Triple trouble for XZ Tau: deep imaging with the Jansky Very Large Array

Abstract

We present new observations of the XZ Tau system made at high angular resolution (55 milliarcsec) with the Karl G. Jansky Very Large Array (VLA) at a wavelength of 7 mm. Observations of XZ Tau made with the VLA in 2004 appeared to show a triple system, with XZ Tau A resolved into two sources, XZ Tau A and XZ Tau C. The angular separation of XZ Tau A and C (0.09 arcsec) suggested a projected orbital separation of around 13 AU with a possible orbital period of around 40 yr. Our observations were obtained approximately 8 yr later, a fifth of this putative orbital period, and should therefore allow us to constrain the orbit of XZ Tau C, and evaluate the possibility that a recent periastron passage of C coincided with the launch of extended optical outflows from XZ Tau A. Despite improved sensitivity and resolution compared with previous observations, we find no evidence of XZ Tau C in our data. Components A and B are detected with a signal-to-noise ratio greater than ten; their orbits are consistent with previous studies, although the emission from XZ Tau A appears to be weaker. Three possible interpretations are offered: either XZ Tau C is transiting XZ Tau A, which is broadly consistent with the periastron passage hypothesis, or the emission seen in 2004 was that of a transient, or XZ Tau C does not exist. A fourth interpretation, that XZ Tau C was ejected from the system, is dismissed due to the lack of angular momentum redistribution in the orbits of XZ Tau A and XZ Tau B that would result from such an event. Our observations are insufficient to distinguish between the remaining possibilities, at least not until we obtain further VLA observations at a sufficiently later time. A further non-detection would allow us to reject the transit hypothesis, and the periastron passage of XZ Tau C as agent of XZ Tau A's outflows.

4 pages, 4 figures, accepted for publication in MNRAS

References in corpus (3)

• The SCUBA HAlf Degree Extragalactic Survey (SHADES) - III. Identification of radio and mid-infrared counterparts to submillimetre galaxies
• The Gould's Belt Very Large Array Survey I: The Ophiuchus complex
• A Multi-Epoch HST Study of the Herbig-Haro Flow from XZ Tauri

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• A 1.3 mm SMA Survey of 29 Variable Young Stellar Objects
• A Dwarf Protoplanetary Disk around XZ Tau B
• Origin and kinematics of the eruptive flow from XZ Tau revealed by ALMA
• Multi-epoch, high spatial resolution observations of multiple T Tauri systems
• Orbital motions and light curves of young binaries XZ Tau and VY Tau
• Misaligned Circumstellar Disks and Orbital Motion of the Young Binary XZ Tau