Перегляд за Автор "Majaess, D. J."

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  • Ескіз
    Документ
    Spectroscopic investigations of Polaris field stars
    (Одеський національний університет імені І. І. Мечникова, 2023) Usenko, I. A.; Miroshnichenko, A. S.; Danford, S.; Turner, D. G.; Majaess, D. J.; Balam, D. D.
    We present the results of an analysis of 28 spectra of 18 Polaris field A–G V stars obtained in 2016–2023. Derived radial velocities and Teff along with distances and reddenings from the Gaia DR3 catalog allowed us to calculate radii of the stars and compare them with calibration relationships “Specral type – Luminosity” for MS stars. As a result, radii and distances for 9 stars were found overestimated compred to those determined photometrically. Therefore, the DR3 distances are unreliable and should be revisited. Accordring to our data for these stars and their photometric distances, 15 objects belong to a possible old open cluster that is currently dissolved in the Polarisfieldatadistance∼70–110pc, whiletwoobjectsbelong to the thick disk, and one belongs to a possible another star group located at a distance of 130 pc.
  • Ескіз
    Документ
    Spectroscopic studies of Polaris: getting back to normal life of a Cepheid?
    (Odesa I. I. Mechnikov National University, 2024) Usenko, Igor O.; Miroshnichenko, A. S.; Danford, S.; Vaidman, N. L.; Turner, D. G.; Majaess, D. J.; Protsyuk, S. V.; Усенко, Ігор Олександрович; Мірошніченко, А. С.; Данфорд, С.; Вайдман, Н. Л.; Тьорнер, Д.; Маджаєсс, Д. Дж.; Процюк, С. В.
    Based on 583 radial velocity (RV) measurements we obtained at the Three College Observatory (TCO, North Carolina, USA) in 2015–2024, (including 396 not previously analyzed from 2020–2024) as well as on 236 RV data from the German amateur R. Bücke (2011–2022), we calculated the pulsation period and amplitude of the Cepheid Polaris Aa system (α UMi). The analysis showed that the pulsation period was stable within a few minutes in 2020–2024. During this time, the pulsation amplitude was increasing and reached the 1960s level (4–6 km s−1), when its sharp decline began. Since its new growth began after Polaris Ab, the system secondary component, passed a periastron, we concluded that the observed amplitude changes were due to its orbital motion. It is clear that Polaris Aa is returning to normal pulsating activity.