HD 51684 - mass and distance Where to find, if it is possible, values of the mass and the distance of HD 51684, please? Many thanks.
HD 51684 is a magnetic Ap star. It has an entry in the recent catalogue of fundamental parameters for magnetic stars by Glagolevskij (2019). This catalogue lists it as having $T_{\rm eff}=7800$ K, and a mass of $2.3 M_\odot$.
These parameters are determined from the photometric properties of the star - i.e. they are not fundamental measurements of the temperature or mass.
The mass quoted by Kervella et al. (2019), in a study of binarity using Gaia data (HD 51684 is a known binary) is $2.195M_\odot$. However this is spurious precision; this mass comes from matching the inferred luminosity and temperature to stellar evolutionary models, not from a measurement of the binary motion.
The distance has been most precisely and accurately determined by Gaia EDR3
The parallax is $4.51 \pm 0.24$ arcsec. Roughly speaking, you can invert that to give a distance of $222 \pm 12$ pc.