[en] One of the primary goals of exoplanetary science is to detect small, temperate planets passing (transiting) in front of bright and quiet host stars. This enables the characterization of planetary sizes, orbits, bulk compositions, atmospheres and formation histories. These studies are facilitated by small and cool M dwarf host stars. Here we report the Transiting Exoplanet Survey Satellite (TESS)[SUP]1[/SUP] discovery of three small planets transiting one of the nearest and brightest M dwarf hosts observed to date, TOI-270 (TIC 259377017, with K-magnitude 8.3, and 22.5 parsecs away from Earth). The M3V-type star is transited by the super-Earth-sized planet TOI-270 b (1.247[SUB]-0.083[/SUB][SUP]+0.089[/SUP]R[SUB]⊕[/SUB]) and the sub- Neptune-sized planets TOI-270 c (2.42 ± 0.13 R[SUB]⊕[/SUB]) and TOI-270 d (2.13 ± 0.12 R[SUB]⊕[/SUB]). The planets orbit close to a mean-motion resonant chain, with periods (3.36 days, 5.66 days and 11.38 days, respectively) near ratios of small integers (5:3 and 2:1). TOI-270 is a prime target for future studies because (1) its near-resonance allows the detection of transit timing variations, enabling precise mass measurements and dynamical studies; (2) its brightness enables independent radial-velocity mass measurements; (3) the outer planets are ideal for atmospheric characterization via transmission spectroscopy; and (4) the quietness of the star enables future searches for habitable zone planets. Altogether, very few systems with small, temperate exoplanets are as suitable for such complementary and detailed characterization as TOI-270.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Günther, Maximilian N.; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Pozuelos Romero, Francisco José ; Space Sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, Liège, Belgium
Dittmann, Jason A.; Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
Dragomir, Diana; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Kane, Stephen R.; Department of Earth and Planetary Sciences, University of California, Riverside, CA, USA
Daylan, Tansu; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Feinstein, Adina D.; Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA
Huang, Chelsea X.; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Morton, Timothy D.; Department of Astronomy, University of Florida, Gainesville, FL, USA
Bonfanti, Andrea ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Bouma, L. G.; Department of Astrophysical Sciences, Princeton University, Princeton, NJ, USA
Burt, Jennifer; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Collins, Karen A.; Center for Astrophysics, Harvard and Smithsonian, Cambridge, MA, USA
Lissauer, Jack J.; NASA Ames Research Center, Moffett Field, CA, USA
Matthews, Elisabeth; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Montet, Benjamin T.; Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA
Vanderburg, Andrew; Department of Astronomy, University of Texas at Austin, Austin, TX, USA
Wang, Songhu; Department of Astronomy, Yale University, New Haven, CT, USA
Winters, Jennifer G.; Center for Astrophysics, Harvard and Smithsonian, Cambridge, MA, USA
Ricker, George R.; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Vanderspek, Roland K.; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Latham, David W.; Center for Astrophysics, Harvard and Smithsonian, Cambridge, MA, USA
Seager, Sara; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Winn, Joshua N.; Department of Astrophysical Sciences, Princeton University, Princeton, NJ, USA
Jenkins, Jon M.; NASA Ames Research Center, Moffett Field, CA, USA
Armstrong, James D.; University of Hawaii Institute for Astronomy, Pukalani, HI, USA
Barkaoui, Khalid; Astrobiology Research Unit, Université de Liège, Liége, Belgium
Batalha, Natalie; Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA, USA
Bean, Jacob L.; Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL, USA
Caldwell, Douglas A.; NASA Exoplanet Science Institute, Caltech/IPAC-NExScI, Pasadena, CA, USA
Ciardi, David R.; NASA Exoplanet Science Institute, Caltech/IPAC-NExScI, Pasadena, CA, USA
Collins, Kevin I.; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
Crossfield, Ian; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Fausnaugh, Michael; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Furesz, Gabor; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Gan, Tianjun; Physics Department and Tsinghua Centre for Astrophysics, Tsinghua University, Beijing, China
