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

Bandyopadhyay, Avrajit; Susmitha, A.

doi:10.1093/mnras/staa671

Cited by 6 publications

(3 citation statements)

References 58 publications

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“…No trends could be seen for A(Li) with [Na/Fe] (as reported in a few globular clusters), [Ca/Fe] (representative of α-element abundances), [Cr/Fe] (an Fe-peak element), and [Ba/Fe] (an n-capture element). We have also marked the abundances of the globular cluster (GC) escapees (Bandyopadhyay et al 2020b) and the CEMP-no star (Bandyopadhyay et al 2018) with red-filled triangles and pink diamonds, respectively, in each of the panels. Lithium could also be detected for both of the GC escapees of this study, SDSS J064655.6+411620.5 and SDSS J193712.01+502455.5 (Bandyopadhyay et al 2020b), and was found to be normal.…”

Section: Lithium Distribution In the Metal-poor Regimementioning

confidence: 99%

“…We have also marked the abundances of the globular cluster (GC) escapees (Bandyopadhyay et al 2020b) and the CEMP-no star (Bandyopadhyay et al 2018) with red-filled triangles and pink diamonds, respectively, in each of the panels. Lithium could also be detected for both of the GC escapees of this study, SDSS J064655.6+411620.5 and SDSS J193712.01+502455.5 (Bandyopadhyay et al 2020b), and was found to be normal. Lithium is a fragile element, and is completely destroyed in a temperature range much lower than that required for the operation of the Mg-Al cycle.…”

Section: Lithium Distribution In the Metal-poor Regimementioning

confidence: 99%

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Li Distribution, Kinematics, and Detailed Abundance Analysis among Very Metal-poor Stars in the Galactic Halo from the HESP-GOMPA Survey

Bandyopadhyay

Susmitha

Nayak

et al. 2022

ApJ

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We present a study on the detailed elemental abundances of newly identified, bright, very metal-poor stars with the detection of lithium, initially observed as part of the SDSS/MARVELS pre-survey. These stars were selected for high-resolution spectroscopic follow-up as part of the HESP-GOMPA survey. In this work, we discuss the Li abundances detected for several stars in the survey, which include main-sequence stars, subgiants, and red giants. Different classes of stars are found to exhibit very similar distributions of Li, which points toward a common origin. We derive a scaling relation for the depletion of Li as a function of temperature for giants and main-sequence stars; the majority of the samples from the literature were found to fall within 1σ (0.19 and 0.12 dex K−1 for giants and dwarfs, respectively) of this relationship. We also report the existence of a slope of the Li abundance as a function of distance from the Galactic plane, indicating mixed stellar populations. Most Li-rich stars are found to be in or close to the Galactic plane. Along with Li, we have derived detailed abundances for C, odd-Z, α-, Fe-peak, and neutron-capture elements for each star. We have also used astrometric parameters from Gaia-EDR3 to complement our study, and derived kinematics to differentiate between the motions of the stars—those formed in situ and those accreted. The stellar population of the Spite plateau, including additional stars from the literature, is found to have significant contributions from stars formed in situ and through accretion. The orbits for the program stars have also been derived and studied for a period of 5 Gyr backwards in time.

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Section: Lithium Distribution In the Metal-poor Regimementioning

confidence: 99%

Section: Lithium Distribution In the Metal-poor Regimementioning

confidence: 99%

Li Distribution, Kinematics, and Detailed Abundance Analysis among Very Metal-poor Stars in the Galactic Halo from the HESP-GOMPA Survey

Bandyopadhyay

Susmitha

Nayak

et al. 2022

ApJ

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“…Stellar parameters were determined using the same methods as described in Bandyopadhyay et al (2018) and Bandyopadhyay et al (2020). Briefly, photometric temperatures were obtained using the available data in the literature and the standard T eff -color relations derived by Alonso et al (1996) and Alonso et al (1999).…”

Section: Observations and Analysismentioning

confidence: 99%

Abundance Analysis of New $r$-Process-Enhanced Stars from the HESP-GOMPA Survey

Bandyopadhyay,

Sivarani,

Beers

2020

Preprint

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We present a study on the detailed chemical abundances of five new relatively bright r-processenhanced stars that were initially observed as part of the SDSS/MARVELS pre-survey. These stars were selected, on the basis of their metallicities and carbon abundances, among a total of 60 stars, for high-resolution spectroscopic follow-up as part of the HESP-GOMPA survey (Hanle Echelle SPectrograph -Galactic survey Of Metal Poor stArs). Here we discuss the three new r-I and two new r-II stars found in this survey. We have carried out a detailed abundance analysis for each of these stars, at a resolving power of R ∼ 30, 000, and compare our results to the existing literature. We could measure three of the first r-process-peak elements (Sr, Y and Zr) in all five stars, while Ba, Ce, Nd, Sm, Eu, and Dy could be detected among the second r-process-peak elements. Thorium could also be detected in one of the targets, which is found to be an actinide-boost star. We have carried out a comparative study among the sub-populations of the r-process-enhanced stars and other stars of the Milky Way halo population to constrain the origin of this class of objects. These bright r-process-enhanced stars provide an excellent opportunity to study the nucleosynthesis history of this population in great detail, and shed light on their chemical-enrichment histories.

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Chemo-dynamics and asteroseismic ages of seven metal-poor red giants from the Kepler field

Puls

Casagrande

Monty

et al. 2021

Monthly Notices of the Royal Astronomical Society

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In this work we combine information from solar-like oscillations, high-resolution spectroscopy and Gaia astrometry to derive stellar ages, chemical abundances and kinematics for a group of seven metal-poor Red Giants and characterise them in a multidimensional chrono-chemo-dynamical space. Chemical abundance ratios were derived through classical spectroscopic analysis employing 1D LTE atmospheres on Keck/HIRES spectra. Stellar ages, masses and radii were calculated with grid-based modelling, taking advantage of availability of asteroseismic information from Kepler. The dynamical properties were determined with Galpy using Gaia EDR3 astrometric solutions. Our results suggest that underestimated parallax errors make the effect of Gaia parallaxes more important than different choices of model grid or – in the case of stars ascending the RGB – mass-loss prescription. Two of the stars in this study are identified as potentially evolved halo blue stragglers. Four objects are likely members of the accreted Milky Way halo, and their possible relationship with known accretion events is discussed.

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

Cited by 6 publications

References 58 publications

Li Distribution, Kinematics, and Detailed Abundance Analysis among Very Metal-poor Stars in the Galactic Halo from the HESP-GOMPA Survey

Li Distribution, Kinematics, and Detailed Abundance Analysis among Very Metal-poor Stars in the Galactic Halo from the HESP-GOMPA Survey

Abundance Analysis of New $r$-Process-Enhanced Stars from the HESP-GOMPA Survey

Chemo-dynamics and asteroseismic ages of seven metal-poor red giants from the Kepler field

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