Exploring the formation by core accretion and the luminosity evolution of directly imaged planets: The case of HIP 65426 b
Gabriel-Dominique Marleau, Gavin A. L. Coleman, Adrien Leleu, Christoph Mordasini
备注：
17 pages, 11 figures. A&A in press. Bern EXoplanet cooling curves (BEX) available upon request. v2: Language and other minor changes; Fig. 4 now has labels summarising a possible formation pathway discussed in the text
A low-mass companion to the two-solar mass star HIP65426 has recently been detected by SPHERE at around 100 au from its host. Explaining the presence of super-Jovian planets at large separations, as revealed by direct imaging, is currently an open question.
We want to derive statistical constraints on the mass and initial entropy of HIP65426b and to explore possible formation pathways of directly imaged objects within the core-accretion paradigm, focusing on HIP65426b.
Constraints on the planet's mass and post-formation entropy are derived from its age and luminosity combined with cooling models. For the first time, the results of population synthesis are also used to inform the results. Then, a formation model that includes N-body dynamics with several embryos per disc is used to study possible formation histories and the properties of possible additional companions. Finally, the outcomes of two- and three-planet scattering in the post-disc phase are analysed, taking tides into account.
The mass of HIP65426b is found to be Mp = 9.9 +1.1 -1.8 MJ using the hot population and Mp = 10.9 +1.4 -2.0 MJ with the cold-nominal population. Core formation at small separations from the star followed by outward scattering and runaway accretion at a few hundred AU succeeds in reproducing the mass and separation of HIP65426b. Alternatively, systems having two or more giant planets close enough to be on an unstable orbit at disc dispersal are likely to end up with one planet on a wide HIP65426b-like orbit with a relatively high eccentricity (>~ 0.5).
If this scattering scenario explains its formation, HIP65426b is predicted to have a high eccentricity and to be accompanied by one or several roughly Jovian-mass planets at smaller semi-major axes, which also could have a high eccentricity. This could be tested by further direct-imaging as well as radial-velocity observations.
Precise dynamical masses of new directly imaged companions from combining relative astrometry, radial velocities, and Hipparcos-Gaia eDR3 accelerations
MIRACLES: atmospheric characterization of directly imaged planets and substellar companions at 4-5 $μ$m. I. Photometric analysis of $β$ Pic b, HIP 65426 b, PZ Tel B and HD 206893 B
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Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales（迪亚斯·波萨莱斯大学工程与科学学院天体物理研究所）；Millennium Nucleus on Young Exoplanets and their Moons (YEMS)（年轻系外行星及其卫星千年核心计划）；INAF-Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；Departamento de Física, Universidad de Santiago de Chile（圣地亚哥智利大学物理系）；Center for Interdisciplinary Research in Astrophysics and Space Science (CIRAS), Universidad de Santiago de Chile（圣地亚哥智利大学天体物理学与空间科学跨学科研究中心）；Department of Physics and Astronomy, Texas A&M University（德克萨斯农工大学物理与天文学系）；European Southern Observatory（欧洲南方天文台）
A Candidate Innermost Fifth Planet In the HR 8799 System Revealed By JWST NIRISS Aperture Masking Interferometry
University of California, San Diego（加州大学圣迭戈分校）；Leiden Observatory（莱顿天文台）；IPAC, Caltech（加州理工学院IPAC）；Macquarie University（麦考瑞大学）；University of Sydney（悉尼大学）；University of Victoria（维多利亚大学）
A Roman Coronagraph Spectroscopic Mode Demonstration
University of Texas-San Antonio（德克萨斯大学圣安东尼奥分校）；Subaru Telescope, National Astronomical Observatory of Japan（昴望远镜，日本国立天文台）；University of California-Santa Cruz（加州大学圣克鲁兹分校）；University of Michigan（密歇根大学）；NASA Goddard Spaceflight Center（美国宇航局戈达德太空飞行中心）；National Astronomical Observatory of Japan（日本国立天文台）
ELemental abundances of Planets and brown dwarfs Imaged around Stars (ELPIS): II. The Jupiter-like Inhomogeneous Atmosphere of the First Directly Imaged Planetary-Mass Companion 2MASS 1207 b
A Binary Flux Calibrator Reveals the Scientific Potential of Short-integration JWST MIRI Imaging to Directly Detect sub-Jupiter Exoplanets
Eureka Scientific Inc.（Eureka科学公司）；University of Michigan（密歇根大学）；Max Planck Institute for Astronomy（马克斯·普朗克天文学研究所）；University of California Santa Cruz（加州大学圣克鲁兹分校）；Massachusetts Institute of Technology（麻省理工学院）；Johns Hopkins APL（约翰斯·霍普金斯大学应用物理实验室）