Gillon, Michaël ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Exotic
Guerrero, Natalia; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Horne, Keith; SUPA Physics and Astronomy, University of St Andrews, St Andrews, UK
Howell, Steve B.; NASA Ames Research Center, Moffett Field, CA, USA
Ireland, Michael; Research School of Astronomy and Astrophysics, Australian National University, Canberra, Australian Capital Territory, Australia
Isopi, Giovanni; Campo Catino Astronomical Observatory, Guarcino, Italy
Jehin, Emmanuel ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Kielkopf, John F.; Department of Physics and Astronomy, University of Louisville, Louisville, KY, USA
Lepine, Sebastien; Department of Physics and Astronomy, Georgia State University, Atlanta, GA, USA
Mallia, Franco; Campo Catino Astronomical Observatory, Guarcino, Italy
Matson, Rachel A.; NASA Ames Research Center, Moffett Field, CA, USA
Myers, Gordon; American Association of Variable Star Observers (AAVSO), Hillsborough, CA, USA
Palle, Enric; Instituto de Astrofísica de Canarias (IAC), La Laguna, Tenerife, Spain
Quinn, Samuel N.; Center for Astrophysics, Harvard and Smithsonian, Cambridge, MA, USA
Relles, Howard M.; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Rojas-Ayala, Bárbara; Departamento de Ciencias Físicas, Universidad Andrés Bello, Las Condes, Santiago, Chile
Schlieder, Joshua; NASA Goddard Space Flight Center, Greenbelt, MD, USA
Sefako, Ramotholo; South African Astronomical Observatory, Cape Town, South Africa
Shporer, Avi; Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA, USA
Suárez, Juan C.; Department of Física Teórica y del Cosmos, Universidad de Granada, Granada, Spain
Tan, Thiam-Guan; Perth Exoplanet Survey Telescope, Perth, Western Australia, Australia
Ting, Eric B.; NASA Ames Research Center, Moffett Field, CA, USA
Twicken, Joseph D.; SETI Institute/NASA Ames Research Center, Moffett Field, CA, USA)
Ricker, G. R. et al. Transiting Exoplanet Survey Satellite (TESS). Proc. SPIE 9143, 20 (2014).
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).
Van Eylen, V. et al. An asteroseismic view of the radius valley: stripped cores, not born rocky. Mon. Not. R. Astron. Soc. 479, 4786–4795 (2018).
Owen, J. E. & Wu, Y. Kepler planets: a tale of evaporation. Astrophys. J. 775, 105 (2013).
Fortney, J. J., Marley, M. S. & Barnes, J. W. Planetary radii across five orders of magnitude in mass and stellar insolation: application to transits. Astrophys. J. 659, 1661–1672 (2007).
Chen, J. & Kipping, D. Probabilistic forecasting of the masses and radii of other worlds. Astrophys. J. 834, 17 (2017).
Deck, K. M., Agol, E., Holman, M. J. & Nesvorný, D. TTVFast: an efficient and accurate code for transit timing inversion problems. Astrophys. J. 787, 132 (2014).
Mayor, M. et al. Setting new standards with HARPS. Messenger 114, 20–24 (2003).
Pepe, F. A. et al. ESPRESSO: the Echelle spectrograph for rocky exoplanets and stable spectroscopic observations. Proc. SPIE 7735, 77350F (2010).
Crossfield, I. J. M. et al. A nearby M star with three transiting super-Earths discovered by K2. Astrophys. J. 804, 10 (2015).
Montet, B. T. et al. Stellar and planetary properties of K2 campaign 1 candidates and validation of 17 planets, including a planet receiving Earth-like insolation. Astrophys. J. 809, 25 (2015).
Dittmann, J. A. et al. A temperate rocky super-Earth transiting a nearby cool star. Nature 544, 333–336 (2017).
Lissauer, J. J. et al. Architecture and dynamics of Kepler’s candidate multiple transiting planet systems. Astrophys. J. Suppl. Ser. 197, 8 (2011).
Batalha, N. E. et al. PandExo: a community tool for transiting exoplanet science with JWST HST. Publ. Astron. Soc. Pacif. 129, 064501 (2017).
Kempton, E. M. R. et al. A framework for prioritizing the TESS planetary candidates most amenable to atmospheric characterization. Publ. Astron. Soc. Pacif. 130, 114401 (2018).
Hansen, B. M. S. & Murray, N. Testing in situ assembly with the Kepler planet candidate sample. Astrophys. J. 775, 53 (2013).
Millholland, S., Wang, S. & Laughlin, G. Kepler multi-planet systems exhibit unexpected intra-system uniformity in mass and radius. Astrophys. J. Lett. 849, 33 (2017).
Luger, R. & Barnes, R. Extreme water loss and abiotic O2 buildup on planets throughout the habitable zones of M dwarfs. Astrobiology 15, 119–143 (2015).
