AX J1745.6-2901 is a low-mass X-ray binary with an accreting neutron star, showing clear evidence for highly ionized absorption. Strong ionized Fe Kα and Kβ absorption lines are always observed during the soft state, whereas they disappear during the hard state. We computed photoionization stability curves for the hard and the soft states, under

Using the photoionization code CLOUDY, we compute photoionization models for the giant extragalactic H II region NGC 2363 and compare them with optical observational data. We mainly focus on F(Hβ), Ne, EW(Hβ), and the ratios of I(λ5007), I(λ4363), I(λ3727), I(λ6300), I(λ6720), and I(λ4686) to I(Hβ). We discuss the variations of the emission spectra

We present results of photometry and photopolarimetry of the Wolf-Rayet eclipsing binary system HD 5980 in the Small Magellanic Cloud, which underwent an unexpected eruption during 1994, transforming its spectrum into a Luminous Blue Variable-like one. CCD photometry was performed during the post-outburst declining phase. Pre-outburst

This project presents the principal conclusions of a long series of infrared and visible observations of blazars taken from 1987-92. The data fall broadly into three classes: spectropolarimetry in the range 4000-9500A of a small sample of selected AGNs; polarimetry of a sample of a dozen blazars and some twenty low polarisation quasars (LPQs)

We study the variability of solar activity using new photospheric proxies originally developed for the analysis of stellar magnetism with the CoRoT and Kepler photometric observations. These proxies were obtained by tracking the temporal modulations in the observations associated with the spots and magnetic features as the Sun rotates. We analyzed

With high angular resolution, high temporal cadence and a stable point spread function, the Solar Optical Telescope (SOT) onboard the Hinode satellite is the ideal instrument for the study of magnetic flux emergence and its manifestations on the solar surface. In this presentation, we focus on the development of ephemeral regions and small active