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 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