Serindag, D. B. & Snellen, I. A. G. Testing the detectability of extraterrestrial O2 with the extremely large telescopes using real data with real noise. Astrophys. J. Lett. 871, 7 (2019).
Schwieterman, E. W. et al. Identifying planetary biosignature impostors: spectral features of CO and O4 resulting from abiotic O2/O3 production. Astrophys. J. 819, L13 (2016).
Takai, K. et al. Cell proliferation at 122 °C and isotopically heavy CH4 production by a hyperthermophilic methanogen under high-pressure cultivation. Proc. Natl Acad. Sci. 105, 10949–10954 (2008).
Noack, L. et al. Water-rich planets: how habitable is a water layer deeper than on Earth? Icarus 277, 215–236 (2016).
Kane, S. R. Worlds without moons: exomoon constraints for compact planetary systems. Astrophys. J. 839, L19 (2017).
Kopparapu, R. K. et al. Habitable zones around main-sequence stars: dependence on planetary mass. Astrophys. J. Lett. 787, 29 (2014).
Günther, M. N. et al. Stellar flares from the first TESS data release: exploring a new sample of M-dwarfs. Preprint at https://arxiv.org/abs/1901.00443 (2019).
Newton, E. R., Irwin, J., Charbonneau, D., Berta-Thompson, Z. K. & Dittmann, J. A. The impact of stellar rotation on the detectability of habitable planets around M dwarfs. Astrophys. J. Lett. 821, 19 (2016).
Lammer, H. et al. Coronal mass ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. II. CME-induced ion pick up of Earth-like exoplanets in close-in habitable zones. Astrobiology 7, 185–207 (2007).
Cohen, O. et al. The interaction of Venus-like, M-dwarf planets with the stellar wind of their host star. Astrophys. J. 806, 41 (2015).
Tilley, M. A., Segura, A., Meadows, V., Hawley, S. & Davenport, J. Modeling repeated M dwarf flaring at an Earth-like planet in the habitable zone: atmospheric effects for an unmagnetized planet. Astrobiology 19, 64–86 (2019).
Gillon, M. et al. Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature 542, 456–460 (2017).
Stassun, K. G. et al. The TESS input catalog and candidate target list. Astron. J. 156, 102 (2018).
Muirhead, P. S. et al. A catalog of cool dwarf targets for the transiting exoplanet survey satellite. Astron. J. 155, 180 (2018).
Jenkins, J. M. The impact of solar-like variability on the detectability of transiting terrestrial planets. Astrophys. J. 575, 493–505 (2002).
Jenkins, J. M. et al. Transiting planet search in the Kepler pipeline. In Software and Cyberinfrastructure for Astronomy Vol. 7740,77400D (SPIE, 2010).
Smith, J. C. et al. Kepler presearch data conditioning II—A Bayesian approach to systematic error correction. Publ. Astron. Soc. Pacif. 124, 1000 (2012).
Stumpe, M. C. et al. Multiscale systematic error correction via wavelet-based bandsplitting in Kepler data. Publ. Astron. Soc. Pacif. 126, 100 (2014).
Jenkins, J. M. et al. The TESS science processing operations center. In Software and Cyberinfrastructure for Astronomy IV Vol. 9913, 99133E (SPIE, 2016).
Jenkins, J. M. (ed) Kepler Data Processing Handbook KSCI-19081-002 (NASA, 2017).
Cameron, A. C. Extrasolar planets: astrophysical false positives. Nature 48–50 (2012).
Günther, M. N. et al. A new yield simulator for transiting planets and false positives: application to the next generation transit survey. Mon. Not. R. Astron. Soc. 465, 3379–3389 (2017).
Günther, M. N. et al. Unmasking the hidden NGTS-3Ab: a hot Jupiter in an unresolved binary system. Mon. Not. R. Astron. Soc. 478, 4720–4737 (2018).
Lissauer, J. J. et al. Almost all of Kepler’s multiple-planet candidates are planets. Astrophys. J. 750, 112 (2012).
Muirhead, P. S. et al. Characterizing the cool KOIs. VI. H- and K-band spectra of Kepler M dwarf planet-candidate hosts. Astrophys. J. Suppl. Ser. 213, 5 (2014).
Gillon, M. et al. Temperate Earth-sized planets transiting a nearby ultracool dwarf star. Nature 533, 221–224 (2016).
