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.

In order to investigate the effect of dust production on the molecular absorption, we model the dust continuum and the 7.5 and 13.7 μm acetylene absorption features in the Spitzer IRS spectra of 148 carbon stars in the Large Magellanic Cloud (LMC). Our preliminary investigation does not find a strong correlation between the dust-production rate and the column density of acetylene for the LMC sample. However, we will construct more models at high optical depths and probe a larger range of dust properties for more robust results.

We present radiative transfer modelling of the dust around U Ant, a well-studied detached-shell source. U Ant is among the >400 sources targeted by the Nearby Evolved Stars Survey (NESS; PI: P. Scicluna), and the procedure used to model this source will be applied to the rest of the AGB sample in NESS.

We present preliminary results of a study aimed at identifying and characterizing the Asymptotic Giant Branch (AGB) stars in the outer Galaxy using the color-color diagram (CCD) that combines the Spitzer Space Telescope and 2MASS photometry: Ks – [8.0] vs. Ks – [24]. Our initial study concentrates on a region in the outer Galactic plane around a galactic longitude l of 105°, where we identified 777 O-rich and 200 C-rich AGB star candidates.

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.

The determination of the star formation history is a key goal for understanding galaxies. In this regard, nearby galaxies in the Local Group offer us a complete suite of galactic environment that is perfect for studying the connection between stellar populations and galaxy evolution. In this paper, we present the star formation history of M31 using long period variable stars that are prime targets for studying the galaxy formation and evolution because of their evolutionary phase. In this method, at first, we convert the near-infrared K-band magnitude of evolved stars to mass and age and from this we reconstruct the star formation and evolution of the galaxy.

We characterized the dusty circumstellar nebula and central star of the C-rich bipolar planetary nebula (PN) NGC 6781 using our own Herschel data augmented with the archival data from UV to radio and constructed one of the most comprehensive photoionization PN models ever produced consisting of the ionized, atomic and molecular gas components as well as the dust component. We reproduced the observed spectral energy distribution (SED), constrained by 136 observational data points. The total nebula mass was estimated to be 0.41 M⊙, with a significant fraction (about 70 %) of it existing in the photo-dissociation region (PDR) surrounding the ionized nebula. This finding demonstrates the critical importance of the PDR in PNe, which are typically recognized as the hallmark of ionized/H+ region. It is therefore essential to characterize the PDR of the circumstellar nebula to understand material recycling in the Milky Way and other galaxies.

We performed a far-IR imaging survey of the circumstellar dust shells of 144 evolved stars as a mission program of the AKARI infrared astronomical satellite. Our objectives were to characterize the far-IR surface brightness distributions of the cold dust component in the circumstellar dust shells. We found that (1) far-IR emission was detected from all but one object, (2) roughly 60–70 % of the target sources showed some extension, (3) 29 sources were newly resolved in the far-IR in the vicinity of the target sources, (4) the results of photometry measurements were reasonable with respect to the entries in the AKARI/FIS Bright Source Catalogue, and (5) an IR two-color diagram would place the target sources in a roughly linear distribution that may correlate with the age of the circumstellar dust shell.

We present the current status update of the Herschel Planetary Nebula Survey Plus project (HerPlaNS+) based on the original General Observer HerPlaNS survey program during the OT1 cycle and the follow-up exhaustive archival search of PN observations using the PACS and SPIRE instruments on-board the Herschel Space Observatory.

We observed two proto-planetary nebulae, HD 56126 representing a source with an elliptical circumstellar shell, and IRAS 16594−4656 representing a source with a bipolar circumstellar shell, with ALMA in the 12CO and 13CO J=3−2 lines and neighboring continuum to see how the morpho-kinematics of CO gas and dust emission properties in their circumstellar environments differ.

The AKARI Far-IR All-Sky Survey (AFASS) maps produced by the AKARI Infrared Astronomical Satellite enabled us to probe the far-IR sky for objects having surface brightnesses greater than a few to a couple of dozen MJy sr−1. Recently, we have verified that, if AFASS-measured fluxes are properly corrected for using the aperture correction method based on the empirical point-spread-function templates derived directly from the AFASS maps, point-source photometry measured from the AFASS maps reproduces fluxes in the AKARI bright source catalogue (BSC). We have surveyed the far-IR sky in the AFASS for Galactic planetary nebulae (PNe) based on the University of Hong Kong/Australian Astronomical Observatory/Strasbourg Observatory Hα Planetary Nebula database (HASHPNDB), preliminarily yielding far-IR fluxes for roughly 1000 Galactic PNe including a few hundreds of PNe not listed in the AKARI/BSC.

