Gaia DR2 was released in April 2018 and contains a photometric catalogue of more than 1 billion sources. This release contains colour information in the form of integrated BP and RP photometry in addition to the latest G-band photometry. The level of uncertainty can be as good as 2 mmag with some residual systematics at the 10 mmag level. The addition of colour information greatly enhances the value of the photometric data for the scientific community. A high level overview of the photometric processing, with a focus on the improvements with respect to Gaia DR1, was given. The definition of the Gaia photometric system, a crucial part of the calibration of the photometry, was also explained. Finally, some of the photometric improvements expected for the next data release were described.

A sample of AGB/RGB stars with an excess of Li abundances is considered in order to estimate their mass loss rates. Our method is based on a correlation between the Li abundances and the stellar luminosity, using a modified version of the Reimers formula. We have adopted a calibration based on an empirical correlation between the mass loss rate and stellar parameters. We conclude that most Li-rich stars have lower mass loss rates compared with the majority of AGB/RGB stars, which show no evidences of Li enhancements, so that the Li enrichment process is probably not associated with an increased mass loss rate.

Dwarf galaxies provide us many important clues to understanding of galaxy formation. By using the current version of our own semi-analytic model of galaxy formation, in which cosmic structure forms and evolves based on the cold dark matter model of cosmology, we analyze dwarf galaxies. We find that the model well reproduces many properties such as magnitudes, sizes, and velocity dispersions of, especially, dwarf elliptical galaxies. We also find that the dynamical response of the gravitational potential well of dwarf galaxies to the supernova-induced gas removal plays a very important role to obtain large sizes and small velocity dispersions as observed.

Low and intermediate mass stars evolve to the asymptotic red giant branch (AGB) late in their lives. These are surrounded by a circumstellar envelope (CSE) filled with gas and dust. The dust is formed close to the star at sublimation radii and is pushed away by the stellar wind. The dust in turn pushes gases from the envelope into the interstellar medium, thus enriching it with metals. This poster summary is a general description of the next piece of a larger project, whereas the first half has been published by Nicolaes et al. (2018). We now aim to use radiative transfer simulations to model spectral energy distributions (SED) of dust and fit them to far-infrared observations for the same 40 sources. We will use 2D and 3D simulations and models containing several dust species simultaneously.

The IAU Strategic Plan for 2020-2030 presents an overview of all of the activities of the IAU along with priorities, key goals, mandates, and specific actions. Here future plans and goals are outlined for the Office of Astronomy for Development (OAO).

The Compact Lightweight Absolute Radiometer (CLARA) is orbiting Earth on-board the Norwegian NorSat-1 micro-satellite since 14th of July 2017. The first light total solar irradiance (TSI) measurement result of CLARA is 1360.18 W m−2 for the so far single reliable Channel B. Channel A and C measured significantly lower (higher) TSI values and were found being sensitive to satellite pointing instabilities. These channels most likely suffer from electrical interference between satellite components and CLARA, an effect that is currently under investigation. Problems with the satellite attitude control currently inhibit stable pointing of CLARA to the Sun.

Barium (Ba) stars form via mass-transfer in binary systems, and can subsequently interact with their white dwarf companion in a second stage of binary interaction. We used observations of main-sequence Ba systems as input for our evolutionary models, and try to reproduce the orbits of the Ba giants. We show that to explain short and sometimes eccentric orbits, additional interaction mechanisms are needed along the RGB.

Massive stars lose a considerable amount of mass during their lifetime. When the star explodes as a supernova (SN), the resulting shock wave expands in the medium created by the stellar mass-loss. Thermal X-ray emission from the SN depends on the square of the density of the ambient medium, which in turn depends on the mass-loss rate (and velocity) of the progenitor wind. The emission can therefore be used to probe the stellar mass-loss in the decades or centuries before the star’s death.

We have aggregated together data available in the literature, or analysed by us, to compute the X-ray lightcurves of almost all young supernovae detectable in X-rays. We use this database to explore the mass-loss rates of massive stars that collapse to form supernovae. Mass-loss rates are lowest for the common Type IIP supernovae, but increase by several orders of magnitude for the highest luminosity X-ray SNe.

