NGTS-8b and NGTS-9b: two non-inflated hot-Jupiters

Jean C. Costes, Christopher A. Watson, Claudia Belardi, Ian P. Braker, Matthew R. Burleigh, Sarah L. Casewell, Philipp Eigmüller, Maximilian N. Günther, James A. G. Jackman, Louise D. Nielsen, Maritza G. Soto, Oliver Turner, David R. Anderson, Daniel Bayliss, François Bouchy, Joshua T. Briegal, Edward M. Bryant, Juan Cabrera, Alexander Chaushev, Szilard CsizmadiaAnders Erikson, Samuel Gill, Edward Gillen, Michael R. Goad, Simon Hodgkin, Matthew J. Hooton, James S. Jenkins, James McCormac, Maximiliano Moyano, Didier Queloz, Heike Rauer, Liam Raynard, Alexis M. S. Smith, Andrew P. G. Thompson, Rosanna H. Tilbrook, Stephane Udry, Jose I. Vines, Richard G. West, Peter J. Wheatley

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We report the discovery, by the Next Generation Transit Survey (NGTS), of two hot-Jupiters NGTS-8b and NGTS-9b. These orbit a V = 13.68 K0V star (Teff = 5241 ± 50 K) with a period of 2.49970 days, and a V = 12.80 F8V star (Teff = 6330 ± 130 K) in 4.43527 days, respectively. The transits were independently verified by follow-up photometric observations with the SAAO 1.0-m and Euler telescopes, and we report on the planetary parameters using HARPS, FEROS and CORALIE radial velocities. NGTS-8b has a mass, 0.93 ^{+0.04}_{-0.03} MJ and a radius, 1.09 ± 0.03 RJ similar to Jupiter, resulting in a density of 0.89 ^{+0.08}_{-0.07} g cm-3. This is in contrast to NGTS-9b, which has a mass of 2.90 ± 0.17 MJ and a radius of 1.07 ± 0.06 RJ, resulting in a much greater density of 2.93^{+0.53}_{-0.49} g cm-3. Statistically, the planetary parameters put both objects in the regime where they would be expected to exhibit larger than predicted radii. However, we find that their radii are in agreement with predictions by theoretical non-inflated models.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society, Advance Access
Early online date20 Nov 2019
Publication statusEarly online date - 20 Nov 2019


  • techniques: photometric
  • stars: individual: NGTS-8 and NGTS-9 planetary systems
  • planets and satellites: detection


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