scholarly journals A high-resolution spectroscopic study of two new Na- and Al-rich field giants–likely globular cluster escapees in the Galactic halo

2020 ◽  
Vol 494 (1) ◽  
pp. 36-43
Author(s):  
Avrajit Bandyopadhyay ◽  
Sivarani Thirupathi ◽  
Timothy C Beers ◽  
A Susmitha
Keyword(s):  
High Resolution ◽  
Spectroscopic Study ◽  
Globular Cluster ◽  
Galactic Halo ◽  
Light Element ◽  
Echelle Spectrograph ◽  
Chemical Enrichment ◽  
Giant Stars ◽  
Shed Light

ABSTRACT The stars SDSS J0646+4116 and SDSS J1937+5024 are relatively bright stars that were initially observed as a part of the SDSS/MARVELS pre-survey. They were selected, on the basis of their weak CH G bands, along with a total of 60 others, in the range of halo globular cluster (GC) metallicities for high-resolution spectroscopic follow-up as a part of the HESP-GOMPA survey (Hanle Echelle SPectrograph – Galactic survey Of Metal Poor stArs). The stars exhibit typical nucleosynthesis signatures expected from the so-called second-generation stars of GCs. The light-element anticorrelation of Mg–Al is detected, along with elevated abundances of Na. Carbon is found to be depleted, which is compatible with expectation. Lithium is also detected in SDSS J0646+4116 and SDSS J1937+5024; the measured abundances are similar to those of normal halo giant stars. These bright escapees provide a unique opportunity to study the nucleosynthesis events of GC in great detail, and shed light on their chemical-enrichment histories.

scholarly journals Searching for chemical relics of first stars with LAMOST and Subaru

2015 ◽  
Vol 11 (S317) ◽  
pp. 51-56
Author(s):  
Haining Li ◽  
Wako Aoki ◽  
Gang Zhao ◽  
Satoshi Honda ◽  
Norbert Christlieb ◽  
...  
Keyword(s):  
High Resolution ◽  
Galactic Halo ◽  
Heavy Elements ◽  
Red Giants ◽  
Halo Formation ◽  
First Stars ◽  
Joint Project ◽  
Large Sample ◽  
Shed Light

AbstractWe report progresses of a joint project on searching for extremely metal-poor (EMP) stars based on LAMOST survey and Subaru follow-up observation. Follow-up high-resolution snapshot spectra have been obtained for 70 objects, resulting in 42 EMP stars. A number of chemically interesting objects have already been identified, including (1) Two UMP (ultra metal-poor) stars with [Fe/H] ~ −4.0. One of them is the second UMP turnoff star with Li detection. (2) A super Li-rich (A(Li) ~ 3.1) EMP giant. This is the most metal-poor and extreme example of Li enhancement in giants known to date, and will shed light on Li production during the evolution of red giants. (3) A few EMP stars showing extreme overabundance in heavy elements. Detailed abundances of these extreme objects and statistics obtained by the large sample of EMP stars will provide important constraints on the Galactic halo formation.

scholarly journals Globular cluster contributions to Galactic halo assembly

2012 ◽  
Vol 10 (H16) ◽  
pp. 286-287
Author(s):  
Sarah L. Martell
Keyword(s):  
Star Formation ◽  
Globular Cluster ◽  
Second Generation ◽  
Galactic Halo ◽  
Cluster Formation ◽  
Light Element ◽  
Element Abundances ◽  
Giant Stars ◽  
Red Giant

AbstractI discuss a search for red giant stars in the Galactic halo with light-element abundances similar to second-generation globular cluster stars, and discuss the implications of such a population for globular cluster formation models and the balance between in situ star formation and accretion for the assembly of the Galactic halo.

scholarly journals The Chemical Composition of Giants in the Globular Cluster ω Cen

1988 ◽  
Vol 132 ◽  
pp. 541-544
Author(s):  
Verne V. Smith
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Globular Cluster ◽  
Red Giants ◽  
Echelle Spectrograph ◽  
Blue Edge ◽  
Giant Stars ◽  
Wide Range ◽  
Ccd Detector

High-resolution, high S/N spectra have been obtained for 22 giant stars in the globular cluster ω Cen. These stars span a wide range of temperature and position on the giant branch and include some of the S-type and Barium star members. Spectra were obtained on the CTIO 4m telescope with the echelle spectrograph and CCD detector. Initial abundance results for Iron, Calcium, and Oxygen are presented for three stars: one of the most luminous cluster red-giants, a giant on the blue edge of the ω Cen giant branch, and an extreme Barium star member.

scholarly journals Constant light element abundances suggest that the extended P1 in NGC 2808 is not a consequence of CNO-cycle nucleosynthesis

