We present an examination of high-resolution, ultraviolet (UV) spectroscopy from Hubble Space Telescope of the photospheric spectrum of the O-supergiant in the massive X-ray binary HD 226868 = Cyg X-1. We analyzed this and ground-based optical spectra to determine the effective temperature and gravity of the O9.7 Iab supergiant. Using non-LTE, line

Context: We present the results of a near-infrared photometric and spectroscopic study of the star-forming region G61.48+0.09. Aims: The purpose of this study is to characterize the stellar content of the cluster and to determine its distance, extinction, age, and mass. Methods: The stellar population was studied by using color-magnitude diagrams

The plenoptic wavefront sensor combines measurements at pupil and image planes in order to obtain wavefront information from different points of view simultaneously, being capable to sample the volume above the telescope to extract the tomographic information of the atmospheric turbulence. After describing the working principle, a laboratory setup

Context: Observations made with the spectropolarimeter onboard the HINODE satellite have detected abundant horizontal magnetic fields in the internetwork quiet Sun. Aims: We compare the results for the horizontal fields obtained at 630 nm with ground-based observations at 1.56 μm, where the sensitivity to magnetic fields is higher than in the

The Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) Coma Cluster Treasury Survey is a deep two-passband imaging survey of the nearest very rich cluster of galaxies, covering a range of galaxy density environments. The imaging is complemented by a recent wide field redshift survey of the cluster conducted with Hectospec on the 6.5-m

The ancient Egyptians had just one calendar in operation, the civil one, during most of their history and before the overwhelming influence of Hellenic culture. This calendar may have been invented for a specific purpose in the first half of the third millennium B.C., when the previous local Nile-based lunar calendars were rendered useless, as the