8 results on '"Basu, Sarbani"'
Search Results
2. Observational constraints on the origin of the elements
- Author
-
Magg, Ekaterina, primary, Bergemann, Maria, additional, Serenelli, Aldo, additional, Bautista, Manuel, additional, Plez, Bertrand, additional, Heiter, Ulrike, additional, Gerber, Jeffrey M., additional, Ludwig, Hans-Günter, additional, Basu, Sarbani, additional, Ferguson, Jason W., additional, Gallego, Helena Carvajal, additional, Gamrath, Sébastien, additional, Palmeri, Patrick, additional, and Quinet, Pascal, additional
- Published
- 2022
- Full Text
- View/download PDF
3. Observational constraints on the origin of the elements IV. Standard composition of the Sun
- Author
-
Magg, Ekaterina, Bergemann, Maria, Serenelli, Aldo, Bautista, Manuel, Plez, Bertrand, Heiter, Ulrike, Gerber, Jeffrey M., Ludwig, Hans-Guenter, Basu, Sarbani, Ferguson, Jason W., Gallego, Helena Carvajal, Gamrath, Sebastien, Palmeri, Patrick, Quinet, Pascal, Magg, Ekaterina, Bergemann, Maria, Serenelli, Aldo, Bautista, Manuel, Plez, Bertrand, Heiter, Ulrike, Gerber, Jeffrey M., Ludwig, Hans-Guenter, Basu, Sarbani, Ferguson, Jason W., Gallego, Helena Carvajal, Gamrath, Sebastien, Palmeri, Patrick, and Quinet, Pascal
- Abstract
Context. The chemical composition of the Sun is required in the context of various studies in astrophysics, among them in the calculation of standard solar models (SSMs) used to describe the evolution of the Sun from the pre-main-sequence to its present age. Aims. In this work, we provide a critical re-analysis of the solar chemical abundances and corresponding SSMs. Methods. For the photospheric values, we employed new high-quality solar observational data collected with the IAG facility, state-of-the art non-equilibrium modelling, new oscillator strengths, and different atmospheric models, including the MARCS model, along with averages based on Stagger and CO5BOLD 3D radiation-hydrodynamics simulations of stellar convection. We performed new calculations of oscillator strengths for transitions in O I and N I. For O I, which is a critical element with regard to the interior models, calculations were carried out using several independent methods. We investigated our results in comparison with the previous estimates. Results. We find an unprecedented agreement between the new estimates of transition probabilities, thus supporting our revised solar oxygen abundance value. We also provide new estimates of the noble gas Ne abundance. In addition, we discuss the consistency of our photospheric measurements with meteoritic values, taking into account the systematic and correlated errors. Finally, we provide revised chemical abundances, leading to a new value proposed for the solar photospheric present-day metallicity of Z/X=0.0225, which we then employed in SSM calculations. We find that the puzzling mismatch between the helioseismic constraints on the solar interior structure and the model can be resolved thanks to this new chemical composition.
- Published
- 2022
- Full Text
- View/download PDF
4. Observational constraints on the origin of the elements
- Author
-
Collaborative Research Centres (Germany), University of Heidelberg, German Research Foundation, Max Planck Society, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), European Commission, Centre National D'Etudes Spatiales (France), European Research Council, Swedish National Space Agency, Magg, Ekaterina, Bergemann, Maria, Serenelli, Aldo, Bautista, Manuel, Plez, Bertrand, Heiter, Ulrike, Gerber, Jeffrey M., Ludwig, Hans-Günter, Basu, Sarbani, Ferguson, Jason W., Carvajal Gallego, Helena, Gamrath, Sébastien, Palmeri, Patrick, Quinet, Pascal, Collaborative Research Centres (Germany), University of Heidelberg, German Research Foundation, Max Planck Society, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), European Commission, Centre National D'Etudes Spatiales (France), European Research Council, Swedish National Space Agency, Magg, Ekaterina, Bergemann, Maria, Serenelli, Aldo, Bautista, Manuel, Plez, Bertrand, Heiter, Ulrike, Gerber, Jeffrey M., Ludwig, Hans-Günter, Basu, Sarbani, Ferguson, Jason W., Carvajal Gallego, Helena, Gamrath, Sébastien, Palmeri, Patrick, and Quinet, Pascal
- Abstract
[Context] The chemical composition of the Sun is required in the context of various studies in astrophysics, among them in the calculation of standard solar models (SSMs) used to describe the evolution of the Sun from the pre-main-sequence to its present age., [Aims] In this work, we provide a critical re-analysis of the solar chemical abundances and corresponding SSMs., [Methods] For the photospheric values, we employed new high-quality solar observational data collected with the IAG facility, state-of-the art non-equilibrium modelling, new oscillator strengths, and different atmospheric models, including the MARCS model, along with averages based on Stagger and CO5BOLD 3D radiation-hydrodynamics simulations of stellar convection. We performed new calculations of oscillator strengths for transitions in O I and N I. For O I, which is a critical element with regard to the interior models, calculations were carried out using several independent methods. We investigated our results in comparison with the previous estimates., [Results] We find an unprecedented agreement between the new estimates of transition probabilities, thus supporting our revised solar oxygen abundance value. We also provide new estimates of the noble gas Ne abundance. In addition, we discuss the consistency of our photospheric measurements with meteoritic values, taking into account the systematic and correlated errors. Finally, we provide revised chemical abundances, leading to a new value proposed for the solar photospheric present-day metallicity of Z/X = 0.0225, which we then employed in SSM calculations. We find that the puzzling mismatch between the helioseismic constraints on the solar interior structure and the model can be resolved thanks to this new chemical composition.
