Is it possible to derive Metallicity/Age/Radial Velocity/Rotational Velocity/Surface Gravity of a star from Hipparcos data files or are do they require individual studying?
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asked Mar 17, 2017 at 18:38
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Hipparcos measured the parallax (distance) of stars, along with their colors in two wavelength regions (B_Tycho, "blue" and V_Tycho, "green"). Using the color information you can make a reasonable estimate for the stellar temperature, and coupled with the parallactic distance, this would allow you to get an estimate for the stellar radius.
But Hipparcos does not provide us with any good information about stellar metallicities, ages*, radial velocity, rotation, or surface gravity.
* - aside from stars that you can group in position and velocity space to identify as belonging to stellar moving groups with defined ages.
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$\begingroup$ Thanks for the answer, I thought that would be the case. When you talk about B_Tycho and V_Tycho, you're talking U-B and B-V indices right? $\endgroup$ Commented Mar 17, 2017 at 21:49
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1$\begingroup$ Nope. Hipparcos had an onboard photomultiplier that measured photometry on several million stars. The filters it used were close to Johnson-Cousins B and V, but not quite. So all the stars in the Hipparcos (and Tycho) catalogs have "Tycho magnitudes" in these particular filters. The color index you can measure for each star is then B_Tyhco - V_Tycho. This also means that the transformation from (B_Tycho-V_Tycho) to temperature will not be quite the same as Johnson-Cousins (B-V) to temperature. $\endgroup$– ThomasCommented Mar 17, 2017 at 22:11