The Radial and Rotational Velocities of PSO J318.5338-22.8603, a Newly Confirmed Planetary-mass Member of the β Pictoris Moving Group
Abstract
PSO J318.5338-22.8603 is an extremely red planetary-mass object that has been identified as a candidate member of the β Pictoris moving group based on its spatial position and tangential velocity. We present a high-resolution K-band spectrum of PSO J318.5338-22.8603. Using a forward modeling Markov Chain Monte Carlo approach, we report the first measurement of the radial velocity and v sin(I) of PSO J318.5-22, -{6.0}-1.1+0.8 km s-1, and {17.5}-2.8+2.3 km s-1, respectively. We calculate the space velocity and position of PSO J318.5-22 and confirm that it is a member of the β Pictoris moving group. Adopting an age of 23 ± 3 Myr for PSO J318.5-22, we determine a mass of 8.3 ± 0.5 MJup and an effective temperature of {1127}-26+24 K using evolutionary models. PSO J318.5338-22.8603 is intermediate in mass and temperature to the directly imaged planets β Pictoris b and 51 Eridani b, making it an important benchmark object in the sequence of the planetary-mass members of the β Pictoris moving group. Combining our v sin(I) measurement with recent photometric variability data, we constrain the inclination of PSO J318.5-22 to >29° and its rotational period to 5-10.2 hr. The equatorial velocity of PSO J318.5-22 indicates that its rotation is consistent with an extrapolation of the velocity-mass relationship for solar system planets.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2016
- DOI:
- 10.3847/0004-637X/819/2/133
- arXiv:
- arXiv:1601.04717
- Bibcode:
- 2016ApJ...819..133A
- Keywords:
-
- brown dwarfs;
- infrared: stars;
- planets and satellites: atmospheres;
- stars: rotation;
- techniques: radial velocities;
- techniques: spectroscopic;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 8 pages, 5 figures, 2 tables, ApJ accepted