Exoplanets and Stellar Physics

Research group

Research theme

Sub department

About

Related research groups

A New Third Planet and the Dynamical Architecture of the HD33142 HD 33142 Planetary System

ASTRONOMICAL JOURNAL 164:4 (2022) ARTN 156

Authors:

Trifon Trifonov, Anna Wollbold, Martin Kuerster, Jan Eberhardt, Stephan Stock, Thomas Henning, Sabine Reffert, R Paul Butler, Steven S Vogt, Ansgar Reiners, Man Hoi Lee, Bertram Bitsch, Mathias Zechmeister, Florian Rodler, Volker Perdelwitz, Lev Tal-Or, Jan Rybizki, Paul Heeren, Davide Gandolfi, Oscar Barragan, Olga Zakhozhay, Paula Sarkis, Marcelo Tala Pinto, Diana Kossakowski, Vera Wolthoff, Stefan S Brems, Vera Maria Passegger
More details from the publisher

One year of AU Mic with HARPS - II. Stellar activity and star-planet interaction

Monthly notices of the Royal Astronomical Society, 512, 5067

Authors:

Klein, Baptiste ; Zicher, Norbert ; Kavanagh, Robert D.; Nielsen, Louise D. ; Aigrain, Suzanne ; Vidotto, Aline A. ; Barragán, Oscar ; Strugarek, Antoine; Nicholson, Belinda ; Donati, Jean-François search by orcid ; Bouvier, Jérôme

Abstract:

We present a spectroscopic analysis of a 1-yr intensive monitoring campaign of the 22-Myr old planet-hosting M dwarf AU Mic using the HARPS spectrograph. In a companion paper, we reported detections of the planet radial velocity (RV) signatures of the two close-in transiting planets of the system, with respective semi-amplitudes of 5.8 ± 2.5 and 8.5 ± 2.5 m s-1 for AU Mic b and AU Mic c. Here, we perform an independent measurement of the RV semi-amplitude of AU Mic c using Doppler imaging to simultaneously model the activity-induced distortions and the planet-induced shifts in the line profiles. The resulting semi-amplitude of 13.3 ± 4.1 m s-1 for AU Mic c reinforces the idea that the planet features a surprisingly large inner density, in tension with current standard models of core accretion. Our brightness maps feature significantly higher spot coverage and lower level of differential rotation than the brightness maps obtained in late 2019 with the SPIRou spectropolarimeter, suggesting that the stellar magnetic activity has evolved dramatically over a ~1-yr time span. Additionally, we report a 3σ detection of a modulation at 8.33 ± 0.04 d of the He I D3 (5875.62 Å) emission flux, close to the 8.46-d orbital period of AU Mic b. The power of this emission (a few 1017 W) is consistent with 3D magnetohydrodynamical simulations of the interaction between stellar wind and the close-in planet if the latter hosts a magnetic field of ~10 G. Spectropolarimetric observations of the star are needed to firmly elucidate the origin of the observed chromospheric variability.
More details from the publisher
Full PDF text
Details from ArXiV

One year of AU Mic with HARPS - I. Measuring the masses of the two transiting planets

Monthly Notices of the Royal Astronomical Society, Volume 512, Issue 2, pp.3060-3078

Authors:

Norbert Zicher, Oscar Barragán, Baptiste Klein, Suzanne Aigrain, James E. Owen, Davide Gandolfi, Anne-Marie Lagrange, Luisa Maria Serrano, Laurel Kaye, Louise Dyregaard Nielsen, Vinesh Maguire Rajpaul, Antoine Grandjean, Elisa Goffo, Belinda Nicholson

Abstract:

The system of two transiting Neptune-sized planets around the bright, young M-dwarf AU Mic provides a unique opportunity to test models of planet formation, early evolution, and star-planet interaction. However, the intense magnetic activity of the host star makes measuring the masses of the planets via the radial velocity (RV) method very challenging. We report on a 1-yr, intensive monitoring campaign of the system using 91 observations with the HARPS spectrograph, allowing for detailed modelling of the ~600 ms−1 peak-to-peak activity-induced RV variations. We used a multidimensional Gaussian Process framework to model these and the planetary signals simultaneously. We detect the latter with semi-amplitudes of Kb = 5.8 ± 2.5 ms−1 and Kc = 8.5 ± 2.5 ms−1, respectively. The resulting mass estimates, Mb = 11.7 ± 5.0 M⊕ and Mc = 22.2 ± 6.7 M⊕, suggest that planet b might be less dense, and planet c considerably denser than previously thought. These results are in tension with the current standard models of core-accretion. They suggest that both planets accreted a H/He envelope that is smaller than expected, and the trend between the two planets' envelope fractions is the opposite of what is predicted by theory.
More details from the publisher
Full PDF text
Details from ArXiV

Atmospheric dynamics of temperate sub-Neptunes. Part I: dry dynamics

(2021)

Authors:

Hamish Innes, Raymond T Pierrehumbert
More details from the publisher
Details from ArXiV

Convection modeling of pure-steam atmospheres

Astrophysical Journal Letters American Astronomical Society 923:1 (2021) L15

Authors:

Xianyu Tan, Maxence Lefèvre, Raymond T Pierrehumbert

Abstract:

Condensable species are crucial to shaping planetary climate. A wide range of planetary climate systems involve understanding nondilute condensable substances and their influence on climate dynamics. There has been progress on large-scale dynamical effects and on 1D convection parameterization, but resolved 3D moist convection remains unexplored in nondilute conditions, though it can have a profound impact on temperature/humidity profiles and cloud structure. In this work, we tackle this problem for pure-steam atmospheres using three-dimensional, high-resolution numerical simulations of convection in postrunaway atmospheres. We show that the atmosphere is composed of two characteristic regions, an upper condensing region dominated by gravity waves and a lower noncondensing region characterized by convective overturning cells. Velocities in the condensing region are much smaller than those in the lower, noncondensing region, and the horizontal temperature variation is small. Condensation in the thermal photosphere is largely driven by radiative cooling and tends to be statistically homogeneous. Some condensation also happens deeper, near the boundary of the condensing region, due to triggering by gravity waves and convective penetrations and exhibits random patchiness. This qualitative structure is insensitive to varying model parameters, but quantitative details may differ. Our results confirm theoretical expectations that atmospheres close to the pure-steam limit do not have organized deep convective plumes in the condensing region. The generalized convective parameterization scheme discussed in Ding & Pierrehumbert is appropriate for handling the basic structure of atmospheres near the pure-steam limit but cannot capture gravity waves and their mixing which appear in 3D convection-resolving models.
More details from the publisher
Details from ORA
More details