The 2011 Periastron Passage of the Be Binary δ Scorpii
We describe the results of the world-wide observing campaign of the highly eccentric Be binary system δ Scorpii 2011 periastron passage which involved...
The 2023 Outburst of the Gaia Alerted EXor Gaia23bab
Episodic accretion is a fundamental process in the build-up of the stellar mass. EX Lupi-type eruptive young stars (EXors) represent one of the main types of...
Fast radio burst FRB 20180916B in its host galaxy SDSS J015800.28+654253.0 at 149 Mpc is by far the closest-known FRB with a robust host galaxy association. The...
Historically, 3C 66A has been considered a relative quiescent blazar. For that reason, 3C 66A was selected as a comparison source for OJ 287 in the OJ-94...
The Absolute Age of the Globular Cluster M15 Using Near-infrared Adaptive Optics Images from PISCES/LBT.
We present deep near-infrared J, {K}{{s}} photometry of the old, metal-poor Galactic globular cluster M15 obtained with images collected with the LUCI1 and...
The Accretion Mode in Sub-Eddington Supermassive Black Holes: Getting into the Central Parsecs of Andromeda
The inner kiloparsec regions surrounding sub-Eddington (luminosity less than 10 -3 in Eddington units, L Edd) supermassive black holes (BHs) often show a...
The Acoustic Cutoff Frequency of the Sun and the Solar Magnetic Activity Cycle
The acoustic cutoff frequency—the highest frequency for acoustic solar eigenmodes—is an important parameter of the solar atmosphere as it determines the upper...
The ACS LCID Project. I. Short-Period Variables in the Isolated Dwarf Spheroidal Galaxies Cetus and Tucana
We present the first study of the variable star populations in the isolated dwarf spheroidal galaxies (dSphs) Cetus and Tucana. Based on Hubble Space Telescope...
The ACS LCID Project. II. Faint Variable Stars in the Isolated Dwarf Irregular Galaxy IC 1613
We present the results of a new search for variable stars in the Local Group (LG) isolated dwarf galaxy IC 1613, based on 24 orbits of F475W and F814W...