Common envelope evolution (CEE) occurs in some binary systems involving asymptotic giant branch (AGB) or red giant branch (RGB) stars, and understanding this process is crucial for understanding the origins of various transient phenomena. CEE has been shown to be highly asymmetrical and global 3D simulations are needed to help understand the dynamics. We perform and analyze hydrodynamic CEE simulations with the adaptive mesh refinement (AMR) code AstroBEAR, and focus on the role of accretion onto the companion star. We bracket the range of accretion rates by comparing a model that removes mass and pressure using a subgrid accretion prescription with one that does not. Provided a pressure-release valve, such as a bipolar jet, is available, super-Eddington accretion could be common. Finally, we summarize new results pertaining to the energy budget, and discuss the overall implications relating to the feasibility of unbinding the envelope in CEE simulations.

RCW 98 is an HII region with an active star formation in its immediate neighbourhood. At least three early-type stars ionize it and it contains the bright rimmed cloud. Our observations of this region in the optical regime shows that RCW 98 is a complex and dynamical region. We have created a simple model of the dust distribution in this object, but it is not fully consistent with the optical observations. We also study the effects of ionizing stars on the dust.

Understanding how, when and where complex organic and potentially prebiotic molecules are formed is a fundamental goal of astrochemistry. Since its beginning the Atacama Large Millimeter/submillimeter Array (ALMA) has demonstrated its capabilities for studies of the chemistry of solar-type stars. Its high sensitivity and fine spectral and angular resolution makes it possible to study the chemistry of young stars on Solar System scales. We here present an unbiased spectral survey, Protostellar Interferometric Line Survey (PILS), of the astrochemical template source and Class 0 protostellar binary IRAS 16293-2422 using ALMA. The high quality ALMA data have allowed us to detect a wealth of species previously undetected toward solar-type protostars as well as the interstellar medium in general. Also, the data show the presence of numerous rare isotopologues of complex organic molecules and other species: the exact measurements of the abundances of the complex organic molecules and their isotopologues shed new light onto the formation of these species and provide a chemical link between the embedded protostellar stages and the early Solar System.

Models of magnetically driven accretion reproduce many observational properties of T Tauri stars. For the more massive Herbig Ae/Be stars, the corresponding picture has been questioned lately, in part driven by the fact that their magnetic fields are typically one order of magnitude weaker. Indeed, the search for magnetic fields in Herbig Ae/Be stars has been quite time consuming, with a detection rate of about 10% (e.g. Alecian et al. 2008), also limited by the current potential to detect weak magnetic fields. Over the last two decades, magnetic fields were found in about twenty objects (Hubrig et al. 2015) and for only two Herbig Ae/Be stars was the magnetic field geometry constrained. Ababakr, Oudmaijer & Vink (2017) studied magnetospheric accretion in 56 Herbig Ae/Be stars and found that the behavior of Herbig Ae stars is similar to T Tauri stars, while Herbig Be stars earlier than B7/B8 are clearly different. The origin of the magnetic fields in Herbig Ae/Be stars is still under debate. Potential scenarios include the concentration of the interstellar magnetic field under magnetic flux conservation, pre-main-sequence dynamos during convective phases, mergers, or common envelope developments. The next step in this line of research will be a dedicated observing campaign to monitor about two dozen HAeBes over their rotation cycle.

A long-standing problem of the general paradigm of low-mass star formation is the “luminosity problem”: protostars are less luminous than theoretically predicted. One possible solution is that the accretion process is episodic. FU Orionis-type stars (FUors) are thought to be the visible examples for objects in the high accretion state and it is still debated what physical mechanism triggers the phenomenon. For many of these objects their disk properties are still largely unknown so we conducted a deep, high spatial resolution (down to 20 au) ALMA Band 6 (1.3 mm) dust continuum survey of a sub-sample of known FUors. Here we present preliminary results of our survey, including the mass, size and spectral slope of each disk.

The name of Kepler is inseparably associated with the supernova of 1604 (SN 1604; V843 Ophiuchi), but there are reasons why Galileo Galilei might also claim to leave his name on that phenomenon, given the assiduousness of his observations.

By compiling abundances from red and blue supergiants (SGs) within the Local Universe, I present the Mass-Metallicity relation (MZR) using stellar tracers, demonstrating the excellent internal consistency. Comparing this result with nebular tracers, those empirically calibrated to direct-method studies provide the most consistent results.

Previous theoretical studies can only explain part of the observed intermediate-mass binary pulsars (IMBPs) with short orbital periods. Note that an ONe white dwarf (WD) accreting mass from a He star may experience the accretion-induced collapse process and eventually form IMBPs, known as the ONe WD+He star scenario. By investigating the evolution of a large number of ONe WD+He star binaries, we found that the ONe WD+He star scenario can form IMBPs including pulsars with 5 – 340 ms spin periods, and the orbital periods range from 0.04 to 900 d. Compared with the observed IMBPs, this scenario can cover almost all of the IMBPs with short orbital periods. Thus, we suggest that the ONe WD+He star channel is responsible for the formation of IMBPs with short orbital periods.

We present studies of Long Period Variables (LPVs) in our Galaxy based on astrometric VLBI observations of H2O and SiO masers. The Galactic Miras and OH/IR stars are our main targets. For Miras, we present the distribution of the LPVs on the MK – log P plane. Galactic Miras show consistency with PLR in the LMC except for some fainter sources. Parallaxes of the LPVs determined from VLBI and Gaia are compared. There seems to be some offset.

