Fundamental parameters of barium and CH stars from asteroseismic analysis: HD 33409, HD 20084 and HD 66812

Abstract

Asteroseismic analysis of stars using space mission data, such as the transiting exoplanet survey satellite (TESS) allows us to derive accurate fundamental parameters of stars. Barium and CH stars are believed to be in binary systems with a now invisible white dwarf companion. Knowledge of accurate fundamental parameters of these stars is essential to understand the origin of the peculiar abundance patterns observed in these stars. In this work, we have presented estimates of the fundamental parameters derived using asteroseismic analysis for three objects HD 33409, HD 20084 and HD 66812 selected from barium and CH stars catalogs. We have analysed the TESS photometric data using lightkurve Python package employing the aperture photometry, derived the asteroseismic parameters, and using scaling relations, calculated the stellar parameters. We have estimated power excess $(\nu _{\max })$ at $44.50\pm 0.50$ $\mu \mathrm{Hz}$ and large frequency separation $(\Delta \nu )$ to be $4.77\pm 0.10$ $\mu \mathrm{Hz}$ for HD 33409. These two values for HD 20084 and HD 66812 are ($48.50\pm 0.50$ $\mu \mathrm{Hz}$, $4.88\pm 0.10$ $\mu \mathrm{Hz}$) and ($22.50\pm 0.50$ $\mu \mathrm{Hz}$, $2.47\pm 0.10$ $\mu \mathrm{Hz}$), respectively. Our results showed that the primary component is a giant branch star with mass, radius, surface gravity and luminosity $\log (L/L_{\odot }$) of $1.46\pm 0.07$ $M_{\odot }$, $10.54 \pm 0.12$ $R_{\odot }$, $2.56 \pm 0.01$ dex and 1.71, respectively, for HD 33409. These values for HD 20084 and HD 66812 are ($1.84 \pm 0.07$ $M_{\odot }$, $11.21\pm 0.12$ $R_{\odot }$, $2.60\pm 0.01$ dex, 1.87) and ($2.78\pm 0.07$ $M_{\odot }$, $20.26\pm 0.12$ $R_{\odot }$, $2.27\pm 0.01$ dex, 2.37), respectively. The estimated stellar parameters obtained from asteroseismology are compared with literature values whenever possible and found to be in fair agreement with spectroscopic estimates. Stellar mass derived using parallax method is also found to be in close agreement in the case of HD 33409 and HD 20084. While the parallax method gives mass value of 4 $M_{\odot }$ for HD 66812, the asteroseismic estimate is much smaller ${\sim }$2.78 $M_{\odot }$ for this object.

Appendix: Phase vs normalized flux plots

See Figures 11 and 12.

Figure 11

Phase vs. normalized flux plots for HD 33409 for sectors 1–8 and 10–13. The object was not observed in sector 9.

Figure 12

Rotation phase vs. normalized flux plots for HD 20084 (for sectors 19, 20, 25, 26 and 40) and HD 66812 (for sectors 7, 8, 34 and 35).