Subjects -> ASTRONOMY (Total: 94 journals)
Showing 1 - 46 of 46 Journals sorted alphabetically
Advances in Astronomy     Open Access   (Followers: 51)
Annual Review of Astronomy and Astrophysics     Full-text available via subscription   (Followers: 39)
Annual Review of Earth and Planetary Sciences     Full-text available via subscription   (Followers: 63)
Artificial Satellites     Open Access   (Followers: 23)
Astrobiology     Hybrid Journal   (Followers: 14)
Astronomical & Astrophysical Transactions: The Journal of the Eurasian Astronomical Society     Hybrid Journal   (Followers: 6)
Astronomical Journal     Full-text available via subscription   (Followers: 8)
Astronomical Review     Open Access   (Followers: 4)
Astronomische Nachrichten     Hybrid Journal   (Followers: 4)
Astronomy & Geophysics     Hybrid Journal   (Followers: 48)
Astronomy and Astrophysics     Full-text available via subscription   (Followers: 60)
Astronomy and Astrophysics     Open Access   (Followers: 32)
Astronomy and Computing     Hybrid Journal   (Followers: 2)
Astronomy Letters     Hybrid Journal   (Followers: 22)
Astronomy Reports     Hybrid Journal   (Followers: 15)
Astronomy Studies Development     Open Access   (Followers: 12)
Astroparticle Physics     Hybrid Journal   (Followers: 8)
Astrophysical Bulletin     Hybrid Journal   (Followers: 3)
Astrophysical Journal     Full-text available via subscription   (Followers: 19)
Astrophysical Journal Letters     Full-text available via subscription   (Followers: 14)
Astrophysical Journal Supplement Series     Full-text available via subscription   (Followers: 14)
Astrophysics     Hybrid Journal   (Followers: 29)
Astrophysics and Space Science     Hybrid Journal   (Followers: 46)
Astrophysics and Space Sciences Transactions (ASTRA)     Open Access   (Followers: 56)
Astropolitics: The International Journal of Space Politics & Policy     Hybrid Journal   (Followers: 12)
Celestial Mechanics and Dynamical Astronomy     Hybrid Journal   (Followers: 11)
Chinese Astronomy and Astrophysics     Full-text available via subscription   (Followers: 24)
Colloid Journal     Hybrid Journal   (Followers: 3)
Comptes Rendus Physique     Full-text available via subscription   (Followers: 2)
Computational Astrophysics and Cosmology     Open Access   (Followers: 3)
COSPAR Colloquia Series     Full-text available via subscription   (Followers: 11)
Earth, Moon, and Planets     Hybrid Journal   (Followers: 55)
Earth, Planets and Space     Open Access   (Followers: 74)
EAS Publications Series     Full-text available via subscription   (Followers: 8)
EPL Europhysics Letters     Partially Free   (Followers: 8)
Experimental Astronomy     Hybrid Journal   (Followers: 39)
Expert Opinion on Astronomy and Astrophysics     Open Access   (Followers: 7)
Extreme Life, Biospeology & Astrobiology - International Journal of the Bioflux Society     Full-text available via subscription   (Followers: 6)
Few-Body Systems     Hybrid Journal   (Followers: 1)
Foundations of Physics     Hybrid Journal   (Followers: 41)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 12)
Galaxies     Open Access   (Followers: 6)
Globe, The     Full-text available via subscription   (Followers: 4)
Gravitation and Cosmology     Hybrid Journal   (Followers: 4)
Icarus     Hybrid Journal   (Followers: 75)
International Journal of Advanced Astronomy     Open Access   (Followers: 28)
International Journal of Astrobiology     Hybrid Journal   (Followers: 4)
International Journal of Astronomy     Open Access   (Followers: 19)
