A5025187817- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- History and Developments in Astronomy
- Nuclear physics research studies
- High-pressure geophysics and materials
- Astronomical and nuclear sciences
- Pulsars and Gravitational Waves Research
- Adaptive optics and wavefront sensing
- Solar and Space Plasma Dynamics
- Computational Drug Discovery Methods
- thermodynamics and calorimetric analyses
- Nuclear Physics and Applications
- Galaxies: Formation, Evolution, Phenomena
- bioluminescence and chemiluminescence research
- Photocathodes and Microchannel Plates
- Geophysics and Gravity Measurements
- Particle accelerators and beam dynamics
- Astrophysical Phenomena and Observations
Indian Institute of Astrophysics
2015-2024
Indian Institute of Science Education and Research Pune
2021
We analyze a set of published elemental abundances from sample CH stars which are based on high resolution spectral analysis ELODIE and SUBARU/HDS spectra. All the were derived local thermodynamic equilibrium usingmodel atmospheres, thus, they represent largest homogeneous abundance data available for up to date. For this reason, we can use constrain physics nucleosynthesis occurring in low mass AGB stars. have been polluted past an already extinct companion thus show s-process enriched...
Our ability to extract information from the spectra of stars depends on reliable models stellar atmospheres and appropriate techniques for spectral synthesis. Various model codes strategies analysis are available today. We aim compare results deriving parameters using different atmosphere strategies. The focus is set high-resolution spectroscopy cool giant stars. Spectra representing four were made various groups individuals working in area synthesis, asking them derive data provided....
MSE is an 11.25m aperture observatory with a 1.5 square degree field of view that will be fully dedicated to multi-object spectroscopy. More than 3200 fibres feed spectrographs operating at low (R ~ 2000 - 3500) and moderate 6000) spectral resolution, approximately 1000 fibers high 40000) resolution. designed enable transformational science in areas as diverse tomographic mapping the interstellar intergalactic media; in-situ chemical tagging thick disk halo stars; connecting galaxies their...
We present results of an analysis high-resolution spectra obtained with the Subaru Telescope High Dispersion Spectrograph, two Carbon-Enhanced Metal-Poor stars, HE 1305+0007 and 1152-0355, classical CH star HD 5223. All these stars have relatively low effective temperatures (4000-4750 K) high carbon abundances. The stellar atmospheric parameters indicate that they all surface gravities consistent a location on red-giant branch, metallicities [Fe/H] = -2.0 (HE 1305+0007, 5223) [Fe/H]= -1.3...
We have derived the stellar atmospheric parameters, effective temperature T$_{eff}$, microturbulent velocity $\zeta$, surface gravity log g, and metallicity [Fe/H] for HE 0017+0055, 2144-1832, 2339-0837, HD 145777, CD-27 14351 from local thermodynamic equilibrium analyses using model atmospheres. Elemental abundances of C, N, $\alpha$-elements, iron-peak elements, several neutron-capture elements are estimated equivalent width measurement technique as well spectrum synthesis calculations in...
Results from high-resolution spectral analyses of a selected sample CH stars are presented. Detailed chemical composition studies these objects, which could reveal abundance patterns that in turn provide information regarding nucleosynthesis and evolutionary status, scarce the literature. We conducted detailed for objects based on high resolution (R ~ 42000) spectra. The spectra were taken ELODIE archive cover wavelength range 3900 to 6800 A, range. estimated stellar atmospheric parameters,...
We present detailed chemical analyses for a sample of 12 stars selected from the CH star catalogue Bartkevicius. The includes two confirmed binaries, four objects that are known to show radial velocity variations and rest with no information on binary status. A primary objective is examine if all these exhibit abundances characteristics stars, based composition study using high-resolution spectra. have used (R ∼ 42 000) spectra ELODIE archive. These cover 3900 6800 Å in wavelength range....
The low-mass metal-poor stars in the Galaxy that preserve their atmosphere, chemical imprints of gas clouds from which they were formed can be used as probes to get insight into origin and evolution elements early galaxy, star formation nucleosynthesis. Among stars, a large fraction, so-called carbon-enhanced (CEMP) exhibits high abundance carbon. These exhibit diverse patterns, particularly for heavy elements, based on are classified different groups. diversity patterns points at scenarios....
A comprehensive abundance analysis providing rare insight into the chemical history of lead stars is still lacking.We present results from high resolution (R ∼ 50 000), spectral analyses three CH stars, HD 26, 198269, 224959, and, a carbon star with dusty envelope, 100764.Previous studies on these objects are limited by both and wavelength regions differ significantly each other.We have undertaken to re-analyse composition based Subaru spectra covering 4020 6775 Å .Considering local...
Barium stars are one of the important probes to understand origin and evolution slow neutron-capture process elements in Galaxy. These extrinsic stars, where observed s-process element abundances believed have an now invisible companions that produced these at their Asymptotic Giant Branch phase evolution. We attempted nucleosynthesis, as well physical properties companion through a detailed comparison elemental 10 barium with predictions from AGB nucleosynthesis models, FRUITY. For we...
Elemental abundances of CH stars can provide observational constraints for theoretical studies on the nucleosynthesis and evolution low- intermediate-mass stars. However, available abundance data in literature are quite scanty. In our pursuit to generate a homogeneous database elemental we have performed detailed chemical study sample 12 potential star candidates based high resolution spectroscopy. We present first time analysis objects HE 0308-1612, CD-28 1082, HD 30443, 87853. For other...
