Stellar and substellar companions from Gaia EDR3

To identify gravitationally bound visual companions of our sample, we search the Gaia EDR3 catalog for common proper motion (CPM) candidates. The detection of tangential velocity anomalies with a median accuracy of 26cm/s per parsec of distance is demonstrated with the EDR3. This improvement by a factor 2.5 in accuracy compared to the Gaia DR2 results in PMa detection limits on companions well into the planetary mass regime for many targets.

We identify 37515 Hipparcos stars presenting a PMa at significant level (S/N>3), that is, a fraction of 32% (compared to 30% for the DR2) and 12914 (11%) hosting CPM bound candidate companions. Including the Gaia EDR3 RUWE>1.4 as an additional indicator, 50,720 stars of the Hipparcos catalog (43%) exhibit at least one signal of binarity. Among the Gaia EDR3 stars located within 100 pc, we find CPM bound candidate companions for 39,490 stars (7.3% of the sample).

The search for companions using a combination of the PMa, CPM and RUWE indicators significantly improves the exhaustivity of the multiplicity survey. The detection of CPM companions of very bright stars (heavily saturated on the Gaia detectors) that are classical benchmark objects for stellar physics provides a useful proxy to estimate their distance with a higher accuracy than Hipparcos.