NGTS -1b: A hot Jupiter transiting an M -dwarf Journal: Monthly Notices of the Royal Astronomical Society Manuscript ID MN-17-3244-MJ Manuscript type: Main Journal Date Submitted by the Author: 13-Sep-2017 Complete List of Authors: Bayliss, Daniel; Observatoire Astronomique de l’Universit ́e de Gen`eve, Gillen, Edward; University of Cambridge, Cavendish Astrophysics Eigmüller, Philipp; Deutsches Zentrum für Luft und Raumfahrt, Institut für Planetenforschung McCormac, James; University of Warwick, Physics Alexander, Richard; University of Leicester, Physics & Astronomy; Armstrong, David; University of Warwick, Physics Booth, Rachel; Queen's University Belfast, Astrophysics Research Centre, School of Mathematics & Physics Bouchy, Francois; Observatoire Astronomique de l’Université de Genève, Département d'Astronomie Burleigh, Matthew Cabrera, Juan; DLR Casewell, Sarah Chaushev, Alexander; Department of Physics and Astronomy, Leicester Institute of Space and Earth Observation, University of Leicester, LE1 7RH Chazelas, Bruno Csizmadia, Szilard Erikson, Anders Faedi, Francesca; University of Warwick, Department of Physics Foxell, Emma; University of Warwick Department of Physics Gaensicke, Boris; University of Warwick, Department of Physics Goad, Michael; University of Leicester, Physics and Astronomy Grange, Andrew Guenther, Maximilian; University of Cambridge, Cavendish Laboratory Hodgkin, Simon; Cambridge University, Institute of Astronomy Jackman, James Jenkins, James; Universidad de Chile, Astronomy Lambert, Greg; University of Cambridge, Cavendish Astrophysics Louden, Tom; University of Warwick, Physics Metrailler, Lionel; Universite de Geneve Observatoire Astronomique Moyano, Maximiliano; Universidad Católica del Norte, Instituto de Astronomía Pollacco, Don; University of Warwick, Physics Poppenhaeger, Katja; Queen's University Belfast, Astrophysics Research Centre; Harvard-Smithsonian Center for Astrophysics, Queloz, Didier; Universite de Geneve Observatoire Astronomique Raddi, Roberto; University of Warwick, Department of Physics Rauer, Heike; DLR Page 1 of 10 1 2 3 4 Raynard, Liam; Department of Physics and Astronomy, Leicester Institute 5 of Space and Earth Observation, University of Leicester, LE1 7RH Smith, Alexis 6 Soto, Martiza; Universidad de Chile Facultad de Ciencias Fisicas y 7 Matematicas 8 Thompson, Andrew; Queen's University Belfast School of Mathematics and 9 Physics, Astrophysics Research Centre 10 Titz-Weider, Ruth; Deutsches Zentrumf für Luft- und Raumfahrt, Institut 11 für Planetenforschung 12 Udry, Stephane; Geneva University, Astronomy (Geneva Observatory) 13 Walker, S.; warwick Watson, Christopher; Queen's University Belfast, Mathematics & Physics 14 West, Richard; University of Warwick, Department of Physics 15 Wheatley, P.J.; University of Warwick, Department of Physics 16 techniques: photometric < Astronomical instrumentation, methods, and 17 Keywords: 18 techniques, (stars:) planetary systems < Stars, stars: individual:... < Stars 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Page 2 of 10 1 2 3 MNRAS 000,1–10(2017) Preprint13September2017 CompiledusingMNRAS LATEX style file v3.0 4 5 6 7 NGTS-1b: A hot Jupiter transiting an M-dwarf 8 9 10 1⋆ 2 3 4,5 11 Daniel Bayliss, Edward Gillen, Philipp Eigmuller,¨ James McCormac, 6 4,5 7 1 12 Richard D. Alexander, David J. Armstrong, Rachel S. Booth, Fran¸cois Bouchy, 13 Matthew R. Burleigh,6 Juan Cabrera,3 Sarah L. Casewell,6 Alexander Chaushev,6 14 1 3 3 4 15 Bruno Chazelas, Szilard Csizmadia, Anders Erikson, Francesca Faedi, 16 Emma Foxell,4 Boris T. G¨ansicke,4,5 Michael R. Goad,6 Andrew Grange,6 Max- 17 imilian N. Gunther,¨ 2 Simon T. Hodgkin,8 James Jackman,4 James S. Jenkins,9,10 18 2 4,5 1 11 19 Gregory Lambert, Tom Louden, Lionel Metrailler, Maximiliano Moyano, 20 Don Pollacco,4,5 Katja Poppenhaeger,7 Didier Queloz,2 Roberto Raddi,4 21 Heike Rauer,3 Liam Raynard,6 Alexis M. S. Smith,3 Maritza Soto,9 An- 22 7 3 1 4 23 drew P. G. Thompson, Ruth Titz-Weider, St´ephane Udry, Simon. R. Walker, 24 Christopher A. Watson,7 Richard G. West,4,5 Peter J. Wheatley,4,5 25 1Observatoire de Gen`eve, Universit´ede Gen`eve, 51 Ch. des Maillettes, 1290 Sauverny, Switzerland 2 26 Astrophysics Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK 3Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany 27 4Dept. of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK 28 5Centre for Exoplanets and Habitability, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK 29 6Department of Physics and Astronomy, Leicester Institute of Space and Earth Observation, University of Leicester, LE1 7RH, UK 7 30 Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, BT7 1NN Belfast, UK 8Institute of Astronomy, University of Cambridge, Madingley Rise, Cambridge CB3 0HA, UK 31 9Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile 32 10 Centro de Astrof´ısica y Tecnolog´ıas Afines (CATA), Casilla 36-D, Santiago, Chile. 