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SUMMARY:Direct detection of cold exoplanets with JWST - Elisabeth Matthews
  (MPIA)
DTSTART:20231107T130000Z
DTEND:20231107T140000Z
UID:TALK208150@talks.cam.ac.uk
CONTACT:Dr Emily Sandford
DESCRIPTION:Observing substellar companions with multiple techniques allow
 s for the best possible understanding of their formation\, evolution\, and
  atmospheric physics. Radial velocity (RV) observations are biased toward 
 planets on short orbits\, while high contrast imaging (HCI) is biased towa
 rds planets on very long orbits: in general\, RV and HCI data are not avai
 lable for the same substellar companions. In rare cases\, however\, long-t
 erm dynamical accelerations allow us to pinpoint prime HCI systems\, and d
 irectly detect their substellar companions. This combination provides a ra
 re but exceptionally detailed view of these companions: we can simultaneou
 sly measure precise dynamical masses\, bolometric luminosities\, and atmos
 pheric compositions\, and characterize the orbits of these companions. Mas
 s/luminosity measurements have indicated a confusing tension: several brow
 n dwarfs appear to be over- or under-luminous relative to their dynamical 
 mass. Orbital measurements\, meanwhile\, indicate that brown dwarf compani
 ons are typically much more eccentric than their giant planet counterparts
 \, shedding light on the diverse formation paths of these objects. In some
  cases\, circumstellar debris disks can be directly detected and character
 ized\, and their interactions with giant planets in the system constrained
 . \n\nTo date\, the RV+HCI technique has only been possible for brown dwar
 f companions\, and for the very youngest exoplanets -  but with JWST this 
 technique will likely allow for the first coronagraphic images of a solar-
 age exoplanet\, paving the way to detailed characterization of cool (~300K
 ) exoplanet atmospheres through spectroscopic observations and photometric
  variability campaigns. I will present my work to identify long-term RV tr
 ends\, and use Hipparcos and Gaia astrometric information to further selec
 t and characterize the best HCI targets. I will particularly highlight som
 e early results from my recent JWST program\, where we collected coronagra
 phic images of the nearby Eps Ind A\, a ~4Gyr star with a massive radial v
 elocity companion (~3Mj)\, in the hopes of directly detecting that planet.
  I will also discuss an ongoing VLT/SPHERE program to identify new brown d
 warfs based on RV trends\, and also highlight a particularly puzzling obje
 ct identified via this method: the HD4113C brown dwarf\, which shows a str
 iking and as-yet unexplained mass/luminosity tension. I will also present 
 our work to image systems with circumstellar debris dust\, and to characte
 rize the disks themselves through scattered light imaging.
LOCATION:Ryle seminar room + ONLINE - Details to be sent by email
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