We have developed a new version of the SD model for type Ia supernovae (SNe Ia) in which a common envelope (CE) is assumed to form if the mass-transfer rate between a carbon/oxygen white dwarf (CO WD) and its companion exceeds a critical accretion rate. Based on this model, we found that both SN 2002cx-like and SN Ia-CSM objects may share a similar origin, i.e. these peculiar objects may originate from the explosion of hybrid carbon/oxygen/neon white dwarfs (CONe WDs) in SD systems, where SNe Ia-CSM explode in systems with a massive CE of ∼1 M⊙, while SN 2002cx-like events correspond to events without a massive CE.

We present a high-resolution optical spectrum of the symbiotic nova RR Tel obtained with MIKE at Magellan-Clay telescope. RR Tel is a wide binary system of a hot white dwarf and a Mira with an orbital period of a few decades, where the white dwarf is accreting through gravitational capture of some fraction of material shed by the Mira. We find broad emission features at 6825, 7082, 7023, and 7053 Å, which are formed through Raman scattering of far-UV O VI ⋋⋋ 1032 and 1038 Å, C II ⋋⋋ 1036 and 1037 Å with atomic hydrogen. Raman O VI features exhibit clear double-peak profiles indicative of an accretion flow with a characteristic speed ∼ 30 km s−1, whereas the Raman C II features have a single Gaussian profile. We perform a profile analysis of the Raman O VI by assuming that O VI emission traces the accretion flow around the white dwarf with a fiducial scale of 1 AU. A comparison of the restored fluxes of C II ⋋⋋ 1036 and 1037 from Raman C II features with the observed C II ⋋ 1335 multiplet is consistent with the distance of RR Tel ∼ 2.6 kpc based on interstellar extinction of C II.

We investigate, in the light of new diagnostic diagrams, the role of shocks in the ionization profile of type-I planetary nebulae, and their relation to the empirical derivation of chemical abundances. We apply our technique to two well-known type-I objects: NGC 2440 and NGC 6302. Our results indicate that shocks play a very important role in the spectra of both nebulae and, since the presence of shocks reinforces the flux of low ionization lines, this artificial reinforcement can lead to incorrect chemical abundances, when they are derived through Ionization Correction Factors, at least for type-I PNe.

Binary evolution can produce different blue-straggler binaries, for example, blue stragglers with a bright, red component, or with a faint, blue component. In globular clusters, these blue-straggler binaries are generally observed as a single star, because two components can not be distinguished. Therefore, these blue-straggler binaries can be located in different regions of the color-magnitude diagram of globular clusters, e.g. blue sequence and red sequence observed in M30. We suggest that binary evolution can contribute to the blue stragglers in both of the sequences. Some blue stragglers in the blue sequence may have a faint white dwarf companion, while the red sequence includes some binaries experiencing mass transfer. It should be noted that the red sequence may also have other binaries, for example, the binaries just finished the mass transfer, and the binaries including a blue straggler (the accretors) that have evolved away from the blue sequence.

The Kepler object KOI 2700b was discovered recently as the second exoplanet with a comet-like dusty tail. We aimed at verifying the disintegrating-planet scenario of KOI 2700b by modeling its light curve and to put constraints on various tail and planet properties, as was done in the case of KIC 12557548b. Here, we describe some selected results of our analysis.

A search for asteroid families among the Hildas and Jupiter Trojans was performed with the use of a new set of proper elements. The proper elements were calculated by the empirical method. Besides well known families, several new probable families were found in addition.

Based on the data from the Next Generation Virgo cluster Survey (NGVS), we statistically study the photometric properties of globular clusters (GCs), ultra-compact dwarfs (UCDs) and dwarf nuclei in the Virgo core (M87) region. We found an obvious negative color (g - z) gradient in GC system associate with M87, i.e. GCs in the outer regions are bluer. However, such color gradient does not exist in UCD system, neither in dwarf nuclei system around M87. In addition, we found that many UCDs are surrounded by extended, low surface brightness envelopes. The dwarf nuclei and UCDs show different spatial distributions from GCs, with dwarf nuclei and UCDs (especially for the UCDs with visible envelopes) lying at larger distances to the Virgo center. These results support the view that UCDs (at least for a fraction of UCDs) are more tied to dwarf nuclei than to GCs.

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.