A5082642536- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astronomical and nuclear sciences
- Education and Learning Interventions
- Advanced Chemical Physics Studies
- History and Developments in Astronomy
- Nuclear physics research studies
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
Max Planck Institute for Astronomy
2023-2025
Heidelberg University
2025
Australian National University
2024
Abstract Stars that formed with an initial mass of over 50 M ⊙ are very rare today, but they thought to be more common in the early Universe. The fates those early, metal-poor, massive stars highly uncertain. Most expected directly collapse black holes, while some may explode as a result rotationally powered engines or pair-creation instability. We present chemical abundances J0931+0038, nearby low-mass star identified follow-up SDSS-V Milky Way Mapper, which preserves signature unusual...
Context . Abundances of s- and r-process elements in Sun-like stars constrain nucleosynthesis extreme astrophysical events, such as compact binary mergers explosions highly magnetised rapidly rotating massive stars. Aims We measure solar abundances yttrium (Y) europium (Eu) using 3D non-local thermal equilibrium (NLTE) models. use the model to determine abundance Y, also explore model’s ability reproduce centre-to-limb variation its lines. In addition, we Eu disc-centre integrated flux...
We performed a detailed spectroscopic analysis of three extremely metal-poor RR Lyrae stars, exploring uncharted territories at these low metallicities for this class stars. Using high-resolution spectra acquired with HARPS-N TNG, UVES VLT, and PEPSI LBT, employing Non-Local Thermodynamic Equilibrium (NLTE) spectral synthesis calculations, we provide abundance measurements Fe, Al, Mg, Ca, Ti, Mn, Sr. Our findings indicate that the stars have [Fe/H] = -3.40 \pm 0.05, -3.28 0.02, -2.77 0.05 HD...
We performed a detailed spectroscopic analysis of three extremely metal-poor RR Lyrae stars, exploring uncharted territories at these low metallicities for this class stars. Using high-resolution spectra acquired with HARPS-N TNG, UVES VLT, and PEPSI LBT, employing Non-Local Thermodynamic Equilibrium (NLTE) spectral synthesis calculations, we provide abundance measurements Fe, Al, Mg, Ca, Ti, Mn, Sr. Our findings indicate that the stars have Fe/H = -3.40 ± 0.05, -3.28 0.02, -2.77 0.05 HD...
Abstract Historically, various methods have been employed to understand the origin of elements, including observations elemental abundances which compared Galactic Chemical Evolution (GCE) models. It is also well known that 1D Local Thermodynamic Equilibrium (LTE) measurements fail accurately capture abundances. Non-LTE (NLTE) effects may play a significant role, and neglecting them leads erroneous implications in galaxy modelling. In this paper, we calculate 3D NLTE seven key iron-peak...
ABSTRACT Yttrium (Y), a key s-process element, is commonly used in nucleosynthesis studies and as Galactic chemical clock when combined with magnesium (Mg). We study the applicability of previously assumed local thermal equilibrium (LTE) line formation assumption Y abundance main-sequence red giant stars, probe impact NLTE (non-LTE) effects on [Y/Mg] ratio, proposed stellar age indicator. derive parameters, ages, abundances Fe, Mg, for 48 solar analogue stars from high-resolution spectra...
Stellar mergers and accretion events have been crucial in shaping the evolution of Milky Way (MW). These dynamically identified chemically characterised using red giants main-sequence stars. RR Lyrae (RRL) variables can play a role tracing early formation MW since they are ubiquitous, old (t$\ge$10 Gyr) low-mass stars accurate distance indicators. We exploited Data Release 3 GALAH survey to identify 78 field RRLs suitable for chemical analysis. Using synthetic spectra calculations, we...
Most heavy elements beyond the iron peak are synthesized via neutron capture processes. The nature of astrophysical sites processes is still very unclear. In this work we explore observational constraints chemical abundances s-process and r-process on neutron-capture by applying Galactic evolution (GCE) models to data from Gaia-ESO large spectroscopic stellar survey. For r-process, [Eu/Fe]-[Fe/H] distribution suggests a short delay time site that produces Eu. Other independent observations...
Context. The chemical evolution history of slow neutron-capture elements in the Milky Way is still a matter debate, especially metal-poor regime ([Fe/H] < −1). Aims. Based on Gaia -ESO spectroscopic data, recent study investigated [Fe/H] > −1. Here, we aim to complement this down = −3, and focus Ba, Y, Sr, along with abundance ratios [Ba/Y] [Sr/Y], which give comprehensive views s -process nucleosynthesis channels. Methods. We measured local thermodynamic equilibrium (LTE) non-local...
Accurate measurements of europium abundances in cool stars are essential for an enhanced understanding the r-process mechanisms. We measure abundance Eu solar spectra and a sample metal-poor Galactic halo disk, with metallicities ranging from \GG{$-2.4$} to $-0.5$ dex, using non-local thermodynamic equilibrium (NLTE) line formation. compare these Chemical Evolution (GCE) models \GG{explore impact NLTE corrections on contribution site chemical evolution. In this work, we use formation, as...
Separating stars enriched in the s- and r-processes of nucleosynthesis is usually achieved by analyzing element ratios s-process elements (like Ba or La) to r-process Eu). The situation becomes more complex when CEMP-rs stars, which are carbon-enriched metal-poor objects a mixture r-elements. These objects, possibly resulting from i-process nucleosynthesis, notoriously difficult classify based on elemental ratios. Recent theoretical studies have outlined, however, that s-, i-, produce...
Stars formed with initial mass over 50 Msun are very rare today, but they thought to be more common in the early universe. The fates of those early, metal-poor, massive stars highly uncertain. Most expected directly collapse black holes, while some may explode as a result rotationally powered engines or pair-creation instability. We present chemical abundances J0931+0038, nearby low-mass star identified followup SDSS-V Milky Way Mapper, which preserves signature unusual nucleosynthesis from...
As a key to chemical evolutionary studies, the distribution of elements in galactic provides wealth information understand individual star formation histories galaxies. The r-process is complex nucleosynthesis process, and origin heavily debated. Europium (Eu) viewed as an almost pure element. Accurate measurements europium abundances cool stars are essential for enhanced understanding mechanisms. We measure abundance Eu solar spectra sample metal-poor Galactic halo disk, with metallicities...
Yttrium (Y), a key s-process element, is commonly used in nucleosynthesis studies and as Galactic chemical clock when combined with magnesium (Mg). We study the applicability of previously assumed LTE line formation assumption Y abundance main-sequence red giant stars, probe impact NLTE effects on [Y/Mg] ratio, proposed stellar age indicator. derive parameters, ages, abundances Fe, Mg, for 48 solar analogue stars from high-resolution spectra acquired within Gaia-ESO survey. For Y, we present...
Recently Lian et al. (2023), thanks to Gaia-ESO data, studied the chemical evolution of neutron-capture elements in regime [Fe/H]>-1. We aim here complement this study down [Fe/H]=-3, and focus on Ba, Y, Sr, abundance ratios [Ba/Y] [Sr/Y], which give comprehensive views s-process nucleosynthesis channels. measured LTE NLTE abundances Sr 323 Galactic metal-poor stars using high-resolution optical spectra with high S/N. used spectral fitting code TSFitPy, together 1D model atmospheres...