Variable, circularly polarized radio emission from the Young Stellar Object [BHB2007]-1: another ingredient of a unique system

TL;DR

This study reports variable, circularly polarized radio emission from the young stellar object [BHB2007]-1, suggesting magnetic activity and jet interactions, while not detecting emission from the proposed sub-stellar companion.

Contribution

First detection of circular polarization in radio emission from [BHB2007]-1, providing insights into magnetic fields and emission mechanisms in this system.

Findings

Detected 15-20% circular polarization in some observations.

No evidence of emission from the hypothesized sub-stellar object.

Radio emission shows slow variability without short flares.

Abstract

The young stellar object [BHB2007]-1 has been extensively studied in the past at radio, millimeter, and infrared wavelengths. It shows a gap in the disk and previous observations claimed the possible emission from a forming sub-stellar object, in correspondence to the disk gap. Here, we analyze a set of 8 Karl Jansky Very Large Array (VLA) observations at 15 GHz and spread over a month. We infer a slowly variable emission from the star, with a $\sim 15 \text{-} 20\%$ circular polarization detected in two of the eight observations. The latter can be related to the magnetic fields in the system, while the unpolarized and moderately varying component can be indicative of free-free emission associated with jet induced shocks or interaction of the stellar wind with dense surrounding material. We discard any relevant short flaring activities when sampling the radio light curves down to 10 seconds and find no clear evidence of emission from the sub-stellar object inferred from past observations, although deeper observations could shed further light on this.