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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 709984.0, MPI für Astronomie / Publikationen_mpia
Physical and orbital properties of b Pictoris b
Authors:Bonnefoy, M.; Marleau, G. -. D.; Galicher, R.; Beust, H.; Lagrange, A. -. M.; Baudino, J. -. L.; Chauvin, G.; Borgniet, S.; Meunier, N.; Rameau, J.; Boccaletti, A.; Cumming, A.; Helling, C.; Homeier, D.; Allard, F.; Delorme, P.
Date of Publication (YYYY-MM-DD):2014
Title of Journal:Astronomy and Astrophysics
Start Page:id.L9 (6 pp)
Audience:Not Specified
Abstract / Description:The intermediate-mass star <ASTROBJ>beta Pictoris</ASTROBJ> is known to be surrounded by a structured edge-on debris disk within which a gas giant planet was discovered orbiting at 8-10 AU. The physical properties of <ASTROBJ>beta Pic b</ASTROBJ> were previously inferred from broad- and narrow-band 0.9-4.8 mum photometry. We used commissioning data of the Gemini Planet Imager (GPI) to obtain new astrometry and a low-resolution (R ~ 35-39) J-band (1.12-1.35 mum) spectrum of the planet. We find that the planet has passed the quadrature. We constrain its semi-major axis to <=10 AU (90% prob.) with a peak at 8.9+0.4-0.6 AU. The joint fit of the planet astrometry and the most recent radial velocity measurements of the star yields a planet dynamical mass lower than 20 MJup (>=96% prob.). The extracted spectrum of beta Pic b is similar to those of young L1-1.5+1 dwarfs. We used the spectral type estimate to revise the planet luminosity to log (L/L&sun;) = -3.90 ± 0.07. The 0.9-4.8 mum photometry and spectrum are reproduced for Teff = 1650 ± 150 K and a log g <= 4.7 dex by 12 grids of PHOENIX-based and LESIA atmospheric models. For the most recent system age estimate (21 ± 4 Myr), the bolometric luminosity and the constraints on the dynamical mass of beta Pic b are only reproduced by warm- and hot-start tracks with initial entropies Si> 10.5 kB/baryon. These initial conditions may result from an inefficient accretion shock and/or a planetesimal density at formation higher than in the classical core-accretion model. Considering a younger age for the system or a conservative formation time for beta Pic b does not change these conclusions. Appendices are available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201424041/olm">http://www.aanda.org</A>
Free Keywords:techniques: photometric; techniques: spectroscopic; planetary systems; stars: individual:&beta; Pic
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-6361 %R 10.1051/0004-6361/201424041
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