Search Publications
Hubble Space Telescope study of resolved red giant stars in the outer halos of nearby dwarf starburst galaxies
van der Marel, R. P.; Aloisi, A.; Annibali, F. +2 more
Context. Central starbursts in galaxies are an extreme example of ongoing galaxy evolution. The outer parts of galaxies contain a fossil record of galaxy formation and evolution processes in the more distant past. The characterization of resolved stellar populations allows one a detailed study of these topics.
Aims: We observed the outer part…
Distinguishing post-AGB impostors in a sample of pre-main sequence stars
Vieira, R. G.; Szczerba, R.; Stasińska, G. +2 more
Context. A sample of 27 sources, cataloged as pre-main sequence stars by the Pico dos Dias Survey (PDS), is analyzed to investigate a possible contamination by post-AGB stars. The far-infrared excess due to dust present in the circumstellar envelope is typical of both categories: young stars and objects that have already left the main sequence and…
Distances and stellar population properties for 12 elliptical galaxies
Cantiello, M.; Capaccioli, M.; Brocato, E.
Aims: We use the surface brightness fluctuation (SBF) technique to derive the distances and analyse the radial behaviour of stellar populations in a sample of 12 elliptical galaxies. The data are I-band images collected with the FORS1 camera at the Very Large Telescope (VLT), drawn from the ESO archive. The main purpose of our analysis is to …
Quasi-periodic flares in EXO 2030+375 observed with INTEGRAL
Klochkov, D.; Santangelo, A.; Ferrigno, C. +5 more
Context. Episodic flaring activity is a common feature of X-ray pulsars in HMXBs. In some Be/X-ray binaries flares were observed in quiescence or prior to outbursts. EXO 2030+375 is a Be/X-ray binary showing "normal" outbursts almost every ~46 days, near periastron passage of the orbital revolution. Some of these outbursts were occasionally monito…
The nearby eclipsing stellar system δ Velorum. III. Self-consistent fundamental parameters and distance
Schertl, D.; Kervella, P.; Natta, A. +6 more
Context. The triple stellar system δ Vel (composed of two A-type and one F-type main-sequence stars) is particularly interesting because it contains one of the nearest and brightest eclipsing binaries. It therefore presents a unique opportunity to determine independently the physical properties of the three components of the system, as well as its…
Spectroastrometry of rotating gas disks for the detection of supermassive black holes in galactic nuclei. II. Application to the galaxy Centaurus A (NGC 5128)
Marconi, A.; Capetti, A.; Axon, D. J. +3 more
We measure the black hole mass in the nearby active galaxy Centaurus A (NGC 5128) using a new method based on spectroastrometry of a rotating gas disk. The spectroastrometric approach consists in measuring the photocenter position of emission lines for different velocity channels. In a previous paper we focused on the basic methodology and the adv…
HST-ACS photometry of the isolated dwarf galaxy VV124=UGC 4879. Detection of the blue horizontal branch and identification of two young star clusters
Bellazzini, M.; Galleti, S.; Perina, S. +1 more
We present deep V and I photometry of the isolated dwarf galaxy VV124=UGC 4879, obtained from archival images taken with the Hubble Space Telescope - Advanced Camera for Surveys. In the color-magnitude diagrams of stars at distances greater than 40″ from the center of the galaxy, we clearly identify a well-populated, old horizontal branch (HB) for…
RXTE and XMM observations of intermediate polar candidates
Mukai, K.; Tomsick, J. A.; Norton, A. J. +1 more
Aims: We aim to determine the credentials of nine candidate intermediate polars in order to confirm whether or not they are magnetic cataclysmic variables.
Methods: Frequency analysis of RXTE and XMM data was used to search for temporal variations that could be associated with the spin period of the magnetic white dwarf. X-ray spectral a…
Photospheric and coronal abundances in solar-type stars: the peculiar case of τ Bootis
Sanz-Forcada, J.; Maggio, A.; Scelsi, L.
Aims: Chemical abundances in solar-type stars are still a much debated topic in many respects. In particular, planet-hosting stars are known to be metal-rich, but whether or not this peculiarity applies also to the chemical composition of the outer stellar atmospheres is still to be clarified. More in general, coronal and photospheric abundan…
Origin of craters on Phoebe: comparison with Cassini's data
di Sisto, R. P.; Brunini, A.
Context. Phoebe is one of the irregular satellites of Saturn. The images taken by the Cassini-Huygens spacecraft have allowed us to analyze its surface and the craters on it.
Aims: We study the craters on Phoebe produced by both Centaur objects from the scattered disk (SD) and plutinos that have escaped from the 3:2 mean motion resonance with…