Gas-to-dust ratios in Asymptotic Giant Branch (AGB) stars are used to calculate gas masses from measured dust masses and vice versa, but can vary widely and are rarely directly measured. In this work, we present spatially resolved gas and dust masses for a sample of 8 nearby AGB stars, using JCMT CO-line and continuum observations, and compare them. This serves as a pilot study for the Nearby Evolved Stars Survey (NESS; PI: P. Scicluna) project which will provide similar observations of ∼400 AGB stars in a volume-limited sample.

We use a matched filter to detect compact groups of old, metal-poor stars that we term FOSSILs (Fragments of Old Stellar Systems in Limbo). With size scales on the order of 10 arcminutes, distances ranging from 2 to 200 kpc, and memberships ranging from a handful to several dozen stars, these FOSSILs stand out from the surrounding field and are presumably signatures of, or debris from, ancient star clusters and dwarf galaxies. They may be localized concentrations of stars within more extensive tidal streams, and in some cases may be the signatures of extant but heretofore undetected ultrafaint galaxies. Using magnitudes and colors from the Pan-STARRs survey, we detect ∼ 70 such FOSSILs at 5 σ or greater in a 2200 square degree region in the vicinity of the north Galactic pole. A subsample of more populous FOSSILs that could be candidate ultrafaint dwarf galaxies suggests a total population of 200 such objects within 200 kpc of the Galactic center. Spectroscopic and astrometric follow-up of these FOSSILs will be required to determine the nature of these structures, deepen our understanding of the make-up and accretion history of the Galactic halo, and perhaps alleviate the missing satellites problem.

The Nearby Evolved Stars Survey aims to observe over 400 evolved stars within 2 kpc, to determine why, and how much, our Galaxy cares about AGB stars. This contribution presents a brief introduction to the survey and data. NESS is an open project. Anyone is welcome to get involved and we aim to make as much data and code available to the community as possible.

We have been intensely monitoring photometric variability in proto-planetary nebulae (PPNe) over the past 25 years and radial velocity variability over the past ten years. Pulsational variability has been obvious, in both the light and velocity, although the resulting curves are complex, with multiple periods and varying amplitudes. Observed periods range from 25 to 160 days, and the periods and amplitudes reveal evolutionary trends. We will present our observational results to date for approximately 30 PPNe, and discuss these results, including the search for period changes that might help constrain post-AGB evolutionary timescales.

Local Group dwarf galaxies are a unique astrophysical laboratory because they are the only objects in which we can reliably and precisely characterize the star formation histories of low-mass galaxies going back to the epoch of reionization. There are of order 100 known galaxies less massive than the Small Magellanic Cloud within ~1 Megaparsec of the Milky Way, with a vide variety of star formation history, gas content, and mass to light ratios. In this overview the current understanding of the formation and evolution of low-mass galaxies across cosmic time will be presented, and the possibility of drawing links between the properties of individual systems and the broader Local Group and cosmological context will be discussed. Local Group dwarfs will remain a uniquely powerful testbed to constrain the properties of dark matter and to evaluate the performance of simulations for the foreseeable future.

While the observed polarization maps of spatially resolved post-AGB objects usually require numerical modelling of radiative transfer, it is useful to have known analytical solutions of the polarized radiative transfer equation (PRTE) as benchmarks of computer codes in the simplest model cases. We consider two such solutions: cylindrically symmetric Green’s function for an infinite medium and cylindrically symmetric inner eigenfunctions of PRTE.

The chemical abundances of the gas-phase and stellar components of disc galaxies are relevant to understand their formation and evolution. It has been shown that an inside-out disc formation yields negative chemical profiles. However, a large spread in metallicity gradients, including positive ones, has been reported by recent and more precise observations, suggesting the action of other physics processes such as gas outflows and inflows, radial migration, and mergers and interactions. Cosmological simulations that includes chemical models provide a tools to tackle the origin of the metallicity profiles and the action of those processes that might affect them as a function of time. I present a summary of the current state-of-knowledge from a numerical point of view and discuss the main results from the analysis of the EAGLE simulations.

Younger and fully convective stars are much more active than our Sun, producing many superflares. Here we estimate the impact of the superflares UV radiation on living organisms on the surface of orbiting planets in the habitable zone of the star. For this we study two active stars, Kepler-96 (solar type) and TRAPPIST-1 (M dwarf). Kepler-96, with an age of 2.4 Gyr, is at the same stage of the Sun when the first multicellular organisms appeared on Earth. The biological impact of super flares are studied on a hypothetical Earth at 1AU of Kepler-96 and on planets TRAPPIST-1e, f, and g for three atmospheres scenarios: an Archean and Present-day atmospheres with and without ozone. We estimated the survival rates of two bacteria and concluded that life would only survive on the surface of these planets if their atmosphere had an ozone layer, or in shallow waters of an ocean.

The factors controlling strong mass loss from evolved stars remain elusive, frustrating efforts to parameterise mass loss in models of evolved stars. We herein describe evidence we have collected to show that the mass-loss rate of stars is controlled by stellar pulsations, and that we are close to providing improved prescriptions for mass-loss rates from many kinds of evolved stars.