Discovery of a young low-mass brown dwarf transiting a fast-rotating F-type star by the Galactic Plane eXoplanet (GPX) survey
Vanderburg, A.; Molina, D.; Bonfanti, A.; Collins, K. A.; Demangeon, O. D. S.; Gillon, M.; Jenkins, J. M.; Seager, S.; Krushinsky, V. V.; Jehin, E.; Bretton, M.; Barkaoui, K.; Benkhaldoun, Z.; Kiefer, F.; Hébrard, G.; Almenara, J. M.; Bieryla, A.; Dalal, S.; Latham, D. W.; Ricker, G.; Vanderspek, R.; Stassun, K. G.; Tsantaki, M.; Joner, M. D.; Spencer, M.; Stevens, D. J.; Mullally, S. E.; Charbonneau, D.; Jensen, E. L. N.; Quintana, E. V.; Pepper, J.; Beskakotov, A.; Henze, C. E.; Wilson, P. A.; Pozuelos, F. J.; Baştürk, Ö.; Yalçınkaya, S.; Burdanov, A. Y.; Girardin, E.; Naves, R.; Benni, P.; Belinski, A.; Kashaev, F.; Kim, T.; Kang, W.; Antonyuk, K.; Dyachenko, V. V.; Rastegaev, D. A.; Mitrofanova, A. A.; Kuznetsov, E. D.; Popov, A.; Sokov, E.; Sokova, I.; Marchini, A.; Papini, R.; Salvaggio, F.; Banfi, M.; Torun, Ş.; Ivanov, K.; Valyavin, G.; Pakštienė, E.; Hentunen, V. -P.; Shadick, S.; Wünsche, A.; Garlitz, J.; Jongen, Y.; Grau Horta, F.
United States, Spain, Russia, Austria, Belgium, France, Portugal, Italy, Morocco, South Korea, United Kingdom, Turkey, Lithuania, Finland, Canada, Switzerland
Abstract
We announce the discovery of GPX-1 b, a transiting brown dwarf with a mass of 19.7 ± 1.6 MJup and a radius of 1.47 ± 0.10 RJup, the first substellar object discovered by the Galactic Plane eXoplanet (GPX) survey. The brown dwarf transits a moderately bright (V = 12.3 mag) fast-rotating F-type star with a projected rotational velocity $v\sin {\, i_*}=40\pm 10$ km s-1. We use the isochrone placement algorithm to characterize the host star, which has effective temperature 7000 ± 200 K, mass 1.68 ± 0.10 $\mathrm{\it M}_\odot$, radius 1.56 ± 0.10 $\mathrm{\it R}_\odot$, and approximate age $0.27_{-0.15}^{+0.09}$ Gyr. GPX-1 b has an orbital period of ~1.75 d and a transit depth of 0.90 ± 0.03 per cent. We describe the GPX transit detection observations, subsequent photometric and speckle-interferometric follow-up observations, and SOPHIE spectroscopic measurements, which allowed us to establish the presence of a substellar object around the host star. GPX-1 was observed at 30-min integrations by TESS in Sector 18, but the data are affected by blending with a 3.4 mag brighter star 42 arcsec away. GPX-1 b is one of about two dozen transiting brown dwarfs known to date, with a mass close to the theoretical brown dwarf/gas giant planet mass transition boundary. Since GPX-1 is a moderately bright and fast-rotating star, it can be followed-up by the means of the Doppler tomography.