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An eclipsing substellar binary in a young triple system discovered by SPECULOOS

Abstract

Mass, radius and age are three of the most fundamental parameters for celestial objects, enabling insight into the evolution and internal physics of stars, brown dwarfs and planets. Brown dwarfs are hydrogen-rich objects that are unable to sustain core fusion reactions but are supported against collapse by electron degeneracy pressure1. As they age, brown dwarfs cool, reducing their radius and luminosity. Young exoplanets follow a similar behaviour. Brown dwarf evolutionary models are relied upon to infer the masses, radii and ages of young brown dwarfs2,3. Similar models are also used to infer the mass and radius of directly imaged exoplanets4. Unfortunately, only sparse empirical mass, radius and age measurements are currently available, and so the models remain mostly unvalidated. Double-line eclipsing binaries provide the most direct route towards the absolute determination of the masses and radii of stars5,6,7. Here we report the discovery by SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) of the 2M1510A triple system, consisting of a nearby, eclipsing, double-line brown dwarf binary and a widely separated tertiary brown dwarf companion. We find that the system is a member of Argus, a 45 ± 5 million-year-old moving group8,9. The system’s age matches those of currently known directly imaged exoplanets so 2M1510A provides an opportunity to benchmark evolutionary models of brown dwarfs and young planets. We find that widely used evolutionary models3 do reproduce the mass, radius and age of the binary components remarkably well, but overestimate their luminosity by up to 0.65 magnitudes, which could result in underestimations of 20% to 35% of photometric masses for directly imaged exoplanets and young-field brown dwarfs.

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Fig. 1: Data demonstrating that 2M1510A is a substellar eclipsing binary.
Fig. 2: Mass–radius diagram showing the position of the 2M1510Aab eclipsing pair (shown in black with their 1σ uncertainties).
Fig. 3: Radius and luminosity measurements as a function of system age, for stars, brown dwarfs and giant exoplanets with their 1σ uncertainties.

Data availability

All reduced photometric timeseries will be made available for download at the CDS, and on request to A.H.M.J.T. Raw SPECULOOS CCD frames will become available through the ESO archive in January 2021; they can be requested from the authors before this date. Eventually the archive will also contain lightcurves for all reference stars in the frames as well. Our UVES spectra are now publicly available on the ESO archive, and can be found by searching the archive for ProgID 299.C-5046 and 2100.C-5024. MONET-South raw images can be made available upon request. NIRSPEC spectra are available at the Keck Observatory Archive, and can be found be searching the archive for Principal Investigator A.J.B. and programmes U009, U010 and U136. SpeX spectra are now available via SPLAT (https://github.com/aburgasser/splat). Requests concerning the data used in this publication can be addressed to A.H.M.J.T. and A.J.B. Figure 1 contains SPECULOOS photometry, as well as UVES and NIRSPEC spectra.

Code availability

The photometric reduction packages use standard public routines such as PyRAF and astropy. Radial velocities were extracted from UVES and NIRSpec data from a code built from elements of SPLAT (https://github.com/aburgasser/splat). The amelie code combines ellc and emcee (see text), which are both public codes. amelie can be made available upon request, and a stable version is planned to be released on GitHub.

References

  1. 1.

    Kumar, S. S. On the nature of Van Briesbroeck’s star BD +4 4048 B. Astron. J. 68, 283 (1963).

    ADS  Google Scholar 

  2. 2.

    Burrows, A. et al. A nongray theory of extrasolar giant planets and brown dwarfs. Astrophys. J. 491, 856 (1997).

    ADS  Google Scholar 

  3. 3.

    Baraffe, I. et al. New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit. Astron. Astrophys. 577, A42 (2015).

    Google Scholar 

  4. 4.

    Baraffe, I. et al. Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458. Astron. Astrophys. 402, p701–712 (2003).

    ADS  Google Scholar 

  5. 5.

    Hilditch, R. W. An Introduction to Close Binary Stars (Cambridge Univ. Press, 2001).

  6. 6.

    Torres, G., Andersen, J. & Giménez, A. Accurate masses and radii of normal stars: modern results and applications. Astron. Astrophys. Rev. 18, 67–127 (2010).

    ADS  Google Scholar 

  7. 7.

    David, T. J. et al. Age determination in Upper Scorpius with eclipsing binaries. Astrophys. J. 872, 161 (2019).

    ADS  Google Scholar 

  8. 8.

