Abstract
About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet1,2. All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (R⊕), or apparently rocky planets smaller than 2 R⊕. Such lack of planets of intermediate size (the ‘hot Neptune desert’) has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6 R⊕ and a mass of 29 M⊕, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite3 revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet’s mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0\({}_{-2.9}^{+2.7}\)% of the total mass. With an equilibrium temperature around 2,000 K, it is unclear how this ‘ultrahot Neptune’ managed to retain such an envelope. Follow-up observations of the planet’s atmosphere to better understand its origin and physical nature will be facilitated by the star’s brightness (Vmag = 9.8).
This is a preview of subscription content, access via your institution
Access options
Access Nature and 54 other Nature Portfolio journals
Get Nature+, our best-value online-access subscription
$29.99 / 30 days
cancel any time
Subscribe to this journal
Receive 12 digital issues and online access to articles
$119.00 per year
only $9.92 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Data availability
The photometric data that support the findings of this study are publically available from the Mikulski Archive for Space Telescopes (http://archive.stsci.edu/) under the TESS mission link. All radial-velocity data are available from the corresponding author upon reasonable request. Raw and processed spectra can be obtained from the European Southern Observatory’s data archive at http://archive.eso.org.
Code availability
All codes necessary for the reproduction of this work are publically available through the GitHub repository, as follows: EMPEROR, https://github.com/ReddTea/astroEMPEROR; Juliet, https://github.com/nespinoza/juliet; SPECIES, https://github.com/msotov/SPECIES ; ARIADNE, https://www.github.com/jvines/astroARIADNE.
Change history
13 October 2020
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
References
Sanchis-Ojeda, R. et al. A study of the shortest-period planets found with Kepler. Astrophys. J. 787, 47 (2014).
Winn, J. N., Sanchis-Ojeda, R. & Rappaport, S. Kepler-78 and the ultra-short-period planets. New Astron. Rev. 83, 37–48 (2018).
Ricker, G. R. et al. Transiting Exoplanet Survey Satellite (TESS). J. Astron. Telesc. Instrum. Syst. 1, 014003 (2015).
Jenkins, J. M. et al. The TESS Science Processing Operations Center. Proc. SPIE 9913, 99133E (2016).
Gaia Collaboration et al. The Gaia mission. Astron. Astrophys. 595, A1 (2016).
Gaia Collaboration et al. Gaia data release 2. Summary of the contents and survey properties. Astron. Astrophys. 616, A1 (2018).
Wheatley, P. J. et al. The Next Generation Transit Survey (NGTS). Mon. Not. R. Astron. Soc. 475, 4476–4493 (2018).
Robin, A. C., Reylé, C., Derriére, S. & Picaud, S. A synthetic view on structure and evolution of the Milky Way. Astron. Astrophys. 409, 523–540 (2003).
Pepe, F. et al. HARPS: a new high-resolution spectrograph for the search of extrasolar planets. Proc. SPIE 4008, 582–592 (2000).
Fűrész, G., Szentgyorgyi, A. H. & Meibom, S. in Precision Spectroscopy in Astrophysics (eds Santos, N. C. et al.) 287–290 (Springer, 2008).
Siverd, R. J. et al. NRES: the network of robotic echelle spectrographs. Proc. SPIE 10702, 107026C (2018).
Espinoza, N., Kossakowski, D. & Brahm, R. Juliet: a versatile modelling tool for transiting and non-transiting exoplanetary systems. Mon. Not. R. Astron. Soc. 490, 2262–2283 (2019).
Mazeh, T., Holczer, T. & Faigler, S. Dearth of short-period neptunian exoplanets: a desert in period-mass and period-radius planes. Astron. Astrophys. 589, A75 (2016).
Lopez, E. D. & Fortney, J. J. Understanding the mass-radius relation for sub-Neptunes: radius as a proxy for composition. Astrophys. J. 792, 1 (2014).
Lundkvist, M. S. et al. Hot super-Earths stripped by their host stars. Nat. Commun. 7, 11201 (2016).
Lopez, E. D. Born dry in the photoevaporation desert: Kepler’s ultra-short-period planets formed water-poor. Mon. Not. R. Astron. Soc. 472, 245–253 (2017).
Owen, J. E. & Wu, Y. The evaporation valley in the Kepler planets. Astrophys. J. 847, 29 (2017).
Ehrenreich, D. et al. A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b. Nature 522, 459–461 (2015).