International Journal of Astronomy and Astrophysics     Open Access   (Followers: 29)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 13)
International Letters of Chemistry, Physics and Astronomy     Open Access   (Followers: 12)
ISRN Astronomy and Astrophysics     Open Access   (Followers: 7)
Journal for the History of Astronomy     Full-text available via subscription   (Followers: 19)
Journal of Astrobiology & Outreach     Open Access   (Followers: 3)
Journal of Astronomical Instrumentation     Open Access   (Followers: 3)
Journal of Astronomical Telescopes, Instruments, and Systems     Hybrid Journal   (Followers: 5)
Journal of Astrophysics     Open Access   (Followers: 26)
Journal of Astrophysics and Astronomy     Open Access   (Followers: 52)
Journal of Atmospheric and Solar-Terrestrial Physics     Hybrid Journal   (Followers: 199)
Journal of Cosmology and Astroparticle Physics     Hybrid Journal   (Followers: 38)
Journal of Geophysical Research : Planets     Full-text available via subscription   (Followers: 178)
Journal of Geophysical Research : Space Physics     Full-text available via subscription   (Followers: 178)
Journal of High Energy Astrophysics     Full-text available via subscription   (Followers: 22)
Kinematics and Physics of Celestial Bodies     Hybrid Journal   (Followers: 10)
KronoScope     Hybrid Journal   (Followers: 1)
Macalester Journal of Physics and Astronomy     Open Access   (Followers: 4)
MNASSA : Monthly Notes of the Astronomical Society of South Africa     Full-text available via subscription   (Followers: 1)
Molecular Astrophysics     Full-text available via subscription   (Followers: 1)
Monthly Notices of the Royal Astronomical Society     Hybrid Journal   (Followers: 14)
Monthly Notices of the Royal Astronomical Society : Letters     Hybrid Journal  
Nature Astronomy     Hybrid Journal   (Followers: 8)
New Astronomy     Hybrid Journal   (Followers: 27)
New Astronomy Reviews     Full-text available via subscription   (Followers: 17)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
NRIAG Journal of Astronomy and Geophysics     Open Access   (Followers: 5)
Open Astronomy     Open Access   (Followers: 2)
Physics of the Dark Universe     Open Access   (Followers: 4)
Planetary and Space Science     Hybrid Journal   (Followers: 101)
Planetary Science     Open Access   (Followers: 52)
Proceedings of the International Astronomical Union     Full-text available via subscription   (Followers: 2)
Publications of the Astronomical Society of Australia     Hybrid Journal   (Followers: 2)
Publications of the Astronomical Society of Japan     Hybrid Journal   (Followers: 3)
Publications of the Astronomical Society of the Pacific     Full-text available via subscription   (Followers: 4)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 17)
Research in Astronomy and Astrophysics     Full-text available via subscription   (Followers: 29)
Revista Mexicana de Astronomía y Astrofísica     Open Access   (Followers: 2)
Science China Physics, Mechanics & Astronomy     Hybrid Journal   (Followers: 4)
Solar Physics     Hybrid Journal   (Followers: 34)
Solar System Research     Hybrid Journal   (Followers: 14)
Space Science International     Open Access   (Followers: 192)
Space Science Reviews     Hybrid Journal   (Followers: 97)
Space Weather     Full-text available via subscription   (Followers: 24)
Transport and Aerospace Engineering     Open Access   (Followers: 13)
Universe     Open Access   (Followers: 5)
Similar Journals
Journal Cover
Journal of Astrophysics and Astronomy
Journal Prestige (SJR): 0.266
Number of Followers: 52  

