Astronomy and Astrophysics, volume 566A, 85-85 (2014/6-1)
First spectroscopic observations of the substellar companion of the young debris disk star PZ Telescopii.
SCHMIDT T.O.B., MUGRAUER M., NEUHAEUSER R., VOGT N., WITTE S., HAUSCHILDT P.H., HELLING C. and SEIFAHRT A.
Abstract (from CDS):
In 2010 a substellar companion to the solar analog pre-main sequence star PZ Tel and member of the approximately 12Myr old β Pic moving group was found by high-contrast direct imaging independently by two teams. In order to determine the basic parameters of this companion more precisely and independent of evolutionary models, hence age-independent, we obtained follow-up spectroscopic observations of the primary and companion. We used the Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) at the Very Large Telescope Unit 4/Yepun of ESO's Paranal Observatory in the H+K band and processed the data using the spectral deconvolution technique. The resulting spectrum of the companion was then compared to a grid of Drift-Phoenix synthetic model spectra, a combination of a general-purpose model atmosphere code with a non-equilibrium, stationary cloud and dust model, using a χ2 minimization analysis. We find a best fitting spectral type of G6.5 for PZ Tel A. The extracted spectrum of the substellar companion, at a spatial position compatible with earlier orbit estimates, yields a temperature Teff=2500+138–115K, a visual extinction AV=0.53+0.84–0.53mag, a surface gravity of logg=3.50+0.51–0.30dex, and a metallicity at the edge of the grid of [M/H]=0.30–0.30dex. We derive a luminosity of log(Lbol/L☉)=-2.66+0.06–0.08, a radius of R =2.42+0.28–0.34RJup, and a mass of M=7.5+16.9–4.3MJup for the PZ Tel companion, which is consistent with most earlier estimates using photometry alone. Combining our results with evolutionary models, we find a best-fitting mass of about 21 Jupiter masses at an age corresponding to the recently determined lithium depletion age of 7+4–2Myr. Hence, the PZ Tel companion is most likely a wide brown dwarf companion in the 12+8–4Myr old β Pic moving group.
brown dwarfs - stars: pre-main sequence - stars: atmospheres - planetary systems - planets and satellites: formation - stars: individual: PZ Tel