Vidal-Madjar, A. et al. Detection of oxygen and carbon in the hydrodynamically escaping atmosphere of the extrasolar planet HD 209458b. Astrophys. J. Lett. 604, L69–L72 (2004).
Casasayas-Barris, N. et al. Atmospheric characterization of the ultra-hot Jupiter MASCARA-2b/KELT-20b. Detection of CaII, FeII, NaI, and the Balmer series of H (Hα, Hβ, and Hγ) with high-dispersion transit spectroscopy. Astron. Astrophys. 628, 9 (2019).
Nortmann, L. et al. Ground-based detection of an extended helium atmosphere in the Saturn-mass exoplanet WASP-69b. Science 362, 1388–1391 (2018).
West, R. G. et al. NGTS-4b: A sub-Neptune transiting in the desert. Mon. Not. R. Astron. Soc. 486, 5094–5103 (2019).
Owen, A. E. & Jackson, A. P. Planetary evaporation by UV, X-ray radiation: basic hydrodynamics. Mon. Not. R. Astron. Soc. 425, 2931–2947 (2012).
Ionov, D. E., Pavlyuchenkov, Y. N. & Shematovich, V. I. Survival of a planet in short-period Neptunian desert under effect of photoevaporation. Mon. Not. R. Astron. Soc. 476, 5639–5644 (2018).
Jackson, A. P., Davis, T. A. & Wheatley, P. The coronal X-ray-age relation and its implications for the evaporation of exoplanets. Mon. Not. R. Astron. Soc. 422, 2024–2043 (2012).
Chadney, J. M. et al. XUV-driven mass loss from extrasolar giant planets orbiting active stars. Icarus 250, 357–367 (2015).
King, G. W. et al. The XUV environments of exoplanets from Jupiter-size to super-Earth. Mon. Not. R. Astron. Soc. 478, 1193–1208 (2018).
Kubyshkina, D. et al. Grid of upper atmosphere models for 1–40 M⊕ planets: application to CoRoT-7 b and HD 219134 b,c. Astron. Astrophys. 619, A151 (2018).
Valsecchi, F. et al. Tidally-driven Roche-lobe overflow of hot Jupiters with MESA. Astrophys. J. 813, 101 (2015).
Fischer, D. A. & Valenti, J. The planet–metallicity correlation. Astrophys. J. 622, 1102–1117 (2005).
Smith, J. C. et al. Kepler presearch data conditioning II—a Bayesian approach to systematic error correction. Publ. Astron. Soc. Pac. 124, 1000–1014 (2012).
Stumpe, M. C. et al. Multiscale systematic error correction via wavelet-based bandsplitting in Kepler data. Publ. Astron. Soc. Pac. 126, 100–114 (2014).
Twicken, J. D. et al. Kepler data validation I architecture, diagnostic tests,and data products for vetting transiting planet candidates. Publ. Astron. Soc. Pac. 130, 064502 (2018).
Li, J. et al. Kepler data validation II—transit model fitting and multiple-planet search. Publ. Astron. Soc. Pac. 131, 024506 (2019).
Smith, A. M. S. et al. Shallow transit follow-up from Next-Generation Transit Survey: simultaneous observations of HD106315 with 11 identical telescopes. Astron. Nachr. 341, 273–282 (2020).
McCormac, J. et al. DONUTS: a science frame autoguiding algorithm with sub-pixel precision, capable of guiding on defocused stars. Publ. Astron. Soc. Pac. 125, 548–556 (2013).
Fressin, F. et al. The false positive rate of Kepler and the occurrence of planets. Astrophys. J. 766, 81 (2013).
Raghavan, D. et al. A survey of stellar families: multiplicity of solar-type stars. Astrophys. J. Suppl. Ser. 190, 1–42 (2010).
Lindegren, L. et al. The astrometric core solution for the Gaia mission. Overview of models, algorithms, and software implementation. Astron. Astrophys. 538, A78 (2012).
Michalik, D., Lindegren, L., Hobbs, D. & Lammers, U. Joint astrometric solution of HIPPARCOS and Gaia. A recipe for the hundred thousand proper motions project. Astron. Astrophys. 571, A85 (2014).
Lindegren, L. et al. Gaia data release 1. Astrometry: one billion positions, two million proper motions and parallaxes. Astron. Astrophys. 595, A4 (2016).
