I will present results from our recent work on collecting and analysing multiwavelength light curves for targets from the Nearby Evolved Stars Survey ([NESS][1]; [Scicluna et al. 2022][2]). The NESS collaboration is studying $\approx$800 asymptotic giant branch (AGB) and red supergiant (RSG) stars in the Solar Neighbourhood (d $\lesssim$ 3 kpc) in order to obtain a robust understanding of the...
Till date, period-luminosity relations of Galactic Miras are scarce in the literature because their distances were poorly known. This has changed with the advent of Gaia parallaxes. A further limitation is the lack of multi-epoch IR photometry for significant samples of Miras; single-epoch 2MASS photometry results in large scatter because of the stars' large amplitude variability. We combined...
Red giants and supergiants lose substantial fraction of their mass during their evolution and thus significantly contribute to the chemical enrichment of the interstellar medium. While the dust-driven wind coupled with pulsations can mostly explain the observed mass-loss rates of red giants on the asymptotic giant branch, this is not the case for red supergiants.
We obtained several epochs...
The conditions in Mira variable atmospheres make them wonderful laboratories to study a variety of stellar physics such as molecule+grain formation, dust production, shock chemistry, stellar winds, mass-loss, opacity driven pulsation, and shocks.
We are currently curating a Reference Set of 106 Mira variables based upon over a decade of synoptic observations made with the Palomar Testbed...
Carbon stars are crucial dust producers in the Universe.
These Asymptotic Giant Branch (AGB) stars play a significant role in the creation of a considerable portion of the molecules observed in the Interstellar Medium (ISM), contributing to the interstellar reddening not only within our Galaxy but also in other galaxies.
Despite their importance, a self-consistent estimation of the...
Asymptotic Giant Branch (AGB) undergo complex dynamics, including convection, pulsation and shockwaves. These processes trigger strong stellar winds, enriching the interstellar medium with various elements, and impact astronomical measurements, amplifying uncertainties in the determination of fundamental stellar parameters. Gaia Data Release 3 provides the parallax for about 2 million variable...
AGB stars play a pivotal role in understanding galactic populations, producing essential elements such as carbon, oxygen, and nitrogen. Despite their significance, unresolved questions persist regarding their evolution, including the transition from oxygen-rich to carbon-rich states and the impact of mass loss. The recent release of Gaia DR3 presents a remarkable opportunity to expand the...
The Galactic content in s-process neutron-capture elements is still poorly known and the chemical evolution of these species are frequently debated.
Fortunately, thanks to Gaia/GSP-spec cerium and neodynium abundances at the surface of thousands stars, the chemical content of the Galaxy in these two second peak s-elements has been recently explored.
This has been complemented by lead...
The technetium-rich (Tc-rich) M stars reported in the literature (Little-Marenin & Little 1979; Uttenthaler et al. 2013; Shetye et al. 2022) are puzzling objects since no isotope of technetium has a half-life longer than a few million years. Hence, 99Tc, the longest-lived isotope along the s-process path, is expected to be detected only in thermally-pulsing stars enriched with other s-process...
Stellar convection plays an important role in many astrophysical processes, including energy transport, pulsation, dynamos and winds on evolved stars. A direct characterization of convective structures in terms of size, contrast, and life-span is quite challenging because stars are still pretty far and convective patterns are small.
Most of our knowledge about stellar convection comes from...
It is believed that stellar mass loss increases as a star evolves along the AGB, and that it is higher the more massive the star is. However, there is little evidence that supports these beliefs. In addition, it has been proposed, but not firmly established, that the MLR characteristics on the AGB are frequently (strongly) affected by the presence of a nearby companion. These are troublesome...
Mass-loss from asymptotic giant branch and red supergiant stars drive
local galactic chemical evolution, but one of the main uncertainties
in quantifying this process is the spatial and temporal variations in
mass-loss across the evolved star population. A large sample of
sources is needed to recover the statistical mass-loss rate, and
variation thereof, as a function of observable...
Severe mass-loss is the reason behind the ending of the asymptotic giant branch (AGB) stellar evolutionary stage, this phase having a high importance for the recycling of heavy elements within the interstellar medium. A very intricate process, many clues regarding the formation and evolution of AGB winds are still hidden in the close and extended environments of AGB stars. Believed to form...
