An uncombed inversion of multiwavelength observations reproducing the net circular polarization in a sunspot's penumbra
Context. The penumbra of sunspots has a complex magnetic field topology whose three-dimensional organization remains unclear after more than a century of...
An underlying clock in the extreme flip-flop state transitions of the black hole transient Swift J1658.2-4242
Aims: Flip-flops are top-hat-like X-ray flux variations, which have been observed in some transient accreting black hole binary systems, and feature...
An Unexplained Origin for the Unusual Globular Cluster System in the Ultradiffuse Galaxy FCC 224
We study the quiescent ultradiffuse galaxy FCC 224 in the Fornax cluster using Hubble Space Telescope (HST) imaging, motivated by peculiar properties of its...
We report the discovery of an unusual low-ionization broad absorption line quasar at z=1.776 which exhibits absorption lines from many excited states of Fe II...
An unusual transient in the extremely metal-poor Galaxy SDSS J094332.35+332657.6 (Leoncino Dwarf)
We have serendipitously discovered that Leoncino Dwarf, an ultrafaint, low-metallicity record-holder dwarf galaxy, may have hosted a transient source, and...
An unusually low-density super-Earth transiting the bright early-type M-dwarf GJ 1018 (TOI-244)
Context. Small planets located at the lower mode of the bimodal radius distribution are generally assumed to be composed of iron and silicates in a proportion...
An updated MILES stellar library and stellar population models
Aims: We present a number of improvements to the MILES library and stellar population models. We correct some small errors in the radial velocities of the stars...
An updated stellar census of the Quintuplet cluster
Context. Found within the central molecular zone, the Quintuplet is one of the most massive young clusters in the Galaxy. As a consequence it offers the...