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SUMMARY:Stellar and substellar companions from Gaia EDR3 and Hipparcos ast
 rometry - Pierre Kervella\, Observatoire de Paris
DTSTART:20220208T130000Z
DTEND:20220208T140000Z
UID:TALK169223@talks.cam.ac.uk
CONTACT:Dr Mathias Nowak
DESCRIPTION:In order to study their binary fraction\, we searched for comp
 anions of Hipparcos catalog stars from the proper motion anomaly (PMa) the
 y induce on their host star. This quantity\, defined as the difference bet
 ween the short-term proper motion vectors measured by Gaia (2014-2017) and
  the long-term Hipparcos-Gaia proper motion (1991-2016)\, is a sensitive a
 strometric tracer of the presence of massive orbiting companions. Thanks t
 o the precision of Gaia and the long Hip-Gaia time baseline\, the median a
 ccuracy we obtain on the tangential velocity anomaly reaches 26 cm/s per p
 arsec of distance. For nearby stars\, this enables us to identify low mass
  companions\, well into the planetary regime. I will present the examples 
 of the detection of several exoplanets previously known from radial veloci
 ty (Eps Eri b\, Eps Ind Ab\, Pi Men b). In addition\, we searched the Gaia
  EDR3 catalog for spatially resolved bound companions of nearby stars with
 in 100pc\, based on a common proper motion (CPM) approach. I will present 
 an overview of our results on the PMa and CPM analyses. We obtain a binary
  fraction of 43% for the Hipparcos catalog stars\, including several hundr
 ed planetary mass companion candidates. The characterization of these exop
 lanet candidates using a combination of Gaia data with various observing t
 echniques (imaging\, interferometry\, transits\, radial velocity) appears 
 particularly promising.
LOCATION:Ryle seminar room + ONLINE - Details to be sent by email
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