Related papers: Modelling the Astronomical Silicate Features: I. O…
Using the technique of spectral disentangling, it is possible to determine the individual spectra of the components of a multiple star system from composite spectra observed at a range of orbital phases. This method has several advantages:…
Observations of exoplanet transit spectra are essential to understanding the physics and chemistry of distant worlds. The effects of opacity sources and many physical processes combine to set the shape of a transit spectrum. Two such key…
One of the well-known problems of producing instruments for Extremely Large Telescopes is that their size (and hence cost) scales rapidly with telescope aperture. To try to break this relation alternative new technologies have been…
Based on the classical Lorentz model of the index of refraction, a new method is presented for the extraction of the complex index of refraction from the extinction efficiency of homogeneous and layered dielectric spheres that…
Context. Interstellar ice is the main form of metal species in dark molecular clouds. Experiments and observations have shown that the ice is significantly processed after the freeze-out of molecules onto grains. The processing is caused by…
Many things in current interstellar dust studies are taken as well understood givens by much of the community. For example, it is widely held that interstellar dust is made up of only three components, i.e., astronomical silicates, graphite…
Absorption-line spectroscopy is a powerful tool used to estimate element abundances in the nearby as well as distant universe. The accuracy of the abundances thus derived is, naturally, limited by the accuracy of the atomic data assumed for…
Quantitative thermodynamical, dynamical and magnetic properties of the solar and stellar plasmas are obtained by interpreting their emergent non-polarized and polarized spectrum. This inference requires the selection of a set of spectral…
Conventional ground-based optical telescopes, even those with large apertures, primarily observe stars, close binaries, and multiple systems as unresolved point sources through photometric measurements. Spectroscopy can identify multiple…
We present preliminary results on on-sky test of sky subtraction methods for fiber-fed spectrograph. Using dedicated observation with FLAMES/VLT in I-band, we have tested the accuracy of the sky subtraction for 4 sky subtraction methods:…
A model of spheroidal particles is used to calculate the steady-state temperature of dust grains immersed in the interstellar radiation field. It is found that the temperature of non-spherical grains with the aspect ratios a/b <= 2 deviates…
We examine the thermal infrared spectra of large dust grains of different chemical composition and mineralogy. Strong resonances in the optical properties result in detectable spectral structure even when the grain is much larger than the…
Ice mantles on dust grains play a central role in astrochemistry. Water and complex organic molecules (COMs) are thought to first form on the ice mantles and subsequently are released into the gas phase due to star formation activity.…
Resolving fine details of astronomical objects provides critical insights into their underlying physical processes. This drives in part the desire to construct ever-larger telescopes and interferometer arrays and to observe at shorter…
We compute the desorption rate of icy mantles on dust grains as a function of the size and composition of both the grain and the mantle. We combine existing models of cosmic ray (CR) related desorption phenomena with a model of CR transport…
The optical and infrared spectra of a wide variety of `cool' astronomical objects including the Sun, sunspots, K-, M- and S-type stars, carbon stars, brown dwarfs and extrasolar planets are reviewed. The review provides the necessary…
Spectra of late-type stars are usually analyzed with static model atmospheres in local thermodynamic equilibrium (LTE) and a homogeneous plane-parallel or spherically symmetric geometry. The energy balance requires particular attention, as…
We study the chemical evolution of interstellar grain mantle by varying the physical parameters of the interstellar medium (ISM). To mimic the exact interstellar condition, gas grain interactions via accretion from the gas phase and…
The knowledge of isotopic and elemental abundances of the pristine solar system material provides a fundamental test of galactic chemical evolution models, while the composition of the solar photosphere is a reference pattern to understand…
In this work we study in details the influence of pure astronomical refraction on solar metrologic measurements made from ground-based full disk imagery and provide the tools for correcting the measurements and estimating the associated…