The ALMA Movie: Orbital Motion of the Class II binary XZ Tau from the Multi-epoch Archival Data
Abstract
We report our analyses of the multi-epoch (2015-2017) ALMA archival data of an archetypal Class II binary system XZ Tau. The dust continuum images show compact ( 0.11 x 0.05 arcsec 15 x 7 au), elongated circumstellar disks (CSDs) around the individual binary stars (XZ Tau A and B). The circumbinary disk surrounding the entire binary system is, on the other hand, not detected in the dust-continuum emission, in contrast to the ALMA results of the Class I protobinary systems of L1551 IRS 5 and NE located in the same region. The position and inclination angles of the CSDs (θ 15 deg and i 64 deg) are identical in both stars of XZ Tau, suggesting the co-planar configuration of the CSDs and the orbital plane of the binary. Furthermore, we have found a clear sign of the shift of the relative positions of the CSDs from the multi-epoch data, implying the detection of the orbital motion of the binary. The 12CO (2-1) emission traces Keplerian rotations in both of the CSDs, which enables us to derive the masses of XZ Tau A and B to be 0.5 Msun and 0.2 Msun, respectively. There is another, extended 12CO component outside the CSDs, which may trace the associated outflows or the infalling protostellar envelope. From the derived stellar masses and the de-projected binary separation ( 0.2 arcsec 30 au), the orbital period of the binary is estimated to be P 860 yr, which appears to be consistent with the detected motions of the continuum emission. Our analyses of the multi-epoch ALMA archival data demonstrates the feasibility of the time-domain science with the ALMA, the ALMA movie. We will discuss these results and our follow-up, subsequent observations of XZ Tau to better constrain the orbital motion and to further demonstrate the feasibility of the ALMA movie.
- Publication:
-
ALMA2019: Science Results and Cross-Facility Synergies
- Pub Date:
- December 2019
- DOI:
- 10.5281/zenodo.3585382
- Bibcode:
- 2019asrc.confE..92I
- Keywords:
-
- Zenodo community alma2019caligari