We present the results of spectroscopy and multi-wavelength photometry of luminous and variable star candidates in the nearby spiral galaxies NGC 2403 and M81. We discuss specific classes of stars, the Luminous Blue Variables (LBVs), B[e] supergiants (sgB[e]), and the high luminosity yellow hypergiants. We identify two new LBV candidates, and three sgB[e] stars in M81. We also find that some stars previously considered LBV candidates are actually field stars. The confirmed and candidate LBVs and sgB[e] stars together with the other confirmed members are shown on the HR Diagrams for their respective galaxies. We also present the HR Diagrams for the two "SN impostors", V37 (SN2002kg) and V12(SN1954J) in NGC 2403 and the stars in their immediate environments.

We investigate the properties, composition, and dynamics of dust formation and growth for a diverse set of core-collapse supernovae (CCSNe), with 15, 20, and 25 M ⊙ progenitor masses, explosion energies ranging from 0.5 to 120 foe, and varied engine type. These explosions are evolved with a 1D Lagrangian hydrodynamics code out to a minimum of 1157 days to model the ejecta as it expands and cools. A multigrain dust nucleation and growth model is applied to these results. We find that higher explosion energies lead to an earlier onset of dust formation, smaller grain sizes, and larger silicate abundances. Further, we see that nuclear burning during the explosion leads to enhanced formation of silicate dust. Finally, we build composite models from our suite to predict the efficiency of CCSN dust production as a function of metallicity.

Abstract. The distribution of the magnetic field on the solar surface is as yet unknown in detail, but of considerable importance for solar physics in general. We have observed two different solar regions, one containing a small pore, the other region comprising a network in the light of the Fe  λ6301.5 Å and Fe  λ6302.5 Å lines at the German Vacuum Tower Telescope of the Observatorio del Teide (Tenerife, Spain) with the "Göttingen" Fabry-Pérot Interferometer. By applying image reconstruction techniques to broad-and narrowband filtergrams we obtained continuum images, line core images, as well as line-of-sight velocity and magnetic field maps. We present scatter plots of the line core intensity vs. the Doppler velocity and the vertical component of the magnetic field, which reveal that the line core brightness is not a clear indicator for magnetic fields in the solar atmosphere. Furthermore, we estimate the swaying motion of flux tubes to be mostly smaller than 0. 3 and thus in good agreement with the predictions of theoretical dynamic models. Finally, we show how the choice of the observed solar target influences the results and their interpretation. We claim that generalizations can mislead, and strongly depend on the presence or absence of solar (magnetic) features in the analyzed data.

High resolution 2D-spectro-polarimetric observations have been used to analyse the magnetic field and flow topologies of a penumbral connection between two opposite polarity solar pores. A filamentary structured Evershed-like material flow from one pore to the other along the magnetic field lines has been detected. The flow channels are co-spatial with bright penumbral filaments close to the pore which feeds the flow and the clear brightness-velocity relation vanishes close to the pore which represents the sink of the flow. The boundary between umbra and penumbra of the two pores show significant differences: bright comet-like penumbral grains represent endings of penumbral filaments at the flow sources whereas no such grains were found at the sinks of the flow. Furthermore, a systematic variation of the asymmetries of measured Stokes V profiles across the penumbral connection have been found. The obtained results are in accordance with the widely-accepted uncombed penumbra hypothesis and the moving flux tube model.

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