arXiv subjects

P. Ventura

Publications and source records attributed to P. Ventura.

At least 19 recordsLinked to original sources

arXiv2026

Globular Clusters in the Time of the JWST. I. Survey Design and First Results on Multiple Populations and Beyond

Globular clusters (GCs) host multiple stellar populations with distinct chemical compositions, but their properties among very low-mass stars remain poorly constrained. The James Webb Space Telescope (JWST) enables precise infrared studies that are highly sensitive to abundance variations in cool stars. We initiate a homogeneous survey of Galactic GCs, based primarily on deep JWST GO-8960 observations and complemented by archival JWST and Hubble Space Telescope data, to characterize multiple populations across a wide range of cluster properties. In this first paper, we present the survey and initial NIRCam results. We analyze eleven GCs, deriving high-precision photometry and astrometry to measure proper motions. Multiple populations are detected among low-mass stars in all clusters, with diverse behaviors. We find discrete main sequences in NGC 288, NGC 6723, and NGC 2808, and more continuous distributions in NGC 104 and the Type II clusters NGC 1851 and NGC 6656. The bulge clusters NGC 6528, NGC 6553, and NGC 6440 show patterns consistent with varying helium and oxygen abundances that do not scale simply with cluster mass. In Terzan 5 and Liller 1, we identify populations spanning different ages and helium variations within the old population of Terzan 5. We also detect an M-dwarf gap in NGC 104 around 0.35 solar masses, consistent with the Jao Gap of field stars and open clusters. This work establishes the foundation for a homogeneous JWST survey of Galactic GCs and provides a valuable dataset for studies of cluster evolution, Galactic stellar populations, and background extragalactic sources.

astro-ph.GA↗

arXiv2026

A deep HST view of the open cluster NGC2158: binaries, mass functions, and M-dwarf discontinuity

A significant fraction of stars in both the Galactic field and stellar clusters are members of binary systems. Understanding their properties is therefore essential for a comprehensive view of stellar structure, evolution, and cluster dynamics. Despite extensive studies of cluster binaries, key issues remain unresolved, particularly for photometric binaries among low-mass stars. While the binary fraction in the field strongly depends on stellar mass, cluster studies have generally suggested an approximately constant fraction over the limited mass ranges explored. In addition, the mass function (MF) of very low-mass stars is still poorly constrained in clusters older than a few hundred Myr. We use deep Hubble Space Telescope imaging of the intermediate-age open cluster NGC 2158 to investigate its binary population and derive the luminosity and MFs down to ~0.14 solar masses, enabling the first detailed analysis of binaries in this cluster. We measure a global binary fraction of 38%, consistent with other open clusters, and find a clear mass dependence: it decreases from ~52% at 1.0 solar masses to ~11% at 0.2 solar masses. This trend mirrors that of Galactic field stars, suggesting similar binary properties. The MF is characterized by three regimes: high-mass stars (alpha= -2.49 +- 0.19), low-mass stars (alpha= -1.11 +- 0.09), and very low-mass stars (alpha= -0.08 +- 0.07). The slope change near 1.0 solar mass agrees with recent surveys, though we find a deficit below ~0.3 solar masses. We also detect a main-sequence discontinuity around ~0.3 solar masses, possibly linked to the 3He-driven instability predicted by stellar models and analogous to the Jao Gap seen in nearby field stars.

astro-ph.SR↗

arXiv2026

Noble gases Neon and argon: a role for the chemical patterns of multiple populations in globular clusters?

We focus on the sodium destruction in models reaching the high hot bottom burning temperatures needed to efficiently cycle oxygen to nitrogen in AGB models at the nominal [Fe/H] of the cluster NGC 2808. We increase the initial neon abundance by a factor 2-4 with respect to the "standard" abundances obtained by scaling the solar values down to the metallicity of this cluster, and explore the average abundances in the ejecta obtained by adopting smaller mass-loss rates. Higher neon produces higher sodium in the AGB envelope. Lowering the mass-loss rate allows both to keep reasonably large sodium abundances and to increase the depletion of oxygen and magnesium. A balance between the lower mass-loss rates and the necessity of not increasing too much the episodes of third dredge up gives a neon abundance larger by a factor two and a mass-loss rate smaller by a factor four as best compromise. Comparison with the abundances in NGC 2808 shows a better agreement than the standard models for all the patterns of abundances, but the extreme stars (group E) requires models slightly less rich in iron. t Thus, we propose that the extreme population in NGC 2808 is composed of stars having a slightly smaller metallicity, and sketch a possible scenario for its formation, in the framework of the hierarchical clusters assembly scenario. Abundances of potassium are larger by $\sim 0.2 dex$ in the E group, but the explanation in terms of burning of the initial argon requires a drastic increase of the relevant cross section. The abundances of neon and argon at low metallicities may be an important tool to better reproduce the abundances of light elements in the framework of the AGB model for globular clusters.