Lindegren, L. Gaia data release 2. The astrometric solution. Astron. Astrophys. 616, A2 (2018).
van Leeuwen, F. Validation of the new Hipparcos reduction. Astron. Astrophys. 474, 653–664 (2007).
Rey, J. et al. The SOPHIE search for northern extrasolar planets. XII. Three giant planets suitable for astrometric mass determination with Gaia. Astron. Astrophys. 601, A9 (2017).
Brown, T. M. et al. Las Cumbres Observatory Global Telescope Network. Publ. Astron. Soc. Pac. 125, 1031 (2013).
Fulton, B. J. & Petigura, E. A. The California–Kepler Survey. VII. Precise planet radii leveraging Gaia DR2 reveal the stellar mass dependence of the planet radius gap. Astron. J. 156, 264 (2018).
Buchhave, L. A. et al. HAT-P-16b: A 4 MJ planet transiting a bright star on an eccentric orbit. Astrophys. J. 720, 1118–1125 (2010).
Horne, K. An optimal extraction algorithm for CCD spectroscopy. Publ. Astron. Soc. Pac. 98, 609–617 (1986).
Buchhave, L. A. et al. An abundance of small exoplanets around stars with a wide range of metallicities. Nature 486, 375–377 (2012).
Anglada-Escudé, G. & Butler, R. P. The HARPS-TERRA project. I. Description of the algorithms, performance, and new measurements on a few remarkable stars observed by HARPS. Astrophys. J. Suppl. Ser. 200, 15 (2012).
Zechmeister, M. & Kürster, M. The generalised Lomb–Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms. Astron. Astrophys. 496, 577–584 (1986).
Benedict, G. F. et al. The solar neighborhood. XXXVII: the mass–luminosity relation for main-sequence M dwarfs. Astron. J. 152, 141 (2016).
Brahm, R., Jordán, A. & Espinoza, N. CERES: a set of automated routines for echelle spectra. Publ. Astron. Soc. Pac. 129, 034002 (2017).
Ciardi, D. R., Beichman, C. A., Horch, E. P. & Howell, S. B. Understanding the effects of stellar multiplicity on the derived planet radii from transit surveys: implications for Kepler, K2, and TESS. Astrophys. J. 805, 16 (2015).
Furlan, E. et al. The Kepler follow-up observation program. I. A catalog of companions to Kepler stars from high-resolution imaging. Astron. J. 153, 71 (2017).
Ziegler, C. et al. SOAR TESS survey. I: sculpting of tess planetary systems by stellar companions. Astron. J. 159, 19 (2020).
Soto, M. G. & Jenkins, J. S. Spectroscopic parameters and atmospheric chemistries of stars (SPECIES). I. Code description and dwarf stars catalogue. Astron. Astrophys. 615, A76 (2018).
Brahm, R., Jordán, A., Hartman, J. & Bakos, G. ZASPE: A code to measure stellar atmospheric parameters and their covariance from spectra. Mon. Not. R. Astron. Soc. 467, 971–984 (2017).
Kurucz, R. L. in The Stellar Populations of Galaxies IAU Symposium Vol. 149 (eds Barbuy, B. & Renzini, A.) 225 (1992).
Sneden, C. A. Carbon and Nitrogen Abundances in Metal-Poor Stars. PhD thesis, Univ. Texas at Austin (1973).
Castelli, F. & Kurucz, R. L. New grids of ATLAS9 model atmospheres. In Symposium of the International Astronomical Union A20 (Astronomical Society of the Pacific, 2003).
Dotter, A. MESA isochrones and stellar tracks (MIST) 0: methods for the construction of stellar isochrones. Astrophys. J. Suppl. Ser. 222, 8 (2016).
Yi, S. et al. Toward better age estimates for stellar populations: the Y2 isochrones for solar mixture. Astrophys. J. Suppl. Ser. 136, 417–437 (2001).
Husser, T. O. et al. A new extensive library of PHOENIX stellar atmospheres and synthetic spectra. Astron. Astrophys. 553, A6 (2013).
Allard, F., Homeier, D. & Freytag, B. Models of very-low-mass stars, brown dwarfs and exoplanets. Phil. Trans. R. Soc. Lond. Ser. A 379, 2765–2777 (2012).
Hauschildt, P. H., Allard, F. & Baron, E. The NextGen Model Atmosphere grid for 3000 ≤ Teff ≤ 10,000 K. Astrophys. J. 512, 377–385 (1999).
