The duration of a starburst is a fundamental parameter affecting the evolution of galaxies yet, to date, observational constraints on the durations of starbursts are not well established. We present the recent star formation histories (SFHs) of 18 nearby dwarf galaxies and rigorously quantify the duration of their starburst events using a uniform

We report the discovery of a T8.5 dwarf, which is a companion to the M4 dwarf Wolf 940. At a distance of 12.50+0.75-0.67 pc, the angular separation of 32 arcsec corresponds to a projected separation of 400 au. The M4 primary displays no Hα emission, and we apply the age-activity relations of West et al. to place a lower limit on the age of the

The near-UV NH3360 feature has been measured in a sample of 35 early-type galaxies spanning a wide range of masses and environments. We found that, contrary to what is seen with Mg- and C-sensitive Lick-style indices, NH3360 does not vary significantly with galaxy velocity dispersion. When compared with solar-scaled stellar population models N/Fe

We propose a new chemical evolution model aimed at explaining the chemical properties of globular clusters (GCs) stars. Our model depends upon the existence of (i) a peculiar pre-enrichment phase in the GC's parent galaxy associated with very low-metallicity Type II supernovae (SNe II) and (ii) localized inhomogeneous enrichment from a single Type

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We describe the highly variable X-ray and UV emission of V458 Vul (Nova Vul 2007), observed by Swift between 1 and 422 days after outburst. Initially bright only in the UV, V458 Vul became a variable hard X-ray source due to optically thin thermal emission at kT = 0.64 keV with an X-ray band unabsorbed luminosity of 2.3 × 1034 erg s-1 during days