Vanderspek, R. et al. TESS discovery of an ultra-short-period planet around the nearby M dwarf LHS 3844. Astrophys. J. Lett. 871, 24 (2019).
Quinn, S. N. et al. Near-resonance in a system of sub-Neptunes from TESS. Preprint at https://arxiv.org/abs/1901.09092 (2019).
Twicken, J. D. et al. Kepler data validation. I. Architecture, diagnostic tests, and data products for vetting transiting planet candidates. Publ. Astron. Soc. Pacif. 130, 064502 (2018).
Li, J. et al. Kepler data validation II. Transit model fitting and multiple-planet search. Publ. Astron. Soc. Pacif. 131, 024506 (2019).
Rizzuto, A. C. et al. Zodiacal Exoplanets In Time (ZEIT). VIII. A two-planet system in Praesepe from K2 campaign 16. Astron. J. 156, 195 (2018).
Winters, J. G. et al. The solar neighborhood. XXXV. Distances to 1404 m dwarf systems within 25 pc in the southern sky. Astron. J. 149, 5 (2015).
Gaia Collaboration et al. Gaia data release 2. Summary of the contents and survey properties. Astron. Astrophys. 616, A1 (2018).
Winters, J. G. et al. The solar neighborhood. XLV. The stellar multiplicity rate of M dwarfs within 25 pc. Astron. J. 157, 216 (2019).
Brown, T. M. et al. Las Cumbres observatory global telescope network. Publ. Astron. Soc. Pacif. 125, 1031 (2013).
Jehin, E. et al. TRAPPIST: Transiting Planets And Planetesimals Small Telescope. Messenger 145, 2–6 (2011).
Simcoe, R. A. et al. FIRE: A facility class near-infrared echelle spectrometer for the Magellan telescopes. Publ. Astron. Soc. Pacif. 125, 270 (2013).
Newton, E. R., Charbonneau, D., Irwin, J. & Mann, A. W. An empirical calibration to estimate cool dwarf fundamental parameters from H-band spectra. Astrophys. J. 800, 85 (2015).
Lenzen, R. et al. NAOS-CONICA first on sky results in a variety of observing modes. In Instrument Design and Performance for Optical/Infrared Ground-based Telescopes (eds Iye, M. & Moorwood, A. F. M.) Vol. 4841, 944–952 (SPIE, 2003).
Rousset, G. et al. NAOS, the first AO system of the VLT: on-sky performance. In Adaptive Optical System Technologies II (eds Wizinowich, P. L. & Bonaccini, D.) Vol. 4839, 140–149 (SPIE, 2003).
Morton, T. D. An efficient automated validation procedure for exoplanet transit candidates. Astrophys. J. 761, 6 (2012).
Morton, T. D. VESPA: false positive probabilities calculator. Astrophysics Source Code Library 2015ascl.soft03011M (2015).
Gaia Collaboration et al. The Gaia mission. Astron. Astrophys. 595, A1 (2016).
Skrutskie, M. F. et al. The Two Micron All Sky Survey (2MASS). Astron. J. 131, 1163–1183 (2006).
Zacharias, N. et al. The fourth US naval observatory CCD astrograph catalog (UCAC4). Astron. J. 145, 44 (2013).
Stassun, K. G. & Torres, G. Evidence for a systematic offset of −80 μas in the Gaia DR2 parallaxes. Astrophys. J. 862, 61 (2018).
Jao, W.-C. et al. Distance-dependent offsets between parallaxes for nearby stars and Gaia DR1 parallaxes. Astrophys. J. Lett. 832, 18 (2016).
Benedict, G. F. et al. The solar neighborhood. XXXVII: the mass-luminosity relation for main-sequence M dwarfs. Astron. J. 152, 141 (2016).
Boyajian, T. S. et al. Stellar diameters and temperatures. II. Main-sequence K- and M-stars. Astrophys. J. 757, 112 (2012).
Mann, A. W. et al. How to constrain your M dwarf. II. The mass−luminosity−metallicity relation from 0.075 to 0.70 solar masses. Astrophys. J. 871, 63 (2019).
Mann, A. W., Feiden, G. A., Gaidos, E., Boyajian, T. & von Braun, K. How to constrain your M dwarf: measuring effective temperature, bolometric luminosity, mass, and radius. Astrophys. J. 804, 64 (2015).
Pecaut, M. J. & Mamajek, E. E. Intrinsic colors, temperatures, and bolometric corrections of pre-main-sequence stars. Astrophys. J., Suppl. Ser. 208, 9 (2013).
