Near-IR observations of the young star [BHB2007]-1: A sub-stellar companion opening the gap in the disk

TL;DR

This study uses high-contrast near-infrared imaging to detect a probable sub-stellar companion around a young star, which may explain disk features and asymmetries observed in multiple wavelengths.

Contribution

First direct detection of a sub-stellar companion inside a disk cavity using near-IR imaging, linking it to disk structure and asymmetries.

Findings

Detected a companion with 37-47 M_Jup at 50 au from the star.

Observed asymmetric disk brightness likely caused by a shadow from a misaligned inner disk.

Companion's mass and location are consistent with the observed disk cavity size.

Abstract

The presence of planets or sub-stellar objects still embedded in their native protoplanetary disks is indirectly suggested by disk sub-structures like gaps, cavities, and spirals. However, these companions are rarely detected. We present VLT/NACO high-contrast images in $J$, $H$, $K_S$, and $L^{\prime}$ band of the young star [BHB2007]-1 probing the inclined disk in scattered light and revealing the probable presence of a companion. The point source is detected in the $L^{\prime}$ band in spatial correspondence with complementary VLA observations. This object is constrained to have a mass in the range of 37-47 M$_{Jup}$ and is located at 50 au from the central star, inside the 70 au-large disk cavity recently imaged by ALMA, that is absent from our NACO data (down to 20 au). This mass range is compatible with the upper end derived from the size of the ALMA cavity. The NIR disk brightness is highly asymmetric around the minor axis, with the southern side 5.5 times brighter than the northern side. The constant amount of asymmetry across all wavelengths suggests that it is due to a shadow cast by a misaligned inner disk. The massive companion that we detect could, in principle, explain the possible disk misalignment, as well as the different cavity sizes inferred by the NACO and ALMA observations. The confirmation and characterization of the companion is entrusted to future observations.