Multiplicity is one of the most fundamental observable properties of massive O-type stars and offers a promising way to discriminate between massive star formation theories. Nevertheless, companions at separations between 1 and 100 milli-arcsec (mas) remain mostly unknown due to intrinsic observational limitations. At a typical distance of 2 kpc, this corresponds to projected physical separations of 2-200 AU. The Southern MAssive Stars at High angular resolution survey (smash+) was designed to fill this gap by providing the first systematic interferometric survey of Galactic massive stars. We observed 117 O-type stars with VLTI/PIONIER and 162 O-type stars with NACO/SAM, respectively probing the separation ranges 1-45 and 30-250 mas and brightness contrasts of ∆H < 4 and ∆H < 5. Taking advantage of NACO's field-of-view, we further uniformly searched for visual companions in an 8 -radius down to ∆H = 8. This paper describes the observations and data analysis, reports the discovery of almost 200 new companions in the separation range from 1 mas to 8 and presents the catalog of detections, including the first resolved measurements of over a dozen known long-period spectroscopic binaries.Excluding known runaway stars for which no companions are detected, 96 objects in our main sample (δ < 0 • ; H < 7.5) were observed both with PIONIER and NACO/SAM. The fraction of these stars with at least one resolved companion within 200 mas is 0.53. Accounting for known but unresolved spectroscopic or eclipsing companions, the multiplicity fraction at separation ρ < 8 increases to f m = 0.91 ± 0.03. The fraction of luminosity class V stars that have a bound companion reaches 100% at 30 mas while their average number of physically connected companions within 8 is f c = 2.2 ± 0.3. This demonstrates that massive stars form nearly exclusively in multiple systems. The nine non-thermal radio emitters observed by smash+ are all resolved, including the newly discovered pairs HD 168112 and CPD−47 • 2963. This lends strong support to the universality of the wind-wind collision scenario to explain the non-thermal emission from O-type stars.

Intermediate-mass stars end their lives by ejecting the bulk of their envelope via a slow dense wind back into the interstellar medium, to form the next generation of stars and planets. Stellar pulsations are thought to elevate gas to an altitude cool enough for the condensation of dust, which is then accelerated by radiation pressure from starlight, entraining the gas and driving the wind. However accounting for the mass loss has been a problem due to the difficulty in observing tenuous gas and dust tens of milliarcseconds from the star, and there is accordingly no consensus on the way sufficient momentum is transferred from the starlight to the outflow. Here, we present spatially-resolved, multi-wavelength observations of circumstellar dust shells of three stars on the asymptotic giant branch of the HR diagram. When imaged in scattered light, dust shells were found at remarkably small radii (<~ 2 stellar radii) and with unexpectedly large grains (~300 nm radius). This proximity to the photosphere argues for dust species that are transparent to starlight and therefore resistant to sublimation by the intense radiation field. While transparency usually implies insufficient radiative pressure to drive a wind, the radiation field can accelerate these large grains via photon scattering rather than absorption - a plausible mass-loss mechanism for lower-amplitude pulsating stars.Comment: 13 pages, 1 table, 6 figure

The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument is a multipurpose highcontrast imaging platform designed for the discovery and detailed characterization of exoplanetary systems and serves as a testbed for high-contrast imaging technologies for ELTs. It is a multi-band instrument which makes use of light from 600 to 2500 nm allowing for coronagraphic direct exoplanet imaging of the inner 3 λ/D from the stellar host. Wavefront sensing and control are key to the operation of SCExAO. A partial correction of low-order modes is provided by Subaru's facility adaptive optics system with the final correction, including high-order modes, implemented downstream by a combination of a visible pyramid wavefront sensor and a 2000-element deformable mirror. The well corrected NIR (y-K bands) wavefronts can then be injected into any of the available coronagraphs, including but not limited to the phase induced amplitude apodization and the vector vortex coronagraphs, both of which offer an inner working angle as low as 1 λ/D. Non-common path, loworder aberrations are sensed with a coronagraphic low-order wavefront sensor in the infrared (IR). Low noise, high frame rate, NIR detectors allow for active speckle nulling and coherent differential imaging, while the HAWAII 2RG detector in the HiCIAO imager and/or the CHARIS integral field spectrograph (from mid 2016) can take deeper exposures and/or perform angular, spectral and polarimetric differential imaging. Science in the visible is provided by two interferometric modules: VAMPIRES and FIRST, which enable sub-diffraction limited imaging in the visible region with polarimetric and spectroscopic capabilities respectively. We describe the instrument in detail and present preliminary results both on-sky and in the laboratory.