  This is an Open Access Journal Open Access journal
ISSN (Print) 0973-7758 - ISSN (Online) 0250-6335
Published by Springer-Verlag Homepage  [2626 journals]
  • The Periodic Table

    • Abstract: Abstract In this article, a historical overview of the development of the Periodic Table has been sketched. After Mendeleev published his Periodic Table in 1869, 55 more elements have been discovered. Of these 55 elements, 35 are radioactive; most of them never existed on Earth earlier. The excitement of the discovery of these unstable elements has been emphasized in this article. In conclusion, the dynamicity of the Periodic Table and its future have been projected.
      PubDate: 2020-12-31
  • Status of nuclear physics behind nucleosynthesis processes: The role of
           exotic neutron-rich nuclei

    • Abstract: Abstract We give a brief overview of the current status of important nuclear physics inputs, like reaction rates, in hydrostatic and explosive nucleosynthesis. Recently, it has been proposed that exotic neutron-rich nuclei play an important role even in the formation of heavy elements via the r-process. The main problems here are identification, abundance estimation of seed nuclei in these processes, and their pathways. We will try to highlight how improved nuclear structure and reaction calculations can affect our present understanding of radiative capture rates of light-mass and medium-mass nuclei, which in turn can drastically influence the abundance of heavier-mass elements.
      PubDate: 2020-12-23
  • Oxygen abundances of carbon-enhanced stellar population in the halo

    • Abstract: Abstract The large fraction of carbon-enhanced metal-poor (CEMP) stars at lower metallicities makes them an interesting class of objects to be probed further in greater detail. They show different abundance patterns of neutron-capture elements and based on that CEMP stars are further divided into four categories. Abundances of C, N and O, along with other elements, are required to understand the different nucleosynthetic origins of the subclasses and their progenitors. We studied nine bright carbon-enhanced stars from the Milky Way halo in a metallicity range from −0.8 to −2.5. They show enhancement in C, N, O and Ba and exhibit radial velocity variation. This indicates the presence of a binary companion which might have contributed to the enhanced carbon and s-process abundance through mass transfer during its asymptotic-giant-branch (AGB) phase of evolution. Their abundance pattern of C, N and O favors low-mass nature for their binary companion.
      PubDate: 2020-12-18
  • Evolution of lithium in low-mass giants: an observational perspective

    • Abstract: Abstract The overabundance of lithium in low-mass red giants has been a topic of interest for over four decades. Low-mass stars are expected to destroy lithium gradually throughout their lifetimes. Against this expectation, about \(1\%\) of red giants in the Galaxy show anomalously large Li which, in the literature, are known as lithium-rich giants. The advent of large-scale stellar surveys (LAMOST, GALAH, Kepler, Gaia) coupled with high-resolution spectra enabled to find important clues about Li enhancement origin in red giants. These new studies suggest Li enhancement is mostly associated with the red clump region, post-He-flash. Here, we will describe our recent results along with current updates in the field.
      PubDate: 2020-12-18
  • Merged white dwarfs and nucleosynthesis

    • Abstract: Abstract Orbital decay mechanisms argue that double white dwarf mergers are inevitable, but extremely rare. Whilst some mergers result in explosions, the survivors re-ignite helium and burn brightly for tens of thousands or millions of years. Candidate survivors include extreme helium stars, R CrB variables and various classes of helium-rich subluminous star. Nuclear waste on the survivors’ surfaces provides evidence of the stars’ nuclear history prior to and their nucleosynthesis during the merger. Extensive and deep spectroscopic surveys offer rich prospects for future discoveries.
      PubDate: 2020-12-18
  • UVIT/AstroSat studies of blue straggler stars and post-mass transfer
           systems in star clusters: detection of one more blue lurker in M67

    • Abstract: Abstract The blue straggler stars (BSSs) are main-sequence (MS) stars, which have evaded stellar evolution by acquiring mass while on the MS. The detection of extremely low mass (ELM) white dwarf (WD) companions to two BSSs and one yellow straggler star (YSS) from our earlier study using UVIT/AstroSat, as well as WD companions to main-sequence stars (known as blue lurkers) suggest a good fraction of post-mass transfer binaries in M67. Using deeper UVIT observations, here we report the detection of another blue lurker in M67, with an ELM WD companion. The post-mass transfer systems with the presence of ELM WDs, including BSSs, are formed from Case A/B mass transfer and are unlikely to show any difference in surface abundances. We find a correlation between the temperature of the WD and the \(v\ \sin i\) of the BSSs. We also find that the progenitors of the massive WDs are likely to belong to the hot and luminous group of BSSs in M67. The only detected BSS+WD system by UVIT in the globular cluster NGC 5466 has a normal WD and suggests that open cluster like environment might be present in the outskirts of low density globular clusters.
      PubDate: 2020-12-17
  • i-Process nucleosynthesis: Observational evidences from CEMP stars