This paper presents mass, temperature profile, and the variation of Planck’s function in different regions around asymptotic giant branch (AGB) stars. The physics of the interstellar medium (ISM) is extremely complex because the medium is very inhomogeneous and is made of regions with fairly diverse physical conditions. We studied the dust environment such as flux, temperature, mass, and inclination angle of the cavity structure around C-rich asymptotic giant branch stars in 60 μm and 100 μm wavelengths band using Infrared Astronomical Survey. We observed the data of AGB stars named IRAS 01142+6306 and IRAS 04369+4501. Flexible image transport system image was downloaded from Sky View Observatory; we obtained the surrounding flux density using software Aladin v2.5. The average dust color temperature and mass are found to be 25.08 K, 23.20 K and 4.73 × ;1026 kg (0.00024 M⊙), 2.58 × 1028 kg (0.013 M⊙), respectively. The dust color temperature ranges from 18.76 K ± 3.16 K to 33.21K ± K and 22.84 K ± 0.18 K to 24.48 K ± 0.63 K. The isolated cavity like structure around the AGB stars has an extension of 45.67 pc × 17.02 pc and 42.25 pc × 17.76 pc, respectively. The core region is found to be edge-on having an inclination angle of 79.46° and 73.99°, respectively.

We carried out simultaneous observations of H2O and OH masers, and radio continuum at 1.3 cm with the Karl G. Jansky Very Large Array (VLA) towards 4 water-fountain candidates. Water fountains (WFs) are evolved stars, in the AGB and post-AGB phase, with collimated jets traced by high-velocity H2O masers. Up to now, only 15 sources have been confirmed as WFs through interferometric observations. We are interested in the discovery and study of new WFs. A higher number of these sources is important to understand their properties as a group, because they may represent one of the first manifestations of collimated mass-loss in evolved stars. These observations will provide information about the role of magnetic fields in the launching of jets in WFs. Our aim is to ascertain the WF nature of these candidates, and investigate the spatial distribution of the H2O and OH masers.

We follow up on a previous finding that Miras containing the third dredge-up (3DUP) indicator technetium (Tc) in their atmosphere form a different sequence of K – [22] colour as a function of pulsation period than Miras without Tc. A near-to-mid-infrared colour such as K – [22] is a good probe for the dust mass-loss rate (MLR) of these AGB stars. Contrary to what one might naïvely expect, Tc-poor Miras show redderK – [22] colours (i.e. higher dust MLRs) than Tc-rich Miras at a given period. In the follow-up work, the previous sample is extended and the analysis is expanded towards other colours and ISO dust spectra to check if the previous finding is due to a specific dust feature in the 22 μm band. We also investigate if the same two sequences can be revealed in the gas MLR. Different hypotheses to explain the observation of two sequences in the P vs. K – [22] diagram are discussed and tested, but so far none of them convincingly explains the observations.

The chemistry within the outflow of an AGB star is determined by its elemental C/O abundance ratio. Thanks to the advent of high angular resolution observations, it is clear that most outflows do not have a smooth density distribution, but are inhomogeneous or “clumpy”. We have developed a chemical model that takes into account the effect of a clumpy outflow on its gas-phase chemistry by using a theoretical porosity formalism. The clumpiness of the model increases the inner wind abundances of all so-called unexpected species, i.e. species that are not predicted to be present assuming an initial thermodynamic equilibrium chemistry. By applying the model to the distribution of cyanopolyynes and hydrocarbon radicals within the outflow of IRC+10216, we find that the chemistry traces the underlying density distribution.

To investigate the binary hypothesis in the formation of planetary nebulae, we have been doing long-term photometry and radial velocity (RV) monitoring of bright post-AGB stars which possess bipolar or ellipsoidal nebulae but no indication of a disk in their spectral energy distribution, indicative of a binary companion. RV’s are determined by cross correlating high-resolution spectra with a line mask. Stellar variability and companions both deform the cross correlation function (CCF) and induce periodic variations in the RV. To uniformly quantify the asymmetry of the CCF from a Gaussian, we propose to fit the CCF profile with a Gauss-Hermite series and determine all CCF parameters (RV, skewness, FWHM, and depth) in one single fit. We analyze the correlation and time series of these CCF parameters for V448 Lac and conclude that its RV variability is most likely due to stellar pulsation and not to an orbiting body.

Silicon carbide together with amorphous carbon are the main components of dust grains in the atmospheres of C-rich AGB stars. Small gaseous Si-C bearing molecules (such as SiC, SiCSi, and SiC2) are efficiently formed close to the stellar photosphere. They likely condense onto dust seeds owing to their highly refractory nature at the lower temperatures (i.e., below about 2500 K) in the dust growth zone which extends a few stellar radii from the photosphere. Beyond this region, the abundances of Si-C bearing molecules are expected to decrease until they are eventually reformed in the outer shells of the circumstellar envelope, owing to the interaction between the gas and the interstellar UV radiation field. Our goal is to understand the time-dependent chemical evolution of Si-C bond carriers probed by molecular spectral line emission in the circumstellar envelope of IRC+10216 at millimeter wavelengths.

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.

WD+AGB star systems have been suggested as an alternative way for producing type Ia supernovae (SNe Ia), known as the core-degenerate (CD) scenario. In the CD scenario, SNe Ia are produced at the final phase during the evolution of common-envelope through a merger between a carbon-oxygen (CO) WD and the CO core of an AGB secondary. However, the rates of SNe Ia from this scenario are still uncertain. In this work, I carried out a detailed investigation on the CD scenario based on a binary population synthesis approach. I found that the Galactic rates of SNe Ia from this scenario are not more than 20% of total SNe Ia due to more careful treatment of mass transfer, and that their delay times are in the range of ∼90 − 2500 Myr, mainly contributing to the observed SNe Ia with short and intermediate delay times.

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.