astro-ph.SR↗

arXiv2026

MgAl burning chain in M 54: the globular cluster-like properties of a nuclear star cluster

In this study, we present the chemical abundances of Fe, Mg, Al, Si, and K for a sample of 233 likely member stars of M 54. All the stars were observed with the FLAMES high-resolution multi-object spectrograph mounted at the VLT. Our analysis confirmed the presence of a large metallicity range in M 54, with the majority of the stars having -1.8 < [Fe/H] < -1.0 dex and few stars with [Fe/H] > -1.0 dex. The mean value of the total sample is [Fe/H] = -1.40 (σ = 0.22 dex). A Markov Chain Monte Carlo analysis revealed that the observed spread in [Fe/H] is compatible with a non-null intrinsic iron dispersion. We also found that the metallicity distribution function and the broadening of the red giant branch of M 54 are not compatible with a single age, but instead they suggest a wide age range from ~ 13 Gyr to ~ 1 - 2 Gyr or a smaller age range if a significant He enhancement (Y ~ 0.35/0.40) is present in the most metal-rich stars. We identified among the stars in M 54 the entire pattern of anticorrelations linked to the MgAl burning cycle. In particular, the metal-rich component displays a higher level of H-burning with the presence of more extended anticorrelations than the metal-poor component. No Mg-poor ([Mg/Fe]<0.0 dex) stars are identified in M 54. The evidence collected so far cannot be explained neither with a globular cluster-like scenario nor with a galactic chemical evolution. The chemical properties of M 54 can be explained within a scenario where this system formed through the merging of two globular clusters, the metal-poor one with standard characteristics and the more metal-rich one with more pronounced chemical anomalies, a possibly younger than the first one. M 54 is confirmed as a key stellar system for explaining the chemical evolution of a nuclear star cluster.

astro-ph.SR↗

arXiv2026

An analysis of the J-method from the perspective of the AGB evolution

The JAGB method has been proposed as a distance indicator for Local Group galaxies. We investigate the populations of the J region in the (J-K,J) colour-magnitude plane of the Large and Small Magellanic Clouds (LMC and SMC), aiming to distinguish general features of the J luminosity function (JLF) from those sensitive to the stellar population of each galaxy. Using a population synthesis approach based on stellar evolution and dust formation modelling, we predict the distribution of stars within the J region and compare it with observations. Stars in this region are identified as recently formed C-stars that have not yet accumulated large amounts of carbon. Typically, 2--3 $M_\odot$ stars remain longer in the J region, while lower-mass stars evolve faster. The JLF of the LMC, peaked at the expected magnitudes for these stars, confirms this picture. In the SMC, the J flux distribution is shifted to higher magnitudes, indicating an older population with lower-mass progenitors.

astro-ph.GA↗

arXiv2025

The stellar to sub-stellar masses transition in 47 Tuc

Context: The study of the Globular Cluster 47 Tuc offers the opportunity to shed new light on the debated issue on the presence of multiple populations in Globular Clusters, as recent results from HST photometry and high-resolution spectroscopy outlined star-to-star differences in the surface chemical composition. Aims: The goal of the present investigation is the interpretation of recent JWST data of the low main sequence of 47 Tuc, in order to explore the stellar to sub-stellar transition, to derive the mass distribution of the individual sources and to disentangle stars from different populations. Methods: Stellar evolution modelling of low-mass stars of metallicity [Fe/H]=-0.78 and oxygen content [O/Fe]=+0.4 and [O/Fe]=0 is used to simulate the evolution of the first and the second generation of the cluster. The comparison between the calculated sequences with the data points is used to characterize the individual objects, to split the different stellar components and to infer the current mass function of the cluster. Results: The first generation of 47 Tuc harbours 45 % of the overall population of the cluster, the remaining 55 % making up the second generation. The transition from the stellar to the sub-stellar domain is found at $0.074 M_{\odot}$ and $0.07 M_{\odot}$ for the first and second generations, respectively. The mass function of both the stellar generations are consistent with a Kroupa-like profile down to $0.22 M_\odot$.

