A Fresh Look at AGB Stars in Galactic Open Clusters with Gaia: Impact on Stellar Models and the Initial–Final Mass Relation

Marigo, Paola; Bossini, D.; Trabucchi, Michele; Addari, Francesco; Girardi, L.; Cummings, Jeffrey D.; Pastorelli, Giada; Tio, Piero Dal; Costa, Guglielmo; Bressan, A.

doi:10.3847/1538-4365/ac374a

Cited by 19 publications

(16 citation statements)

References 204 publications

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“…Using the same relation, we can claim that a fraction of the AGB stars that polluted our sample of Ba stars were more massive than the expected 3 M limit, since we found that several WDs have masses around or higher than 0.8 M . This is the case even taking into account the kink that Marigo et al (2020Marigo et al ( , 2022 find for WDs of about 0.70 -0.75 M with carbon AGB progenitors. Most IFMRs (e.g.…”

Section: A Comment On Nucleosynthesis Predictionsmentioning

confidence: 89%

Barium and related stars, and their white-dwarf companions. III. The masses of the white dwarfs

Escorza¹,

Rosa²

2023

Preprint

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Context. Masses are one of the most difficult stellar properties to measure. In the case of the white-dwarf (WD) companions of Barium (Ba) stars, the situation is worse. These stars are dim, cool, and difficult to observe via direct methods. However, Ba stars were polluted by the Asymptotic Giant Branch (AGB) progenitors of these WDs with matter rich in heavy elements, and the properties of their WD companions contain key information about binary interaction processes involving AGB stars and about the slow neutron capture process (s-process) of nucleosynthesis.Aims. With this study, we aim to determine accurate and assumption-free masses for the WD companions of as many Ba stars as possible. We want to provide new observational constraints that can help us learn about the formation and evolution of these postinteraction binary systems and about the nucleosythesis processes that took place in the interiors of their AGB progenitors. Methods. We combined archival radial-velocity data with Hipparcos and Gaia astrometry using the software package orvara, a code designed to simultaneously fit a single Keplerian model to any combination of these types of data using a parallel-tempering Markov chain Monte Carlo method. We adopted Gaussian priors for the Ba star masses and for the parallaxes, and assumed uninformative priors for the orbital elements and the WD masses. Results. We determined new orbital inclinations and companion masses for 60 Ba star systems. These results include a couple of new orbits and several improved orbits for the longest-period systems. Additionally, we unravelled a new triple system that was not known before and constrained the orbits and the masses of the two companions. Conclusions. The WD mass distribution presented in this work is compatible with that of field WDs and with the distributions published before for Ba star companions. A few WD companions have masses higher than 0.8 M , considering 1-σ uncertainties. This indicates that they might come from AGB stars that are more massive than 3 M . These masses are higher than what the abundance ratios on Ba star atmospheres and theoretical models of the s-process of nucleosynthesis seem to expect, raising interesting questions about the formation of these systems.

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Section: A Comment On Nucleosynthesis Predictionsmentioning

confidence: 89%

Barium and related stars, and their white-dwarf companions. III. The masses of the white dwarfs

Escorza¹,

Rosa²

2023

Preprint

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“…1. The faint companion could be a 1.3 M WD, implying an AGB progenitor of a rather high mass, of the order of 6 M (Marigo et al 2022). However, massive AGB stars are not A new exploration of the nucleosynthesis parameter space could add to this discussion.…”

Section: Summary Discussion and Conclusionmentioning

confidence: 99%

A neutron star candidate in the long-period binary 56 UMa

Escorza

Karinkuzhi

Jorissen

et al. 2023

A&A

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Context. 56 UMa is a wide binary system that contains a chemically peculiar red giant and a faint companion. Due to its surface chemical abundances, the red giant was classified as a barium (Ba) star. This implies that the companion has to be a white dwarf, since Ba stars form when mass is transferred to them from an s-process rich Asymptotic Giant Branch (AGB) star. However, in the case of 56 UMa, the companion might be too massive to be the progeny of an AGB star that efficiently produced s-process elements such as barium. Aims. In this Letter, we revisit the orbital parameters of the system and perform a full spectral analysis with the goal of investigating the Ba-star classification of the giant and unravelling the nature of its faint companion. Methods. We combined radial-velocity and astrometric data to refine the orbital parameters of the system, including the orbital inclination and the companion mass. Then, we re-determined the stellar parameters of the giant and its chemical abundances using high-resolution HERMES spectra. Finally, we investigated the morphology of the interstellar gas in the vicinity of the system. Results. The faint component in 56 UMa has a mass of 1.31 ± 0.12 M , which, together with the mixed s+r abundance profile of the red giant, confirms that the giant is not a standard barium star. Additionally, the clear identification of a cavity surrounding 56 UMa could indicate that a supernova explosion occurred about 10 5 years ago in the system, suggesting that the faint companion might be a neutron star. However, finding an evolutionary scenario that explains all the observables is not trivial, so we discuss different possible configurations of the system and their respective merits.

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“…Grady et al 2020). A limited number of Mira variables in clusters also validate the period-age connection although confident assignment of membership has only been possible recently with Gaia data (Grady et al 2019;Marigo et al 2022). Although the period-age relation has been approximately calibrated empirically (Feast & Whitelock 2000b), relatively few theoretical models reproducing the behaviour exist (Wyatt & Cahn 1983;Eggen 1998;Trabucchi & Mowlavi 2022) and the lack of detailed reproduction of the period-luminosity relations of fundamental mode pulsation from theoretical models suggests the period-age relations still have some associated uncertainty and there is a need for accurate data-driven calibrations.…”

Section: Introductionmentioning

confidence: 90%

A kinematic calibration of the O-rich Mira variable period-age relation from Gaia

Zhang¹,

Sanders²

2023

Preprint

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Empirical and theoretical studies have demonstrated that the periods of Mira variable stars are related to their ages. This, together with their brightness in the infrared, makes them powerful probes of the formation and evolution of highly-extincted or distant parts of the Local Group.Here we utilise the Gaia DR3 catalogue of long-period variable candidates to calibrate the period-age relation of the Mira variables. Dynamical models are fitted to the O-rich Mira variable population across the extended solar neighbourhood and then the resulting solar neighbourhood period-kinematic relations are compared to external calibrations of the agekinematic relations to derive a Mira variable period-age relation of 𝜏 ≈ (6.9 ± 0.3) Gyr(1 + tanh((330 d − 𝑃)/(400 ± 90)d). Our results compare well with previous calibrations using smaller datasets as well as the period-age properties of Local Group cluster members. This calibration opens the possibility of accurately characterising the star formation and the impact of different evolutionary processes throughout the Local Group.

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A Fresh Look at AGB Stars in Galactic Open Clusters with Gaia: Impact on Stellar Models and the Initial–Final Mass Relation

Cited by 19 publications

References 204 publications

Barium and related stars, and their white-dwarf companions. III. The masses of the white dwarfs

Barium and related stars, and their white-dwarf companions. III. The masses of the white dwarfs

A neutron star candidate in the long-period binary 56 UMa

A kinematic calibration of the O-rich Mira variable period-age relation from Gaia

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