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Transit detection of the long-period volatile-rich super-Earth ν2 Lupi d with CHEOPS

Accepted version
Peer-reviewed

Type

Article

Change log

Abstract

Exoplanets transiting bright nearby stars are key objects for advancing our knowledge of planetary formation and evolution. The wealth of photons from the host star gives detailed access to the atmospheric, interior, and orbital properties of the planetary companions. ν2 Lupi (HD 136352) is a naked-eye (V=5.78) Sun-like star that was discovered to host three low-mass planets with orbital periods of 11.6, 27.6, and 107.6 days via radial velocity monitoring (Udry et al. 2019). The two inner planets (b and c) were recently found to transit (Kane et al. 2020), prompting a photometric follow-up by the brand-new CHaracterisingExOPlanetsSatellite(CHEOPS). Here, we report that the outer planet d is also transiting, and measure its radius and mass to be 2.56±0.09 R and 8.82±0.94 M, respectively. With its bright Sun-like star, long period, and mild irradiation ($\sim$5.7 times the irradiation of Earth), ν2 Lupi d unlocks a completely new region in the parameter space of exoplanets amenable to detailed characterization. We refine the properties of all three planets: planet b likely has a rocky mostly dry composition, while planets c and d seem to have retained small hydrogen-helium envelopes and a possibly large water fraction. This diversity of planetary compositions makes the ν2 Lupi system an excellent laboratory for testing formation and evolution models of low-mass planets.

Description

Keywords

astro-ph.EP, astro-ph.EP

Journal Title

Nature Astronomy

Conference Name

Journal ISSN

2397-3366
2397-3366

Volume Title

5

Publisher

Springer Science and Business Media LLC

Rights

All rights reserved
Sponsorship
STFC (ST/T003081/1)