Cygnus X-3 is a microquasar consisting of an accreting compact object orbiting around a Wolf-Rayet star. It has been detected at radio frequencies and up to high-energy γ rays (above 100 MeV). However, many models also predict a very high energy (VHE) emission (above hundreds of GeV) when the source displays relativistic persistent jets or

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Spectra of high-metallicity [12+log(O/H)>~8.2] HII regions, where oxygen auroral lines are measurable in both the O+ and O++ zones, have been extracted from the Data Release 6 of the Sloan Digital Sky Survey (SDSS). Our final sample consists of 181 SDSS spectra of HII regions in galaxies in the redshift range from ~0.025 to ~0.17. The t2,O-t3,O

A goal of the IPHAS survey is to determine the frequency and nature of emission-line sources in the Galactic plane. According to our selection criteria, K 3-22 is a candidate symbiotic star, but it was previously classified as a planetary nebula. To determine its nature, we acquired a low-resolution optical spectrum of K 3-22. Our analysis of our

Context. Accurate parameters of the host stars of exoplanets are needed for interpreting the new planetary systems. The CoRoT satellite recently discovered a transiting rocky planet with a density similar to the inner planets in our solar system, a so-called super Earth. The mass was determined using ground-based follow-up spectroscopy, which also

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