2019 ◽  
Vol 485 (3) ◽  
pp. 4128-4133 ◽  
Author(s):  
I Cabrera-Ziri ◽  
C Lardo ◽  
A Mucciarelli
Keyword(s):  
Mass Fraction ◽  
Globular Clusters ◽  
Light Element ◽  
Complete Characterization ◽  
Alternative Mechanism ◽  
Abundance Pattern ◽  
Element Abundances ◽  
Chemical Enrichment ◽  
Giant Stars ◽  
Cno Cycle

Abstract Recent photometric results have identified a new population among globular cluster stars. This population, referred to as the ‘extended P1', has been suggested to be the manifestation of a new abundance pattern where the initial mass fraction of He changes among cluster stars that share the same CNO values. The current paradigm for the formation of the multiple stellar populations in globular clusters assumes that variations in He are the product of chemical ‘enrichment’ by the ashes of the CNO-cycle (which changes He and other elements like C, N and O simultaneously). We obtained MIKE@Magellan spectra of six giant stars in NGC 2808, a cluster with one of the strongest examples of the extended P1 population. We provide the first complete characterization of the light elements abundances for the stars along a significant range of the extended P1 photometric group. The stars from our sample appear to be homogeneous in C, N, O, Na, Mg and Al. The lack of a significant change in these products of the CNO-cycle suggests that unlike the rest of the populations identified to date, the photometric changes responsible for the extended P1 feature are a consequence of an alternative mechanism. Our measurements are consistent with the interpretations where the changes of the He mass fraction among these stars could be a consequence of p–p chain nucleosynthesis (which could increase the He in stars without affecting heavier elements). Having said that, direct measurements of He are necessary to conclude if variations of this element are present among extended P1 stars.

scholarly journals Observed Abundance Features and their Implications for Chemical Evolution

2004 ◽  
Vol 21 (2) ◽  
pp. 242-247
Author(s):  
Takuji Tsujimoto ◽  
Toshikazu Shigeyama
Keyword(s):  
Chemical Evolution ◽  
Globular Cluster ◽  
Milky Way ◽  
Galactic Halo ◽  
Cluster Formation ◽  
Abundance Trends ◽  
Nearby Galaxies ◽  
Star Formation Histories ◽  
Chemical Evolution Model ◽  
Shed Light

AbstractWe describe the star formation histories of the Milky Way dwarf spheroidal galaxy and the globular cluster ω Centauri in terms of an inhomogeneous chemical evolution model developed for the Galactic halo. The observed abundance trends seen in neutron-capture elements together with α-elements constrain our models to shed light on the histories of these nearby galaxies and ω Cen. The origin of low-α stars and a new picture of the globular cluster formation scenario induced by cloud–cloud collisions are also presented.

scholarly journals Chemical Abundances in Giant Stars of the Tidally Disrupted Globular Cluster NGC 6712 from High‐Resolution Infrared Spectroscopy

2008 ◽  
Vol 689 (2) ◽  
pp. 1020-1030 ◽  
Author(s):  
David Yong ◽  
Jorge Meléndez ◽  
Katia Cunha ◽  
Amanda I. Karakas ◽  
John E. Norris ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
High Resolution ◽  
Globular Cluster ◽  
Chemical Abundances ◽  
Giant Stars

scholarly journals CNO and Li abundances in Barium-enriched stars

2006 ◽  
Vol 2 (S239) ◽  
pp. 304-306 ◽  
Author(s):  
Natalia A. Drake ◽  
Claudio B. Pereira
Keyword(s):  
Light Element ◽  
Element Abundance ◽  
Synthetic Spectrum ◽  
Isotopic Ratios ◽  
Red Giants ◽  
Echelle Spectrograph ◽  
Abundance Pattern ◽  
Giant Stars ◽  
Cno Cycle ◽  
Low Metallicity

AbstractCNO and Li abundances and 12C/13C isotopic ratios have been derived for two metal-poor Ba giants, HD 104340 and HD 206983, and two CH subgiants, HD 50264 and HD 87080. High resolution spectra obtained with the 1.52 m telescope and the FEROS echelle spectrograph at ESO, La Silla, Chile, were used in this study. CNO and Li abundances so as 12C/13C isotopic ratios were determined by applying the synthetic spectrum method to the lines of C2, CH, CN, [O I’ and Li I. Our analysis showed that the giant stars studied here have quite different natures: HD 206983 is a metal-poor barium star while HD 104340, although showing enhancement of s-process elements, should not be considered as a classical barium star: its barium syndrome can be explained by internal nucleosynthesis. The low metallicity giant HD 104340 can experience deeper convective mixing and, consequently, a larger dredge-up of CNO-cycle products compared to normal red giants. Light element abundance pattern of HD 104340 resembles anomalies resulting from the appearance on the stellar surface of material enriched in triple-α and CNO cycling.

scholarly journals Galactic or extragalactic chemical tagging for NGC 3201?

