相关论文: Fullerenes in circumstellar and interstellar envir…
In the interstellar medium carbon exists in the form of two stable isotopes $^{12}$C and $^{13}$C and their ratio is a good indicator of nucleosynthesis in galaxies. However, chemical fractionation can potentially significantly alter this…
Circumstellar envelopes (CEs) around evolved stars are an active site for the production of molecules. After evolving through the Asymptotic Giant Branch (AGB), proto-planetary nebula (PPN), to planetary nebula (PN) phases, CEs ultimately…
Episodic accretion plays an important role in the evolution of young stars. Although it has been under investigation for a long time, the origin of such episodic accretion events is not yet understood. We investigate the dust and gas…
Filamentary structures are often identified in column density maps of molecular clouds, and appear to be important for both low- and high-mass star formation. Theoretically, these structures are expected to form in regions where the…
The Diffuse Interstellar Bands (DIBs) are absorption features seen in the spectra of astronomical objects, that arise in the interstellar medium. Today more than 500 DIBs have been observed mostly in the optical and near-infrared…
Recent analyses of nebular spectra have resulted in discrepant abundances from CNO forbidden and recombination lines. We consider independent methods of determining ion abundances for emission nebulae, comparing ion emission measures with…
Emission lines in X-ray spectra of clusters of galaxies reveal the presence of heavy elements in the diffuse hot plasma (the Intra Cluster Medium, or ICM) in virial equilibrium in the dark matter potential well. The relatively simple…
We have made subarcsecond-resolution images of the central 10" of the Wolf-Rayet dwarf galaxy He 2-10 at 11.7 microns, using the Long Wavelength Spectrometer on the Keck Telescope. The spatial distribution of the infrared emission roughly…
This study explores the molecular origins of plateaus and continuum underlying IR and FIR bands emitted by compact nebulae, especially proto-planetary nebulae. Computational organic chemistry codes are used to deliver the vibrational…
Neutral Fe lines are the most abundant in the spectrum of late stars. They are used to obtain different basic stellar parameters such as relative abundances, surface gravity, and effective temperature. However, the centers of many of these…
We report the results of deep infrared observations of brown dwarf candidates in the Trapezium cluster in Orion. Analysis of the JHK color-color diagram indicates that a large fraction (approx 65% +/- 15%) of the observed sources exhibit…
Based on our prior accurate determination of fundamental parameters for 36 Galactic A-, F- and G-type supergiants and bright giants (luminosity classes I and II), we undertook a non-LTE analysis of the carbon abundance in their atmospheres.…
Turbulent fragmentation determines where and when protostellar cores form, and how they contract and grow in mass from the surrounding cloud material. This process is investigated, using numerical models of self-gravitating molecular cloud…
We present a Spitzer/IRS low-resolution mid-infrared spectrum (5-14 micron) of the luminous transient discovered in the nearby galaxy NGC 300 in May 2008. The spectrum, obtained three months after discovery, shows that the transient is very…
It is generally recognized that the interstellar medium has a vast range of densities and temperatures. While these two properties are usually anticorrelated with each other, there are nevertheless variations in their product, i.e., the…
We present a model of the interaction of interstellar dust grains with a stellar environment, that predicts the distribution of interstellar dust grains in the size range between $0.1 {\rm \mu m}$ and $1 {\rm \mu m}$ around a star for the…
It is shown that the C60-fullerene anion has a hydrogen-like spectrum.
Context: Molecular hydrogen (H2) is the most abundant molecule in the circumstellar (CS) environments of young stars, and is a key element in giant planet formation. The measurement of the H2 content provides the most direct probe of the…
In the first paper in this series, we proposed a new framework in which to model the chemical evolution of globular clusters. This model, is predicated upon the assumption that clusters form within an interstellar medium enriched locally by…
Context: The geometry of the circumstellar envelopes (CSE) surrounding Be stars is still uncertain, although it is often assumed that they are formed by a disk around the stellar equator and a hot polar wind. Achernar (Alpha Eri) is the…