Metal-poor ultracool dwarfs (ultracool subdwarfs, including very-low-mass stars and brown dwarfs) are tracers of the pristine chemical composition at early phases in the assembly of the Milky Way. They are poorly understood because they are extremely faint and rare. Our aims are to improve the knowledge of ultracool subdwarf candidates, to break

The evolution of surface magnetic features on stars, such as spots and faculae, produces modulations in light curves. These modulations allow us to measure the surface rotation period, P_rot, of stars from the main sequence (e.g., McQuillan et al. 2014; Santos et al. 2019, 2021) to the red-giant (Ceillier et al. 2017) phase. Nevertheless, the

TESS is a powerful engine for studying stellar variability. However, it has been challenging to adopt methods used for other space missions, such as Kepler, to infer rotation periods and solar-like oscillation frequencies in TESS data. The availability of multiple sectors of data for most targets, improved stability, and the release of new

We measure the stacked lensing signal in the direction of galaxy clusters in the Dark Energy Survey Year 3 (DES Y3) redMaPPer sample, using cosmic microwave background (CMB) temperature data from SPT-3G, the third-generation CMB camera on the South Pole Telescope (SPT). Here, we estimate the lensing signal using temperature maps constructed from

Despite thousands of extrasolar planets discovered to date, the dominant mechanisms forming planets and the timescales of planetary migration and atmospheric evaporation remain to be probed observationally. To shed light on these mechanisms, we performed a combined photometric and spectroscopic analysis of several young transiting systems at

Mercator Array for Radial VELocities (MARVEL) is an ensemble of four 80-cm off the shelf telescopes feeding a single stabilised high-resolution (R>90 000) echelle spectrograph. The facility is currently under construction and will be located on La Palma (Canary Islands), next to the Mercator telescope. The facility is designed such that the four