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- ItemSpot evolution on LQ Hya from 2006-2017: Temperature maps based on SOFIN and FIES data(Les Ulis : EDP Sciences, 2019) Cole-Kodikara, Elizabeth M.; Käpylä, Maarit J.; Lehtinen, Jyri J.; Hackman, Thomas; Ilyin, Ilya V.; Piskunov, Nikolai; Kochukhov, OlegContext. LQ Hya is one of the most frequently studied young solar analogue stars. Recently, it has been observed to show intriguing behaviour when analysing long-term photometry. For instance, from 2003-2009, a coherent spot structure migrating in the rotational frame was reported by various authors. However, ever since, the star has entered a chaotic state where coherent structures seem to have disappeared and rapid phase jumps of the photometric minima occur irregularly over time. Aims. LQ Hya is one of the stars included in the SOFIN/FIES long-term monitoring campaign extending over 25 yr. Here, we publish new temperature maps for the star during 2006-2017, covering the chaotic state of the star. Methods. We used a Doppler imaging technique to derive surface temperature maps from high-resolution spectra. Results. From the mean temperatures of the Doppler maps, we see a weak but systematic increase in the surface temperature of the star. This is consistent with the simultaneously increasing photometric magnitude. During nearly all observing seasons, we see a high-latitude spot structure which is clearly non-axisymmetric. The phase behaviour of this structure is very chaotic but agrees reasonably well with the photometry. Equatorial spots are also frequently seen, but we interpret many of them to be artefacts due to the poor to moderate phase coverage. Conclusions. Even during the chaotic phase of the star, the spot topology has remained very similar to the higher activity epochs with more coherent and long-lived spot structures. In particular, we see high-latitude and equatorial spot activity, the mid latitude range still being most often void of spots. We interpret the erratic jumps and drifts in phase of the photometric minima to be caused by changes in the high-latitude spot structure rather than the equatorial spots. © E. M. Cole-Kodikara et al. 2019.
- ItemChemical composition of the RS CVn-type star lambda andromedae(Berlin : de Gruyter, 2010) Tautvaišiené, G.; Barisevičius, G.; Berdyugina, Svetlana V.; Chorniy, Yuriy; Ilyin, Ilya V.Photospheric parameters and chemical composition are determined for the single-lined chromospherically active RS CVn-type star λ And (HD 222107). From the high resolution spectra obtained on the Nordic Optical Telescope, abundances of 22 chemical elements and isotopes, including such key elements as 12C, 13C, N and O, were investigated. The differential line analysis with the MARCS model atmospheres gives Teff = 4830 K, log g = 2.8, [Fe/H] = -0.53, [C/Fe] = 0.09, [N/Fe] = 0.35, [O/Fe] = 0.45, C/N = 2.21, 12C/13C = 14. The 12C/13C ratio for a star of the RS CVn-type is determined for the first time, and its low value gives a hint that extra-mixing processes may start acting in low-mass chromospherically active stars below the bump of the luminosity function of red giants.
- ItemChemical composition of the RS CVn-type star 33 Piscium(Berlin : de Gruyter, 2011) Barisevičius, G.; Tautvaišiené, Gražina G.; Berdyugina, Svetlana V.; Chorniy, Yuriy; Ilyin, Ilya V.Abundances of 22 chemical elements, including the key elements and isotopes such as 12C, 13C, N and O, are investigated in the spectrum of 33 Psc, a single-lined RS CVn-type binary of low magnetic activity. The high resolution spectra were observed on the Nordic Optical Telescope and analyzed with the MARCS model atmospheres. The following main parameters have been determined: Teff = 4750 K, log g = 2.8, [Fe/H] = -0.09, [C/Fe] = -0.04, [N/Fe] = 0.23, [O/Fe] = 0.05, C/N = 2.14, 12C/13C = 30, which show the first-dredge-up mixing signatures and no extra-mixing.
- ItemChemical composition of the RS CVn-type star 29 Draconis(Berlin : de Gruyter, 2010) Barisevičius, G.; Tautvaišiené, Gražina G.; Berdyugina, Svetlana V.; Chorniy, Yuriy; Ilyin, Ilya V.Abundances of 22 chemical elements, including the key elements and isotopes such as 12C, 13C, N and O, are investigated in the spectrum of 33 Psc, a single-lined RS CVn-type binary of low magnetic activity. The high resolution spectra were observed on the Nordic Optical Telescope and analyzed with the MARCS model atmospheres. The following main parameters have been determined: Teff = 4750 K, log g = 2.8, [Fe/H] = -0.09, [C/Fe] = -0.04, [N/Fe] = 0.23, [O/Fe] = 0.05, C/N = 2.14, 12C/13C = 30, which show the first-dredge-up mixing signatures and no extra-mixing.