Peering into the Young Planetary System AB Pic. Atmosphere, Orbit, Obliquity & Second Planetary Candidate
P. Palma-Bifani, G. Chauvin, M. Bonnefoy, P. M. Rojo, S. Petrus, L., Rodet, M. Langlois, F. Allard, B. Charnay, C. Desgrange, D. Homeier, A.-M., Lagrange, J.-L. Beuzit, P. Baudoz, A. Boccaletti, A. Chomez, P. Delorme, S., Desidera, M. Feldt, C. Ginski, R. Gratton, A.-L. Maire

TL;DR
This study thoroughly characterizes the atmosphere, orbit, obliquity, and potential inner companion of the young planetary system AB Pic, revealing a misaligned orbit and suggesting formation via gravitational instability or core accretion.
Contribution
It provides the first detailed atmospheric composition, orbital parameters, and obliquity measurement of AB Pic b, and proposes the existence of an inner planet, advancing understanding of system formation.
Findings
AB Pic b has a semi-major axis of ~190 au and is viewed edge-on.
The atmosphere has an effective temperature of 1700K and a near-solar C/O ratio.
Evidence suggests a possible inner planet of ~6 Jupiter masses within 2-10 au.
Abstract
We aim to revisit the system AB Pic which has a known companion at the exoplanet/ brown-dwarf boundary. We based this study on a rich set of observations to investigate the companion's orbit and atmosphere. We composed a spectrum of AB Pic b merging archival VLT/SINFONI K-band data, with published spectra at J and H-band (SINFONI) and Lp-band (Magellan-AO), and photometric measurements (HST and Spitzer). We modeled the spectrum with ForMoSA, based on two atmospheric models: ExoREM and BT-SETTL13. We determined the orbital properties of b fitting the astrometric measurements from NaCo (2003 and 2004) and SPHERE (2015). The orbital solutions favor a semi-major axis of 190au viewed edge-on. With Exo-REM, we derive a T of 170050K and surface gravity of 4.50.3dex, consistent with previous works, and we report for the first time a C/O ratio of 0.580.08…
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Taxonomy
TopicsStellar, planetary, and galactic studies · Astronomy and Astrophysical Research · SAS software applications and methods