    Gagné, J. et al. BANYAN. VII. A new population of young substellar candidate members of nearby moving groups from the BASS survey. Astrophys. J. Suppl. 219, 33 (2015).

    ADS  Google Scholar 

  9. 9.

    Zuckerman, B. The nearby, young, Argus association: membership, age, and dusty debris disks. Astrophys. J. 870, 27 (2019).

    ADS  Google Scholar 

  10. 10.

    Stassun, K. G., Mathieu, R. D. & Valenti, J. A. Discovery of two young brown dwarfs in an eclipsing binary. Nature 440, p311–314 (2006).

    ADS  Google Scholar 

  11. 11.

    Stassun, K. G. et al. A surprising reversal of temperatures in the brown dwarf eclipsing binary 2MASS J05352184-0546085. Astrophys. J. 664, 1154 (2007).

    ADS  Google Scholar 

  12. 12.

    Stassun, K. G. et al. An empirical correction for activity effects on the temperatures, radii, and estimated masses of low-mass stars and brown dwarfs. Astrophys. J. 756, 47 (2012).

    ADS  Google Scholar 

  13. 13.

    Triaud, A. H. M. J. et al. The EBLM project. I. Physical and orbital parameters, including spin-orbit angles, of two low-mass eclipsing binaries on opposite sides of the brown dwarf limit. Astron. Astrophys. 549, A19 (2013).

    Google Scholar 

  14. 14.

    Hodžić, V. et al. WASP-128b: a transiting brown dwarf in the dynamical-tide regime. Mon. Not. R. Astron. Soc. 481, 5091–5097 (2018).

    ADS  Google Scholar 

  15. 15.

    Cutri, R. M. et al. VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Centre de Données astronomique de Strasbourg, 2003); http://adsabs.harvard.edu/abs/2003yCat.2246….0C

  16. 16.

    Gizis, J. E. Brown dwarfs and the TW Hydrae association. Astrophys. J. 575, 484–492 (2002).

    ADS  Google Scholar 

  17. 17.

    Bailer-Jones, C. A. et al. Estimating distance from parallaxes. IV. Distances to 1.33 billion stars in Gaia Data Release 2. Astron. J. 156, 58 (2018).

    ADS  Google Scholar 

  18. 18.

    Delrez, L. et al. SPECULOOS: a network of robotic telescopes to hunt for terrestrial planets around the nearest ultracool dwarfs. Proc. SPIE 10700, 11 (2018).

    Google Scholar 

  19. 19.

    Gillon, M. et al. Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature 542, 456–460 (2017).

    ADS  Google Scholar 

  20. 20.

    McLean, I. S. et al. Design and development of NIRSPEC: a near-infrared echelle spectrograph for the Keck II telescope. Proc. SPIE 3354, 566 (1998).

    ADS  Google Scholar 

  21. 21.

    Dekker, H. et al. Design, construction, and performance of UVES, the echelle spectrograph for the UT2 Kueyen Telescope at the ESO Paranal Observatory. Proc. SPIE 4008, 534 (2000).

    ADS  Google Scholar 

  22. 22.

    Maxted, P. F. L. ellc: A fast, flexible light curve model for detached eclipsing binary stars and transiting exoplanets. Astron. Astrophys. 591, A111 (2016).

    ADS  Google Scholar 

  23. 23.

    Foreman-Mackey, D. et al. emcee: the MCMC hammer. Publ. Astron. Soc. Pacif. 125, 306 (2013).

    ADS  Google Scholar 

  24. 24.

    Dupuy, T. J., Brandt, T. D., Kratter, K. M. & Bowler, B. P. A model-independent mass and moderate eccentricity for β Pic b. Astrophys. J. Lett. 871, 4 (2019).

    ADS  Google Scholar 

  25. 25.

    Liu, M. C., Dupuy, T. & Allers, K. N. The Hawaii Infrared Parallax Program. II. Young ultracool field dwarfs. Astrophys. J. 833, 96 (2016).

    ADS  Google Scholar 

  26. 26.

    Lagrange, A.-M. et al. A probable giant planet imaged in the β Pictoris disk. VLT/NaCo deep L’-band imaging. Astron. Astrophys. 493, L21–L25 (2009).

    ADS  Google Scholar 

  27. 27.

    Triaud, A. H. M. J. et al. The EBLM Project IV. Spectroscopic orbits of over 100 eclipsing M dwarfs masquerading as transiting hot-Jupiters. Astron. Astrophys. 608, A129 (2017).

