Context. Sunspot umbrae show a change in the dominant period of their oscillations from five minutes (3.3 mHz) in the photosphere to three minutes (5.5 mHz) in the chromosphere. Aims: In this paper, we explore the two most popular models proposed to explain the three-minute oscillations: the chromospheric acoustic resonator and the propagation of

Recent observations of the solar photosphere revealed the presence of elongated filamentary bright structures inside sunspot umbrae, called umbral filaments (UFs). These features differ in morphology, magnetic configuration, and evolution from light bridges (LBs) that are usually observed to intrude in sunspots. To characterize a UF observed in the

Over 2,000 stars were observed for one month with a high enough cadence in order to look for acoustic modes during the survey phase of the Kepler mission. Solar-like oscillations have been detected in about 540 stars. The question of why no oscillations were detected in the remaining stars is still open. Previous works explained the non-detection

Context. The X-shooter Spectral Library (XSL) is an empirical stellar library at medium spectral resolution covering the wavelength range from 3000 Å to 24 800 Å. This library aims to provide a benchmark for stellar population studies. Aims: In this work, we present a uniform set of stellar atmospheric parameters, effective temperatures, surface

We present precise photospheric parameters of 282 M dwarfs determined from fitting the most recent version of PHOENIX models to high-resolution CARMENES spectra in the visible (0.52-0.96 μm) and NIR wavelength range (0.96-1.71 μm). With its aim to search for habitable planets around M dwarfs, several planets of different masses have been detected

While optical and quantum efficiency are on the rise, and spectrographs becoming massively multiplexed, measuring spectral energy distributions of astronomical sources with accuracy remains a challenge. In addition to atmospheric refraction, extinction, variability, and limited apertures of instrument entrance slits and optical fibers, accurate