Variability due to stellar pulsation on the Asymptotic Giant Branch (AGB) has a great potential for applications such as distance measurements, the study the evolution of stars and galaxies, and the estimate of global stellar parameters, as well as to constrain stellar evolutionary models. Given the importance of long-period variables (LPVs) in this sense, and given the lack of recent, updated sets of pulsation models, we computed an extended grid of pulsation models widely covering the space of AGB stellar parameters, including up-to-date opacities and accounting for the chemical evolution associated with third dredge-up events. We present the relevant properties of this grid and discuss the main results it allowed to obtain in terms of the interpretation of the observed properties of LPVs in the Large Magellanic Cloud (LMC).

A Last affiliation changed 3 to 4 against MS. Please check and confirm if it is fine. small number of the sample of 184 carbon stars in the Magellanic Clouds show signs that they are in the act of evolving off of the asymptotic giant branch. Most carbon stars grow progressively redder in all infrared colors and develop stronger pulsation amplitudes as their circumstellar dust shells become optically thicker. The reddest sources, however, have unexpectedly low pulsation amplitudes, and some even show blue excesses that could point to deviations from spherical symmetry as they eject the last of their envelopes. Previously, all dusty carbon-rich AGB stars have been labeled “extreme,” but that term should be reserved for the truly extreme carbon stars. These objects may well hold the clues needed to disentangle what actually happens when a star ejects the last of its envelope and evolves off of the AGB.

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 Asymptotic Giant Branch (AGB) scenario ascribes the multiple populations in old Galactic Globular Clusters (GGC) to episodes of star formation in the gas contaminated by the ejecta of massive AGBs and super-AGBs of a first stellar population. The mass of these AGBs (4-8 M⊙) today populate the Young Massive Clusters (YMC) of the Magellanic Clouds, where rapid rotation and its slowing down play an important role in shaping the color-magnitude diagram features. Consequently, we must reconsider whether the rotational evolution of these masses affects the yields, and whether the resulting abundances are compatible with the chemical patterns observed in GGC. We show the first results of a differential analysis, by computing the hot bottom burning evolution of non-rotating models with increased CNO-Na abundances at the second dredge-up, following the results of MESA rotational models.

At the end of their evolution, asymptotic giant branch (AGB) stars undergo strong pulsation, mass loss, and dust production. Their mass loss results in substantial chemical and dust enrichment of the interstellar medium. Dust evolution models and isotope abundances in presolar grains suggest that AGB stars play a key role in both dust evolution and the star formation process. They are also the brightest stars in galaxies, potentially dominating in the near-infrared. As a result, AGB stars have a significant influence on the evolution and appearance of their host galaxies and thus must be accounted for when interpreting a galaxy’s integrated light. I will highlight new results that describe the impact AGB stars have on galaxies, including how AGB stars are used to probe galaxy evolution.

Nitrogen is among the most abundant chemical elements in the cosmos, and asymptotic giant branch (AGB) stars are fundamental nucleosynthetic sources of N in galaxies. In this work, we show how the observed N/O versus O/H chemical abundance diagram, both in extragalactic systems and in our own Galaxy, can be used to constrain the nucleosynthetic origin of N in the cosmos. In particular, we review the results of our studies with chemical evolution models, embedded in full cosmological chemodynamical simulations.

We report on the Bulge Asymmetries and Dynamic Evolution (BAaDE) survey which has observed 19 000 MSX color selected red giant stars for SiO maser emission at 43 GHz with the VLA and is in the process of observing 9 000 of these stars with ALMA at 86 GHz in the Southern sky. Our setup covers the main maser transitions, as well as those of isotopologues and selected lines of carbon-bearing species. Observations of this set of lines allow a far-reaching catalog of line-of-sight velocities in the dust-obscured regions where optical surveys cannot reach. Our preliminary detection rate is close to 70%, predicting a wealth of new information on the distribution of metal rich stars, their kinematics as function of location in the Galaxy, as well as the occurrence of lines and line ratios between the different transitions in combination with the spectral energy distribution from about 1 to 100 μm. Similar to the OH/IR stars, a clear kinematic signature between disk and bulge stars can be seen. Furthermore, the SiO J = →10 (v=3) line plays a prominent role in the derived maser properties.

We report on new molecular-line observations of the bipolar pre-planetary nebula M 1–92. The new IRAM 30 m MRT and NOEMA data shows the presence of shock induced chemistry in the nebula. From the derived [17O]/[18O] ratio, we suggest that the sudden mass loss event responsible for the formation of the nebula 1200 yr ago may also have resulted in the premature end of the AGB phase of the central star.

The standard scenario for the production of carbon-enhanced extremely metal-poor (CEMP) stars requires a more massive binary companion, which has evolved through the AGB stage and transferred carbon-rich material to the surface of the surviving, likewise extremely metal-poor (EMP) star. Evidently, the binary companion plays a key role in this process.

In order to characterise the polluting star, if any, the stage of evolution of the observed star (whether RGB or AGB), and whether pulsations exist, must be known. The Gaia DR2 parallaxes and photometry should contain the answer.

Symbiotic stars (SySts) are long-period interacting binaries composed of a hot compact star, an evolved giant star, and a tangled network of gas and dust nebulae. Presently, we know 252 SySts in the Milky Way and 62 in external galaxies. However, these numbers are still in striking contrast with the predicted population of SySts in our Galaxy. In this contribution, I present the concept and the early results from RAMSES II (Raman Search for Extragalactic Symbiotic Stars), a Gemini/GMOS Upgrade Project which makes use of the Raman OVI 6830Å band as a powerful photometric tool to identify new SySts, within and beyond the Galaxy.

