Exoplanets

Title:Searching for long-period companions to TESS planet hosts

De Rosa, Robert J.

Robert J De Rosa (ESO), Matias Jones (ESO), Rebekah Dawson (Penn State), Eric Nielsen (New Mexico State) Pedro Figueira (ESO), Julien Milli (IPAG), Zahed Wahhaj (ESO)

Abstract: We present the results of an astrometric search for stellar and substellar companions to nearby bright TESS planet-hosting stars. Long-period stellar and substellar companions can play a significant role in the formation and dynamical evolution of planetary systems. During formation, outer companions can truncate protoplanetary disks and decrease the efficiency of the planetary formation process. On longer timescales they can significantly alter the architecture of the inner system. An outer companion on a sufficiently misaligned orbit can induce eccentricity-driven migration, moving the planets far closer to the star than at the epoch of formation. Speckle imaging surveys of these hosts have revealed strong correlations between binary and planet properties, but these surveys are not sensitive to low-mass stellar or substellar companions. By combining absolute astrometry from Hipparcos and Gaia we have identified several TESS planet host stars that have very strong evidence of long-period companions that have been missed in previous speckle observations. We present limits on their masses and orbital properties and discuss potential follow-up observations to detect them.

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Title: Envelope structure around accreting planets: accretion vs. luminosity shocks

Matias Montesinos

Matías Montesinos (UVM, NPF), Juan Garrido-Deutelmoser (PUC), Amelia Bayo (UV, NPF), Johan Olofsson (UV, NPF)

Abstract: The most commonly accepted mechanism for planets to grow during the protoplanetary phase involves accretion of gas and dust. The pilling-up of material during this process is expected to be a luminous mechanism. The first direct image of a forming planet is the case of PDS 70b, where a strong hot spot, with particular Hα emission, was detected (Keppler et al., 2018). It has been shown that Hα high-contrast imaging is an indicator of accretion. Hα emission and accretion rates are therefore strongly connected; however, it is unclear how to extrapolate Hα luminosity values into planet accretion rates besides using the empirical classical TTauri relation which is only valid for stars (Natta et al. 2004). In this work, we present a coherent scenario where we compute -using performant 3D numerical hydro-simulations- planetary accretion rate, along with its corresponding shock luminosity, to later be related in a single accretion-luminosity description. We suggest that planetary accretion rates must be computed at the ionization radius (defined by the gas ionization degree) rather than the typical Hill radius commonly used.

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Title: Unveiling the origins of AB Pic b through its orbit and atmosphere

Paulina Palma-Bifani

Paulina Palma-Bifani (U. de Chile), G. Chauvin, M. Bonnefoy, P. Rojo, S. Petrus,

L. Rodet, M. Langlois, F. Allard, D. Homeier, B. Charnay & C. Desgrange

Abstract: How do we discriminate an exoplanet from a brown dwarf (BD)? This question has been fiercely debated considering definitions based on either their physical properties (like the mass or the ability to fuse deuterium) or their formation. BD usually are considered as failed stars but if they formed as binary it has been observed that they overlap in separation and mass with the population of giant planets formed in protoplanetary disks. Both populations have however a potentially different chemical composition. Exploring the origin and nature of companions can therefore be approached by peering into their atmospheres. We analyze raw medium-resolution (R ~ 4000) SINFONI data in K-band (1.96 – 2.45 μm) from AB Pic b together with literature data on visible wavelengths, J-, H-, and L-bands. We modeled its spectra with ForMoSA using different atmospheric grids to study the formation history of this companion. From the results we derived physical parameters as the spectral type, effective temperature, gravity, metallicity and the C/O ratio which we then used as starting point to investigate the formation history of AB Pic b.

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