astro-ph.SR↗

arXiv2025

Dating N loud AGNs at high redshift: GS3073 as a snapshot of wCen like evolution of a nuclear star cluster

In this paper we address two major questions raised by recent James Webb Space Telescope observations of the young Universe, namely: 1) what are the seed initial masses, and how rapidly have supermassive black holes (BHs) with masses of 1e6-1e8Msun grown in active galactic nuclei (AGN) hosted by very young galaxies? 2) What are the plausible explanations for the super solar abundances of nitrogen in a fraction of young galaxies at high redshift, both with and without evidence of a massive central black hole? We focus mainly on the system GS3073. This system shows an exceptionally large log(N/O)=+0.42(+0.13/-0.10) in the gas close to the AGN. We show here that this abundance is consistent with the composition of gas ejected from massive asymptotic giant branch stars. Moreover, this system shows chemical properties matching those expected at a specific point of the evolution of the abundances in the extreme populations of the former nuclear star cluster wCentauri (wCen). This analogy, along with the N/O, C/O and Fe/O abundances in GS3073, lead to an estimate of an age range of 270-440 Myr for this object, much smaller than the redshift (z=5.5) age of about 1 Gyr. We also adopt the same criteria to estimate an age for GNz11. These two determinations constrain the BH mass versus age relation: accretion on the BH must proceed at intermittent superEddington rates in the first phases, and at a much lower rate after the first half gigayear of life of the Universe. The intermittency of accretion is also a fundamental requirement to allow the formation of the extreme (N rich, O depleted, He rich) populations today observed in wCen for a large range of metallicities.

astro-ph.CO↗

arXiv2025

A JWST project on 47 Tucanae. Binaries among multiple populations

Almost all globular clusters (GCs) contain multiple populations consisting of stars with varying helium and light-element abundances. These populations include first-population stars, which exhibit similar chemical compositions to halo-field stars with comparable [Fe/H], and second-population stars, characterized by enhanced He and N abundances along with reduced levels of O and C. Nowadays, one of the most intriguing open questions about GCs pertains to the formation and evolution of their multiple populations. Recent works based on N-body simulations of GCs show that the fractions and characteristics of binary stars can serve as dynamic indicators of the formation period of multiple-population in GCs and their subsequent dynamical evolution. Nevertheless, the incidence of binaries among multiple populations is still poorly studied. Moreover, the few available observational studies are focused only on the bright stars of a few GCs. In this work, we use deep images of the GC 47 Tucanae collected with the JWST and HST to investigate the incidence of binaries among multiple populations of M-dwarfs and bright main-sequence stars. To reach this objective, we use UV, optical, and near infrared filters to construct photometric diagrams that allow us to disentangle binary systems and multiple populations. Moreover, we compared these observations with a large sample of simulated binaries. In the cluster central regions, the incidence of binaries among first-population stars is only slightly higher than that of second-population stars. In contrast, in the external regions, the majority (>85%) of the studied binaries are composed of first population stars. Results are consistent with the GC formation scenarios where the second-population stars originate in the cluster's central region, forming a compact and dense stellar group within a more extended system of first-population stars

astro-ph.SR↗

arXiv2025

Mass loss along the red giant branch of the intermediate stellar populations in NGC6752 and NGC2808

The morphology of the Horizontal Branch (HB) in Globular Clusters (GC) is among the early evidences that they contain multiple populations of stars. Indeed, the location of each star along the HB depends both on its initial helium content (Y) and on the global average mass loss along the red giant branch ($μ$). In most GCs, it is generally straightforward to analyse the first stellar population (standard Y), and the most extreme one (largest Y), while it is more tricky to look at the "intermediate" populations (mildly enhanced Y). In this work, we do this for the GCs NGC6752 and NGC2808; wherever possible the helium abundance for each stellar populations is constrained by using independent measurements present in the literature. We compare population synthesis models with photometric catalogues from the Hubble Space Telescope Treasury survey to derive the parameters of these HB stars. We find that the location of helium enriched stars on the HB is reproduced only by adopting a higher value of $μ$ with respect to the first generation stars in all the analysed stellar populations. We also find that $μ$ correlates with the helium enhancement of the populations. This holds for both clusters. This finding is naturally predicted by the model of ''pre-main sequence disc early loss'', previously suggested in the literature, and is consistent with the findings of multiple-populations formation models that foresee the formation of second generation stars in a cooling flow.