INTRODUCTORY PARAGRAPHThe massive evolved Wolf-Rayet stars sometimes occur in colliding-wind binary systems in which dust plumes are formed as a result of the collision of stellar winds 1 . These structures are known to encode the parameters of the binary orbit and winds 2,3,4 . Here, we report observations of a previously undiscovered Wolf-Rayet system, 2XMM J160050.7-514245, with a spectroscopically determined wind speed of ≈ 3400 km s −1 . In the thermal infrared, the system is adorned with a prominent ≈ 12 ′′ spiral dust plume, revealed by proper motion studies to be expanding at only ≈ 570 km s −1 . As the dust and gas appear coeval, these observations are inconsistent with existing models of the dynamics of such colliding wind systems 5,6,7 . We propose that this contradiction can be resolved if the system is capable of launching extremely anisotropic winds. Near-critical stellar rotation is known to drive such winds 8,9 , suggesting this Wolf-Rayet system as a potential Galactic progenitor system for long-duration gamma-ray bursts.Corresponding author: J. R. Callingham callingham@astron.nl 2 CALLINGHAM ET AL. MAIN BODYWolf-Rayet (WR) stars represent the final stage of the evolution of the most massive stars before ending their lives as supernovae. Late-type carbon-rich WR stars with binary companions have the potential to produce spiral "Pinwheel" patterns in which dust forms at the interface between the colliding stellar winds 2,10 . As the orbital motion entangles the winds, the form of the plume encodes the primary wind and orbital parameters, forming rare and powerful laboratories for testing our understanding of the mass-loss in WR stars. For well studied Pinwheels such as WR 104 2,4 , WR 98a 3 and WR 140 11,12 , nearly complete solutions can be obtained that tightly constrain the wind speeds, wind-momentum ratio, and orbital parameters. For WR 104 and WR 140, the dust (studied by its proper motion in the thermal infrared) and the gas (the dominant wind component in the line of sight revealed by spectroscopy) have been shown to be co-moving, as expected for spherical stellar winds.Additionally, WR stars play a significant role in the chemistry and kinetic energy budget of the interstellar medium 1 , and are considered to be likely progenitors to long-duration gamma-ray bursts (GRBs) 13,14 . A key ingredient in most models for the production of long-duration GRBs is rapid rotation of the WR progenitor star 13 . For stars that have solar-like metallicity, as observed for most Galactic WR stars 15,16 , line-driven winds rapidly rob the star of angular momentum. One channel to produce near critical-rotation of the WR star before undergoing a core-collapse supernova is through binary interaction 17 . Unfortunately debates over the role of rotation remain largely in the domain of theory as it has proven extremely difficult to place any observational constraints on the rotation of WR stars. Because WR spectra are generally formed in their extended dense winds 18 , obtaining rotational velocity from fitting t...

Direct images of protoplanets embedded in disks around infant stars provide the key to understanding the formation of gas giant planets like Jupiter. Using the Subaru Telescope and Hubble Space Telescope, we find evidence for a jovian protoplanet around AB Aurigae orbiting at a wide projected separation (~93 au), likely responsible for multiple planet-induced features in the disk. Its emission is reproducible as reprocessed radiation from an embedded protoplanet. We also identify two structures located at 430-580 au that are candidate sites of planet formation. These data reveal planet formation in the embedded phase and a protoplanet discovery at wide, > 50 au separations characteristic of most imaged exoplanets. With at least one clump-like protoplanet and multiple spiral arms, the AB Aur system may also provide the evidence for a long-considered alternative to the canonical model for Jupiter's formation: disk (gravitational) instability.