A tale of two transition disks: alma long-baseline observations of iso-oph 2 reveal two closely packed nonaxisymmetric rings and a similar to 2 au cavity

Abstract

ISO-Oph 2 is a wide-separation (240 au) binary system where the primary star harbors a massive (M-dust similar to 40M(circle plus)) ring-like disk with a dust cavity similar to 50 au in radius and the secondary hosts a much lighter (M-dust similar to 0.8M(circle plus)) disk. As part of the high-resolution follow-up of the "Ophiuchus Disk Survey Employing ALMA" (ODISEA) project, we present 1.3 mm continuum and(12)CO molecular line observations of the system at 002 (3 au) resolution. We resolve the disk around the primary into two nonaxisymmetric rings and find that the disk around the secondary is only similar to 7 au across and also has a dust cavity (r similar to 2.2 au). Based on the infrared flux ratio of the system and the M0 spectral type of the primary, we estimate the mass of the companion to be close to the brown-dwarf limit. Hence, we conclude that the ISO-Oph 2 system contains the largest and smallest cavities, the smallest measured disk size, and the resolved cavity around the lowest-mass object (M similar to 0.08M) in Ophiuchus. From the(12)CO data, we find a bridge of gas connecting both disks. While the morphology of the rings around the primary might be due to an unseen disturber within the cavity, we speculate that the bridge might indicate an alternative scenario in which the secondary has recently flown by the primary star causing the azimuthal asymmetries in its disk. The ISO-Oph 2 system is therefore a remarkable laboratory to study disk evolution, planet formation, and companion-disk interactions.