astro-ph.SR↗

arXiv2025

Planetary Nebulae of the Large Magellanic Cloud II: the connection with the progenitors' properties

The study of planetary nebulae (PNe) offers the opportunity of evaluating the efficiency of the dust production mechanism during the very late asymptotic giant branch (AGB) phases. We study the relationship between the properties of PNe, particularly the gas and dust content, with the mass and metallicity of the progenitor stars, to understand how dust production works in the late AGB phases, and to shed new light on the physical processes occurring to the stars and the material in their surroundings since the departure from the AGB until the PN phase. We consider a sample of 9 PNe in the Large Magellanic Cloud, 7 out of which characterized by the presence of carbonaceous dust, the remaining 2 with silicates. For these stars the masses and the metallicity of the progenitor stars were estimated. We combine results from stellar evolution and dust formation modelling with those coming from the analysis of the spectral energy distribution, to find the relation between the dust and gas mass of the PNe considered and the The physical properties of carbon-rich PNe are influenced by the mass of the progenitor star. Specifically, the dust-to-gas ratio in the nebula increases from 5x10^{-4}to 6x10^{-3} as the progenitor star's mass increases from approximately 0.9Msun to 2Msun. This change is partly influenced by the effective temperature of the PNe, and it occurs because higher-mass carbon stars are more efficient at producing dust. Consequently, as the progenitor's mass increases, the gas mass of the PNe decreases, since the larger amounts of dust lead to greater effects from radiation pressure, which pushes the gas outwards. No meaningful conclusions can be drawn by the study of the PNe with silicate-type dust, because the sub-sample is made up of 2 PNe only, one of which is almost dust-free.

astro-ph.SR↗

arXiv2024

Hubble Space Telescope survey of Magellanic Cloud star clusters. Binaries among the split main sequences of NGC 1818, NGC 1850, and NGC 2164

Nearly all star clusters younger than ~600 Myr exhibit extended main sequence turn offs and split main sequences (MSs) in their color-magnitude diagrams. Works based on both photometry and spectroscopy have firmly demonstrated that the red MS is composed of fast-rotating stars, whereas blue MS stars are slow rotators. Nevertheless, the mechanism responsible for the formation of stellar populations with varying rotation rates remains a topic of debate. Potential mechanisms proposed for the split MS include binary interactions, early evolution of pre-main sequence stars, and the merging of binary systems, but a general consensus has yet to be reached. These formation scenarios predict different fractions of binaries among blue- and red-MS stars. Therefore, studying the binary populations can provide valuable constraints that may help clarify the origins of the split MSs. We use high-precision photometry from the Hubble Space Telescope (HST) to study the binaries of three young Magellanic star clusters exhibiting split MS, namely NGC 1818, NGC 1850, and NGC 2164. By analyzing the photometry in the F225W, F275W, F336W, and F814W filters for observed binaries and comparing it to a large sample of simulated binaries, we determine the fractions of binaries within the red and the blue MS. We find that the fractions of binaries among the blue MS are higher than those of red-MS stars by a factor of ~1.5, 4.6, and ~1.9 for NGC 1818, NGC 1850, and NGC 2164, respectively. We discuss these results in the context of the formation scenarios of the split MS.

astro-ph.SR↗

arXiv2023

GN-z11: witnessing the formation of second generation stars and an accreting massive black hole in a massive star cluster

We explore the possibility that the N-rich young proto-galaxy GN-z11 recently observed at z=10.6 by the James Webb Space Telescope is the result of the formation of second generation stars from pristine gas and Asymptotic Giant Branch (AGB) ejecta in a massive globular cluster or nuclear star cluster. We show that a second generation forming out of gas polluted by the ejecta of massive AGB stars and mixed with gas having a standard composition accounts for the unusually large N/O in the GN-z11 spectrum. The timing of the evolution of massive (4-7.5M$_{\odot}$) AGBs also provides a favourable environment for the growth of a central stellar mass black hole to the Active Galactic Nucleus stage observed in GN-z11. According to our model the progenitor system was born at an age of the Universe of $\simeq 260 - 380$Myr, well within the pre-reionization epoch.