    • Abstract: Abstract The surface chemical compositions of a large fraction of carbon-enhanced metal-poor (CEMP) stars, the so-called CEMP-r/s stars, are known to exhibit enhancement of both s-process and r-process elements. For these stars, the heavy-element abundances cannot be explained either by s-process or r-process nucleosynthesis alone, as the production sites of s-process and r-process elements are very different, and these two processes produce distinct abundance patterns. Thus, the observational evidence of the double enhancement seen in CEMP-r/s stars remains a puzzle as far as the origin of the elements is concerned. In this work, we have critically analysed the observed abundances of heavy elements in a sample of eight CEMP-r/s stars from the literature to trace the origin of the observed double enhancement. Towards this, we have conducted a parametric-model-based analysis to delineate the contributions of s-process and r-process nucleosynthesis to the observed elemental abundances. We have further examined if the i-process (intermediate-process) nucleosynthesis that occurs at high neutron density (n \({\sim }\,10^{15}\)  cm \(^{-3}\) ) produced during proton ingestion from a H-rich envelope to the intershell region of an AGB star, which is capable of producing both r-process and s-process elements in a single stellar site, could explain the observed abundance patterns of the sample stars. Our analysis shows that the observed abundance patterns of the selected sample of CEMP-r/s stars could be fairly well reproduced using the i-process model yields.
      PubDate: 2020-12-17
  • Carbon-enhanced metal-poor stars enriched in s-process and r-process

    • Abstract: Abstract We present an on-going project consisting of analysis of a sample of twenty-five metal-poor stars, most of them carbon-enriched and thus tagged carbon-enhanced metal-poor (CEMP) stars, observed with the high-resolution HERMES spectrograph mounted on the Mercator telescope (La Palma), the UVES spectrograph on VLT (ESO Chile), or the HIRES spectrograph on KECK (Hawaii). This sample consists of CEMP-s stars, which are CEMP stars enriched in slow-neutron-capture (s-process) elements, as well as CEMP-rs stars enriched with both s-process and rapid-neutron-capture (r-process) elements. We also included an r-process-enriched star for comparison purposes. The origin of the abundance differences between CEMP-s and CEMP-rs stars is presently unknown. It has been claimed that the i-process (intermediate nucleosynthesis process), whose site still remains to be identified, could better reproduce CEMP-rs abundances than the s-process. We aim at understanding whether the i-process and its putative site can reproduce the abundance pattern measured in CEMP-rs stars.
      PubDate: 2020-12-17
  • Post-AGB stars as tracers of the origin of elements in the universe

    • Abstract: Abstract The chemical evolution of galaxies is governed by the chemical yields from stars, especially from Asymptotic Giant Branch (AGB) stars. This underlines the importance of understanding how AGB stars produce their elements by obtaining accurate stellar nucleosynthetic yields. Although AGB nucleosynthesis has general validity, critical uncertainties (such as the treatment of convective-driven mixing processes and mass loss) exist in current stellar models. Observations from post-Asymptotic Giant Branch (post-AGB) stars serve as excellent tools to quantify the strongest discrepancies, and eliminate crucial uncertainties that hamper stellar modelling. Our recent studies of post-AGB stars have shown an intriguing chemical diversity that ranges from stars that are extremely enriched in carbon and s-process elements to the discovery of the first post-AGB star with no traces of carbon nor s-process elements. Additionally, AGB nucleosynthesis is significantly affected by a binary companion. These results reflect the complexity that surrounds the element production in AGB stars. In this review, I will briefly present the intriguing chemical diversity observed in post-AGB stars and its implications on element/isotope production in AGB stars and stellar nucleosynthetic yields.
      PubDate: 2020-12-14
  • Recent advances in RV Tauri stars

