SIMBAD references

2026AJ....171...80W - Astron. J., 171, 80 (2026/February-0)

Keck Observations in the INfrared of Taurus and ρ Oph Exoplanets And Ultracool Dwarfs (KOINTREAU) I: A Planetary-mass Companion and a Disk-obscured Stellar Companion Discovered in Taurus.

WALKER S.A.U., LIU M.C., MAWET D., BOND C., CHUN M., MARTINEZ R.A., PHILLIPS M.W., WILLIAMS J.P., ZHANG Z., REN B.B., STAPELFELDT K., UYAMA T. and WALLACK N.

Abstract (from CDS):

We present the first discoveries from Keck Observations in the Infrared of Taurus and ρ Oph Exoplanets and Ultracool dwarfs (KOINTREAU), an adaptive optics imaging survey of young stars in the Taurus and ρ Oph star-forming regions using the Keck infrared pyramid wavefront sensor. We have found two faint (ΔK∼7 mag), wide-separation companions to two ≈3 Myr old Taurus members. Relative astrometry for these systems shows that both companions are bound to their host stars. We obtained near-infrared spectra of these companions using the Infrared Telescope Facility/SpeX (R ∼100) and the Gemini North InfraRed Spectrograph (Gemini/GNIRS; R ∼ 1000-2000), and combined these with photometry from our NIRC2 imaging, the Pan-STARRS survey, and Spitzer/IRAC archival imaging to constrain their properties. One companion, KOINTREAU-1b (at a projected separation of 690 au), has an average near-infrared spectral type of M9 ± 2, a gravity classification of VL-G, and a changing spectral type between the SpeX (M7) and GNIRS (L1) observations. We estimate this object's mass to be $10.{6}_{-2.3}^{+2.5}$MJup, making KOINTREAU-1b the fifth planetary-mass companion found in Taurus. The other companion, KOINTREAU-2b (projected separation 560 au), has a spectral type of M4.5 ± 1 but is ≈4 mag underluminous relative to other Taurus stars of the same spectral type. We detect exceptionally strong He I 1.083 μm emission from this object, indicative of outflows driven by ongoing accretion, but with a conspicuous lack of accompanying H emission. We conclude that KOINTREAU-2b is a young star obscured by an edge-on disk and observed in scattered light. Finally, we derive a distortion solution for NIRC2 imaging, which shows a 0$\mathop{.}\limits^{\unicode{x000b0}}$118 difference in position angle from the previous distortion solution.

Abstract Copyright: © 2026. The Author(s). Published by the American Astronomical Society.

Journal keyword(s): M dwarf stars - Pre-main sequence stars - Occulting disks - Circumstellar disks - Substellar companion stars - Direct imaging - Observational astronomy - Infrared spectroscopy - Adaptive optics - Exoplanet astronomy

Status at CDS : Large table(s) will be appraised for possible ingestion in VizieR.

Simbad objects: 35

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