We present narrowband imagery and long-slit intermediate-resolution spectroscopy of the multiple-shell planetary nebulae NGC 2438 and NGC 5882. A comparative study of the chemical abundances of the main nebulae and their surrounding halos shows a moderate N/O enrichment of the central regions. The oxygen abundances appear constant throughout the

We present optical and NIR (near infrared) follow up observations of the GRB 001109 from 1 to 300 days after the burst. No transient emission was found at these wavelengths within this GRB's (Gamma Ray Burst) 50 arcsec radius BeppoSAX error box. Strong limits (3σ) are set with: R ⪆ 21, 10.2 h after the GRB; I ⪆ 23, 11.4 h after the GRB; H ⪆ 20.7, 9

The neutron star transient and 11 Hz X-ray pulsar IGR J17480-2446, recently discovered in the globular cluster Terzan 5, showed unprecedented bursting activity during its 2010 October-November outburst. We analyzed all X-ray bursts detected with the Rossi X-ray Timing Explorer and confirmed their thermonuclear origin, despite the fact that many do

According to star formation histories (SFHs), Local Group dwarf galaxies can be broadly classified in two types: those forming most of their stars before z = 2 (fast) and those with more extended SFHs (slow). The most precise SFHs are usually derived from deep but not very spatially extended photometric data; this might alter the ratio of old to

The electron temperatures of high-metallicity [12 + log(O/H) > 8.2] HII regions have been studied. The empirical flux-flux relations which express the nebular-to-auroral [OIII] line ratio Q3,O (as well as the nebular-to-auroral [OII] line ratio Q2,O, and the nebular-to-auroral [NII] line ratio Q2,N) in terms of the nebular R3 and R2 line fluxes in

This paper addresses some questions which have arisen from the use of the Sérsic r1/n law in modelling the luminosity profiles of early-type galaxies. The first issue deals with the trend between the half-light radius and the structural parameter n. We show that the correlation between these two parameters is not only real, but also a natural