astro-ph.SR↗

arXiv2023

Dust from evolved stars: a pilot analysis of the AGB to PN transition

We present a novel approach to address dust production by low- and intermediate-mass stars. We study the asymptotic giant branch (AGB) phase, during which the formation of dust takes place, from the perspective of post-AGB and planetary nebula (PN) evolutionary stage. Using results from stellar evolution and dust formation modelling, we interpret the spectral energy distribution of carbon-dust-rich sources currently evolving through different evolutionary phases, believed to descend from progenitors of similar mass and chemical composition. Comparing the results of different stages along the AGB to PNe transition, we can provide distinct insights on the amount of dust and gas released during the very late AGB phases. While the post-AGB traces the history of dust production back to the tip of the AGB phase, investigating the PNe is important to reconstruct the mass-loss process experienced after the last thermal pulse. The dust surrounding the post-AGB was formed soon after the tip of the AGB. The PNe dust-to-gas ratio is $\sim10^{-3}$, 2.5 times smaller than what expected for the same initial mass star during the last AGB interpulse, possibly suggesting that dust might be destroyed during the PN phase. Measuring the amount of dust present in the nebula can constrains the capacity of the dust to survive the central star heating.

astro-ph.SR↗

arXiv2023

A deep dive into the Type II Globular Cluster NGC 1851

About one-fifth of the Galactic globular clusters (GCs), dubbed Type II GCs, host distinct stellar populations with different heavy elements abundances. NGC 1851 is one of the most studied Type II GCs, surrounded by several controversies regarding the spatial distribution of its populations and the presence of star-to-star [Fe/H], C+N+O, and age differences. This paper provides a detailed characterization of its stellar populations through Hubble Space Telescope (HST), ground-based, and Gaia photometry. We identified two distinct populations with different abundances of s-process elements along the red-giant branch (RGB) and the sub-giant branch (SGB) and detected two sub-populations among both s-poor (canonical) and s-rich (anomalous) stars. To constrain the chemical composition of these stellar populations, we compared observed and simulated colors of stars with different abundances of He, C, N, and O. It results that the anomalous population has a higher CNO overall abundance compared to the canonical population and that both host stars with different light-element abundances. No significant differences in radial segregation between canonical and anomalous stars are detected, while we find that among their sub-populations, the two most chemical extremes are more centrally concentrated. Anomalous and canonical stars show different 2D spatial distributions outside ~3 arcmin, with the latter developing an elliptical shape and a stellar overdensity in the northeast direction. We confirm the presence of a stellar halo up to ~80 arcmin with Gaia photometry, tagging 14 and five of its stars as canonical and anomalous, respectively, finding a lack of the latter in the south/southeast field.

astro-ph.GA↗

arXiv2023

Hubble Space Telescope survey of Magellanic Cloud star clusters. UV-dim stars in young clusters

Young and intermediate-age star clusters of both Magellanic Clouds exhibit complex color-magnitude diagrams. In addition to the extended main-sequence turn-offs (eMSTOs), commonly observed in star clusters younger than ~2 Gyr, the clusters younger than ~800 Myr exhibit split main sequences (MSs). These comprise a blue MS, composed of stars with low-rotation rates, and a red MS, which hosts fast-rotating stars. While it is widely accepted that stellar populations with different rotation rates are responsible for the eMSTOs and split MSs, their formation and evolution are still debated. A recent investigation of the ~1.7 Gyr old cluster NGC1783 detected a group of eMSTO stars extremely dim in UV bands. Here, we use multi-band Hubble Space Telescope photometry to investigate five star clusters younger than ~200 Myr, including NGC1805, NGC1818, NGC1850, and NGC2164 in the Large Magellanic Cloud, and the Small-Magellanic Cloud cluster NGC330. We discover a group of bright MS stars in each cluster that are significantly dim in the F225W and F275W bands, similar to what is observed in NGC1783. Our result suggests that UV-dim stars are common in young clusters. The evidence that most of them populate the blue MS indicates that they are slow rotators. As a byproduct, we show that the star clusters NGC1850 and BHRT5b exhibit different proper motions, thus corroborating the evidence that they are not gravitationally bound.

astro-ph.SR↗

arXiv2023

An insight into Capella (alpha Aurigae): from the extent of core overshoot to its evolutionary history

