Functional relationships for $T_{\rm {eff}}$ and log~$g$ in F-G supergiants from $uvby\beta$ photometry

TL;DR

This paper develops functional relationships using $uvbyeta$ photometry to estimate effective temperature and gravity in F-G supergiants, applicable to both young and evolved stars, with some limitations in predicting absolute magnitudes.

Contribution

It introduces new functional relationships for estimating $T_{ m eff}$ and log~$g$ from photometry, extending their applicability to evolved supergiants.

Findings

Gravity can be predicted from $ riangle [c_1]$ with 0.26 dex uncertainty.

$T_{ m eff}$ relationships are valid for both young and evolved supergiants.

No reliable calibration for predicting $M_V$ from photometric indices.

Abstract

From photoelectric $uvby\beta$ data and recent accurate synthetic and spectroscopic values of $T_{\rm eff}$ and log~$g$ for 50 F-G supergiants, we have calculated functional relationships that lead to initial estimates of effective temperature and gravities for these types of stars. It is shown that while the $T_{\rm eff}$ relationships are calculated using the data on young massive supergiants, they are also valid for evolved stars of similar temperatures like post-AGB and RV Tau stars. The gravity can also be predicted from the $\Delta [c_1]$ index with an uncertainty of about 0.26 dex. Although a clear and significant trend between $M_V$ and $\Delta [c_1]$ is seen, no calibration is found that predicts accurate values of $M_V$.