Search Publications
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…
Photometric observations of asteroid 4 Vesta by the OSIRIS cameras onboard the Rosetta spacecraft
Sierks, H.; Mottola, S.; Barucci, M. A. +2 more
Aims: We report on new observations of asteroid 4 Vesta obtained on 1 May 2010 with the optical system OSIRIS onboard the ESA Rosetta mission. One lightcurve was taken at a phase angle (52°) larger than achievable from ground-based observations together with a spectrophotometric sequence covering the 260 to 990 nm wavelength range.
Metho…
Searching for the 511 keV annihilation line from galactic compact objects with the IBIS gamma ray telescope
De Cesare, G.
Context. The first detection of a gamma ray line with an energy of about 500 keV from the center of our Galaxy dates back to the early seventies. Thanks to the astrophysical application of high spectral resolution detectors, it was soon clear that this radiation was due to the 511 keV photons generated by electron-positron annihilation. Even thoug…
Recovering Swift-XRT energy resolution through CCD charge trap mapping
Campana, S.; Cusumano, G.; Moretti, A. +13 more
The X-ray telescope on board the Swift satellite for gamma-ray burst astronomy has been exposed to the radiation of the space environment since launch in November 2004. Radiation causes damage to the detector, with the generation of dark current and charge trapping sites that result in the degradation of the spectral resolution and an increase of …
Extreme warm absorber variability in the Seyfert galaxy Mrk 704
Bianchi, S.; Ponti, G.; Guainazzi, M. +8 more
Context. In about half of the Seyfert galaxies, the X-ray emission is absorbed by an optically thin, ionized medium, the so-called "warm absorber", whose origin and location is still a matter of debate.
Aims: The aim of this paper is to constrain the warm absorber further by studying its variability.
Methods: We analyzed the X-ray spectr…