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EP: Fachverband Extraterrestrische Physik

EP 3: Astrophysik/Astrobiologie

EP 3.7: Talk

Tuesday, February 26, 2013, 15:45–16:00, HS 9

Mass determination of young directly imaged planet candidates and brown dwarfs — •Tobias Schmidt¹, Ralph Neuhäuser¹, Andreas Seifahrt², and Markus Mugrauer¹ — ¹Astrophysikalisches Institut und Universitäts-Sternwarte, 07745 Jena, Germany — ²Department of Astronomy and Astrophysics, University of Chicago, USA

About 25 sub-stellar companions with large separations (>~ 50 AU) are confirmed. The origin and early evolution of these objects is still under debate. While often these sub-stellar companions are regarded as brown dwarfs, they could possibly also be massive planets, mass estimates are very uncertain so far. They are companions to primary stars or brown dwarfs in young associations and star forming regions like Lupus and Chamaeleon, hence their ages and distances are well known, in contrast to free-floating brown dwarfs.

Here we present how mass estimates of such young directly imaged companions can be derived. An empirical classification by medium-resolution spectroscopy is currently not possible, because a spectral sequence that is taking the lower gravity into account, is not existing. This problem leads to an apparent mismatch between spectra of old field type objects and young low-mass companions. We show that from spectra of the objects, using light concentration by an AO, temperature, extinction, metallicity and surface gravity can be derived and that this procedure allows a mass determination in combination with luminosities by the direct observations, as done by us for e.g. GQ Lup, CT Cha or UScoCTIO 108 and PZ Tel.