Search Publications
Constraints on thick disc and halo parameters from HST photometry of field stars in the Galaxy
Santiago, B. X.; Kerber, L. O.; Javiel, S. C.
We analyse a sample of over 1000 stars from 32 fields imaged in the V and I bands with the Wide Field and Planetary Camera, on board of the Hubble Space Telescope. The fields are located at Galactic latitudes | b | >= 15deg and in various directions on the sky. We consider models for the structure of the Galaxy with different choices…
Physical parameters of sdB stars from spectral energy distributions
Jeffery, C. S.; Aznar Cuadrado, R.
The atmospheric parameters of 34 hot subdwarf B stars have been obtained using a combination of 61 short and long-wave IUE spectra, together with new and existing optical and infrared photometric data. Using a grid of high-gravity helium-deficient model atmospheres and a chi 2-minimization procedure, 15 single sdB stars and 19 composite…
Photoelectric effect on dust grains across the L1721 cloud in the rho Ophiuchi molecular complex
Boulanger, F.; Habart, E.; Pineau des Forêts, G. +3 more
We present ISO-LWS measurements of the main gas cooling lines, [C+] 158 mu m and [O0] 63 mu m towards a moderate opacity molecular cloud (Av ~ 3), L1721, illuminated by the B2 star nu Sco (chi = 5-10). These data are combined with an extinction map and IRAS dust emission images to test our understanding of gas heat…
XMM-Newton detection of a Comptonized accretion disc in the quasar PKS 0558-504
Dadina, M.; O'Brien, P. T.; Reeves, J. N. +6 more
We present XMM-Newton observations of the bright quasar PKS 0558-504. The 0.2-10 keV spectrum is dominated by a large, variable soft X-ray excess. The fastest flux variations imply accretion onto a Kerr black hole. The XMM-Newton data suggest the presence of a ``big blue bump'' in PKS 0558-504 extending from the optical band to ~ 3 keV. The soft X…
Abundances of planetary nebulae NGC 7662 and NGC 6741
Pottasch, S. R.; Beintema, D. A.; Feibelman, W. A. +1 more
The ISO and IUE spectra of the elliptical nebulae
Gas-phase SO 2 in absorption towards massive protostars
van Dishoeck, E. F.; Tielens, A. G. G. M.; Boonman, A. M. S. +1 more
We present the first detection of the nu3 ro-vibrational band of gas-phase SO2 in absorption in the mid-infrared spectral region around 7.3µm of a sample of deeply embedded massive protostars. Comparison with model spectra shows that the derived excitation temperatures correlate with previous C2H2 …
Mid and Far IR properties of late-type galaxies in the Coma and A1367 clusters: ISOCAM and ISOPHOT observations
Contursi, A.; Boselli, A.; Gavazzi, G. +3 more
We present Mid (MIR) and Far (FIR) Infrared observations of 18 spiral/irregular galaxies belonging to the Coma and A1367 clusters, carried out with the CAM and PHOT instruments on board the ISO satellite. Complementary photometry from the UV to the Near Infrared (NIR) together with Hα imaging, HI and 12CO line measurements allow us to s…
BeppoSAX observations of Narrow-Line Seyfert 1 galaxies. II. Ionized iron features in Arakelian 564
Brandt, W. N.; Fiore, F.; Guainazzi, M. +8 more
The BeppoSAX observations of the bright Narrow-Line Seyfert 1 galaxy Ark 564 are presented along with a high quality optical spectrum taken at the 1.5 m telescope at La Silla. The 0.1-10 keV X-ray spectrum is characterized by a strong soft component which is best described by blackbody-like emission with a temperature of ~ 160 eV. At higher energi…
The impact of bars on the mid-infrared dust emission of spiral galaxies: global and circumnuclear properties
Roussel, H.; Sauvage, M.; Madden, S. +6 more
We study the mid-infrared properties of a sample of 69 nearby spiral galaxies, selected to avoid Seyfert activity contributing a significant fraction of the central energetics, or strong tidal interaction, and to have normal infrared luminosities. These observations were obtained with ISOCAM, which provides an angular resolution of the order of 10…
Charge-equilibration of Fe ions accelerated in a hot plasma
Torsti, J.; Kocharov, L.; Kovaltsov, G. A. +2 more
We examine the energy-dependent rates of charge-changing processes of energetic Fe ions in the hot plasma of the solar corona. For ionization of the Fe-ion projectile in collisions with ambient protons, three different methods of estimating the corresponding ionization cross sections are presented and compared. Proton-impact ionization is found to…