    • Abstract: Abstract The availability of multi-wavelength observations and parallaxes from the space missions and very comprehensive models of AGB evolution that include the accretion of matter from the circumbinary disc have strongly impacted our understanding of these enigmatic objects. The important developments made in the recent times are summarized here. The revised estimates of luminosities (derived from better-defined Spectral Energy Distributions (SEDs) and new distances from Gaia DR2) further support the opinion that RV Tauri stars contain a mixture of post-AGB stars and post-RGB stars. Their locations in HR diagram also indicate that the instability strip (IS) of RV Tauri stars have a broader extension in the cooler edge than that of classical Cepheids. A new P−L relation has been calibrated for the galactic Cepheids which have a steeper slope than that derived for the Population II Cepheids and RV Tauri stars in Magellanic clouds . The most significant chemical peculiarity exhibited by RV Tauri stars and other post-AGB stars is the selective depletion of refractory elements that correlates with their condensation temperatures. A large range in the size of depletion as well as in the shapes of the depletion curves has been observed. Earlier models to explain this effect were mostly qualitative. Recent investigators model these depletions using evolutionary codes (e.g. MESA) to evolve stars in the post-AGB phase, while including accretion of metal-poor gas from circumbinary disc. These authors model the accretion rate onto a the binary post-AGB star from a viscously evolving disc for a range of initial accretion rates and disc masses. It is reported that large initial accretion rates and disc masses are required to explain the large depletion and saturated depletion curve that could extend the evolution time of post-AGB star. It is also proposed that the unsaturated depletion curve (with a plateau) are likely to be caused by post-RGB stars.
      PubDate: 2020-12-14
  • Recurrent novae: Single degenerate progenitors of Type Ia supernovae

    • Abstract: Abstract Type Ia supernovae are the result of explosive thermonuclear burning in CO white dwarfs. The progenitors of the Ia supernovae are white dwarfs in an interacting binary system. The donor companion is either a degenerate star (white dwarf) or a non-degenerate star (e.g. red giant). Recurrent novae are interacting binaries with a massive white dwarf accreting from either a main sequence, slightly evolved, or a red giant star. The white dwarf in these systems is a massive, hot white dwarf, accreting at a high rate. Recurrent novae are thought to be the most promising single degenerate progenitors of Type Ia supernovae. Presented here are the properties of a few recurrent novae based on recent outbursts. The elemental abundances and their distribution in the ejected shell are discussed.
      PubDate: 2020-12-14
  • Chemical elements in the Universe: Origin and evolution

    • PubDate: 2020-12-11
  • On the cosmic origin of fluorine

    • Abstract: Abstract The cosmic origin of fluorine, the ninth element of the periodic table, is still under debate. The reason for this fact is the large difficulties in observing stellar diagnostic lines, which can be used for the determination of the fluorine abundance in stars. Here we discuss some recent work on the chemical evolution of fluorine in the Milky Way and discuss the main contributors to the cosmic budget of fluorine.
      PubDate: 2020-12-11
  • Galactic chemical evolution and chemical tagging with open clusters

    • Abstract: Abstract The article presents the consolidated results drawn from the chemical composition studies of Reddy et al. (2012, 2013, 2015, 2016) and Reddy & Lambert (2019), who through the high-dispersion echelle spectra ( \(R = 60000\) ) of red giant members in a large sample of Galactic open clusters (OCs), derived stellar parameters and chemical abundances for 24 elements by either line equivalent widths or synthetic spectrum analyses. The focus of this article is on the issues with radial-metallicity distribution and the potential chemical tags offered by OCs. Results of these studies confirm the lack of an age–metallicity relation for OCs but argue that such a lack of trend for OCs arise from the limited coverage in metallicity compared to that of field stars which span a wide range in metallicity and age. Results demonstrate that the sample of clusters constituting a steep radial metallicity gradient of slope −0.052 ± 0.011 dex kpc \(^{-1}\) at R \(_\mathrm{gc}<\) 12 kpc are younger than 1.5 Gyr and located close to the Galactic midplane ( \( z <\,\) 0.5 kpc). Whereas the clusters describing a shallow slope of −0.015 ± 0.007 dex kpc \(^{-1}\) at R \(_\mathrm{gc}>\) 12 kpc are relatively old with a striking spread in age and height above the midplane (0.5 \(\,< z <\,\) 2.5 kpc). Results of these studies reveal that OCs and field stars yield consistent radial metallicity gradients if the comparison is limited to samples drawn from the similar vertical heights. The computation of Galactic orbits reveals that the outer disk OCs were actually born inward of 12 kpc but the orbital eccentricity has taken them to present locations very far from their birthplaces. Published results for OCs show that the abundances of the heavy elements La, Ce, Nd and Sm but not so obviously Y and Eu vary from one cluster to another across a sample all having about the solar metallicity. For La, Ce, Nd and Sm the amplitudes of the variations at solar metallicity scale approximately with the main s-process contribution to solar system material. Consideration of published abundances of field stars suggest that such a spread in heavy element abundances is present for the thin and thick disk stars of different metallicity. This result provides an opportunity to chemically tag stars by their heavy elements and to reconstruct dissolved open clusters from the field star population.
      PubDate: 2020-12-11
  • Abundances of neutron-capture elements in CH and carbon-enhanced
           metal-poor (CEMP) stars