Abstract We have performed detailed high-resolution spectroscopic analysis on seven metal-poor stars (BD+75 348, BD+09 3019, HD238020, HE0319–0215, HE0507–1653, HE0930–0018, HE1023–1504) and derived their atmospheric parameters T eff , log g [Fe/H], microturbulent velocity ( ξ ). The metallicity range is found to be –2.57 < [Fe/H] –0.42. elemental abundances of 17 light elements 12 heavy are estimated. classified BD+75 348 3019 as strong Ba stars, HD238020 a mild star, the remaining four...
Carbon-rich stars of Population II, such as CH stars, can provide direct information on the role low- to intermediate-mass halo in early Galactic evolution. Thus accurate knowledge stellar population is a critical requirement for building up scenarios chemical In present work, we report several identified sample faint high-latitude carbon from Hamburg survey and discuss their medium-resolution spectra covering wavelength range 4000–6800 Å. Estimation depths (1,0)12C12C λ4737 (1,0)12C13C...
CH stars form a distinct class of objects with characteristic properties like iron deficiency, enrichment carbon and overabundance heavy elements. These can provide strong observational constraints for the theoretical computation nucleosynthesis at low metallicity. An important issue is relative surface density stars, which valuable input to our understanding role low- intermediate-mass in early Galactic chemical evolution. Spectroscopic characterization provides an effective way identifying...
High resolution spectra obtained from the Subaru Telescope Dispersion Spectrograph have been used to update stellar atmospheric parameters and metallicity of star HD 209621. We derived a [Fe/H] = -1.93 for this star, found large enhancement carbon heavy elements, with respect iron. Updates on elemental abundances four s-process elements (Y, Ce, Pr, Nd) along first estimates number other (Sr, Zr, Ba, La, Sm, Eu, Er, Pb) are reported. The parameters, effective temperature, Teff, surface...
We present a comprehensive study of the evolution abundances intermediate mass elements, from C to Zn, in Milky Way halo and local disk. use consistent model describe those two galactic subsystems. The disk are assumed evolve independently, both starting with gas primordial composition, different ways: strong outflow is take place during $\sim$1 Gyr formation, while built by slowly infalling gas. This description halo+disk can correctly account for main observational constraints (at least...
Very little is known about the polarimetric properties of CH stars and carbon-enhanced metal-poor (CEMP) stars, although many these objects have been studied in detail both photometrically spectroscopically. We aim to derive for a large sample CEMP fill this gap. Multiband observations were conducted first run twenty-nine that include twenty-two seven polarization standards. Estimates obtained using standard procedures calculation. Five our do not show any significant over different colours...
Carbon stars, enhanced in carbon and neutron-capture elements, provide wealth of information about the nucleosynthesis history Galaxy. In this work, we present first ever detailed abundance analysis star LAMOSTJ091608.81+230734.6 a elements for object LAMOSTJ151003.74+305407.3. Updates on abundances C, O, Mg, Ca, Cr, Mn Ni LAMOSTJ151003.74+305407.3 are also presented. Our is based high resolution spectra obtained using Hanle Echelle Spectrograph (HESP) attached to Himalayan Chandra Telescope...
We present elemental abundance results for HE 2148-2039 and 2155-2043 based on a detailed high-resolution spectroscopic analysis. The SUBARU/HDS spectra used our analysis have resolution of R~60 000. Although limited information photometry low-resolution spectroscopy are available, we the first time an both objects. Our shows that two objects extremely metal-poor with [Fe/H]< -3. Among neutron-capture elements, abundances only Sr Ba could be determined in programme stars. For [Ba/Fe] is...
ABSTRACT The Carbon-Enhanced Metal-Poor (CEMP) stars with no enhancement of neutron-capture elements, the so-called CEMP-no are believed to be direct descendants first-generation and provide a unique opportunity probe early Galactic nucleosynthesis. We present detailed chemical kinematic analysis for two extremely metal-poor HE 1243 − 2408 0038 0345 using high-resolution (R∼86 000) HERMES spectra. For object 2408, we could make comparison available literature values; however, only limited...
We present elemental abundance results from high resolution spectral analysis of three nitrogen-enhanced barium stars. The is based on spectra obtained with the FEROS attached to 1.52m telescope at ESO, Chile. R~48000 and coverage spans 3500-9000\AA\,. For objects HD 51959 88035, we first time analyses results. Although a few studies are available in literature object 121447, significantly different each other. have therefore carried out detailed chemical composition study for this spectrum...
Medium resolution spectral analysis of candidate Faint High Latitude Carbon (FHLC) stars from Hamburg/ESO survey has given us the potential to discover objects rare types. Two primary characteristics R Coroanae Borealis (RCB) are hydrogen deficiency and weaker CN bands relative C_{2} bands. They also characterized by their characteristic location in J-H, H-K plane with respect cool carbon stars. From a sample 243 FHLC stars, we have discovered hydrogen-deficient (HdC) star HE 1015-2050, at...
Origin of enhanced abundance heavy elements observed in the surface chemical composition carbon-enhanced metal-poor (CEMP) stars still remain poorly understood. Here, we present detailed analysis seven CEMP based on high resolution (R${\sim}$ 50\,000) spectra that reveal enough evidence Asymptotic Giant Branch (AGB) being possible progenitors for these objects. For objects HE0110$-$0406, HE1425$-$2052 and HE1428$-$1950, first time a analysis. Our sample is found to consists one...