Hii regions in galaxy disks can be used as a powerful tool to trace the radial distribution of several of their properties and shed some light on the different relevant processes on galaxy formation and evolution. Among the properties that can be extracted from the study of the ionized gas are the metallicity, the excitation and the hardness of the ionizing field of radiation. In this contribution we focus on the determination of both the ionization parameter (U) and the effective temperature of the ionizing clusters (T) by means of a bayesian-like comparison between the observed relative fluxes of several emission-lines with the predictions from a set of photoionization models. We also show the implications that the use of our method has for the study of the radial variation of both U and T in some very well-studied disk galaxies of the Local Universe.

Supergiant X-ray Binaries host a compact object, generally a neutron star, orbiting an evolved O/B star. Mass transfer proceeds through the intense radiatively-driven wind of the stellar donor, a fraction of which is captured by the gravitational field of the neutron star. The subsequent accretion process onto the neutron star is responsible for the abundant X-ray emission from those systems. They also display variations in time of the X-ray flux by a factor of a few 10, along with changes in the hardness ratios believed to be due to varying absorption along the line-of-sight. We used the most recent results on the inhomogeneities (aka clumps) in the non-stationary wind of massive hot stars to evaluate their impact on the time-variable accretion process. We ran three-dimensional simulations of the wind in the vicinity of the accretor to witness the formation of the bow shock and follow the inhomogeneous flow over several spatial orders of magnitude, down to the neutron star magnetosphere. In particular, we show that the impact of the clumps on the time-variability of the intrinsic mass accretion rate is severely damped by the crossing of the shock, compared to the purely ballistic Bondi-Hoyle-Lyttleton estimation. We also account for the variable absorption due to clumps passing by the line-of-sight and estimate the final effective variability of the mass accretion rate for different orbital separations. These results are confronted to recent analysis of Vela X-1 observations with Chandra by Grinberg et al. (2017). It shows that clumps account well for time-variability at low luminosity but can not generate, per se, the high luminosity activity observed.

The relative abundances of the radionuclides in the solar system at the time of its birth are crucial arbiters for competing hypotheses regarding the birth environment of the Sun. The presence of short-lived radionuclides, as evidenced by their decay products in meteorites, has been used to suggest that particular, sometimes exotic, stellar sources were proximal to the Sun’s birth environment. The recent confirmation of neutron star - neutron star (NS-NS) mergers and associated kilonovae as potentially dominant sources of r-process nuclides can be tested in the case of the solar birth environment using the relative abundances of the longer-lived nuclides. Critical analysis of the 15 radionuclides and their stable partners for which abundances and production ratios are well known suggests that the Sun formed in a typical massive star-forming region (SFR). The apparent overabundances of short-lived radionuclides (e.g. 26Al, 41Ca, 36Cl) in the early solar system appears to be an artifact of a heretofore under-appreciation for the important influences of enrichment by Wolf-Rayet winds in SFRs. The long-lived nuclides (e.g. 238U, 244Pu, 247Cr, 129I) are consistent with an average time interval between production events of 108 years, seemingly too short to be the products of NS-NS mergers alone. The relative abundances of all of these nuclides can be explained by their mean decay lifetimes and an average residence time in the ISM of ∼200 Myr. This residence time evidenced by the radionuclides is consistent with the average lifetime of dust in the ISM and the timescale for converting molecular cloud mass to stars.

This paper discussed whether 17th Century observers left historical records of the plasma tails of comets that would be adequate to enable us to extract the physical parameters of the solar wind. The size of the aberration angle between a comet’s tail and its radius-vector defines the type of the tail: plasma or dust. We considered Bredikhin’s calculations of the parameters for 10 comet tails observed during the Maunder minimum (1645 – 1715). For those comets the angle between the tail’s axis and the radius-vector on average exceeded the value of 10° that is typical for dust tails. It was noted that visual observations of the ion tails of comets are very difficult to make owing to the spectral composition of their radiation, confirming the conclusion that observations of comet tails made in the 17th Century are not suitable for deriving past values of the physical parameters of the solar wind.

More than a decade after fast x-ray transients with an OB supergiant counterpart were identified as a distinct class of wind-accreting sources, we still have not reached a consensus on the physical origin of their similarities and differences with persistent sources. Both kinds seem to extend over the same range of every relevant parameter. Here I argue that, despite this overall overlap, persistent sources have – on average – later-type, more evolved counterparts, and discuss the hypothesis that SFXTs are – on average – a younger population, as well as some of its possible implications.

Using photometric data available in the literature we want to identify the massive stars members of the metal-poor irregular galaxy IC 10 and the clusters and associations that they form. The census of the clusters and associations of these objects is needed to provide information about age and environment on this galaxy that is apparently going through a starburst phase.

Asymptotic giant branch stars play an important role in enriching galaxies by s-process elements. Recent studies have shown that their role in producing s-process elements in the Galactic disc was underestimated and should be reconsidered. Based on high-resolution spectra we have determined abundances of neutron-capture elements in a sample of 310 stars located in the field and open clusters and investigated elemental enrichment patterns according to their age and mean galactocentric distances.