    Google Scholar 

  28. 28.

    Moe, M. & Kratter, K. M. Dynamical formation of close binaries during the pre-main-sequence phase. Astrophys. J. 854, 44 (2018).

    ADS  Google Scholar 

  29. 29.

    Mazeh, T. & Shaham, J. The orbital evolution of close triple systems—the binary eccentricity. Astron. Astrophys. 77, 145–151 (1979).

    ADS  Google Scholar 

  30. 30.

    Fabrycky, D. & Tremaint, S. Shrinking binary and planetary orbits by Kozai cycles with tidal friction. Astrophys. J. 669, 1298–1315 (2007).

    ADS  Google Scholar 

  31. 31.

    Bischoff, K. et al. MONET/North: a very fast 1.2m robotic telescope. Proc. SPIE 6270, id. 62701Q (2006).

    Google Scholar 

  32. 32.

    Bowler, B. P. Imaging extrasolar giant planets. Publ. Astron. Soc. Pacif. 128, 102001 (2016).

    ADS  Google Scholar 

  33. 33.

    Tody, D. The IRAF data reduction and analysis system. Proc. SPIE 627, 733 (1986).

    ADS  Google Scholar 

  34. 34.

    Rayner, J. T. et al. SpeX: a medium-resolution 0.8-5.5 micron spectrograph and imager for the NASA Infrared Telescope Facility. Publ. Astron. Soc. Pacif. 115, 362 (2003).

    ADS  Google Scholar 

  35. 35.

    Vacca, W. D., Cushing, M. C. & Rayner, J. T. A method of correcting near-infrared spectra for telluric absorption. Publ. Astron. Soc. Pacif. 115, 389 (2003).

    ADS  Google Scholar 

  36. 36.

    Cushing, M. C., Vacca, W. D. & Rayner, J. T. Spextool: a spectral extraction package for SpeX, a 0.8-5.5 micron cross-dispersed spectrograph. Publ. Astron. Soc. Pacif. 116, 326 (2004).

    ADS  Google Scholar 

  37. 37.

    Kirkpatrick, J. D. et al. Discoveries from a near-infrared proper motion survey using multi-epoch Two Micron All-Sky Survey data. Astrophys. J. Suppl. 190, 100 (2010).

    ADS  Google Scholar 

  38. 38.

    Allers, K. N. & Liu, M. C. A near-infrared spectroscopic study of young field ultracool dwarfs. Astrophys. J. 772, 79 (2013).

    ADS  Google Scholar 

  39. 39.

    Cruz, K. L. et al. Meeting the cool neighbors. XII. An optically anchored analysis of the near-infrared spectra of L dwarfs. Astron. J. 155, 34 (2018).

    ADS  Google Scholar 

  40. 40.

    Bell, C. P. M., Mamajek, E. E. & Naylor, T. A self-consistent, absolute isochronal age scale for young moving groups in the solar neighbourhood. Mon. Not. R. Astron. Soc. 454, 593 (2015).

    ADS  Google Scholar 

  41. 41.

    Looper, D. L. et al. Discovery of an M9.5 candidate brown dwarf in the TW Hydrae association: DENIS J124514.1-442907. Astrophys. J. Lett. 669, L97 (2007).

    ADS  Google Scholar 

  42. 42.

    Burgasser, A. J. et al. The Brown Dwarf Kinematics Project (BDKP). IV. Radial velocities of 85 late-M and L dwarfs with MagE. Astrophys. J. Suppl. 220, 18 (2015).

    ADS  Google Scholar 

  43. 43.

    Modigliani, A. & Larsen, J. M. FLAMES-UVES Pipeline User Manual VLT-MAN-ESO-19500-3016 (European Southern Observatory, 2018); ftp://ftp.eso.org/pub/dfs/pipelines/uves/uves-fibre-pipeline-manual-18.8.1.pdf

  44. 44.

    Blake, C. H., Charbonneau, D. & White, R. J. The NIRSPEC Ultracool Dwarf Radial Velocity Survey. Astrophys. J. 723, 684 (2010).

    ADS  Google Scholar 

  45. 45.

    Burgasser, A. J. et al. The orbit of the L dwarf + T dwarf spectral binary SDSS J080531.84 + 481233.0. Astrophys. J. 827, 25 (2016).

    ADS  Google Scholar 

  46. 46.

    Burgasser, A. J. et al. The SpeX Prism Library Analysis Toolkit (SPLAT): a data curation model. Astron. Soc. India Conf. Ser. 14, 7–12 (2017).

