Using a specialized technique sensitive to the presence of expanding ionized gas, we have detected a set of three concentric expanding shells in an H II region in the nearby spiral galaxy M33. After mapping the kinematics in Hα with Fabry-Perot spectroscopy, we used slit spectra to measure the intensities of the [S II] doublet at λλ671.9, 673.1 nm

This paper reviews Ladenburg’s development of the phenomenological theory of radiative transitions between the stationary states of an atom put forward by Einstein in 1917. The historical background as well as the far reaching outcomes of his work are considered and discussed; among them the Kramers–Heisenberg quantum dispersion theory that paved

This paper is the first one of a series of two on the role of the optical dispersion in the historical development of early quantum mechanics. As preparation for the successive paper on Ladenburg’s development of the phenomenological theory of radiative transitions between the stationary states of an atom by Einstein, we present here the current

We present a detailed study of the neutral and ionized gas phases in the galactic wind for the nearby starburst galaxy NGC 5394 based on new integral field spectroscopy obtained with the INTEGRAL fibre system at the William Herschel Telescope. The neutral gas phase in the wind is detected via the interstellar Na I D doublet absorption. After a

Context. Solar prominences are subject to both field-aligned (longitudinal) and transverse oscillatory motions, as evidenced by an increasing number of observations. Large-amplitude longitudinal motions provide valuable information on the geometry of the filament-channel magnetic structure that supports the cool prominence plasma against gravity

Utilizing the unique location of red clump giants on colour-magnitude diagrams obtained from various near-infrared surveys, we derived specific reddening-distance relations towards 119 Galactic novae for which independent reddening measurements are available. Using the derived distance-extinction relation and the independent measurements of