Dittmann, J. A., Irwin, J. M., Charbonneau, D. & Newton, E. R. Calibration of the M Earth photometric system: optical magnitudes and photometric metallicity estimates for 1802 nearby M-dwarfs. Astrophys. J. 818, 153 (2016).
Mamajek, E. E. & Hillenbrand, L. A. Improved age estimation for solar-type dwarfs using activity-rotation diagnostics. Astrophys. J. 687, 1264–1293 (2008).
Newton, E. R. et al. The rotation and galactic kinematics of mid-M dwarfs in the solar neighborhood. Astrophys. J. 821, 93 (2016).
Newton, E. R., Mondrik, N., Irwin, J., Winters, J. G. & Charbonneau, D. New rotation period measurements for M dwarfs in the Southern Hemisphere: an abundance of slowly rotating, fully convective stars. Astron. J. 156, 217 (2018).
Günther, M. N. & Daylan, T. allesfitter: flexible star and exoplanet inference from photometry and radial velocity. Astrophysics Source Code Library 2019ascl.soft03003G (2019).
Maxted, P. F. L. ellc: a fast, flexible light curve model for detached eclipsing binary stars and transiting exoplanets. Astron. Astrophys. 591, A111 (2016).
Davenport, J. R. A. et al. Kepler flares. II. The temporal morphology of white-light flares on GJ 1243. Astrophys. J. 797, 122 (2014).
Speagle, J. S. dynesty: a dynamic nested sampling package for estimating Bayesian posteriors and evidences. Preprint at https://arxiv.org/abs/1904.02180 (2019).
Foreman-Mackey, D., Hogg, D. W., Lang, D. & Goodman, J. emcee: the MCMC hammer. Publ. Astron. Soc. Pacif. 125, 306 (2013).
Foreman-Mackey, D., Agol, E., Ambikasaran, S. & Angus, R. celerite: scalable 1D Gaussian processes in C++, Python, and Julia. Astrophysics Source Code Library 2017ascl.soft09008F (2017).
Kass, R. E. & Raftery, A. E. Bayes factors. J. Am. Stat. Assoc. 90, 773–795 (1995).
Seager, S. & Mallén-Ornelas, G. A unique solution of planet and star parameters from an extrasolar planet transit light curve. Astrophys. J. 585, 1038–1055 (2003).
Hippke, M. & Heller, R. Optimized transit detection algorithm to search for periodic transits of small planets. Astron. Astrophys. 623, A39 (2019).
Kovács, G., Zucker, S. & Mazeh, T. A box-fitting algorithm in the search for periodic transits. Astron. Astrophys. 391, 369–377 (2002).
Mandel, K. & Agol, E. Analytic light curves for planetary transit searches. Astrophys. J. Lett. 580, L171 (2002).
Kreidberg, L. batman: BAsic transit model cAlculatioN in Python. Publ. Astron. Soc. Pacif. 127, 1161 (2015).
van Rossum, G. Python tutorial. Technical Report CS-R9526 (Centrum voor Wiskunde en Informatica (CWI), 1995).
van der Walt, S., Colbert, S. C. & Varoquaux, G. The numpy array: a structure for efficient numerical computation. Comput. Sci. Eng. 13, 22–30 (2011).
Jones, E. et al. SciPy: Open source scientific tools for Python (2001); http://www.scipy.org/.
Hunter, J. D. Matplotlib: a 2D graphics environment. Comput. Sci. Eng. 9, 90–95 (2007).
Foreman-Mackey, D. corner.py: scatterplot matrices in Python. J. Open Source Softw. 24, 10.21105/joss.00024 (2016).
Jensen, E. Tapir: a web interface for transit/eclipse observability. Astrophysics Source Code Library 2013ascl.soft06007J (2013).
Collins, K. A., Kielkopf, J. F., Stassun, K. G. & Hessman, F. V. AstroImageJ: image processing and photometric extraction for ultra-precise astronomical light curves. Astron. J. 153, 77 (2017).
Rein, H. & Liu, S.-F. REBOUND: an open-source multi-purpose N-body code for collisional dynamics. Astron. Astrophys. 537, A128 (2012).
Zeng, L., Sasselov, D. D. & Jacobsen, S. B. Mass-radius relation for rocky planets based on PREM. Astrophys. J. 819, 127 (2016).
