We review recent advances in our understanding of massive stars through the analysis of their spectra. Improvements in model atmospheres and analysis methods are briefly discussed. Results obtained for stars in the Local Group are compared and the present status of different open questions, like the temperature scale of OB stars, the Wind Momentum

Understanding the peculiar properties of ultra-diffuse galaxies (UDGs) via spectroscopic analysis is a challenging task requiring very deep observations and exquisite data reduction. In this work, we perform one of the most complete characterizations of the stellar component of UDGs to date using deep optical spectroscopic data from OSIRIS at Gran

We have observed 10 luminous blue stars in M 33 at intermediate dispersion and have determined spectral types and luminosity classes from the blue and red spectrograms by comparing with galactic and SMC stars. Halpha_ profiles have proved to be very useful in disentangling luminosity and metallicity effects, and constitute a valuable diagnostic

To understand the formation and evolution of solar-type stars in the solar neighborhood, we need to measure their stellar parameters to high accuracy. We present a catalogue of accurate stellar parameters for 451 stars that represent the HARPS Guaranteed Time Observations (GTO) “high precision” sample. Spectroscopic stellar parameters were measured

We present a new automatic code (ARES) for the determination of equivalent widths of absorption lines present in stellar spectra. We also describe its use for the determination of fundamental spectroscopic stellar parameters. The code is written in C++ based on the standard method of determining EWs, and is available for the community. We test the

We have obtained projected rotation velocities (vrotsini) of a sample of 19 ultracool dwarfs with spectral types in the interval M6.5-T8 using high-resolution, near-infrared spectra obtained with NIRSPEC and the Keck II telescope. Among our targets there are two young brown dwarfs, two likely field stars, and 15 likely brown dwarfs (30-72 MJup) in