Kurucz, R. et al. ATLAS9 Stellar Atmosphere Programs and 2 km/s Grid Kurucz CD-ROM No. 13 (Smithsonian Astrophysical Observatory, 1993).
Stassun, K. G. & Torres, G. Evidence for a systematic offset of 80 micro-arcseconds in the Gaia DR2 parallaxes. Astron. J. 862, 1–5 (2018).
Schlegel, D. J., Finkbeiner, D. P. & Davis, M. Maps of dust infrared emission for use in estimation of reddening and cosmic microwave background radiation foregrounds. Astrophys. J. 500, 525–553 (1998).
Schlafly, E. F. & Finkbeiner, D. P. Measuring reddening with Sloan Digital Sky Survey stellar spectra and recalibrating SFD. Astrophys. J. 737, 103 (2011).
Speagle, J. S. dynesty: a dynamic nested sampling package for estimating Bayesian posteriors and evidences. Mon. Not. R. Astron. Soc. 493, 3132–3158 (2020).
Pavlenko, Y. V., Jenkins, J. S., Jones, H. R. A., Ivanyuk, O. & Pinfield, D. J. Effective temperatures, rotational velocities, microturbulent velocities and abundances in the atmospheres of the Sun, HD 1835 and HD 10700. Mon. Not. R. Astron. Soc. 422, 542–552 (2012).
McQuillan, A., Mazeh, T. & Aigrain, S. Rotation periods of 34,030 Kepler main-sequence stars: the full autocorrelation sample. Astrophys. J. Suppl. Ser. 211, 24 (2014).
Jenkins, J. S. et al. An activity catalogue of southern stars. Mon. Not. R. Astron. Soc. 372, 163–173 (2006).
Jenkins, J. S. et al. Metallicities and activities of southern stars. Astron. Astrophys. 485, 571–584 (2008).
Jenkins, J. S. et al. Chromospheric activities and kinematics for solar type dwarfs and subgiants: analysis of the activity distribution and the AVR. Astron. Astrophys. 531, A8 (2011).
Jenkins, J. S. et al. New planetary systems from the Calan–Hertfordshire extrasolar planet search. Mon. Not. R. Astron. Soc. 466, 443–473 (2017).
Mamajek, E. E. & Hillenbrand, L. A. Improved age estimation for solar-type dwarfs using activity-rotation diagnostics. Astrophys. J. 687, 1264–1293 (2008).
Kreidberg, L. batman: basic transit model calculation in Python. Publ. Astron. Soc. Pac. 127, 1161–1165 (2015).
Fulton, B. J., Petigura, E. A., Blunt, S. & Sinukoff, E. RadVel: the radial velocity modeling toolkit. Publ. Astron. Soc. Pac. 130, 044504 (2018).
Feroz, F., Hobson, M. P. & Bridges, M. MULTINEST: an efficient and robust bayesian inference tool for cosmology and particle physics. Mon. Not. R. Astron. Soc. 398, 1601–1614 (2009).
Buchner, J. et al. X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue. Astron. Astrophys. 564, A125 (2014).
Espinoza, N. Efficient joint sampling of impact parameters and transit depths in transiting exoplanet light curves. Res. Not. Am. Astron. Soc. 2, 209 (2018).
Kipping, D. M. Efficient, uninformative sampling of limb darkening coefficients for two-parameter laws. Mon. Not. R. Astron. Soc. 435, 2152–2162 (2013).
Eastman, J., Gaudi, B. S. & Algol, E. EXOFAST: A fast exoplanetary fitting suite in IDL. Publ. Astron. Soc. Pac. 125, 83–112 (2013).
Eastman, J. EXOFASTv2: generalized publication-quality exoplanet modeling code. Astrophys. Source Code Library 435, 1710.003 (2017).
Gonzalez, G. The stellar metallicity–giant planet connection. Mon. Not. R. Astron. Soc. 285, 403–412 (1997).
Maldonado, J., Villaver, E. & Eiroa, C. Chemical fingerprints of hot Jupiter planet formation. Astron. Astrophys. 612, A93 (2018).
Jenkins, J. S. et al. A hot Uranus orbiting the super metal-rich star HD 77338 and the metallicity–mass connection. Astrophys. J. 766, 67 (2013).
Buchhave, L. et al. Three regimes of extrasolar planet radius inferred from host star metallicities. Nature 509, 593–595 (2014).