High-mass X-ray binaries (HMXBs) provide an exciting window into the underlying processes of both binary as well as massive star evolution. Because HMXBs are systems containing a compact object accreting from a high-mass star at close orbital separations they are also likely progenitors of gamma-ray bursts and gravitational wave sources. We present classification and age measurements for HMXBs in M33 using a combination of deep Chandra X-ray imaging, and archival Hubble Space Telescope data. We constrain the ages of the HMXB candidates by fitting the color-magnitude diagrams of the surrounding stars, which yield the star formation histories of the surrounding region. Unlike the age distributions measured for HMXB populations in the Magellanic Clouds, the age distribution for the HMXB population in M33 contains a number of extremely young (<5 Myr) sources. We discuss these results the context of the effect of host galaxy properties on the observed HMXB population.

Recent advanced simulations of protoplanetary disks allow us to search for observational constraints to identify the magnetic field activity in protoplanetary disks. With our 3D radiation non-ideal magneto-hydrodynamical (MHD) models including irradiation from an Herbig type star we are able to model the thermal and dynamical evolution in a so far never reached detail (Flock et al. 2017). The activity of the magneto-rotational instability in the inner hot ionized regions comes along with a magnetic dynamo. The oscillations in the mean toroidal magnetic field with a timescale of 10 local orbits can slightly bend the inner dust rim and so the irradiation surface. This causes a clear variability pattern in the near infrared (NIR) emission at the dust inner rim surface. Another way to identify the presence of magnetic fields are to search for polarization signatures. Using 3D non-ideal MHD simulations of the outer disk regions (Flock et al. 2015) we calculate synthetic images of the intrinsically polarized continuum emitted by aspherical grain aligned with the dominantly toroidal magnetic field (Bertrang et al. 2017). Our results show a clear radial polarization pattern for face-on observed disk, similar to recent observations by Ohashi et al. (2018). Additionally, we are even able to see the change of the polarization pattern inside the vortex as the poloidal magnetic field dominates therein.

The X-Shooter Spectral Library (XSL) contains more than 800 spectra of stars across the color-magnitude diagram, that extend from near-UV to near-IR wavelengths (320-2450 nm). We summarize properties of the spectra of O-rich Long Period Variables in the XSL, such as phase-related features, and we confront the data with synthetic spectra based on static and dynamical stellar atmosphere models. We discuss successes and remaining discrepancies, keeping in mind the applications to population synthesis modeling that XSL is designed for.

The INTEGRAL archive developed at INAF-IASF Milano with the available public observations from late 2002 to 2016 is investigated to extract the X-ray properties of 58 High Mass X-ray Binaries (HMXBs). This sample consists of sources hosting either a Be star (Be/XRBs) or an early-type supergiant companion (SgHMXBs), including the Supergiant Fast X-ray Transients (SFXTs). INTEGRAL light curves (sampled at 2 ks) are used to build their hard X-ray luminosity distributions, returning the source duty cycles, the range of variability of the X-ray luminosity and the time spent in each luminosity state. The phenomenology observed with INTEGRAL, together with the source variability at soft X-rays taken from the literature, allows us to obtain a quantitative overview of the main sub-classes of massive binaries in accretion (Be/XRBs, SgHMXBs and SFXTs). Although some criteria can be derived to distinguish them, some SgHMXBs exist with intermediate properties, bridging together persistent SgHMXBs and SFXTs.

Stellar coronal mass ejections (CMEs) may play an important role in stellar and planetary evolution, therefore the knowledge on parameter distributions of this energetic activity phenomenon is highly relevant. During the last years several attempts have been made to detect stellar CMEs of late-type main-sequence and pre main-sequence stars from dedicated optical spectroscopic observations. Up to now only a handful of distinct stellar CME detections are known which contradicts the results from stellar CME modelling, which predict higher CME rates. We report on dedicated ongoing and future observational attempts to detect stellar CMEs and discuss the observational results with respect to the results from stellar CME modelling.

The earliest phases of star formation are characterised by intense mass accretion from the circumstellar disk to the central star. One group of young stellar objects, the FU Orionis-type stars exhibit accretion rate peaks accompanied by bright eruptions. The occurance of these outbursts might solve the luminosity problem of protostars, play a key role in accumulating the final star mass, and have a significant effect on the parameters of the envelope and the disk. In the framework of the Structured Accretion Disks ERC project, we are conducting a systematic investigation of these sources with millimeter interferometry to examine whether they represent normal young stars in exceptional times or they are unusual objects. Our results show that FU Orionis-type stars can be similar to both Class I and Class II systems and may be in a special evolutionary phase between the two classes with their infall-driven episodic eruptions being the main driving force of the transition.

A small subset of Galactic O-stars possess surface magnetic fields that alter the outflowing stellar wind by magnetically confining it. Key to the magnetic confinement is that it induces rotational modulation of spectral lines over the full EM domain; this allows us to infer basic quantities, e.g., mass-loss rate and magnetic geometry. Here, we present an empirical study of the Hα line in Galactic magnetic O-stars to constrain the mass fed from the stellar base into the magnetosphere, using realistic multi-dimensional magnetized wind models, and compare with theoretical predictions. Our results suggest that it may be reasonable to use mass-feeding rates from non-magnetic wind theory if the absolute mass-loss rate is scaled down according to the amount of wind material falling back upon the stellar surface. This provides then some empirical support to the proposal that such magnetic O-stars might evolve into heavy stellar-mass black holes (Petit et al.2017).

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.