HDUST is a 3D, NLTE radiative transfer code based on the Monte Carlo method. We report on recent advancements on the code, which is now capable of handling He and other elements in the NLTE regime and in 3D configurations. In this contribution we show initial comparisons with CMFGEN, made with spherical wind models composed of H + He.

The role of episodic mass loss in evolved massive stars is one of the outstanding questions in stellar evolution theory. Integral field spectroscopy of nebulae around massive stars provide information on their recent mass-loss history. η Car is one of the most massive evolved stars and is surrounded by a complex circumstellar environment. We have conducted a three-dimensional morpho-kinematic analysis of η Car’s ejecta outside its famous Homunculus nebula. SHAPE modelling of VLT MUSE data establish unequivocally the spatial cohesion of the outer ejecta and the correlation of ejecta with the soft X-ray emission.

Observations with powerful X-ray telescopes, such as XMM-Newton and Chandra, significantly advance our understanding of massive stars. Nearly all early-type stars are X-ray sources. Studies of their X-ray emission provide important diagnostics of stellar winds. High-resolution X-ray spectra of O-type stars are well explained when stellar wind clumping is taking into account, providing further support to a modern picture of stellar winds as non-stationary, inhomogeneous outflows. X-ray variability is detected from such winds, on time scales likely associated with stellar rotation. High-resolution X-ray spectroscopy indicates that the winds of late O-type stars are predominantly in a hot phase. Consequently, X-rays provide the best observational window to study these winds. X-ray spectroscopy of evolved, Wolf-Rayet type, stars allows to probe their powerful metal enhanced winds, while the mechanisms responsible for the X-ray emission of these stars are not yet understood.

The properties of the first generation of stars and their supernova (SN) explosions remain unknown due to the lack of their actual observations. Pop III stars may have been very massive and predicted to be exploded as pair-instability SNe, but the observed metal-poor stars show the abundance patterns which are more consistent with yields of core-collapse SNe. We study the multicolor light curves for a metal-free core-collapse SN models (massive stars of 25-100 solar mass range) to determine the indicators for the detection and identification of first generation SNe. We use mixing-fallback supernova explosion models which explain the observed abundance patterns of metal poor stars. Numerical calculations of the multicolor light curves are performed using the multigroup radiation hydrodynamic code STELLA. The calculated light curves of metal-free SNe are compared with our calculations of non-zero metallicity models and observed SNe.

I find high turbulent shearing in a neutron-rich accretion disk surrounding a proto-neutron star formed at the collapse of a rapidly-rotating M ZAMS = 54M ⊙ star. These might be features of superluminous supernovae powered by jets and/or magnetar spin-down.

To this date ψ Per is the only classical Be star that was angularly resolved in radio (by the VLA at λ = 2 cm). Gaussian fit to the azimuthally averaged visibility data indicates a disk size (FWHM) of ~500 stellar radii (Dougherty & Taylor 1992). Recently, we obtained new multi-band cm flux density measurements of ψ Per from the enhanced VLA. We modeled the observed spectral energy distribution (SED) covering the interval from ultraviolet to radio using the Monte Carlo radiative transfer code HDUST (Carciofi & Bjorkman 2006). An SED turndown, that occurs between far-IR and radio wavelengths, is explained by a truncated viscous decretion disk (VDD), although the shallow slope of the radio SED suggests that the disk is not simply cut off, as is assumed in our model. The best-fit size of a truncated disk derived from the modeling of the radio SED is 100+5 −15 stellar radii, which is in striking contrast with the result of Dougherty & Taylor (1992). The reasons for this discrepancy are under investigation.

We have detected 13 new runaway-star candidates of spectral type O combining the TGAS (Tycho-Gaia Astrometric Solution) proper motions from Gaia Data Release 1 (DR1) and the sample from GOSSS (Galactic O-Star Spectroscopic Survey). We have also combined TGAS and Hipparcos proper motions to check that our technique recovers many of the previously known O-type runaways in the sample.

We present the first successful simulations of neutrino-driven supernova explosions in three dimensions (3D) using the Vertex-Prometheus code including sophisticated energy-dependent neutrino transport. The simulated models of 9.6 and 20 solar-mass iron-core stars demonstrate that successful explosions can be obtained in self-consistent 3D simulations, where previous models have failed. New insights into the supernova mechanism can be gained from these explosions. The first 3D model (Melson et al. 2015a) explodes at the same time but more energetically than its axially symmetric (2D) counterpart. Turbulent energy cascading reduces the kinetic energy dissipation in the cooling layer and therefore suppresses neutrino cooling. The consequent inward shift of the gain radius increases the gain layer mass, whose recombination energy provides the surplus for the explosion energy.

The second explosion (Melson et al. 2015b) is obtained through a moderate reduction of the neutral-current neutrino opacity motivated by strange-quark contributions to the nucleon spin. A corresponding reference model without these corrections failed, which demonstrates how close current 3D models are to explosion. The strangeness adjustment is meant as a prototype for remaining neutrino opacity uncertainties.

Observational constraints on the birth and early evolution of massive black holes come from two extreme regimes. At high redshift, quasars signal the rapid growth of billion-solar-mass black holes and indicate that these objects began remarkably heavy and/or accreted mass at rates above the Eddington limit. At low redshift, the smallest nuclear black holes known are found in dwarf galaxies and provide the most concrete limits on the mass of black hole seeds. Here, we review current observational work in these fields that together are critical for our understanding of the origin of massive black holes in the Universe.

The Protoplanetary Discussions conference—held in Edinburgh, UK, from 2016 March 7th–11th—included several open sessions led by participants. This paper reports on the discussions collectively concerned with the multi-physics modelling of protoplanetary discs, including the self-consistent calculation of gas and dust dynamics, radiative transfer, and chemistry. After a short introduction to each of these disciplines in isolation, we identify a series of burning questions and grand challenges associated with their continuing development and integration. We then discuss potential pathways towards solving these challenges, grouped by strategical, technical, and collaborative developments. This paper is not intended to be a review, but rather to motivate and direct future research and collaboration across typically distinct fields based on community-driven input, to encourage further progress in our understanding of circumstellar and protoplanetary discs.

The detection of quasars at z > 6 unveils the presence of supermassive black holes of a few billion solar masses. The rapid formation process of these extreme objects remains a fascinating and open issue. Such discovery implies that seed black holes must have formed early on, and grown via either rapid accretion or BH/galaxy mergers. In this theoretical review, we discuss in detail various BH seed formation mechanisms and the physical processes at play during their assembly. We discuss the three most popular BH formation scenarios, involving the (i) core-collapse of massive stars, (ii) dynamical evolution of dense nuclear star clusters, (iii) collapse of a protogalactic metal free gas cloud. This article aims at giving a broad introduction and an overview of the most advanced research in the field.

This automated catalogue combines all the largest published optical, radio, and X-ray sky catalogues to find probable radio/X-ray associations to optical objects, plus double radio lobes, using uniform processing against all input data. The total count is 1 002 855 optical objects so presented. Each object is displayed with J2000 astrometry, optical and radio/X-ray identifiers, red and blue photometry, and calculated probabilities and optical field solutions of the associations. This is the third and final edition of this method.