Southworth, L. Homogeneous studies of transiting extrasolar planets—IV. Thirty systems with space-based light curves. Mon. Not. R. Astron. Soc. 417, 2166–2196 (2011).
Méndez, A. & Rivera-Valentín, E. G. The equilibrium temperature of planets in elliptical orbits. Astrophys. J. Lett. 837, L1 (2017).
Zeng, L., Sasselov, D. D. & Jacobsen, S. B. Mass–radius relation for rocky planets based on PREM. Astrophys. J. 819, 127 (2016).
Acknowledgements
Funding for the TESS mission is provided by NASA’s Science Mission directorate. We acknowledge the use of public TESS alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. J.S.J. and N.T. acknowledge support by FONDECYT grants 1161218 and 1201371, and partial support from CONICYT project Basal AFB-170002. M.R.D. is supported by CONICYT-PFCHA/Doctorado Nacional-21140646/Chile and Proyecto Basal AFB-170002. J.I.V. acknowledges support of CONICYT-PFCHA/Doctorado Nacional-21191829. This work was made possible owing to ESO Projects 0102.C-0525 (principal investigator, Díaz) and 0102.C-0451 (principal investigator, Brahm). R.B. acknowledges support from FONDECYT Post-doctoral Fellowship Project 3180246. This work is partly supported by JSPS KAKENHI grant numbers JP18H01265 and JP18H05439, and JST PRESTO grant number JPMJPR1775. The IRSF project is a collaboration between Nagoya University and the South African Astronomical Observatory (SAAO) supported by the Grants-in-Aid for Scientific Research on Priority Areas (A) (numbers 10147207 and 10147214) and Optical and Near-Infrared Astronomy Inter-University Cooperation Program, from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan and the National Research Foundation (NRF) of South Africa. We thank A. Fukui, N. Kusakabe, K. Morihana, T. Nagata, T. Nagayama and the staff of SAAO for their kind support for IRSF SIRIUS observations and analyses. C.P. acknowledges support from the Gruber Foundation Fellowship and Jeffrey L. Bishop Fellowship. This research includes data collected under the NGTS project at the ESO La Silla Paranal Observatory. NGTS is funded by a consortium of institutes consisting of the University of Warwick, the University of Leicester, Queen’s University Belfast, the University of Geneva, the Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR; under the ‘Großinvestition GI-NGTS’), the University of Cambridge, together with the UK Science and Technology Facilities Council (STFC; project reference ST/M001962/1 and ST/S002642/1). P.J.W., D.B., B.T.G., S.G., T.L., D.P. and R.G.W. are supported by STFC consolidated grant ST/P000495/1. D.J.A. gratefully acknowledges support from the STFC via an Ernest Rutherford Fellowship (ST/R00384X/1). E.G. gratefully acknowledges support from the David and Claudia Harding Foundation in the form of a Winton Exoplanet Fellowship. M.J.H. acknowledges funding from the Northern Ireland Department for the Economy. M.T. is supported by JSPS KAKENHI (18H05442, 15H02063). A.J., R.B. and P.T. acknowledge support from FONDECYT project 1171208, and by the Ministry for the Economy, Development, and Tourism’s Programa Iniciativa Científica Milenio through grant IC 120009, awarded to the Millennium Institute of Astrophysics (MAS). P.E., A.C. and H.R. acknowledge the support of the DFG priority programme SPP 1992 ‘Exploring the Diversity of Extrasolar Planets’ (RA 714/13-1). We acknowledge the effort of A. Tokovinin in helping to perform the observations and reduction of the SOAR data.
