Search

We observe the brightest member of the Praesepe cluster, ϵ Cnc, to precisely measure the characteristics of the stars in this binary system, en route to a new measurement of the cluster’s age. We present spectroscopic radial velocity measurements and interferometric observations of the sky-projected orbit to derive the masses, which we find to be M 1/M ⊙ = 2.420 ± 0.008 and M 2/M ⊙ = 2.226 ± 0.004. We place limits on the color–magnitude positions of the stars by using spectroscopic and interferometric luminosity ratios while trying to reproduce the spectral energy distribution of ϵ Cnc. We reexamine the cluster membership of stars at the bright end of the color–magnitude diagram using Gaia data and literature radial velocity information. The binary star data are consistent with an age of 637 ± 19 Myr, as determined from MIST model isochrones. The masses and luminosities of the stars appear to select models with the most commonly used amount of convective core overshooting.

We report an analysis of the TESS light curve of the nearby M dwarf Gl 514 that was observed during Sector 50. We search for a transit of the likely super-Earth Gl 514 b that was detected in 2022 in radial velocity data. The planet moves on an eccentric orbit that partly resides within the habitable zone of its host. According to the predictions, a transit may occur with high probability within the observing window covered by Sector 50, and being easily detected, therefore offering a great opportunity for an independent confirmation of the existence of Gl 514 b, and for a better characterization of the planet.

We present an astrometric study of the proper motions (PMs) in the core of the globular cluster NGC 6441. The core of this cluster has a high density and observations with current instrumentation are very challenging. We combine ground-based, high-angular-resolution NACO@VLT images with Hubble Space Telescope ACS/HRC data and measure PMs with a temporal baseline of 15 yr for about 1400 stars in the centermost 15 arcseconds of the cluster. We reach a PM precision of $\sim$30 $��$as yr$^{-1}$ for bright, well-measured stars. Our results for the velocity dispersion are in good agreement with other studies and extend already-existing analyses of the stellar kinematics of NGC 6441 to its centermost region never probed before. In the innermost arcsecond of the cluster, we measure a velocity dispersion of (19.1 $\pm$ 2.0) km s$^{-1}$ for evolved stars. Because of its high mass, NGC 6441 is a promising candidate for harbouring an intermediate-mass black hole (IMBH). We combine our measurements with additional data from the literature and compute dynamical models of the cluster. We find an upper limit of $M_{\rm IMBH} < 1.32 \times 10^4\,\textrm{M}_\odot$ but we can neither confirm nor rule out its presence. We also refine the dynamical distance of the cluster to $12.74^{+0.16}_{-0.15}$ kpc. Although the hunt for an IMBH in NGC 6441 is not yet concluded, our results show how future observations with extremely-large telescopes will benefit from the long temporal baseline offered by existing high-angular-resolution data., 16 pages, 12 figures, 2 tables. Accepted for publication in MNRAS

In the present work we analyzed seven globular clusters selected from their location in the Galactic bulge and with metallicity values in the range $-1.30\lesssim\rm{[Fe/H]}\lesssim-0.50$. The aim of this work is first to derive cluster ages assuming single stellar populations, and secondly, to identify the stars from first (1G) and second generations (2G) from the main sequence, subgiant and red giant branches, and to derive their age differences. Based on a combination of UV and optical filters used in this project, we apply the Gaussian mixture models to distinguish the multiple stellar populations. Applying statistical isochrone fitting, we derive self-consistent ages, distances, metallicities, and reddening values for the sample clusters. An average of $12.3\pm0.4$ Gyr was obtained both using Dartmouth and BaSTI (accounting atomic diffusion effects) isochrones, without a clear distinction between the moderately metal-poor and the more metal-rich bulge clusters, except for NGC 6717 and the inner halo NGC 6362 with $\sim 13.5$ Gyr. We derived a weighted mean age difference between the multiple populations hosted by each globular cluster of $41\pm170$ Myr adopting canonical He abundances; whereas for higher He in 2G stars, this difference reduces to $17\pm170$ Myr, but with individual uncertainties of $500$ Myr., 25 pages, 16 figures and 7 tables. Accepted for publication in ApJ