# 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.

• A very specific question. Would you care to explain the significance of this star to you? – James K Mar 20 at 12:16
• I was just looking for some parameters of several stars and this strikes me to be unclear. Many thanks for demonstrating other ways of searching. – Elena Greg Mar 20 at 12:57
• Not every question has to be long or reveal "motive". This one is clear, concise and answerable as-is. The vote to close because it "should include more details and clarify the problem" is unproductive, clutters the review queue and makes unnecessary work for others – uhoh Mar 21 at 23:21

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.

• Thank you very much – Elena Greg Mar 20 at 12:56

Simbad gives a parallax of 4.0452 mas, which is equivalaent to 1/0.0040452 parsecs.

That is 247 parsecs or 805 light years (but the error bars on that are quite high, 0.59 mas ie from 700 to 940 light years)

It is listed as in spectral class F0, which means up to about 1.5 times the mass of the sun. It is also listed as a double star, so this refers to the major component.

• Thank you very much – Elena Greg Mar 20 at 12:56