Search Publications
Evolution of globular cluster systems in three galaxies of the Fornax cluster
Donnarumma, I.; Capuzzo-Dolcetta, R.
We studied and compared the radial profiles of globular clusters and of the stellar bulge component in three galaxies of the Fornax cluster observed with the WFPC2 of the Hubble Space Telescope (HST). The stars are more concentrated toward the galactic centres than globular clusters, in agreement with what has already been observed in many other g…
The distance to Galactic globular clusters through RR Lyrae pulsational properties
Piersimoni, A. M.; Cassisi, S.; De Santis, R.
By adopting the same approach outlined by De Santis & Cassisi, we evaluate the absolute bolometric magnitude of the zero-age horizontal branch (ZAHB) at the level of the RR Lyrae variable instability strip in selected Galactic globular clusters. This allows us to estimate the ZAHB absolute visual magnitude for these clusters and to investigate…
Ionization structure in accretion shocks with a composite cooling function
Cropper, Mark; Wu, Kinwah; Ramsay, Gavin
We have investigated the ionization structure of the post-shock regions of magnetic cataclysmic variables, using an analytic density and temperature structure model in which effects caused by bremsstrahlung and cyclotron cooling are considered. We find that in the majority of the shock-heated region where H- and He-like lines of the heavy elements…
Scattered light models of the dust shell around HD 179821
Gledhill, T. M.; Takami, M.
The dust shell around the evolved star HD 179821 has been detected in scattered light in near-IR imaging polarimetry observations. Here, we subtract the contribution of the unpolarized stellar light to obtain an intrinsic linear polarization of between 30 and 40 per cent in the shell which seems to increase with radial offset from the star. The J …
A peculiar metal-rich star, HD 135485
Dufton, P. L.; Lennon, D. J.; Ryans, R. S. I. +3 more
Local thermodynamic equilibrium (LTE) absolute and differential abundances are presented for a peculiar metal-rich B-type star, HD 135485. These suggest that HD 135485 has a general enrichment of ~0.5dex in all the metals observed (C, N, O, Ne, Mg, Al, Si, P, S, Cl, Ar, Sc, Ti, Cr, Mn, Fe and Sr), except for nickel. The helium enhancement and henc…
Understanding the atmospheric structure of T Tauri stars - II. UV spectroscopy of RY Tau, BP Tau, RU Lupi, GW Ori and CV Cha
Lanzafame, A. C.; Brooks, D. H.; Costa, V. M. +1 more
We report results from our study of International Ultraviolet Explorer (IUE) data of a group of T Tauri stars (TTS). Comparisons between UV-line fluxes in these stars and in the Sun indicate very high levels of activity in their atmospheres and comparatively higher electron densities. Spectroscopic diagnostic line ratios indicate densities over an…
Far-ultraviolet extinction and diffuse interstellar bands
Krełowski, J.; Megier, A.; Aiello, S. +2 more
We relate the equivalent widths of the major diffuse interstellar bands (DIBs) near 5797 and 5780Å with different colour excesses, normalized by E(B-V), which characterize the growth of interstellar extinction in different wavelength ranges. It is demonstrated that the two DIBs correlate best with different parts of the extinction curve, and the r…
The field of NGC 6397 as a test for Galactic models
Degl'Innocenti, S.; Piotto, G.; Castellani, V. +1 more
Taking advantage of recent Hubble Space Telescope (HST) data for field stars in the region of the Galactic globular cluster NGC 6397, we tested the predictions of several Galactic models with star counts reaching a largely unexplored range of magnitudes, down to V~26.5. After updating the input stellar (V-I) colours, we found that the two-componen…
The milliJansky 12-µm population: first follow-up
Clements, D. L.; Franceschini, A.; Desert, F. -X.
We present the first results of our follow-up programme of optical imaging and spectroscopy of a deep 12-µm survey conducted with the ISO satellite. We find that the objects are typically of fairly low redshift (z~0.1-0.2), but with a tail that extends to high redshifts. The highest redshift object is a previously unknown quasar at z=1.2. Th…
A ROSAT medium-sensitivity Galactic plane survey at 180°< l < 280°
Briggs, K. R.; Micela, G.; Favata, F. +3 more
We have performed a moderately deep soft X-ray (0.1-2keV) survey of the Galactic plane using pointed observations with the ROSAT Position Sensitive Proportional Counter (PSPC). The survey is more than an order of magnitude more sensitive than previous X-ray surveys near the Galactic plane. The data consist of nine fields each of ~10ks exposure, po…