Related papers: Formation depths of Fraunhofer lines
Characteristics of the depression contribution functions are studied for the Stokes line profiles formed in a magnetic field. The form of the depression functions depends mainly on the strength of splitting and the Zeeman component…
Spectropolarimetric results of Fraunhofer lines between 516.3nm and 532.6nm are presented in local upper solar chromosphere, transition zone and inner corona below a height of about 0.04 solar radius above the solar limb. The data were…
During solar flares, spectral lines formed in the photosphere have been shown to exhibit changes to their profiles despite the challenges of energy transfer to these depths. Recent work has shown that deep-forming spectral lines are subject…
Fraunhofer diffraction plays a vital role in experimental physics not only because it accurately describes the behaviour of light in the usual propagation limit, but also because it links the diffracted light with the scattering object…
We investigate general aspects of molecular line formation under conditions which are typical of prestellar cores. Focusing on simple linear molecules, we study formation of their rotational lines by radiative transfer simulations. We…
The atomic spectra and structure of the open d- and f-shell elements are extremely complex, where tens of thousands of transitions between fine structure energy levels can be observed as spectral lines across the infrared and UV per…
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…
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…
We investigate the presence of iron line emission among faint X-ray sources identified in the 1Ms Chandra Deep Field South and in the 2Ms Chandra Deep Field North. Individual source spectra are stacked in seven redshift bins over the range…
Stellar absorption lines of heavy elements can give us various insights into the chemical evolution of the Galaxy and nearby galaxies. Recently developed spectrographs for the near-infrared wavelengths are becoming more and more powerful…
A discharge of nitrogen gas, as created in a microwave-induced plasma, exhibits a very dense molecular emission line spectrum. Emission spectra of this kind could serve as wavelength calibrators for high-resolution astrophysical…
We have observed selected Fraunhofer lines, both integrated over the Full Disk and for a small circular region near the center of the solar disk, on 1,215 days for the past 30 years. Full Disk results: Ca II K 393 nm nicely tracks the 11…
We demonstrate that a common-line method can assemble a 3D oversampled diffracted intensity distribution suitable for high-resolution structure solution from a set of measured 2D diffraction patterns, as proposed in experiments with an…
Motivated by the measurement of redshifted Fe H$\alpha$ lines during type I X-ray bursts on EXO 0748-676 (Cottam, Paerels & Mendez), we study the formation of atomic Fe lines above the photosphere of a bursting neutron star ($k_BT_{\rm eff}…
A new source in solar corona scattering photospheric and chromospheric Fraunhofer spectral lines is detected below a height of one solar radius above solar limb, consisting of tenuous and cool neutral atoms and much fewer once ionized ions.…
Aims: We resolve the length-scales for filament formation and fragmentation (res. <=0.1pc), in particular the Jeans length and cylinder fragmentation scale. Methods: We observed the prototypical high-mass star-forming filament IRDC18223…
Filamentary structures are ubiquitous in observations of real molecular clouds, and also in simulations of turbulent, self-gravitating gas. However, making comparisons between observations and simulations is complicated by the difficulty of…
In active galactic nuclei (AGN), fluorescent Fe K$\alpha$ (iron) line emission is generally interpreted as originating from obscuring material around a supermassive black hole (SMBH) on the scale of a few parsecs (pc). However, recent…
(abbreviated version of the abstract) We study the physics of cyclotron line formation in the high-energy spectra of accreting X-ray pulsars using Monte Carlo methods, assuming that the line-forming region is a low-density electron plasma…
The solar brightness varies on timescales from minutes to decades. A clear identification of the physical processes behind such variations is needed for developing and improving physics-based models of solar brightness variability and…