Abstract. We present 10−15 m spectra of a sample of H ii regions, YSOs and evolved stars that show strong unidenti ed infrared emission features, obtained with the ISO/SWS spectrograph on-board ISO. These spectra reveal a plethora of emission features with bands at 11.0, 11.2, 12.0, 12.7, 13.5 and 14.2 m. These features are observed to vary considerably in relative strength to each-other from source to source. In particular, the 10{15 m spectra of the evolved stars are dominated by the 11.2 m band while for H ii regions the 12.7 is typically as strong as the 11.2 m band. Analysing the ISO data we nd a good correlation between the 11.2 m band and the 3.3 m band, and between the 12.7 m and the 6.2 m band. There is also a correlation between the ratio of the UIR bands to the total dust emission and the 12.7 over 11.2 m ratio. Bands in the 10{15 m spectral region are due to CH out−of−plane (OOP) bending modes of polycyclic aromatic hydrocarbons (PAHs). We summarise existing laboratory data and theoretical quantum chemical calculations of these modes for neutral and cationic PAHs. Due to mode coupling, the exact peak position of these bands depends on the number of adjacent CH groups and hence the observed interstellar 10−15 m spectra can be used to determine the molecular structure of the interstellar PAHs emitting in the dierent regions. We conclude that evolved stars predominantly inject compact 100−200 C-atom PAHs into the ISM where they are subsequently processed, resulting in more open and uneven PAH structures.

Abstract Magnetic reconnection is a process that changes magnetic field topology in highly conducting fluids. Traditionally, magnetic reconnection was associated mostly with solar flares. In reality, the process must be ubiquitous as astrophysical fluids are magnetized and motions of fluid elements

only for a restricted set of astrophysical applications. The relevance of this result for cosmic ray propagation through the microwave background and hadronic models of active galactic nuclei and gamma-ray bursts is briefly discussed. Keywords: nuclear reactions -- elementary particles -- radiation

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to the condensation in the primordial solar nebula. It is shown how the picture based on the chemical equilibrium calculations should be modified. Grain formation has been studied by many people m a wide range of physical conditions especially in connection with astrophysical problems. Much \York has

Abstract. High-resolution spectroscopic observations were obtained for two eclipsing active close binary systems, GK Hydrae and TY Pyxidis. For GK Hya excess emission was observed in the Balmer lines and Mg i b lines while TY Pyx showed excess emission in the Balmer lines and Ca ii H&K lines. The emission from GK Hya arises from a global phenomenon associated solely with the secondary component. The lack of significant He i D3 excess absorption and an analysis of the flux ratio in the Balmer lines suggest that the emission originates in prominencelike material seen off the limb of the star. A marginal broad excess absorption band centered around the Balmer emission peaks may be caused by this material absorbing the stellar continuum against the disk with high (350 km s −1) line-of-sight turbulent velocities. The inference that plage-like regions and associated star-spots are not substantial on this star is in agreement with the lack of spot modulation in the photometric light curve. For TY Pyx the majority of the Hβ excess and a larger proportion of the Ca ii core emission could be attributed to a global phenomenon on the primary. Analysis suggests that very large volumes are responsible for the emission, however, there is no observational evidence for the existence of discrete extended structures around TY Pyx.

Abstract. High-resolution observations of the eclipsing active close binary system ER Vulpeculae have revealed excess emission in the Hα, the Ca ii IRT and the Mg i b lines and excess absorption in the He i D3 line. The emission appears to be from a global phenomenon with the secondary component the more active. Analysis has revealed that the emission arises in plage-like material covering perhaps half of the secondary’s surface. This gives credence to X-ray and UV studies which have indicated that ER Vul is near the saturation limit for dynamo-induced activity. No firm spectroscopic evidence for the existence of extended material around ER Vul was found. A consistent velocity offset of ∼10 km s −1 was observed in the excess Hα emission from the secondary component which may be associated with active regions such as spicules. If so this represents the first observation of the equivalent of solar spicule emission in a stellar system other than the Sun.

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