Research ArticlesAstronomy

Direct imaging discovery of a Jovian exoplanet within a triple-star system

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Science  12 Aug 2016:
Vol. 353, Issue 6300, pp. 673-678
DOI: 10.1126/science.aaf9671
  1. Fig. 1 Near-infrared VLT-SPHERE images of HD 131399Ab and the hierarchical triple-star system HD 131399ABC.

    (A to D) The central regions that are affected by the coronagraph and residual scattered starlight are blocked by a mask (dashed circles), with the location of star A indicated by the crosshairs. (E) Composite of the point spread function (PSF)–subtracted region (dashed region) superposed on the wide-field K1 image showing the stellar components of the system, whose luminosities are adjusted to the level of the planet for clarity. In each image, the luminosity of component A (but not components B and C) has been suppressed by the use of a coronagraph. The images in panels (A) to (C) were processed with angular and spectral differential imaging to subtract the stellar PSF, whereas panel (D) and the PSF-subtracted region of (E) were processed only with angular differential imaging (10). Images in (A) to (D) share the same field orientation.

  2. Fig. 2 Near-infrared spectrum of HD 131399Ab.

    (A) HD 131399Ab spectrum (black) alongside the best-fit model atmosphere in red (18), with Teff = 850 K and log(g) = 3.8 cm/s2, showing water and methane absorption in the atmosphere with the approximate absorption regions indicated by the gray dashed lines. The spectrum of the T-type exoplanet 51 Eri b (16) is shown in blue, scaled by 50% to roughly match the luminosity of HD 131399Ab. Fλ, specific flux; Z/H, metallicity. (B) Near-infrared spectrum of HD 131399Ab and spectra of standard field brown dwarfs (39, 40), with each 1.4- to 2.4-μm spectrum normalized independently in λFλ units (equivalent to power per unit area). The objects’ labels correspond to the object designations from the Two Micron All Sky Survey (J2000 hours and minutes of right ascension) and the spectral type. Vertical error bars indicate 2σ photometric uncertainties horizontal bars denote photometric bandpass.

  3. Fig. 3 J-H color-magnitude diagram of brown dwarfs and directly imaged giant exoplanets.

    HD 131399Ab falls among the methane-dominated T dwarfs near the L-T transition. The L- and T-dwarf data (with parallax-calibrated absolute magnitudes) were obtained from (41), whereas the directly imaged exoplanet data are from (16, 4247). Vertical and horizontal error bars indicate 2σ photometric uncertainties.

  4. Fig. 4 Schematic illustration of the components of the HD 131399 hierarchical triple-star system and comparison to the solar system.

    (A) The dashed ellipse (top left) shows a preliminary orbit for the planet; the dashed curve at the bottom of this panel indicates our best-fit orbit of the BC pair. The orbit shown for the planet has orbital elements that are consistent with the data, although the astrometric uncertainties permit a substantial range of orbits (see the supplementary text for parameter ranges). (B) The image in (A) is reproduced with the orbits of the solar system planets overlaid. The underlying image is a composite image of the actual PSFs superposed on a dark-sky background. The image is composed of SPHERE J-, H-, and K-band PSFs for components A and Ab (colored as blue, green, and red, respectively) and the monochromatic K-band PSF of components B and C. For clarity, the luminosity of the planet is enhanced by a factor of 105, and because only K-band photometry exists for components B and C, their colors have been adjusted to be representative of typical G and K stars.

  5. Fig. 5 Ratio of semimajor axes of planets that orbit one star of a multiple system (satellite, or S-type, planets) to the semimajor axes of their host systems.

    The gray solid line at one-third times the binary separation represents the approximate critical radius of tidal truncation and orbital stability in the coplanar case (25). Although the critical radius varies somewhat for different parameters of stellar mass ratio, eccentricity, and inclination, HD 131399Ab is much closer to the critical radius than any other known exoplanet. For systems in which either the planet or stars lack precise orbital solutions, their projected separations are plotted instead (denoted by triangular plot points instead of circles). This includes HD 131399Ab, although from the results of the preliminary orbit fit, the semimajor axes of this system are indeed similar to the projected separations. See table S4 for the list of included objects and their associated references. MJ, Jupiter mass.

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