Related papers: Understanding and reducing statistical uncertainti…
HII regions, ionized nebulae where massive star formation has taken place, exhibit a wealth of emission lines that are the fundamental basis for estimating the chemical composition of the Universe. For more than 80 years, a discrepancy of…
We have conducted a large-scale survey of 120 planetary nebulae (PNe) to search for the near-infrared emission lines [Kr III] 2.199 and [Se IV] 2.287 microns. The neutron(n)-capture elements Se and Kr may be enriched in a PN if its…
Emission lines in ionized nebulae can provide strong and useful constraints on the properties of both ionizing and non-ionizing stellar populations in regions with star formation, provided that stellar evolution and stellar atmosphere…
(abridged) A complete census of planetary systems around a volume-limited sample of solar-type stars (FGK dwarfs) in the Solar neighborhood with uniform sensitivity down to Earth-mass planets within their Habitable Zones out to several AUs…
The derivation of nebular abundances in galaxies using strong line methods is simple and quick. Various indices have been designed and calibrated for this purpose, and they are widely used. However, abundances derived with such methods may…
Context: Diffusion of species on the dust surface is a key process for determining the chemical composition of interstellar ices. On the dust surface, adsorbed species diffuse from one potential well to another and react with other adsorbed…
Estimates of the gas temperature in planetary nebulae obtained from the [O III] emission line ratio and from the Balmer discontinuity indicate differences reaching up to 6000 K (Liu and Danziger 1993). The [O III] temperature is commonly…
[Abridged] Deep optical observations of the spectra of 12 Galactic planetary nebulae (PNe) and 3 Magellanic Cloud PNe were presented in Paper I by Tsamis et al. (2003b), who carried out an abundance analysis using the collisionally excited…
The work presented forms a part of the IASc-INSA-NASI Summer Research Fellowship (SRFP) project on the physical & chemical properties of planetary nebulae. Spectral observations of NGC3242 recorded using the VBT Observatory (IIA), Kavalur…
A method is presented to derive electron temperatures and densities of planetary nebulae (PNe) simultaneously, using the observed hydrogen recombination spectrum, which includes continuum and line emission. By matching theoretical spectra…
We have carried out optical spectroscopic measurements of emission lines for a sample of Galactic planetary nebulae with Wolf-Rayet (WR) stars and weak emission-line stars (wels). The plasma diagnostics and elemental abundance analysis have…
The rest-frame UV spectra of star-forming galaxies are increasingly important as they become one of the primary windows to probe the physical properties of cosmic dawn (z>8) galaxies with the James Webb Space Telescope. However, the…
An analytic calculation is made of the effect of plasma density fluctuations on some spectroscopic diagnostics commonly used in the study of HII regions and planetary nebulae. To permit an analytic treatment, attention is restricted to the…
This paper outlines a way to determine the ICF using only infrared data. We identify four line pairs, [NeIII] 36$\micron$/[NeII] 12.8$\micron$, [NeIII]~15.6$\micron$ /[NeII] 12.8$\micron$, [ArIII] 9$\micron$/[ArII] 6.9$\micron$, and [ArIII]…
This paper is the fourth and final report on a project designed to study carbon abundances in a sample of planetary nebulae representing a broad range in progenitor mass and metallicity. We present newly acquired optical spectrophotometric…
We obtained nebular spectroscopy of LMC HII regions having classified stellar populations, thereby strongly constraining the ionization input parameters. Using photoionization models, we then evaluate the performance of nebular diagnostics…
A fundamental limitation of traditional Neural Networks (NN) in predictive modelling is their inability to quantify uncertainty in their outputs. In critical applications like positioning systems, understanding the reliability of…
We present a simple method for determining the (correlated) uncertainties of the light element abundances expected from big bang nucleosynthesis, which avoids the need for lengthy Monte Carlo simulations. Our approach helps to clarify the…
We propose a new method for determination of element abundances in stellar atmospheres aimed for the automatic processing of high-quality stellar spectra. The pan-spectral method is based on weighted cumulative line-widths Q of studied…
The abundances of the isotopes of the elements from C to Al produced by the non-explosive CNO, NeNa and MgAl modes of hydrogen burning, as well as by helium burning, are calculated with the thermonuclear rates recommended by the European…