Author information
Authors and Affiliations
Contributions
J.S.J. led the TESS precision radial-velocity follow-up programme, selection of the targets, analysis and project coordination, and wrote the bulk of the paper. M.D., N.T. and R.B. performed the HARPS radial-velocity observations, P.T. observed the star with Coralie and M.D. analysed the activity data from these sources. N.E. performed the global modelling, with P.C.-Z. performing the TTV analysis, and R.B., M.G.S. and A.B. performing the stellar characterization using the spectra and evolutionary models. P.A.P.R. worked on the EMPEROR code and assisted in fitting the HARPS radial velocities. E.D.L. created a structure model for the planet, and in addition to G.W.K. and P.J.W., performed photoevaporation modelling. J.N.W. performed analysis of the system parameters. D.R.C. led the Keck NIRC2 observations and analysis. G.R., R.V., D.W.L., S.S. and J.M.J. have been leading the TESS project, observations, organization of the mission, processing of the data, organization of the working groups, selection of the targets and dissemination of the data products. C.E.H., S.M. and T.K. worked on the SPOC data pipeline. C.J.B. was a member of the TOI discovery team. S.N.Q. contributed to TOI vetting, TFOP organization and TRES spectral analysis. J.L. and C.P. helped with the interpretation of the system formation and evolution. K.A.C. contributed to TOI vetting, TFOP organization, and TFOP SG1 ground-based time-series photometry analysis. G.I., F.M., A.E., K.I.C., M.M., N.N., T.N. and J.P.L. contributed TFOP SG1 observations. J.S.A., D.J.A., D.B., F.B., C.B., E.M.B., M.R.B., J.C., S.L.C., A.C., B.F.C., P.E., A.E., E.F., B.T.G., S.G., E.G., M.N.G., M.R.G., M.J.H., J.A.G.J., T.L., J.M., M.M., L.D.N., D.P., D.Q., H.R., L.R., A.M.S.S., R.H.T., R.T.-W., O.T., S.U., J.I.V., S.R.W., C.A.W., R.G.W., P.J.W. and G.W.K. are part of the NGTS consortium who provided follow-up observations to confirm the planet. E.P. and J.J.L. helped with the interpretation of the result. C.B. performed the observations at SOAR and reduced the data, C.Z. performed the data analysis, and N.L. and A.W.M. assisted in the survey proposal, analysis and telescope time acquisition. All authors contributed to the paper.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data
Extended Data Fig. 1 Normalised TESS pre-search data conditioning timeseries photometry for LTT 9779.
with the optimal model (black curve) overplotted on the data (top). The model residuals are shown in the lower panel.
Extended Data Fig. 2 Independently constrained system parameters from the EMPEROR MCMC runs of the 31 HARPS radial-velocities.
From top to bottom we show the posteriors of the velocity amplitude, the orbital period, and the eccentricity of the orbit. Overplotted on each histogram is a gaussian distribution with the same input parameters as those calculated from the posterior distributions. We also show the values obtained from the distributions. The histograms reveal that the signal is well constrained with the current data in hand, and the period in particular is in excellent agreement with that from the TESS lightcurve.
Extended Data Fig. 3 Spectral line bisector inverse slope measurements as a function of the radial-velocities.
The orange diamonds and blue circles relate to measurements made using HARPS and Coralie, respectively. The best fit linear trend is shown by the dashed line, and a key in the upper left indicates the origin of the data points.
Extended Data Fig. 4 Companion sensitivity for the Keck NIRC2 adaptive optics imaging and the SOAR Adaptive Optics Module (SAM).
For NIRC2 (left), the black points represent the 5σ limits and are separated in steps of 1 FWHM (~ 0.05”); the purple represents the azimuthal dispersion (1σ) of the contrast determinations (see text). The inset image is of the primary target showing no additional companions within 3” of the target. For SAM (right) the black curve also represents the 5σ limit, and the black data points mark the sampling. The inset also shows the speckle image of the star, constructed from the Auto-Correlation Function.
Extended Data Fig. 5 Stellar density as a function of R_p/R*.
when modelling the TESS, NGTS, and LCOGT lightcurves with a log-uniform prior on the stellar density and the planetary eccentricity constrained to be zero.
Extended Data Fig. 6 Observed minus computed mid-transit times of LTT 9779 b.
The residuals (TTV) of the transit times are shown considering the proposed linear ephemeris. The dashed line corresponds to zero variation and the grey area is the propagation of 1σ uncertainties, considering the optimal transit time from EXOFASTv2 and the period from juliet. The epoch 0 is the first lightcurve obtained by TESS and is also the corresponding epoch of the optimal transit time. The TTV values shown in this plot fit accordingly with the proposed linear ephemeris (\({\chi }_{red}^{2}=1.23\)= 1.23).
Supplementary information
Supplementary Information
Supplementary Tables 1 and 2.
Rights and permissions
About this article
Cite this article
Jenkins, J.S., Díaz, M.R., Kurtovic, N.T. et al. An ultrahot Neptune in the Neptune desert. Nat Astron 4, 1148–1157 (2020). https://doi.org/10.1038/s41550-020-1142-z
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1038/s41550-020-1142-z
