mean galactocentric distance
318-321 F4.2 kpc e_Rmean ?=- Uncertainty of mean galactocentric
distance
--------------------------------------------------------------------------------
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] 24-Feb-2025