Kavli Affiliate: David Charbonneau
| First 5 Authors: , , , ,
| Summary:
The Near InfraRed Planet Searcher (NIRPS) joined HARPS on the 3.6-m ESO
telescope at La Silla Observatory in April 2023, dedicating part of its
Guaranteed Time Observations (GTO) program to the radial velocity follow-up of
TESS planet candidates to confirm and characterize transiting planets around M
dwarfs. We report the first results of this program with the characterization
of the TOI-756 system, which consists of TOI-756 b, a transiting sub-Neptune
candidate detected by TESS, as well as TOI-756 c, an additional non-transiting
planet discovered by NIRPS and HARPS. TOI-756 b is a 1.24-day period
sub-Neptune with a radius of 2.81 $pm$ 0.10 $R_oplus$ and a mass of
9.8$^+1.8_-1.6$ $M_oplus$. TOI-756 c is a cold eccentric (e$_c$ = 0.45
$pm$ 0.01) giant planet orbiting with a period of 149.6 days around its star
with a minimum mass of 4.05 $pm$ 0.11 $M_mathrmjup$. Additionally, a linear
trend of 146$~mathrmm,s^-1,mathrmyr^-1$ is visible in the radial
velocities, hinting at a third component, possibly in the planetary or brown
dwarf regime. This system is unique in the exoplanet landscape, standing as the
first confirmed example of such a planetary architecture around an M dwarf.
With a density of 2.42 $pm$ 0.49 g cm$^-3$, the inner planet, TOI-756 b, is
a volatile-rich sub-Neptune. Assuming a pure H/He envelope, we inferred an
atmospheric mass fraction of 0.023 and a core mass fraction of 0.27, which is
well constrained by stellar refractory abundances derived from NIRPS spectra.
It falls within the still poorly explored radius cliff and at the lower
boundary of the Neptune desert, making it a prime target for a future
atmospheric characterization with JWST to improve our understanding of this
population.
| Search Query: ArXiv Query: search_query=au:”David Charbonneau”&id_list=&start=0&max_results=3