    • Abstract: Abstract All the elements heavier than Fe are produced either by the slow (-s) or rapid (-r) neutron-capture process. The neutron density prevailing in the stellar sites is one of the major factors that determines the type of neutron-capture processes. We present the results based on the estimates of corrected value of absolute carbon abundance, [C/N] ratio, carbon isotopic ratio and [hs/ls] ratio obtained from the high-resolution spectral analysis of six stars that include both CH stars and CEMP stars. All the stars show enhancement of neutron-capture elements. Location of these objects in the A(C) vs. [Fe/H] diagram shows that they are Group I objects, with external origin of carbon and neutron-capture elements. Low values of carbon isotopic ratios estimated for these objects may also be attributed to some external sources. As the carbon isotopic ratio is a good indicator of mixing, we have used the estimates of \(^{12}\) C/ \(^{13}\) C ratios to examine the occurrence of mixing in the stars. While the object HD 30443 might have experienced an extra mixing process that usually occurs after red giant branch (RGB) bump for stars with log(L/L \(_{\odot }\) ) > 2.0, the remaining objects do not show any evidence of having undergone any such mixing process. The higher values of [C/N] ratios obtained for these objects also indicate that none of these objects have experienced any strong internal mixing processes. Based on the estimated abundances of carbon and the neutron-capture elements, and the abundance ratios, we have classified the objects into different groups. While the objects HE 0110−0406, HD 30443 and CD−38 2151 are found to be CEMP-s stars, HE 0308−1612 and HD 176021 show characteristic properties of CH stars with moderate enhancement of carbon. The object CD−28 1082 with enhancement of both r- and s-process elements is found to belong to the CEMP-r/s group.
      PubDate: 2020-12-11
  • Fluorine detection in hot extreme helium stars

    • Abstract: Abstract The origin and evolution of hydrogen-deficient stars are not yet adequately understood. Their chemical peculiarities, along with hydrogen-deficiency, makes them stand out from the rest and sheds light on their possible origin. Severe fluorine enrichment (of the order of 800–8000) is one such characteristic feature of a class of hydrogen deficient stars, mainly the RCBs (R Coronae Borealis stars) and cool EHes (Extreme Helium stars) which enforces their close connection. For hot EHes, this relationship with the cooler EHes, based on their fluorine abundance is unexplored. Here, first estimates of fluorine abundances in hot EHes are presented and discussed in the light of their cooler counterparts to try to establish an evolutionary connection. The relation between these fluorine estimates with the other elemental abundances observed in these stars plays a pivotal role to predict the formation and evolution of these exotic stars.
      PubDate: 2020-12-11
  • New measurements of cross sections and S-factors for $$d(p,\gamma
           )^{3}\text{He}$$ d ( p , γ ) 3 He reaction at BBN energies

