I Congreso de Postgrado fcfm: ingeniería, ciencias e innovación

34 Santiago, 10 al 12 de agosto, 2022 A S T RONOM Í A 01 NGTS-21B: AN INFLATED SUPER-JUPITER ORBITING A METAL-POOR K DWARF Douglas R. Alves¹ , ³* , James S. Jenkins² , Jose Vines¹ , ³, Maritza Soto⁴ , NGTS consortium⁵ ¹Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile ²Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile ³Centro de Astrofísica y Tecnologías Afines (CATA), Casilla 36-D, Santiago, Chile ⁴School of Physics and Astronomy, Queen Mary University of London, 327 Mile End Road, London E1 4NS, UK ⁵Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK *Email: douglasalvesastro12@gmail.com ABSTRACT Observations have shown that rocky and mini-Neptune planets orbiting low-mass K and M dwarfs are found in abundance, yet more massive giant planets are much less common. In particular, massive hot Jupiters around such low-mass stars are some of the rarest planets yet known. Here we report the discovery of a massive hot Jupiter orbiting a low-mass star as part of the Next Generation Transit Survey (NGTS). The planet has a mass and radius of 2.36 ± 0.21 M J and 1.33 ± 0.03R J , and an orbital period of only 1.5 days. The host is a K3V ( T eff = 4660 ± 41 K) metal-poor ([Fe/H] = −0.26 ± 0.07 dex) dwarf star with a mass and radius of 0.72 ± 0.04 M ⊙ and 0.86 ± 0.04 R ⊙ . Its age and rotation period of 10.02 + ³ . ²⁹ −7 . 30 Gyr and 17.88 ± 0.08 d respectively, are in accordance with the observed moderately low stellar activity level. When comparing NGTS-21b with currently known transiting hot Jupiters with similar equilibrium temperatures, it is found to have one of the largest measured radii. Inf lation-free planetary structure models suggest the planet’s atmosphere is inf lated by ∼ 18%, the origin of which is possibly a combination of stellar irradiation and tidal heating of the planet. Additionally, NGTS-21b bulk density (1.25 ± 0.15 g/cm3 ) is also amongst the largest within the population of metal-poor giant hosts ([Fe/H] < 0.0), helping to reveal a falling upper boundary in metallicity-planet density parameter space that is in concordance with core accretion formation models. The discovery of rare planetary systems such as NGTS-21 greatly contributes towards better constraints being placed on the formation and evolution mechanisms of massive planets orbiting low-mass stars. ACKNOWLEDGMENTS DRAlv acknowledges support of ANID-PFCHA/Doctorado Nacional-21200343, Chile as well as our NGTS collaborators. REFERENCES [1] Wheatley P. J., et al., 2018, Monthly Notices of the Royal Astronomical Society, 475, 4476 [2] Vines J. I., et al., 2019, Monthly Notices of the Royal Astronomical Society, 489, 4125 [3] McCormac J., et al., 2020, Monthly Notices of the Royal Astronomical Society, 493, 126 [4] Ricker G. R., et al., 2015, Journal of Astronomical Telescopes, Instruments, and Systems, 1, 014003 [5] Bayliss D., et al., 2018, Monthly Notices of the Royal Astronomical Society, 475, 4467