    Google Scholar 

  47. 47.

    Moehler, S. et al. Flux calibration of medium-resolution spectra from 300 nm to 2500 nm: model reference spectra and telluric correction. Astron. Astrophys. 568, A9 (2014).

    Google Scholar 

  48. 48.

    Allard, F., Homeier, D. & Freytag, B. Models of very-low-mass stars, brown dwarfs and exoplanets. Phil. Trans. R. Soc. A 370, 2765–2777 (2012).

    ADS  Google Scholar 

  49. 49.

    Gray, D. F. The Observation And Analysis Of Stellar Photospheres Vol. 20 (Cambridge Astrophysical Series, 1992); http://adsabs.harvard.edu/abs/1992oasp.book…..G

  50. 50.

    Metropolis, N. et al. Equation of state calculations by fast computing machines. J. Chem. Phys. 21, 1087 (1953).

    ADS  MATH  Google Scholar 

  51. 51.

    Hastings, W. K. Monte Carlo sampling methods using Markov chains and their applications. Biometrika 57, 97–109 (1970).

    MathSciNet  MATH  Google Scholar 

  52. 52.

    Geman, S. & Geman, D. Stochastic relaxation, Gibbs distributions, and the Bayesian restoration of images. IEEE Trans. Pattern Anal. Mach. Intell. 6, 721–741 (1984).

    MATH  Google Scholar 

  53. 53.

    Roberts, G. & Rosenthal, J. Optimal scaling of discrete approximations to Langevin diffusions. J. R. Stat. Soc. B 160, 255–268 (1998).

    MathSciNet  MATH  Google Scholar 

  54. 54.

    Kim, S., Prato, L. & McLean, I. S. REDSPEC: NIRSPEC Data Reduction (Astrophysical Source Code Library, 2015); http://adsabs.harvard.edu/abs/2015ascl.soft07017K

  55. 55.

    Gagné, J. et al. BANYAN. XI. The BANYAN σ multivariate Bayesian algorithm to identify members of young associations with 150 pc. Astrophys. J. 856, 23 (2018).

    ADS  Google Scholar 

  56. 56.

    Zuckerman, B. et al. The Tucana/Horologium, Columba, AB Doradus, and Argus associations: new members and dusty debris disks. Astrophys. J. 732, 61 (2011).

    ADS  Google Scholar 

  57. 57.

    Barrado y Navascues, D. et al. Spectroscopy of Very Low Mass Stars and BrownDwarfs in IC 2391: Lithium Depletion and Hα Emission. Astrophys. J. 614, 386 (2004).

  58. 58.

    Torres, C. A., et al. in Handbook of Star Forming Regions. Volume II: The Southern Sky Vol. 5 (ed. Reipurth, B) 757 (ASP Monograph Publ, 2008).

  59. 59.

    von Boetticher, A. et al. The EBLM project. III. A Saturn-size low-mass star at the hydrogen-burning limit. Astron. Astrophys. 604, L6 (2017).

    ADS  Google Scholar 

  60. 60.

    Southworth et al. Absolute dimensions of detached eclipsing binaries—I. The metallic-lined system WW Aurigae. Mon. Not. R. Astron. Soc. 363, 529–542 (2005).

    ADS  Google Scholar 

  61. 61.

    Gelman, A. & Rubin, D. B. Inference from iterative simulation using multiple sequences. Stat. Sci. 7, 4 (1992).

    MATH  Google Scholar 

  62. 62.

    Gelman A., Carlin J., Stern H. & Rubin D. Bayesian Data Analysis 2nd edn (Chapman & Hall/CRC Texts in Statistical Science, Taylor & Francis, 2003).

  63. 63.

    Schwarz, G. Estimating the dimension of a model. Ann. Stat. 6, 2 (1978).

    MathSciNet  Google Scholar 

  64. 64.

    Parviainen, H. & Aigrain, S. LDTK: Limb Darkening Toolkit. Mon. Not. R. Astron. Soc. 453, 3821 (2015).

    ADS  Google Scholar 

  65. 65.

    Husser, T.-O. et al. A new extensive library of PHOENIX stellar atmospheres and synthetic spectra. Astron. Astrophys. 553, A6 (2013).

    Google Scholar 

  66. 66.

    Filippazzo, J. C. et al. Fundamental parameters and spectral energy distributions of young and field age objects with masses spanning the stellar to planetary regime. Astrophys. J. 810, 158 (2015).

