We study high energy processes that occur during the merger of a neutron star (NS) or a black hole (BH) with the core of a red supergaint (RSG). The merger powers a luminous event termed common envelope jets supernova (CEJSN), that might account for lightcurves of peculiar transients. In the CEJSN scenario the NS/BH accretes mass from its surroundings through an accretion disk as it spirals-in inside the RSG’s envelope and core. The compact object launches part of this mass as narrow jets that interact with their environment by depositing their kinetic energy in the envelope and core gas. These jets can serve as production sites of high energy neutrinos and r-process elements.

Wolf-Rayet (WR) stars comprise a class of stars whose spectra are dominated by strong, broad emission lines that are associated with copious mass loss. In the massive-star regime, roughly 90% of the known WR stars are thought to have evolved off the main sequence. Dubbed classical WR (cWR) stars, these hydrogen-depleted objects represent a crucial evolutionary phase preceding core collapse into black holes, and offer a unique window into hot-star wind physics. Their formation is thought to be rooted in either intrinsic mass-loss or binary interactions. Results obtained from analyses using contemporary model atmospheres still fail to reconcile the derived properties of WR stars with predictions from stellar evolution. Importantly, stellar evolution models cannot reproduce the the bulk of cWR stars, a problem that becomes especially severe at subsolar metallicity. Next-generation model atmospheres and upcoming observational campaigns to hunt for undetected companions promise a venue for progress.

With the upcoming third Gaia data release (DR3), the first Gaia astrometric orbital solutions for binary sources will become available. Potentially, many rarely seen single-degenerate massive binaries with a black hole (OB+BH) will be revealed. Here, we investigate how many OB+BHs are expected to be detected as binaries in Gaia astrometry by using tailored models for the massive star population. We use a method based on the astrometric data to investigate how many OB+BH binaries will be uncovered by Gaia. We estimate that∼200 OB+BHs are detectable among the sources in the second Alma Luminous Star massive star catalogue, either in DR3 or in upcoming data releases. Moreover, we show that BH-formation scenarios could be constrained from the distributions of parameters such as the orbital periods and eccentricities.

Because they lose tremendous amounts of mass, cool evolved stars are major sources of dust and molecules for the interstellar medium. Spectro-imaging of the dust-driven winds around these stars has enabled us to identify recurring nonspherical patterns (e.g. spirals, arcs, compressed wind). We use radiative-hydrodynamic simulations of dust-driven winds to study the imprints left in the wind by an orbiting stellar or sub-stellar companion. We designed 3D numerical setup to solve the wind dynamics beyond the dust condensation radius and follow the flow up to several hundreds of stellar radii. Non-uniform grids enable us to capture small scale features such as shocks or disks forming around the orbiting object. Depending on its mass and orbital parameters, we reproduced typical non-spherical features such as arcs, spirals, petals and orbital density enhancements, and identified patterns associated to eccentric orbits.

Considering as many as 70% of massive stars interact with a binary companion (Sana et al.2012, 2014), we created a new model of the optical nebular emission of HII regions by combining the results of the Binary Population and Spectral Synthesis (BPASS, Eldridge, Stanway et al.2017) code with the photoionization code (CLOUDY). This is discussed more in detail in Xiao et al.2018a. Then we use this model to explore a variety of emission-line diagnostics of CCSN host HII regions from the PMAS/PPAK Integral-field Supernova hosts COmpilation (PISCO, Galbany et al.2018). We determine the age, metallicity and gas parameters for H II regions associated with CCSNe, contrasting the above variables to distribution type II and type Ibc SNe. We find their nebular emission and CCSN progenitor types are largely determined by past and ongoing binary interactions, for example mass loss, mass gain and stellar mergers. However we note these two types SNe have little preference in their host environment metallicity measured by oxygen abundance or in progenitor initial mass, except that at lower metallicities supernovae are more likely to be of type II. The BPASS and nebular emission models are available from bpass.auckland.ac.nz and warwick.ac.uk/bpass.

The discovery of a likely companion of the Herbig Ae/Be star HD 142527 motivates the study of the effect that it produces on the SED. The main change on the system configuration is the formation of a gap in the disk in which the companion is embedded, following the orbit of the secondary star. This results in the formation of a wall (at the outer gap edge), which is illuminated by stellar radiation. We present a model for the SED, taking into account all the components of the system: the two stars, the disk with two gaps (one produced by the stellar companion and the other by potential planets), three walls (two associated with the gaps and the other with dust sublimation), optically thin material in the gaps and in a halo. The size of the modeled spherical halo is smaller than found in a previous study.