    • Abstract: Abstract This communication is a summary of our measurements of cross sections and astrophysical S-factors for radiative proton capture on deuteron. The measurements are a part of a new program to study light-ion induced nuclear capture and inelastic scattering reactions relevant to nucleosynthesis and astrophysics. We are primarily interested in the capture reactions relevant to primordial or Big Bang Nucleosynthesis (BBN). Section 1 provides a brief and general overview of nuclear astrophysics and the primary experimental challenges in the measurements of cross sections and S-factors for reactions relevant to nuclear astrophysics. The next section discusses the significance of the \(d(p,\gamma )^{3}\text{He}\) reaction in context of BBN and the need for generating a more precise data in the relevant energy window. The subsequent section is devoted to the experiment and results of measurements of cross sections and astrophysical S-factors for the \(d(p,\gamma )^{3}\text{He}\) reaction at three new BBN energies. One salient features of the measurements is the use of large volume LaBr \(_{3}\) :Ce scintillation detector for measurement of the capture \(\gamma \) -rays. To the best of our knowledge, capture \(\gamma \) -rays for this reaction had so far been measured with NaI(Tl) or HPGe detectors only. The detection efficiency of the detector has been measured experimentally for different monochromatic \(\gamma \) -ray energies. In addition, realistic GEANT4 Monte Carlo simulations have been carried out to generate the response of the detector for \(\gamma \) -ray energies of interest. The measured cross section and astrophysical S(E)-factor for the three incident proton energies are found to be in agreement with the overall trend of the global data set for the BBN region, reported in the literature. The measured S-factors are also found to be in agreement with recent microscopic calculations of Marcucci et al. (2016).
      PubDate: 2020-12-11
  • Chemical composition of the solar surface

    • Abstract: Abstract The Sun provides a standard reference against which we compare the chemical abundances found anywhere else in the Universe. Nevertheless, there is not a unique ‘solar’ composition, since the chemical abundances found in the solar interior, the photosphere, the upper atmosphere, or the solar wind, are not exactly the same. The composition of the solar photosphere, usually preferred as a reference, changes with time due to diffusion, convection, and probably accretion. In addition, we do not know the solar photospheric abundances, inferred from the analysis of the solar spectrum using model atmospheres, with high accuracy, and uncertainties for many elements exceed 25%. This article gives an overview of the methods and pitfalls of spectroscopic analysis, and discusses the chemistry of the Sun in the context of the solar system.
      PubDate: 2020-12-11
  • [Rb/Zr] ratio in Ba stars as a diagnostic of the companion AGB stellar

    • Abstract: Abstract Understanding nucleosynthesis in and evolution of asymptotic giant branch (AGB) stars is of primary importance as these stars are the main producers of some of the key elements in the Universe. They are the predominant sites for slow-neutron-capture nucleosynthesis (s-process). The exact physical conditions and nucleosynthetic processes occurring in the interior of AGB stars are not clearly understood, and that hinders better understanding of the contribution of these stars to the Galactic chemical enrichment. Extrinsic-variable stars that are known to have received products of AGB phase of evolution via binary mass-transfer mechanisms are vital tools in tracing AGB nucleosynthesis. The [Rb/Zr] ratio is an important diagnostic to understand the average neutron density at the s-process site and provides important clues to the mass of companion AGB stars in binaries. In this work we have presented estimates of [Rb/Zr] ratios based on high-resolution spectroscopic analysis for a sample of Ba stars, and discussed how the ratio can be used to understand the characteristics of the AGB star. Results from an analysis based on a parametric model to confirm the mass of the companion AGB star are also presented.
      PubDate: 2020-12-11
  • The horizontal branch morphology of the globular cluster NGC 1261 using

    • Abstract: Abstract We present the results obtained from the UV photometry of the globular cluster NGC 1261 using far-UV (FUV) and near-UV (NUV) images acquired with the Ultraviolet Imaging Telescope (UVIT) on-board the AstroSat satellite. We utilized the UVIT data combined with HST, GAIA, and ground-based optical photometric data to construct the different UV colour-magnitude diagrams (CMDs). We detected blue HB (BHB), and two extreme HB (EHB) stars in FUV, whereas full HB, i.e., red HB (RHB), BHB as well as EHB is detected in NUV CMDs. The 2 EHB stars, identified in both NUV and FUV, are confirmed members of the cluster. The HB stars form a tight sequence in UV-optical CMDs, which is almost aligned with Padova isochrones. This study sheds light on the significance of UV imaging to probe the HB morphology in GCs.
      PubDate: 2020-12-11
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