    ADS  Google Scholar 

  67. 67.

    Hut, P. Tidal evolution in close binary systems. Astron. Astrophys. 99, 126–140 (1981).

    ADS  MATH  Google Scholar 

  68. 68.

    Kiseleva, L. G. et al. Tidal friction in triple stars. Mon. Not. R. Astron. Soc. 300, 292 (1998).

    ADS  Google Scholar 

  69. 69.

    Tokovinin, A. & Moe, M. Formation of close binaries by disc fragmentation andmigration, and its statistical modeling, Mon. Not. R. Astron. Soc. 5158–5171 (2020).

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Acknowledgements

We thank the personnel of ESO who host SPECULOOS at Paranal Observatory, and who have awarded two Director Discretionary Time (DDT) programmes to confirm this object (Prog ID 099.C-0138 and 2100.C-5024, Principal Investigator A.H.M.J.T.). In addition, we thank C. Alvarez, G. Doppman, P. Gomez, H. Hershey and J. Rivera at the Keck Observatory and G. Osterman and E. Volquardsen at the Infra-Red Telescope Facility, for their assistance with the observations reported here. This work also used observations from the Las Cumbres Observatory Global Telescope network, awarded through a DDT programme (PI Alonso). We made use of PyRAF, which is a product of the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA) for NASA. PyRAF uses the Image Reduction and Analysis Facility, which is distributed by the National Optical Astronomy Observatory, which is operated by AURA, under cooperative agreement with the National Science Foundation. We used the SIMBAD database, operated at Centre de Données astronomique de Strasbourg, Strasbourg, France; NASA’s Astrophysics Data System Bibliographic Services; the M, L, T and Y dwarf compendium housed at DwarfArchives.org; and the SpeX Prism Libraries (http://www.browndwarfs.org/spexprism). We recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate and grateful to have the opportunity to conduct observations from this mountain. This research also made use of Astropy (www.astropy.org), a community-developed core python package for astronomy as well as the open-source python packages numpy (www.numpy.org), scipy (www.scipy.org) and matplotlib (www.matplotlib.org). A.H.M.J.T. received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 803193/BEBOP). A.H.M.J.T. also received funding from the Leverhulme Trust (Research Project Grant number RPG-2018-418) and from the Science, Technology and Facilities Council (grant number ST/S00193X/1). A.J.B. acknowledges funding support from the National Science Foundation (award number AST-1517177). The material is based upon work supported by NASA (grant number NNX15AI75G). B.-O.D. acknowledges support from the Swiss National Science Foundation (PP00P2-163967). M.G. received funding from the ERC (FP/2007-2013 grant agreement number 336480/SPECULOOS), from an ARC grant for Concerted Research Actions, financed by the Wallonia-Brussels Federation, from the Simons Foundation, and from the MERAC foundation. M.G. and E.J. are Senior Research Associates at the Fonds de la Recherche Scientifique–Fond National de la Recherche Scientifique. L.D. acknowledges support from the Gruber Foundation Fellowship. V.K.H. is supported by a generous Birmingham Doctoral Scholarship and by a studentship from Birmingham’s School of Physics and Astronomy.

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A.H.M.J.T. led the data acquisition, obtained UVES data, and organised the analysis and interpretation of this system. A.J.B. obtained the NIRSPEC data, extracted radial velocities from NIRSPEC and UVES data, produced early parameters of the system, and performed the spectral typing and assessment of Argus membership. A.B. and V.K.H. led the photometric follow-up. A.B., E.D., C.M., P.P.P., L.D. and M.G. reduced the photometric data. V.K.H. produced the global analysis. M.G., E.J., D.S., B.-O.D., D.Q., L.D., C.M., P.P.P., J.d.W., A.H.M.J.T., E.D., A.B. and S.T. participated with the preparation, construction and running of the SPECULOOS facility/survey. J.MC. provided the DONUTS software used for guiding. D.B.G. provided the SpeX data while R.A., F.H. and T.-O.H. participated in the photometric follow-up. V.V.G. calculated stellar models. All authors assisted in writing the manuscript.

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Correspondence to Amaury H. M. J. Triaud or Adam J. Burgasser.

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Triaud, A.H.M.J., Burgasser, A.J., Burdanov, A. et al. An eclipsing substellar binary in a young triple system discovered by SPECULOOS. Nat Astron 4, 650–657 (2020). https://doi.org/10.1038/s41550-020-1018-2

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