Abstract
ABSTRACTWe present the discovery and characterization of two transiting planets observed by TESS in the light curves of the young and bright (V = 9.67) star HD73583 (TOI-560). We perform an intensive spectroscopic and photometric space- and ground-based follow-up in order to confirm and characterize the system. We found that HD73583 is a young (∼500 Myr) active star with a rotational period of 12.08 ± 0.11 d, and a mass and radius of 0.73 ± 0.02 M⊙ and 0.65 ± 0.02 R⊙, respectively. HD 73583 b (Pb = $6.3980420 _{ - 0.0000062 } ^ { + 0.0000067 }$ d) has a mass and radius of $10.2 _{ - 3.1 } ^ { + 3.4 }$ M⊕ and 2.79 ± 0.10 R⊕, respectively, which gives a density of $2.58 _{ - 0.81 } ^ { + 0.95 }$ ${\rm g\, cm^{-3}}$. HD 73583 c (Pc = $18.87974 _{ - 0.00074 } ^ { + 0.00086 }$ d) has a mass and radius of $9.7 _{ - 1.7 } ^ { + 1.8 }$ M⊕ and $2.39 _{ - 0.09 } ^ { + 0.10 }$ R⊕, respectively, which translates to a density of $3.88 _{ - 0.80 } ^ { + 0.91 }$ ${\rm g\, cm^{-3}}$. Both planets are consistent with worlds made of a solid core surrounded by a volatile envelope. Because of their youth and host star brightness, they both are excellent candidates to perform transmission spectroscopy studies. We expect ongoing atmospheric mass-loss for both planets caused by stellar irradiation. We estimate that the detection of evaporating signatures on H and He would be challenging, but doable with present and future instruments.
Highlights
Two of the most noticeable characteristics of the transiting exoplanet population are the so-called “hot Neptunian desert” (Mazeh et al 2016; Lundkvist et al 2016) and the “radius valley” (Fulton et al.2017; Van Eylen et al 2018)
Theoretical evolution models suggest that these gaps are mainly caused by physical mechanisms that occurs during the first Myr of evolution ( 1 Gyr), such as photo-evaporation (e.g., Adams & Laughlin 2006; Kubyshkina et al 2018; Lopez & Fortney 2014; Mordasini 2020; Raymond et al 2009; Owen & Wu 2013) and corepowered mass-loss (e.g., Ginzburg et al 2016; Gupta & Schlichting 2019, 2021)
These tests increased our confidence that none of the transit-signals are the result of systematic effects, such as a temperature change in the satellite, or that they are astrophysical false positives such as background eclipsing binaries or a solar system object passing through the field of view
Summary
Two of the most noticeable characteristics of the transiting exoplanet population are the so-called “hot Neptunian desert” (Mazeh et al 2016; Lundkvist et al 2016) and the “radius valley” (Fulton et al.2017; Van Eylen et al 2018). The Transiting Exoplanet Survey Satellite (TESS; Ricker et al 2015) has discovered a plethora of candidates/exoplanets transiting bright stars (e.g., Bouma et al 2020; Hobson et al 2021; Kossakowski et al 2021; Martioli et al 2021; Mann et al 2021; Newton et al 2019, 2021; Plavchan et al 2020; Rizzuto et al 2020; Zhou et al 2021) These transiting exoplanets are excellent targets to perform followup observations that allow us to further characterise these young systems, e.g., using the radial velocity (RV) method to measure the planetary masses. A TESS Input Catalog (TIC; Stassun et al 2018, 2019). b Gaia Collaboration (2018)
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