- Published
- 2022
5. Evolutionary states of red-giant stars from grid-based modelling
- Author
-
Hekker Saskia, Elsworth Yvonne, Basu Sarbani, and Bellinger Earl
- Subjects
Physics ,QC1-999 - Abstract
From its surface properties it can be difficult to determine whether a red-giant star is in its heliumcore-burning phase or only burning hydrogen in a shell around an inert helium core. Stars in either of these stages can have similar effective temperatures, radii and hence luminosities, i.e. they can be located at the same position in the Hertzsprung-Russell diagram. Asteroseismology – the study of the internal structure of stars through their global oscillations – can provide the necessary additional constraints to determine the evolutionary states of red-giant stars. Here, we present a method that uses grid-based modelling based on global asteroseismic properties (vmax, frequency of maximum oscillation power; and Δv, frequency spacing between modes of the same degree and consecutive radial orders) as well as effective temperature and metallicity to determine the evolutionary phases. This method is applicable even to timeseries data of limited length, although with a small fraction of miss-classifications.
- Published
- 2017
- Full Text
- View/download PDF
6. Stellar Parameters in an Instant with Machine Learning
- Author
-
Bellinger Earl P., Angelou George C., Hekker Saskia, Basu Sarbani, Ball Warrick H., and Guggenberger Elisabet
- Subjects
Physics ,QC1-999 - Abstract
With the advent of dedicated photometric space missions, the ability to rapidly process huge catalogues of stars has become paramount. Bellinger and Angelou et al. [1] recently introduced a new method based on machine learning for inferring the stellar parameters of main-sequence stars exhibiting solar-like oscillations. The method makes precise predictions that are consistent with other methods, but with the advantages of being able to explore many more parameters while costing practically no time. Here we apply the method to 52 so-called “LEGACY“ main-sequence stars observed by the Kepler space mission. For each star, we present estimates and uncertainties of mass, age, radius, luminosity, core hydrogen abundance, surface helium abundance, surface gravity, initial helium abundance, and initial metallicity as well as estimates of their evolutionary model parameters of mixing length, overshooting coeffcient, and diffusion multiplication factor. We obtain median uncertainties in stellar age, mass, and radius of 14.8%, 3.6%, and 1.7%, respectively. The source code for all analyses and for all figures appearing in this manuscript can be found electronically at https://github.com/earlbellinger/asteroseismology
- Published
- 2017
- Full Text
- View/download PDF
7. Isochrones of M67 with an Expanded Set of Parameters
- Author
-
Viani Lucas and Basu Sarbani
- Subjects
Physics ,QC1-999 - Abstract
We create isochrones of M67 using the Yale Rotating Stellar Evolution Code. In addition to metallicity, parameters that are traditionally held fixed, such as the mixing length parameter and initial helium abundance, also vary. The amount of convective overshoot is also changed in different sets of isochrones. Models are constructed both with and without diffusion. From the resulting isochrones that fit the cluster, the age range is between 3.6 and 4.8 Gyr and the distance is between 755 and 868 pc. We also confirm Michaud et al. (2004) claim that M67 can be fit without overshoot if diffusion is included.
- Published
- 2017
- Full Text
- View/download PDF
8. Asteroseismic estimate of helium abundance of 16 Cyg A, B
- Author
-
Verma Kuldeep, Faria João P., Antia H. M., Basu Sarbani, Mazumdar Anwesh, Monteiro Mário J. P. F. G., Appourchaux Thierry, Chaplin William J., García Rafael A., and Metcalfe Travis S.
- Subjects
Physics ,QC1-999 - Abstract
The helium ionization zone in a star leaves a characteristic signature on its oscillation frequencies, which can be used to estimate the helium content in the envelope of the star. We use the oscillation frequencies of 16 Cyg A and B, obtained using 2.5 years of Kepler data, to estimate the envelope helium abundance of these stars. We find the envelope helium abundance to lie in the range 0.231–0.251 for 16 Cyg A and 0.218–0.266 for 16 Cyg B.
- Published
- 2015
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.