Context

TESS is a space mission that seeks to discover thousands of new exoplanets by surveying the entire sky.

Gaia is a space mission aimed at mapping a billion astronomical objects. Gaia collects photometric data, as well as parallax measurements, which are used to calculate distance.

Content

This is a crossmatch of Gaia DR2 and TESS targets of interest, limited to 500 parsecs from the sun, and a maximum Gaia G magnitude of 13.5.

A baseline Gaia DR2 dataset was obtained with the following ADQL query from the Gaia Archive:

select G.source_id,G.ra,G.dec,G.pmra,G.pmdec,        G.parallax,G.parallax_error,G.l,G.b,        G.phot_g_mean_mag,        TBN.tmass_oid from gaiadr2.gaia_source G inner join gaiadr2.tmass_best_neighbour TBN ON TBN.source_id=G.source_id WHERE TBN.number_of_neighbours=1 AND TBN.best_neighbour_multiplicity=1 AND TBN.angular_distance <= 1.0 AND parallax >= 2.0 and phot_g_mean_mag <= 13.5 AND parallax_error IS NOT NULL 

The baseline Gaia DR2 dataset contains 2372846 rows.

A list of TESS targets was obtained from MIT's TESS website. For each of these TESS targets, the closest match was found in the baseline Gaia DR2 dataset, after adjusting for epoch, using Gaia's proper motion estimates. A match was accepted if the angular distance between matched objects is less than 1 arcsecond. But the match was discarded if the second-best match in Gaia DR2 is less than 3 arcseconds from the TESS target.

The number of unique TESS targets is 293511. After the initial pass at cross-matching, we are left with 197421 targets. Rows with duplicate source_id are dropped altogether. This leaves 197365 targets. Finally, we do an analysis of differences between the TESS magnitude and Gaia's G magnitude. Any outliers beyond 4-sigma in the difference distribution were discarded, leaving a final total of 197064 targets.

The cross-matching code is available on GitHub.

Note on Epoch

We're told that the epoch of TESS Input Catalog celestial coordinates should be J2000. However, in testing we find that an epoch of J2020.5 (5 years after Gaia DR2, which is J2015.5) produces a greatly improved match, both in terms of the number of objects matched and the mean angular distance between matched targets.

Acknowledgements

This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

We acknowledge the use of public TOI Release data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Funding for the TESS mission is provided by NASA’s Science Mission directorate.