In many radiative transfer (RT) problems, the sources contain a scattering term that couples all the specific RT equations, one for each frequency and direction, so that solving the problem means solving the system formed by these equations. Each of them is a first-order linear differential equation with its own initial condition assigned at a

I report on the discovery of two faint (~26.8 R mag arcsec-2) tidal tails around the shell elliptical galaxy NGC 3656 (Arp 155). This galaxy had previously been interpreted as a case of accretion, or minor merger. The two tidal tails are inconsistent with a minor merger and point instead to a disk-disk major merger origin. NGC 3656 extends Toomre's

The hypergiant ρ Cas is known for its variable rate of mass loss, with an average value of about 10^-5^Msun_/yr, and the supersonic value for the line-of-sight component of the microturbulent velocity, about 11km/s. Emission components in Hα suggest the presence of a thermally excited outer atmospheric region. Since hydrodynamical turbulence in a

The O III (4959, 5007) lines from spectra of Mrk 817 obtained from a 9-year long period were analyzed. A blue asymmetry of the lines is noticeable. The authors have found that the Narrow Line Region (NLR) of Mrk 817 consists of two subregions (NLR1 and NLR2). NLR1 should be closer to the central source with higher velocity of the emitting emission

Optical R-band imaging data and far-infrared (FIR) Infrared Space Observatory data from Seyfert galaxies are combined to show that the compact optical emission from the nuclear and circumnuclear region correlates reasonably well with the warm FIR emission that is observed in these objects, while the extended optical emission, which essentially

We present the first infrared light curve of GRO J0422+32, and use it along with R-band data and published I- and Cousins R_c-band data to constrain the inclination of the system to be between 10 deg and 26 deg, implying that the black hole mass is greater than ~15Msolar. Remodeling the data with a 30 per cent accretion disc contamination level