Disentangling stellar activity, pulsations, and keplerian motions

Disentangling stellar activity, pulsations, and keplerian motions Binaries workshop, Florence 14-16 October 2025 In collaboration with: Elena Pancino, Nicoletta Sanna, Sharmila Rani, and StarDance Team Deimer Alvarez, 16 October 2025 Deimer Alvarez, 16 October 2025 Cohen+76 Initially the emissions in the H-α wings were interpreted as signature of mass loss from RGB stars. Deimer Alvarez, 16 October 2025 Dupree+84 Dupree+84 suggested that the observed emission wings could arise naturally in a warm chromosphere, without the necessity for a mass loss. Deimer Alvarez, 16 October 2025 Smith+88 Later on temporal variations were found. This suggests differential mass motions in the chromosphere region. Smith+88 suggested that pulsation can be related to the H-α emission. “Should the H-α emission stars be pulsators, then it might be expected that they would exhibit light variations.” Deimer Alvarez, 16 October 2025 Meszaros+08 Meszaros+08,+09 found that some RGB stars in GCs show radial velocity variations (from ~2 to ~7 km/s). This could be due to: ●Binaries ●Pulsations Deimer Alvarez, 16 October 2025 What happens when we put everything together??? ●Active/variable chromosphere ●photometric variations ●radial velocity variations ●line variations Deimer Alvarez, 16 October 2025 Active/variable chromosphere Photometric variations Radial velocity variations Line variations Deimer Alvarez, 16 October 2025 Our platypus: RGB star near the tip, with log(L/L⭗) ~ 3.2 Deimer Alvarez, 16 October 2025 Nicoletta Sanna - Hunting for binary stars and exotic stellar populations - 16/10/2025 Li-rich stars Sanna et al. 2020 scenario PRO CONS 1 RGB bump different Hα 2 (RGB companion) similar Ba II extra - mixing companion 2 (AGB companion) / similar Ba II 2 (planet engulfment) different Hαhigher Li Conclusions More data are needed Sources of UV Excess • Chromospheric and coronal activity Sharmila Rani – Binary Workshop – October 14-16, 2025 • Chromospheric and coronal activity • Accretion Sources of UV Excess Credit: STScI Sharmila Rani – Binary Workshop – October 14-16, 2025 • Chromospheric and coronal activity • Accretion • Circumstellar material Sources of UV Excess Credit: NASA/ESA Sharmila Rani – Binary Workshop – October 14-16, 2025 • Chromospheric and coronal activity • Accretion • Circumstellar material • Presence of a hot companion e.g. white dwarf, subdwarf, etc. Sources of UV Excess Sharmila Rani – Binary Workshop – October 14-16, 2025 Methods to estimate UV Excess • Binary SED Modelling Sharmila Rani – Binary Workshop – October 14-16, 2025 • Binary SED Modelling • Color relation: E0(NUV) = (NUV− J)− (NUV− J)X Where (NUV− J)X = 10.36(J− Ks) + 2.76 Credit: Dixon+2020 Methods to estimate UV Excess Sharmila Rani – Binary Workshop – October 14-16, 2025 Li-rich Stars What are the minimum set of observables required to disentangle the binarity from any kind of activity or pulsations? Sharmila Rani – Binary Workshop – October 14-16, 2025 Credit: BSSL MAUVE • Wavelength range: 200-700 nm (NUV + Visible) • Telescope: 13 cm Cassegrain • Spectrometer: CMOS linear array • Grating: 600 lines/mm • Slit width: 500 μm •λ/Δλ: 20-65 UV Satellite Sharmila Rani – Binary Workshop – October 14-16, 2025 • Does chromospheric activity have any impact on the radial velocity of a star, and if any, how much? • Does chromospheric activity has anything to do with pulsation(s)? • Does any of the above-mentioned effects have any impact on the variation of abundances of some specific elements in peculiar stars? • How can we disentangle keplerian motions from any kind of activity or pulsations? Questions/Discussion Sharmila Rani – Binary Workshop – October 14-16, 2025