2018 ◽  
Vol 614 ◽  
pp. A146 ◽  
Author(s):  
B. Dias ◽  
I. Araya ◽  
J. P. Nogueira-Cavalcante ◽  
L. Saker ◽  
A. Shokry
Keyword(s):  
High Resolution ◽  
Globular Cluster ◽  
High Resolution Spectroscopy ◽  
Low Resolution ◽  
Element Abundances ◽  
Giant Stars ◽  
Mass Size ◽  
Red Giant ◽  
Process Element ◽  
Size Relation

Context. The origin of the globular cluster (GC) NGC 3201 is under debate. Its retrograde orbit points to an extragalactic origin, but no further chemical evidence supports this idea. Light-element chemical abundances are useful to tag GCs and can be used to shed light on this discussion. Aims. Recently it was shown that the CN and CH indices are useful to identify GCs that are anomalous to those typically found in the Milky Way. A possible origin of anomalous clusters is the merger of two GCs and/or the nucleus of a dwarf galaxy. We aim to derive CN and CH band strengths for red giant stars in NGC3201 and compare these with photometric indices and high-resolution spectroscopy and discuss in the context of GC chemical tagging. Methods. We measure molecular band indices of S(3839) and G4300 for CN and CH, respectively from low-resolution spectra of red giant stars. Gravity and temperature effects are removed. Photometric indices are used to indicate further chemical information on C+N+O or s-process element abundances that are not derived from low-resolution spectra. Results. We found three groups in the CN–CH distribution. A main sequence (S1), a secondary less-populated sequence (S2), and a group of peculiar (pec) CN-weak and CH-weak stars, one of which was previously known. The three groups seem to have different C+N+O and/or s-process element abundances, to be confirmed by high-resolution spectroscopy. These are typical characteristics of anomalous GCs. The CN distribution of NGC 3201 is quadrimodal, which is more common in anomalous clusters. However, NGC 3201 does not belong to the trend of anomalous GCs in the mass-size relation. Conclusions. The globular cluster NGC 3201 shows signs that it can be chemically tagged as anomalous: it has an unusual CN–CH relation, indications that pec-S1-S2 is an increasing sequence of C+N+O or s-process element abundances, and a multi-modal CN distribution that seems to correlate with s-process element abundances. The non-anomalous characteristics are that it has a debatable Fe-spread and it does not follow the trend of mass size of all anomalous clusters. Three scenarios are postulated here: (i) if the sequence pec-S1-S2 has increasing C+N+O and s-process element abundances, NGC 3201 would be the first anomalous GC outside of the mass-size relation; (ii) if the abundances are almost constant, NGC 3201 would be the first non-anomalous GC with multiple CN–CH anti-correlation groups; or (iii) it would be the first anomalous GC without variations in C+N+O and s-process element abundances. In all cases, the definition of anomalous clusters and the scenario in which they have an extragalactic origin must be revised.

scholarly journals The Similarity of the Halo Field K Giant Population by the Globular Cluster System of our Galaxy

1988 ◽  
Vol 126 ◽  
pp. 519-520
Author(s):  
Kavan U. Ratnatunga
Keyword(s):  
Globular Cluster ◽  
Galactic Halo ◽  
Cluster System ◽  
Line Of Sight ◽  
Giant Stars ◽  
Abundance Estimates ◽  
Metal Abundance ◽  
Objective Prism ◽  
Globular Cluster System

Line-of-sight velocities and improved metal abundance estimates are available for a representative sample of 58 giants located by an objective prism survey (Ratnatunga and Freeman 1985), in a 20 square degree field near SA 127 (1 = 272, b = +39). These in-situ K-giants of the outer regions of our galactic halo give a direct comparison of the field population with the globular cluster system. Fig. 1 illustrates the distribution of line-of-sight velocity with abundance for the sample of giant stars in SA 127. The mean and dispersion of the sample appears to be discontinuous at [FeH] ~ −0.8. Fig. 2 shows the distribution of [Fe/H] with distance from the Sun for the same stars. The metal stronger giants (filled symbols) represent a population of stars up to 6 kpc above the plane of the disk and have a velocity dispersion of about 50 km/s. In contrast, the metal weaker giants have a typical halo dispersion of about 120 km/s.

Sign in / Sign up

Export Citation Format

Share Document