HD106906b is an ∼ 11ΜJup, ∼ 15 Myr old directly-imaged exoplanet orbiting at an extremely large distance from its host star. The wide separation (7.11′′) between HD106906b and its host star greatly reduces the difficulty in direct-imaging observations, making it one of the most favorable directly-imaged exoplanets for detailed characterization. In this paper, we present HST/WFC3/IR time-resolved observations of HD106906b in the F127M, F139M, and F153M bands. We have achieved ∼ 1% precision in the lightcurves in all three bands. The F127M lightcurve demonstrates marginally-detectable (2.7σ significance) variability with a best-fitting period of 4 hr, while the lightcurves in the other two bands are consistent with flat lines. We construct primary-subtracted deep images and use these images to exclude additional companions to HD106906 that are more massive than 4ΜJup and locate at projected distances of more than ∼ 500 au. We measure the astrometry of HD106906b in two HST/WFC3 epochs and achieve precisions better than 2.5 mas. The position angle and separation measurements do not deviate from those in the 2004 HST/ACS/HRC images for more than 1σ uncertainty. We provide the HST/WFC3 astrometric results for 25 background stars that can be used as reference sources in future precision astrometry studies. Our observations also provide the first 1.4-μm water band photometric measurement for HD106906b. HD106906b’s spectral energy distribution and the best-fitting BT-Settl model have an inconsistency in the 1.4-μm water absorption band, which highlights the challenges in modeling atmospheres of young planetary-mass objects.
|Original language||English (US)|
|State||Published - Jan 22 2020|
- Methods: observational
- Planetary Systems
- Planets and satellites: atmospheres
ASJC Scopus subject areas