33 11Instituto de Astronomia, Universidad Cat´olica del Norte, Casa Central, Angamos 0610, Antofagasta, Chile 34 35 36 Accepted XXX. Received YYY; in original form ZZZ 37 38 ABSTRACT 39 We present the discovery of NGTS-1b, a hot-Jupiter transiting an early M-dwarf T +71 P = 40 host ( eff, =3916 63 K) in a 2.647 d orbit discovered as part of the Next Gener- 41 ∗ − +0.066 ation Transit Survey (NGTS). The planet has a mass of 0.812 0.075 MJ and radius 42 +0.61 − of 1.33 0.33 RJ , making it the largest and most massive planet discovered transiting 43 any M-dwarf.− NGTS-1b is the third transiting giant planet found around an M-dwarf, 44 reinforcing the notion that close-in gas giants can form and migrate similar to the 45 known population of hot Jupiters around solar type stars. The host star shows no signs of activity, and the kinematics hint at the star being from the thick disk popu- 46 K = 47 lation. With a deep (2.5%) transit around a 11.9 host, NGTS-1b will be a strong candidate to probe giant planet composition around M-dwarfs via JWST transmission 48 spectroscopy. 49 50 Key words: techniques: photometric, stars: individual: NGTS-1, planetary systems 51 52 53 54 1 INTRODUCTION Escud´eet al. 2016) and Trappist-1 (Gillon et al. 2017). The interest primarily derives from the fact that the radius ra- 55 M-dwarf stars as planetary hosts are of high interest. Two tio (R Rstar) and mass ratio (M Mstar) for such systems important recent discoveries in the field of exoplanets relate P/ P/ 56 are much higher than equivalent systems with solar-type to planets orbiting M-dwarfs: Proxima Centauri (Anglada- 57 hosts, thus they can be easier to detect via transits and 58 radial velocities. The low intrinsic luminosity of M-dwarfs ⋆ also means that the habitable zone is very close to the host 59 E-mail: [email protected] 60 © 2017 The Authors Page 3 of 10 1 2 3 2 First Author 4 5 star and therefore it is much easier to detect potential hab- third gas giant found to transit an M-dwarf. In Section 2 6 itable planets around these stars, compared to their more we detail the observations that led to the discovery of this 7 massive counterparts. Finally, M-dwarfs are the most pop- planet, including the NGTS survey photometry, high preci- 8 ulous stars in the Galaxy ( 75%; Henry et al. 2006), and sion follow-up photometry, and high resolution spectroscopy. ∼ 9 hence understanding planet formation and planet frequency In Section 3 we analyse the observational data in conjunc- 10 around these low mass stars greatly enhances our knowledge tion with archival photometric data to precisely determine 11 of the full population of planets in the Galaxy. the physical characteristics of NGTS-1b. Finally, in Section4 However, observationally M-dwarfs present some signif- we discuss the results including the significance of this dis- 12 icant drawbacks when searching for exoplanets. Firstly, the covery in terms of planet formation scenarios around low 13 intrinsically low luminosity of M-dwarfs means that on aver- mass stars and the prospects for characterisation via JWST. 14 age they have much fainter apparent magnitudes than solar 15 type stars, making it hard to obtain high precision photome- 16 try or high precision radial velocity measurements. Secondly, 17 the spectra of M-dwarfs are dominated by molecular lines 2 OBSERVATIONS 18 which do not allow the same precision radial velocity mea- The discovery of NGTS-1b was made using the NGTS 19 surements as are afforded by the unblended, sharp metal telescopes in conjunction with high precision photometric lines that can be found in solar-type spectra. Finally the follow-up from Eulercam and high precision spectroscopy 20 low effective temperatures of M-dwarfs means they have a 21 from HARPS. We detail all of these observations in this peak flux well outside the optical wavelength range where Section. 22 most photometry and spectroscopy is targeted. 23 Despite these difficulties there has been progress in iden- 24 tifying exoplanets orbiting M-dwarfs using dedicated facil- 2.1 NGTS Photometry 25 ities. Notably the Earth-sized GJ1132-b (Berta-Thompson 26 et al. 2015) and super-Earth GJ1214-b (Charbonneau et al. NGTS is a fully automated array of twelve 20 cm aperture Newtonian telescopes situated at the ESO Paranal Observa- 27 2009), detected with the M-Earth ground-based transit sur- vey (Nutzman & Charbonneau 2008), have been popular tory in Chile. Each telescope is coupled to an Andor Ikon-L 28 targets for atmospheric characterisation owing to the small Camera featuring a 2K 2K e2V deep-depleted CCD with × 29 radii and close proximity to Earth of their M-dwarf hosts.