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arXiv · 2001.08304

Cloud Atlas: High-precision HST/WFC3/IR Time-Resolved Observations of Directly-Imaged Exoplanet HD106906b

Yifan Zhou·Dániel Apai·Luigi R. Bedin·Ben W. P. Lew·Glenn Schneider·Adam J. Burgasser·Elena Manjavacas·Theodora Karalidi·Stanimir Metchev·Paulo A. Miles-Páez·Nicolas B. Cowan·Patrick J. Lowrance·Jacqueline Radigan
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Abstract

HD106906b is an ~11$M_{\mathrm{Jup}}$, ~15Myr old directly-imaged exoplanet orbiting at an extremely large distance from its host star. The wide separation (7.11 arcsec) 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 4$M_{\mathrm{Jup}}$ 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-micron 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-micron water absorption band, which highlights the challenges in modeling atmospheres of young planetary-mass objects.

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Yifan Zhou, Dániel Apai, Luigi R. Bedin, Ben W. P. Lew, Glenn Schneider, Adam J. Burgasser, Elena Manjavacas, Theodora Karalidi, Stanimir Metchev, Paulo A. Miles-Páez, Nicolas B. Cowan, Patrick J. Lowrance, Jacqueline Radigan. 2020-01-22. Cloud Atlas: High-precision HST/WFC3/IR Time-Resolved Observations of Directly-Imaged Exoplanet HD106906b. https://doi.org/10.3847/1538-3881%2Fab6f65

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