Alves, Douglas R;
Jenkins, James S;
Vines, Jose I;
Nielsen, Louise D;
Gill, Samuel;
Acton, Jack S;
Anderson, DR;
... Osborn, Ares; + view all
(2022)
NGTS-21b: An Inflated Super-Jupiter Orbiting a Metal-poor K dwarf.
Monthly Notices of the Royal Astronomical Society
10.1093/mnras/stac2884.
(In press).
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Abstract
We report the discovery of NGTS-21b , 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 MJ and 1.33 ± 0.03 RJ, and an orbital period of 1.543 days. The host is a K3V (Teff = 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 despite its large mass. Inflation-free planetary structure models suggest the planet’s atmosphere is inflated by ∼21%, while inflationary models predict a radius consistent with observations, thus pointing to stellar irradiation as the probable origin of NGTS-21b’s radius inflation. Additionally, NGTS-21b’s 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.
| Type: | Article |
|---|---|
| Title: | NGTS-21b: An Inflated Super-Jupiter Orbiting a Metal-poor K dwarf |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/stac2884 |
| Publisher version: | https://doi.org/10.1093/mnras/stac2884 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | techniques: photometric, stars: individual: NGTS-21, planetary systems |
| UCL classification: | UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10158146 |
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