Results 81 to 90 of about 4,372,191 (364)

Planetary nebulae in the inner Milky Way: new abundances [PDF]

, 2009
The study of planetary nebulae in the inner-disk and bulge gives important information on the chemical abundances of elements such as He, N, O, Ar, Ne, and on the evolution of these abundances, which is associated with the evolution of intermediate-mass ...
Cavichia, O., Costa, R. D. D., Maciel, W. J.   +2 more
core   +2 more sources

Chemical abundances of the Typhon stellar stream

Monthly Notices of the Royal Astronomical Society, 2022
ABSTRACT We present the first high-resolution chemical abundances of seven stars in the recently discovered high-energy stream Typhon. Typhon stars have apocentres r ≳ 100 kpc, making this the first detailed chemical picture of the Milky Way’s very distant stellar halo.
Alexander P Ji, Rohan P Naidu, Kaley Brauer, Yuan-Sen Ting, Joshua D Simon   +4 more
openaire   +2 more sources

YOUNG STARS AND IONIZED NEBULAE IN M83: COMPARING CHEMICAL ABUNDANCES AT HIGH METALLICITY [PDF]

, 2016
We present spectra of 14 A-type supergiants in the metal-rich spiral galaxy M83. We derive stellar parameters and metallicities and measure a spectroscopic distance modulus (4.9 ± 0.2 Mpc), in agreement with other methods.
F. Bresolin, R. Kudritzki, M. Urbaneja, W. Gieren, I. Ho, G. Pietrzyński   +5 more
semanticscholar   +1 more source

A stepwise emergence of evolution in the RNA world

FEBS Letters, EarlyView.
How did biological evolution emerge from chemical reactions? This perspective proposes a gradual scenario of self‐organization among RNA molecules, where catalytic feedback on random mixtures plays the central role. Short oligomers cross‐ligate, and self‐assembly enables heritable variations. An event of template‐externalization marks the transition to
Philippe Nghe
wiley   +1 more source

Generalized Te([O iii])–Te(He i) Discrepancies in Ionized Nebulae: Possible Evidence of Case B Deviations and Temperature Inhomogeneities

The Astrophysical Journal
The physics of recombination lines in the He i singlet system is expected to be relatively simple, supported by accurate atomic models. We examine the intensities of He i singlets λ 3614,  λ 3965,  λ 5016,  λ 6678, and  λ 7281 and the triplet He i λ 5876
J. E. Méndez-Delgado, E. D. Skillman, E. Aver, C. Morisset, C. Esteban, J. García-Rojas, K. Kreckel, N. S. J. Rogers, F. F. Rosales-Ortega, K. Z. Arellano-Córdova, S. R. Flury, E. Reyes-Rodríguez, M. Orte-García, S. Tan   +13 more
doaj   +1 more source

Circulating histones as clinical biomarkers in critically ill conditions

FEBS Letters, EarlyView.
Circulating histones are emerging as promising biomarkers in critical illness due to their diagnostic, prognostic, and therapeutic potential. Detection methods such as ELISA and mass spectrometry provide reliable approaches for quantifying histone levels in plasma samples.
José Luis García‐Gimenez, Juan Carlos Ruiz‐Rodríguez, Ricard Ferrer, Raquel Durá, Antonio Artigas, Iván Bajaña, David Bolado López de Andujar, Irene Cánovas‐Cervera, Adrián Ceccato, Luis Chiscano‐Camón, Elena Climent‐Martinez, Georgia García Fernández, Gemma Goma, Verónica Monforte, Beatriz Quevedo‐Sánchez, Adolf Ruiz‐Sanmartín, Antonio Sierra‐Rivera, Nieves Carbonell Monleón   +17 more
wiley   +1 more source

Chemical abundances in Seyfert galaxies – IX. Helium abundance estimates

Monthly Notices of the Royal Astronomical Society, 2022
ABSTRACT For the first time, the helium abundance relative to hydrogen (He/H), which relied on direct measurements of the electron temperature, has been derived in the narrow line regions (NLRs) from a local sample of Seyfert 2 nuclei.
O L Dors, M Valerdi, P Freitas-Lemes, A C Krabbe, R A Riffel, E B Amôres, R Riffel, M Armah, A F Monteiro, C B Oliveira   +9 more
openaire   +2 more sources

Two groups of red giants with distinct chemical abundances in the bulge globular cluster NGC 6553 through the eyes of APOGEE [PDF]

, 2016
Multiple populations revealed in globular clusters (GCs) are important windows to the formation and evolution of these stellar systems. The metal-rich GCs in the Galactic bulge are an indispensable part of this picture, but the high optical extinction in
B. Tang, R. Cohen, D. Geisler, R. Schiavon, S. Majewski, S. Villanova, R. Carrera, O. Zamora, D. A. García-Hernández, M. Shetrone, P. Frinchaboy, A. Meza, J. Fernández-Trincado, R. Muñoz, Chien-Cheng Lin, R. Lane, C. Nitschelm, K. Pan, D. Bizyaev, D. Bizyaev, D. Oravetz, A. Simmons   +21 more
semanticscholar   +1 more source

Hot Stars in Stellar Populations of Galaxies

Galaxies
Star-forming galaxies are hosts of dominant populations of recently formed, hot, massive stars, which give rise to conspicuous stellar spectral features and provide the ionizing fluxes. Strong outflows of these stars shape their properties.
Claus Leitherer
doaj   +1 more source

Chemical abundances and metallicity of Planetary Nebulae [PDF]

Symposium - International Astronomical Union, 1997
Confrontations of the dredge-up theory with observed patterns of chemical abundances of planetary nebulae (PNs) have been carried out by many authors (see, e.g., Kaler & Jacoby 1990, 1991; Stasińska & Tylenda 1990). Although these studies suggest that the observational abundance ratios of PNs can qualitatively be explained by the current dredge-
C. Y. Zhang, Sun Kwok
openaire   +2 more sources