The binary star alpha Aurigae (otherwise known as Capella) is extremely important to understand the core hydrogen and helium burning phases of the stars, as the primary star is likely evolving through the core helium burning phase, and the masses of the two components are 2.5 Msun and 2.6 Msun, which fall into a mass range for which the extention of the core overshoot during the main sequence phase is uncertain. We aim at deriving the extent of the core overshoot experienced during the core burning phases and testing the efficiency of the convective transport of energy in the external envelope, by comparing results from stellar evolution modelling with the results from the observations. We consider evolutionary tracks calculated on purpose for the present work, for the primary and secondary star of Capella. We determine the extent of the extra-mixing from the core during the main sequence evolution and the age of the system, by requiring that the effective temperatures and surface gravities of the model stars reproduce those derived from the observations at the same epoch. We further check consistency between the observed and predicted surface chemistry of the stars. Consistency between results from stellar evolution modelling and the observations of Capella is found when extra-mixing from the core is assumed, the extent of the extra-mixed zone being of the order of 0.25 H_P. The age of the system is estimated to be 710 Myr. These results allow to nicely reproduce the observed surface chemistry, particularly the recent determination of the 12C/13C ratio based on LBT (Large Binocular Telescope) and VATT (Vatican Advanced Technology Telescope) observations

astro-ph.SR↗

arXiv2023

On the role of dust and mass loss in the extended main sequence turnoff of star clusters: the case of NGC 1783

The Color Magnitude Diagram (CMD) morphology of the "extended" main sequence turnoff (eMSTO) and upper main sequence (MS) of the intermediate age ($\lesssim 2$ Gyr) Large Magellanic Cloud Cluster NGC 1783 shows the presence of a small group of UV-dim stars, that, in the ultraviolet Hubble Space Telescope filters, are located at colors on the red side of the typical "fan" shape displayed by the eMSTO. We model the UV-dim stars by assuming that some of the stars which would intrinsically be located on the left side of the eMSTO are obscured by a ring of dust due to grain condensation at the periphery of the excretion disc expelled when they spin at the high rotation rates typical of stars in the Be stage. A reasonably low optical depth at 10$μ$ is necessary to model the UV-dim group. Introduction of dust in the interpretation of the eMSTO may require a substantial re-evaluation of previous conclusions concerning the role of age and/or rotation spreads in the MC clusters: the entire eMSTO can be populated by dusty stars, and the reddest UV-dim stars simply represents the tail of the distribution with both maximum obscuration and the dust ring seen along the line of sight. The model stars having higher rotational projected velocity ($v \sin$ i) are predicted to be preferentially redder than the slowly-rotating stars. The mass loss responsible for the dust may also cause the non-monotonic distribution of stars in the upper main sequence, with two peaks and gaps showing up in the UV CMD.

astro-ph.SR↗

arXiv2023

The intense production of silicates during the final AGB phases of intermediate mass stars

The formation of silicates in circumstellar envelopes of stars evolving through the AGB is still debated given the uncertainties affecting stellar evolution modelling, the description of the dust formation process, and the capability of silicate grains to accelerate stellar outflows via radiation pressure. We study the formation of dust in the winds of intermediate mass (M $\geq 4 M_{\odot}$) stars of solar metallicity while evolving through the AGB phase. We tested the different treatments of the mass-loss mechanism by this class of stars, with the aim of assessing their contribution to the general enrichment of silicates of the interstellar medium of galaxies. We consider a sub-sample of AGB stars, whose SED is characterised by deep absorption features at $10$ and $18μ$m, which can be regarded as the class of stars providing the most relevant contribution to the silicates' production across the Universe. Results from stellar evolution and dust formation modelling were used to fit the observed SED and to reproduce, at the same time, the detected pulsation periods and the derived surface chemical composition. This analysis leads to the derivation of tight constraints on the silicates' production rates experienced by these sources during the final AGB stages. Two out of the four sources investigated are interpreted as stars currently undergoing HBB, evolving through phases close to the stage when the mass-loss rate is largest. The remaining two stars are likely evolving through the very final AGB phases, after HBB was turned off by the gradual consumption of the convective mantle. Mass-loss rates of the order of $1-2\times 10^{-4} M_{\odot}/$yr are required when looking for consistency with the observational evidence. These results indicate the need for a revision of the silicate yields by intermediate mass stars, which are found to be $\sim 3$ times higher than previously determined.

astro-ph.SR↗