2014/07/01 by M. Bonnefoy, G.-D. Marleau, G. -D. Marleau +16 · 2 citations
Physics and Astronomy · #Astro and Planetary Science #Astrometry #Astrophysics and Star Formation Studies #Debris disk #Giant planet #Luminosity #Orbital inclination #Photometry (optics) #Planet #Planetary system #Planetesimal #Radial velocity #Stellar, planetary, and galactic studies #astro-ph.EP
paper · pdf · doi:10.1051/0004-6361/201424041
published as A&A 567, L9 (2014) · 4 pages, 4 figures, 2 tables. 4 online appendices. Accepted for publication in A&A letters
openalex publication_date 2014/07/01 · arxiv created 2014/07/15 · arxiv updated 2014/09/05 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The intermediate-mass star β Pictoris 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 β Pic b were previously inferred from broad- and narrow-band 0.9−4.8 μm 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 μm) 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 β 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⊙) = −3.90 ± 0.07. The 0.9−4.8 μm 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 β 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 β Pic b does not change these conclusions.