Towards Understanding The B[e] Phenomenon: VI. Nature and Spectral Variations of HD 85567

TL;DR

This study provides detailed spectroscopic and photometric analysis of HD 85567, constraining its fundamental parameters, distance, and nature, and concludes it is likely a binary system rather than a pre-main-sequence star.

Contribution

It offers new high-resolution spectroscopic data and comprehensive analysis that clarify the star's parameters and evolutionary status, challenging previous classifications.

Findings

HD 85567 has T_eff = 15000 K and log g ~ 4.0.

Distance to HD 85567 is approximately 1300 pc.

The star is unlikely to be a pre-main-sequence Herbig Ae/Be star.

Abstract

We report the results of high-resolution ($R \sim 80,000$) spectroscopic observations of the emission-line object HD 85567, which has been classified as a FS CMa type object or a pre-main-sequence star. The main goal is to put more constraints on the object's fundamental parameters as well as on its nature and evolutionary state. Absorption lines in the spectrum of HD 85567 were found similar to those of mid B--type dwarfs and correspond to the following fundamental parameters: T$_{\rm eff} = 15000\pm500$ K, $v \sin i = 31\pm3$ km s$^{-1}$, $\log g \sim 4.0$. The interstellar extinction, A$_V$ $= 0.50\pm0.02$ mag, was measured using the strengths of some diffuse interstellar bands. We also obtained $UBV(RI)_{\rm c}$ images of a $10^{\prime} \times 10^{\prime}$ region around the object. Photometry of projectionally close stars was used to derive an interstellar extinction law in this direction and resulted in a distance of 1300$\pm$100 pc to the object and a luminosity of $\log$ (L/L$_\odot) = 3.3\pm0.2$. We found no significant radial velocity variations of the absorption lines in the spectra of HD 85567 obtained during two month-long periods of time in 2012 and 2015. Our analysis of the spectroscopic and photometric data available for the star led us to a conclusion that it cannot be a pre-main-sequence Herbig Ae/Be star. We argue that the circumstellar gas and dust were produced during the object's evolution as most likely a binary system, which contains an undetected secondary component and is unlikely to be a merger product.