Prof. Dpto. Física de la Tierra y Astrofísica, UCM @Fisicas_UCM @unicomplutense, @IPARCOS_UCM, @ObservaUCM cool stars & exoplanets @CARMENES_exopl, @GaiaESO
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ALT Rocky planets the size of Earth or larger are expected to undergo one or more giant impacts during the final stages of their formation. Some of these collisions occur after protoplanetary disk dissipation, potentially driving the loss of primordial hydrogen-rich atmospheres through elevated surface temperatures. However, whether giant impacts promote atmospheric loss or retention remains unclear because they both heat planetary interiors and increase atmospheric gravitational binding. Here we model the evolution of rocky planets after their largest post-disk giant impact, accounting self-consistently for the concurrent increase in gravitational binding energy and mantle thermal energy. Whereas the entire accreted mass contributes to the increase in gravitational binding energy, only part of the impact energy raises mantle temperature. Mantle melting consumes energy as latent heat, while the impactor's metallic core transfers little energy to the mantle and remains superheated at depth.
ALT Co-natal stars, wide binaries that form from the same molecular cloud, should harbor the same stellar composition. Observations indicate stellar abundance differences in a small fraction of these co-natal systems. The stellar abundance differences have been attributed to the ingestion of planets by their host stars. We analyze a previous sample of co-natal stars to determine the composition of the planets that were ingested. The abundance differences in these co-natal pairs can show a positive abundance difference of the refractory elements (Fe, Mg, Si) paired with a positive, zero, or negative abundance difference of volatiles (O, C, S). Positive trends of refractory and volatile abundance differences can be explained (at minimum) with the ingestion of a single planet by one of the stars. Positive trends of refractory abundance differences paired with zero or negative abundance differences of oxygen and carbon imply that both stars are required to ingest planets formed at different lo
ALT Modelling data from modern spectroscopic surveys and time-resolved spectropolarimetric observations requires stellar synthetic spectra to be computed rapidly over wide wavelength ranges from line lists that increasingly reach hundreds of millions of transitions. Spectropolarimetric analyses of magnetically active stars additionally demand a solution of the polarised radiative transfer problem. We present FastSpec, a new LTE spectrum synthesis code designed around two goals: increased raw computational speed and broad astrophysical applicability, including the calculation of the full Stokes vector in the presence of a magnetic field. FastSpec computes emergent intensity and flux spectra from plane-parallel and spherical model atmospheres. Chemical and ionisation equilibrium is obtained from the updated SME equation-of-state package, continuum opacities follow the ATLAS family of routines, hydrogen bound-bound and bound-free absorption uses the occupation-probability formalism, and line
ALT V1298 Tau is a very young and magnetically active K1V star which hosts a benchmark multi-planetary system to study planet formation and evolutionary history at the earliest stages. Between 2025 and 2026, we conducted a campaign to monitor the variability of V1298 Tau in radio (band C), X-ray, and NUV bands, with the support of publicly available contemporary optical light curve, and to investigate multi-band correlations to link the emission with stellar activity. Radio observations were carried out with the Karl G. Jansky Very Large Array (JVLA) in band C (4.5–6.5 GHz). X-ray and NUV observations were carried out with the Swift satellite over 20 days, ending one month before the begin of the radio campaign. We analysed the temporal variability of peak (integrated) fluxes in the C-band and of X-ray (NUV) luminosities on various timescales, comparing it with the variability observed in the high-cadence optical light curve collected by the ASAS-SN survey. We observed both radio and high-
ALT We report the discovery of 10 stars in the Praesepe and Hyades clusters with unusually slow rotation that are likely not field contamination. Even though our search was general, all slow rotators are in the fully convective domain. We find that the fraction of slow rotators in the clusters is more than 5σ above the distribution expected from field contamination. They provide a potential link between the period distribution of the young open clusters and the field. These stars could be a distinct birth population, or they could be an indication that the onset of strong magnetic breaking is earlier than previously realized in this domain. Photometric variability and X-ray luminosity suggest the later but more data is needed to confirm. Searches for similar populations in younger clusters will help determine when slow rotators first emerge and constrain the timescale and physical mechanisms governing angular-momentum loss in fully convective stars. The discovery of these stars also highli
ALT Open clusters provide uniquely powerful laboratories for studying stellar evolution because their members share a common age and chemical composition. Stellar rotation of low-mass GKM dwarfs in open clusters provides direct empirical constraints on magnetic braking, with implications for stellar interiors, magnetic activity, and star–planet interactions. However, existing cluster rotation samples are dominated by space-based observations, whose limited spatial coverage and short observing baselines can make it difficult to construct an unbiased sample. Long-baseline ground-based time-domain surveys therefore provide an important complement to space-based photometry. I present a catalog of ∼20,000 periodic photometric signals, including stellar rotations, eclipsing-binaries, and classical pulsators, measured from the Zwicky Transient Facility (ZTF) and the All-Sky Automated Survey for Supernovae (ASAS-SN) for members of nearby open clusters and moving groups within 1.5 kpc. This catalog
ALT We use a Monte Carlo analysis to study whether wide binaries can be represented by bound Newtonian orbits, and, if this is the case, whether the distribution of the orbital parameters agrees with expectations. The potential orbits are classified according to the χ² probability of representing star coordinates, parallaxes, velocity components and masses. We apply this analysis to 44 systems previously published, to which we add 26 wide binaries, consisting of twin low-mass (M) stars. We find orbital solutions for 65 systems, and derive the distribution of their orbital parameters. For one system composed of M-type stars, no Newtonian bound solution can be found; however, this pair is a member of the young Argus association and therefore not a suitable target. The remaining four systems that cannot be fit were already identified as likely disrupted binaries. The uncertainty in the separation between the components, given by the parallax error, is by far the dominant error source, and the
ALT Precision spectroscopy underpins quantum sensing, atomic timekeeping, and the search for terrestrial-mass exoplanets. Finding an Earth-Sun analog requires fractional splitting of spectral features that rivals the precision of the best laboratory spectroscopy. This corresponds to resolution of a few parts in 10⁵ of a typical stellar spectral line, or a Doppler velocity precision of less than 10 cm s⁻¹. Only a few astrophysical spectrometers reach this regime, and only by dispersing starlight with large gratings and averaging thousands of lines. Here, we show that comparable precision can be achieved on a single solar line by leveraging techniques used in quantum sensors and optical clocks. A laser is frequency-locked to the 1565 nm solar Fe I line by coupling to a single mode of the solar thermal field and counted against an optical frequency comb referenced to the SI second, thus creating a solar optical clock. Operating at the fundamental photon-noise limit of thermal heterodyne spect
ALT Illustration of a laboratory plasma experiment. Glowing orange, pink and purple plasma rises in finger-like plumes above a wavy teal surface. A row of transparent vertical panels cuts through the plasma, and white arrows on the front panel point in opposite directions.
