High Angular Resolution Radio Observations of the HL/XZ Tau Region: Mapping the 50 AU Protoplanetary Disk around HL Tau and Resolving XZ Tau S into a 13 AU Binary

TL;DR

This study uses high-resolution radio observations to map the protoplanetary disk around HL Tau and reveals that XZ Tau is a triple star system, providing insights into star formation and disk dynamics.

Contribution

It presents the first high-resolution 7 mm observations resolving the XZ Tau system into a close binary, revealing a triple star system and its potential link to observed gas ejections.

Findings

HL Tau has a clumpy disk of about 25 AU radius.

XZ Tau is a triple star system with a 13 AU binary.

Gas ejection may be related to binary periastron passage.

Abstract

We present new 7 mm and archive 1.3 cm high angular resolution observations of the HL/XZ Tau region made with the VLA. At 7 mm, the emission from HL Tau seems to be arising in a clumpy disk with radius of order 25 AU. The 1.3 cm emission from XZ Tau shows the emission from a binary system with 0"3 (42 AU) separation, known from previous optical/IR observations. However, at 7 mm, the southern radio component resolves into a binary with 0"09 (13 AU) separation, suggesting that XZ Tau is actually a triple star system. We suggest that the remarkable ejection of gas from the XZ Tau system observed with the HST may be related to a periastron passage of this newly discovered close binary system.