Orbital and Mass Constraints of the Young Binary System IRAS 16293-2422 A

Abstract

We present 3 mm ALMA continuum and line observations at resolutions of 6.5 au and 13 au, respectively, toward the Class 0 system IRAS 16293-2422 A. The continuum observations reveal two compact sources toward IRAS 16293-2422 A, coinciding with compact ionized gas emission previously observed at radio wavelengths (A1 and A2), confirming the long-known radio sources as protostellar. The emission toward A2 is resolved and traces a dust disk with an FWHM size of ∼12 au, while the emission toward A1 sets a limit to the FWHM size of the dust disk of ∼4 au. We also detect spatially resolved molecular kinematic tracers near the protostellar disks. Several lines of the J=5−4 rotational transition of HNCO, NH 2 CHO, and t-HCOOH are detected, with which we derived individual line-of-sight velocities. Using these together with the CS (J=2−1), we fit Keplerian profiles toward the individual compact sources and derive masses of the central protostars. The kinematic analysis indicates that A1 and A2 are a bound binary system. Using this new context for the previous 30 yr of Very Large Array observations, we fit orbital parameters to the relative motion between A1 and A2 and find that the combined protostellar mass derived from the orbit is consistent with the masses derived from the gas kinematics. Both estimations indicate masses consistently higher (0.5M 1 M 2  2 M  ) than previous estimations using lowerresolution observations of the gas kinematics. The ALMA high-resolution data provides a unique insight into the gas kinematics and masses of a young deeply embedded bound binary system.

FAUST. II. Discovery of a Secondary Outflow in IRAS 15398−3359: Variability in Outflow Direction during the Earliest Stage of Star Formation?

“…A possible explanation for the secondary outflow is that IRAS 15398−3359 is a binary system, launching outflows in two different directions with respect to the plane of the sky. Such binary/multiple systems launching more than one distinct outflow in different directions have been previously observed within IRAS 16293−2422 Source A (van der Wiel et al 2019;Maureira et al 2020), BHR71 (Zapata et al 2018;Tobin et al 2019), NGC 1333 IRAS2A (Tobin et al 2015), and NGC 2264 CMM3 (Watanabe et al 2017). In all these cases, however, the binaries are separated by more than 40−50 au.…”

The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars V. A Characterization of Protostellar Multiplicity

“…For separations <10 au, Class II and Class III YSOs are consistent with the field star multiplicity (Kounkel et al 2019). Such close systems cannot typically be detected toward protostars, aside from a few special cases (e.g., Ortiz-León et al 2017;Maureira et al 2020). For separations between ∼100 au to 1000 au, the MFs/CFs and separation distributions of most YSO populations agree well with the field (aside from Taurus-Auriga) (Reipurth et al 2007;Kraus et al 2011;King et al 2012;Duchêne et al 2018), and the MFs/CFs of protostars in our sample are also in good agreement for this range.…”

Chemical evolution during the formation of a protoplanetary disk

“…Observations of rotation motions around source A suggested the presence of an almost edge-on disk (Pineda et al 2012;Oya et al 2016). More recently, Maureira et al (2020) showed with very high-spatial-resolution observations that component A consists of two compact sources, A1 and A2. A dust disk with a FWHM size of ∼12 au is seen towards A2, while an upper limit of ∼4 au is derived for the disk around A1.…”