Multi-epoch Near-Infrared Interferometry of the Spatially Resolved Disk Around the Be Star Zeta Tau

TL;DR

This study uses multi-epoch near-infrared interferometry to resolve and analyze the asymmetric, precessing circumstellar disk around the Be star Zeta Tau, revealing its geometry and temporal evolution.

Contribution

First multi-epoch interferometric imaging of Zeta Tau's disk, demonstrating disk precession and asymmetry over several years.

Findings

Disk is nearly edge-on with a major axis of ~1.8 mas in H-band.

Detected asymmetry indicating a skewed elliptical Gaussian disk.

Found correlation between disk orientation and V/R ratio, suggesting precession.

Abstract

We present interferometric observations of the Be star Zeta Tau obtained using the MIRC beam combiner at the CHARA Array. We resolved the disk during four epochs in 2007-2009. We fit the data with a geometric model to characterize the circumstellar disk as a skewed elliptical Gaussian and the central Be star as a uniform disk. The visibilities reveal a nearly edge-on disk with a FWHM major axis of ~ 1.8 mas in the H-band. The non-zero closure phases indicate an asymmetry within the disk. Interestingly, when combining our results with previously published interferometric observations of Zeta Tau, we find a correlation between the position angle of the disk and the spectroscopic V/R ratio, suggesting that the tilt of the disk is precessing. This work is part of a multi-year monitoring campaign to investigate the development and outward motion of asymmetric structures in the disks of Be stars.