A deep insight into the Mg-Al-Si nucleosynthesis in massive asymptotic giant branch and super-asymptotic giant branch stars

Ventura, P.; Carini, R.; D’Antona, F.

doi:10.1111/j.1365-2966.2011.18997.x

Cited by 70 publications

(94 citation statements)

References 36 publications

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“…According to Ventura et al (2011), AGB stars with ∼6 M produce the most extreme Mg-Al-Si nucleosynthesis. If such a star was once a binary companion to our presumably old and low-mass field star, the system would have an unusual mass ratio.…”

Section: Discussionmentioning

confidence: 99%

TheGaia-ESO Survey: A globular cluster escapee in the Galactic halo

Lind

Koposov

Battistini

et al. 2015

A&A

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A small fraction of the halo field is made up of stars that share the light element (Z ≤ 13) anomalies characteristic of second generation globular cluster (GC) stars. The ejected stars shed light on the formation of the Galactic halo by tracing the dynamical history of the clusters, which are believed to have once been more massive. Some of these ejected stars are expected to show strong Al enhancement at the expense of shortage of Mg, but until now no such star has been found. We search for outliers in the Mg and Al abundances of the few hundreds of halo field stars observed in the first eighteen months of the Gaia-ESO public spectroscopic survey. One halo star at the base of the red giant branch, here referred to as 22593757-4648029 is found to have [Mg/Fe] = −0.36 ± 0.04 and [Al/Fe] = 0.99 ± 0.08, which is compatible with the most extreme ratios detected in GCs so far. We compare the orbit of 22593757-4648029 to GCs of similar metallicity and find it unlikely that this star has been tidally stripped with low ejection velocity from any of the clusters. However, both chemical and kinematic arguments render it plausible that the star has been ejected at high velocity from the anomalous GC ω Centauri within the last few billion years. We cannot rule out other progenitor GCs, because some may have disrupted fully, and the abundance and orbital data are inadequate for many of those that are still intact.

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Section: Discussionmentioning

confidence: 99%

TheGaia-ESO Survey: A globular cluster escapee in the Galactic halo

Lind

Koposov

Battistini

et al. 2015

A&A

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“…A possible scenario producing very extreme Mg-Al-N nucleosynthesis could be an association with an intermediatemass (∼3-6M e ) AGB star (see Ventura et al 2011;Schiavon et al 2016) in a binary companion. A future work will be dedicated to investigating in more detail other mechanisms, including binary stellar mergers or pollution of the ISM by a previous generation of massive stars.…”

Section: Possible Originsmentioning

confidence: 99%

Discovery of a Metal-Poor Field Giant With a Globular Cluster Second-Generation Abundance Pattern

Fernández-Trincado

Robin

Moreno

et al. 2016

ApJ

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We report on the detection, from observations obtained with the Apache Point Observatory Galactic Evolution Experiment spectroscopic survey, of a metal-poor ([Fe/H]=−1.3 dex) field giant star with an extreme Mg-Al abundance ratio ([Mg/Fe]=−0.31 dex; [Al/Fe]=1.49 dex). Such low Mg/Al ratios are seen only among the second-generation population of globular clusters (GCs) and are not present among Galactic disk field stars. The light-element abundances of this star, 2M16011638-1201525, suggest that it could have been born in a GC. We explore several origin scenarios, studying the orbit of the star in particular to check the probability of its being kinematically related to known GCs. We performed simple orbital integrations assuming the estimated distance of 2M16011638-1201525 and the available six-dimensional phase-space coordinates of 63 GCs, looking for close encounters in the past with a minimum distance approach within the tidal radius of each cluster. We found a very low probability that 2M16011638-1201525 was ejected from most GCs; however, we note that the best progenitor candidate to host this star is GC ω Centauri (NGC 5139). Our dynamical investigation demonstrates that 2M16011638-1201525 reaches a distance < Z 3 kpc max | | from the Galactic plane and minimum and maximum approaches to the Galactic center of R min <0.62 kpc and R max <7.26 kpc in an eccentric (e ∼ 0.53) and retrograde orbit. Since the extreme chemical anomaly of 2M16011638-1201525 has also been observed in halo field stars, this object could also be considered a halo contaminant, likely to have been ejected into the Milky Way disk from the halo. We conclude that 2M16011638-20152 is also kinematically consistent with the disk but chemically consistent with halo field stars.

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“…The synthesis of silicon is possible through the capture of protons by heavier nuclei in the hot layers of the convective envelope in massive AGB stars with initial masses higher than 4 M ⊙ . A description of this so-called "hot bottom burning" (HBB) and the necessary references are available in Ventura et al (2011) devoted to the synthesis of Mg, Al, and Si through HBB.…”

Section: Figure 2 Profiles Of Selected Lines In the Optical Spectrummentioning

confidence: 99%

Peculiarities of the atmosphere and envelope of a post-AGB star, the optical counterpart of IRAS 23304+6347

2015

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Based on high-spectral resolution observations performed with the echelle spectrograph NES of the 6-meter telescope, we have studied the peculiarities of the spectrum and the velocity field in the atmosphere and envelope of the optical counterpart of the infrared source IRAS 23304+6347. We have concluded about the absence of significant variations in the radial velocity Vr inferred from atmospheric absorptions and about its coincidence with the systemic velocity deduced from radio data. The envelope expansion velocity Vexp = 15.5 km/s has been determined from the positions of rotational band lines of the C 2 Swan (0; 0) band. A complex emission-absorption profile of the Swan (0; 1) 5635Å has been recorded. Analysis of the multicomponent NaI D doublet line profile has revealed interstellar components V(IS) = −61.6 and −13.2 km/s as well as a circumstellar component with V(CS) =−41.0 km/s whose position corresponds to the velocity inferred from C 2 features. The presence of the interstellar component with Vr =−61.6 km/s in the spectrum allows d = 2.5 kpc to be considered as a lower limit for the distance to the star. A splitting of the profiles for strong absorptions of ionized metals (YII, BaII, LaII, SiII) attributable to the presence of a short-wavelength component originating in the circumstellar envelope has been detected in the optical spectrum of IRAS 23304+6347 for the first time.

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A deep insight into the Mg-Al-Si nucleosynthesis in massive asymptotic giant branch and super-asymptotic giant branch stars

Cited by 70 publications

References 36 publications

TheGaia-ESO Survey: A globular cluster escapee in the Galactic halo

TheGaia-ESO Survey: A globular cluster escapee in the Galactic halo

Discovery of a Metal-Poor Field Giant With a Globular Cluster Second-Generation Abundance Pattern

Peculiarities of the atmosphere and envelope of a post-AGB star, the optical counterpart of IRAS 23304+6347

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