Samuel Walker | Searcharxiv

arXiv2026

Keck Observations in the INfrared of Taurus and $\rho$ Oph Exoplanets And Ultracool dwarfs (KOINTREAU) II: Two Young Bound Companions to Ophiuchus Stars

We present the second set of discoveries from Keck Observations in the INfrared of Taurus and $\rho$ Oph Exoplanets And Ultracool dwarfs (KOINTREAU), an adaptive optics survey of young stars in the Taurus and $\rho$ Oph star-forming regions using Keck/NIRC2 in conjunction with the Keck infrared pyramid wavefront sensor. We have discovered two faint comoving companions to young stars ISO-Oph 96 and 2MASS J16262785-2625152. The companion to ISO-Oph 96, KOINTREAU-3b, is at a projected separation of 340 au (2.49"). Using our NIRC2 photometry and evolutionary models, and assuming that the companion has the same extinction as its host star, we infer that KOINTREAU-3b has a mass of $3.4\pm0.7$ M$_{\rm Jup}$. The companion to 2MASS J16262785-2625152, KOINTREAU-4b, has a projected separation of 180 au (1.25") and could have a mass of either $11.5^{+1.2}_{-1.6}$ M$_{\rm Jup}$ or $15.3^{+0.7}_{-0.8}$ M$_{\rm Jup}$, depending on whether the host star is a member of $\rho$ Oph or Upper Sco.

astro-ph.EP↗

arXiv2021

An HST/STIS View of Protoplanetary Disks in Upper Scorpius: Observations of Three Young M-Stars

We present observations of three protoplanetary disks in visible scattered light around M-type stars in the Upper Scorpius OB association using the STIS instrument on the Hubble Space Telescope. The disks around stars 2MASS J16090075-1908526, 2MASS J16142029-1906481 and 2MASS J16123916-1859284 have all been previously detected with ALMA, and 2MASS J16123916-1859284 has never previously been imaged at scattered light wavelengths. We process our images using Reference Differential Imaging, comparing and contrasting three reduction techniques - classical subtraction, Karhunen-Loeve Image Projection and Non-Negative Matrix Factorisation, selecting the classical method as the most reliable of the three for our observations. Of the three disks, two are tentatively detected (2MASS J16142029-1906481 and 2MASS J16123916-1859284), with the third going undetected. Our two detections are shown to be consistent when varying the reference star or reduction method used, and both detections exhibit structure out to projected distances of > 200 au. Structures at these distances from the host star have never been previously detected at any wavelength for either disk, illustrating the utility of visible-wavelength observations in probing the distribution of small dust grains at large angular separations.

astro-ph.EP↗