We present a catalog of the observed properties of Mira-type variable stars detected with the Kilodegree Extremely Little Telescope (KELT). Asymptotic giant branch (AGB) candidates were identified in KELT using a combination of photometric data from KELT and 2MASS colors. Of the 4 million objects with KELT photometry, 3332 Mira-like variables were identified. Here, we present their observed periods and luminosities which will place important constraints on future theoretical work on the effect convection has on pulsation periods and mode stability.

We present the results from the abundance analysis of 21 primary stars in Sirius-like systems with various masses of white dwarf companions and orbital separation to understand the origin and nature of Ba stars. Three new Ba dwarfs are found for which masses are relatively low compared to Ba giants. Large fraction of the sample are found to be non-Ba stars, however, some of them have required WD mass and/or close orbital separation. Observed s-process abundances in Ba dwarfs are in good agreement with AGB models of respective WD companion mass, however, it required different pollution factors.

We report on the successful search for CO (2-1) and (3-2) emission associated with OH/IR stars in the Galactic Bulge. We observed a sample of eight extremely red AGB stars with the APEX telescope and detected seven. The sources were selected at sufficient high Galactic latitude to avoid interference by interstellar CO, which hampered previous studies of inner galaxy stars. We also collected photometric data and Spitzer IRS spectroscopy to construct the SEDs, which were analysed through radiative transfer modelling. We derived variability periods of our stars from the VVV and WISE surveys. Through dynamical modelling we then retrieve the total mass loss rates (MLR) and the gas-to-dust ratios. The luminosities range between approximately 4,000 and 5,500 L⊙ and periods are below 700 days. The total MLR ranges between 10−5 and 10−4 M⊙ yr−1. The results are presented in Blommaert et al. 2018 and summarized below.

We have discovered jets in post-AGB binaries. The orbital motion allows us to carry out tomography of the jet as light from the primary star shines through the jet cone. Jets play a major role in many astrophysical environments, from young stellar objects to galaxies. They are also used to study the energetics of accretion phenomena in systems such as red transients and stellar mergers. We use high-resolution, optical, time-series spectra to constrain theories of jet launching, and the impact of jets on the evolution of these post-AGB binaries.

The formation of EHB stars is linked to the lives of AGB stars by indications that such EHB/sdB stars might form in globular clusters with multiple populations linked to AGB evolution. Observations of massive globular clusters, such as ω-Centauri (Bedin et al.2004, Piotto et al.2005) suggest that single EHB stars might form from He-enhanced progenitors (D’Antona et al.2005, D’Antona & Caloi 2008, Lee et al.2005) in environments enriched by AGB ejecta. The studies conducted by Han et al. (2002), Han et al. (2003), and Han et al. (2007) have been able to provide a strong case for the binary formation of EHB/sdB stars in the Galactic field, though binary formation channels in globular clusters is uncertain. Simulations presented here are an extension of the simulations of Han et al. (2002) and Han et al. (2003), for low metallicities to examine the binary EHB population in globular clusters.

We present ALMA observations of the circumstellar envelope around the AGB carbon star TX Psc in molecular CO(2–1) emission, and detect a previously unknown detached shell with filamentary structure and elliptical shape. Up to now, all observed detached shells are found around carbon AGB stars and are of remarkable spherical symmetry. The elliptical shell around TX Psc is the first clear exception to that rule, with TX Psc being classified as rather ’’fresh’’ carbon star, that most likely has only experienced very few thermal pulses yet. We investigate and discuss the 3D structure of the CSE and its most likely formation scenarios, as well as the link of this peculiar detached shell to the AGB evolutionary status of TX Psc.

Using the VLT-SPHERE/ZIMPOL adaptive optics imaging polarimeter, images of a sample of nearby red supergiants (RSGs) were obtained in multiple filters. From these data, we obtain information on geometrical structures in the inner wind, the onset radius and spatial distribution of dust grains as well as dust properties such as grain size. As dust grains may play a role in initiating and/or driving the outflow, this could provide us with clues as to the wind driving mechanism.

Stencel et al. (1986) analyzed IUE spectra of a modest set of cool stars and found that they continue to produce chromospheres even in the presence of high dust levels in their outer atmospheres. This reversed the previous results of Jennings (1973) and Jennings & Dyck (1972). We describe an on-going extension of these studies to a sample of stars representing a broader range in dust/gas ratios, using archival IUE and archival and new HST data on both RGB and AGB stars. Surface fluxes in emission lines will be analyzed to assess the chromospheric activity and obscuration by dust in each star, as those fluxes will follow a different pattern for reduced activity (temperature/density dependent) vs. dust obscuration (wavelength dependent). Wind characteristics will be measured by modeling of wind-reversed chromospheric emission lines.

In this work, we present spectroscopic results of the variable star R Scuti, obtained during the campaign of measures led in 2016 at the Oukaimeden observatory in Morrocco. High resolution spectra (R ≍ 12 000) were obtained between 4289 Å and 7125 Å. This intensive observing campaign spanned over 26 nights from June to November 2016.

Using a hybrid binary population synthesis approach, we modelled the formation and evolution of populations of accreting white dwarfs (WDs) for differing star formation histories. We found that the delay time distribution of SNe Ia in the single degenerate scenario is inconsistent with observations. Additionally, we found that our predicted X-ray and UV emission of populations of accreting WDs are consistent with the X-ray luminosities of early-type galaxies observed by Chandra and the HeII 4686 Å/Hβ line ratio measured in stacked SDSS spectra of passively evolving galaxies. Moreover, we found that the majority of current novae in elliptical-like galaxies have low-mass WDs, long decay times, long recurrence periods and are relatively faint. In contrast, the majority of current novae in spiral-like galaxies have massive WDs, short decay times, short recurrence periods and are relatively bright. Our predicted distribution of mass-loss timescales in an M31-like galaxy is consistent with observations for Andromeda.