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

TL;DR

This paper reports the discovery of two young, bound planetary-mass companions to stars in the Ophiuchus star-forming region, using Keck infrared adaptive optics observations, with estimated masses around 3 to 15 Jupiter masses.

Contribution

It presents new direct imaging detections of two faint companions in the Ophiuchus region, expanding knowledge of planetary-mass objects around young stars.

Findings

Discovered two faint companions to young stars in Ophiuchus.

Estimated companion masses are approximately 3.4 and 11.5-15.3 Jupiter masses.

Companions are at projected separations of 180-340 au.

Abstract

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.