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tcjansen / GSoC

Google Summer of Code with OpenAstronomy: Extending the capabilities of synphot, a Python package for generating synthetic photometry
BSD 3-Clause "New" or "Revised" License
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Enhancement: Gaia queries for stellar properties #2

Closed bmorris3 closed 5 years ago

bmorris3 commented 5 years ago

Enhancement proposal: use astroquery to get the stellar distance and radius like I do in this example, rather than hard-coding the answers into the notebook. You'll need to come up with a more clever way of selecting the correct answer from the query response than choosing the first row, as I did in the example. You might find that the answer is the star closest to the input coordinates. You can measure distances between coordinates using SkyCoord.separation(). 📐

tcjansen commented 5 years ago

Just as an update on this, the astroquery.Gaia table has a column for distance to the input coordinate, so I used that in place of SkyCoord.separation().

As for choosing the star nearest to the given coordinates (which is what I would have suggested as well), it worked great for HAT-P-11, but became a problem when SkyCoord and Gaia disagreed on the RA and Dec of Trappist-1... they give:

SkyCoord: 346.622, -5.0414
Gaia: 346.626, -5.0435

Since Gaia has a source closer to the SkyCoord coordinates than its TRAPPIST-1 coordinates, it selects the wrong object.

What's more, Gaia unfortunately doesn't have a stellar radius for TRAPPIST-1... All to say I think we need to query a different catalog for this star!

bmorris3 commented 5 years ago

Ok, let's supply it with the radius, distance, and effective temperature parameters for TRAPPIST-1 manually from Gillon et al. 2017.