A High-mass Protobinary System with Spatially Resolved Circumstellar Accretion Disks and Circumbinary Disk*

Abstract

High-mass multiples might form via fragmentation of self-gravitational disks or alternative scenarios such as disk-assisted capture. However, only few observational constraints exist on the architecture and disk structure of high-mass protobinaries and their accretion properties. Here we report the discovery of a close (57.9 ± 0.2mas=170au) high-mass protobinary, IRAS17216-3801, where our VLTI/GRAVITY+AMBER near-infrared interferometry allows us to image the circumstellar disks around the individual components with ∼ 3 milliarcsecond resolution. We estimate the component masses to ∼ 20 and ∼ 18M ⊙ and find that the radial intensity profiles can be reproduced with an irradiated disk model, where the inner regions are excavated of dust, likely tracing the dust sublimation region in these disks. The circumstellar disks are strongly misaligned with respect to the binary separation vector, which indicates that the tidal forces did not have time to realign the disks, pointing towards a young dynamical age of the system. We constrain the distribution of the Brγ and COemitting gas using VLTI/GRAVITY spectro-interferometry and VLT/CRIRES spectro-astrometry and find that the secondary is accreting at a higher rate than the primary. VLT/NACO imaging shows L ′ -band emission on 3 − 4× larger scales than the binary separation, matching the expected dynamical truncation radius for the circumbinary disk. The IRAS17216-3801 system is ∼ 3× more massive and ∼ 5× more compact than other high-mass multiplies imaged at infrared wavelengths and the first high-mass protobinary system where circumstellar and circumbinary dust disks could be spatially resolved. This opens exciting new opportunities for studying star-disk interactions and the role of multiplicity in high-mass star formation.

The Extraordinary Outburst in the Massive Protostellar System NGC 6334I-MM1: Flaring of the Water Masers in a North–South Bipolar Outflow Driven by MM1B

“…In CS (6-5) we also detect a single-lobed blueshifted outflow to the NW of MM1B as well as the inner regions of the well-known large-scale NE-SW outflow, bringing the total number of outflows from this massive protostar to at least three, suggesting a dynamic picture of evolution in which the outflow orientation can change by large angles over relatively short periods as reported in other protostars including Cepheus A HW2 (Cunningham et al 2009), Orion Source I (Plambeck et al 2009), and the FU Ori object V1647 Ori (Principe et al 2018). An alternative interpretation is that these outflows arise from a binary or higher-order multiple system with non-coplanar disks still unresolved within MM1B, such as the disk pair found in IRAS 17216-3801 (Kraus et al 2017). We have also detected a highly collimated SE-NW outflow toward the enigmatic line-free, but high dust brightness temperature (∼ 80 K, Brogan et al 2016) millimeter dust core MM4, confirming that it must harbor a protostar.…”

Resolving the MYSO binaries PDS 27 and PDS 37 with VLTI/PIONIER

“…The closure phases are generally sensitive to the PA of the binary, the separation, and the brightness ratio of the binary components. The situation can be even more complex in case of a resolved binary in which one or both components are also resolved but are characterized by different sizes (see, e.g., Kraus et al 2017).…”

A pilot survey of the binarity of Massive Young Stellar Objects withK-band adaptive optics

“…Beuther et al (2017) studied the massive protostar/UCHii region NGC 7538 IRS1 using JVLA data, discovered a binary source at 430 au, and found (misaligned) disks surrounding both objects. Kraus et al (2017) discovered a companion at 58 mas (170 au) from the 20M protostar IRAS 17216-3801. They determined the masses of the two components to be 20 (primary) and 18 M (secondary) using the K-band flux ratios, and also found misaligned disks.…”