Analysis of actinium abundances in the atmosphere of Cepheid HIP13962

1Gopka, VF, 2Shavrina, AV, Yushchenko, VА, Pavlenko, YV, 3Yushchenko, AV, Glazunova, LV
1Scientific Research Institute "Astronomical Observatory" of I.I.Mechnikov Odessa National University, Odesa, Ukraine
2Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
3Astrocamp Contents Research Institute, Goyang, Republic of Korea
Kinemat. fiz. nebesnyh tel (Online) 2022, 38(2):63-73
https://doi.org/10.15407/kfnt2022.02.063
Start Page: Physics of Stars and Interstellar Medium
Language: Ukrainian
Abstract: 

Actinium is radioactive element, which has an isotope 227 Ac with the longest half-live of 21.772(3) years. It is the third element of a group of actinoids, abundance of which can be studied in the atmospheres of stars. Its presence in the atmosphere of a particular star primarily indicates some mechanism in which it is produced. The first studies of the absorption lines of actinium in the spectra of certain stars showed that the appearance of actinium in their spectrum is associated with the presence of deformation of strong lines, in some cases with emission components. To search for absorption lines of actinium in the spectra of stars we attracted attention to such class of stars as Cepheids, which are characterized by deformation of strong lines due to pulsations. The absorption lines of actinium were studied in the spectral interval of 378.0...887.7 nm for the runaway star and Cepheid HIP13962 using the spectra, obtained in 2014 with a 1.8-meter telescope at Bohunsan Optical Astronomical Observatory (BOAO, South Korea) with a spectral resolution greater than R = 80,000. Using the archived HIP 13962 spectrum for 1995 in the wavelength range of 400.0...680.0 nm with a spectral resolution of R = 42,000, which obtained with the 1.93-m telescope of the Haute Provence observatory (France). The modelling are shown that the abundance of actinium in the atmosphere of HIP 13962 logN(Ac) = –1.2 on the scale logN(H) = 12.0, when using the model atmosphere with Teff = = 5930 K, logg = 1.0, Vmicro = 6 km/s. This value turns out to be 0.2 more at an increase in the effective temperature Teff = 6250K: logN(Ac) = –1.0 on the hydrogen scales logN(H) = = 12.0.

Keywords: abundances, Cepheids, radioactive isotopes, star: HIP 13962, stellar evolution