Search Publications
XMM-Newton observations of the Seyfert 1 galaxy Mrk 335
Gondoin, P.; Santos-Lleo, M.; Orr, A. +1 more
We report on an XMM-Newton observation of the Seyfert 1 galaxy Mrk 335 performed in December 2000. The power law component of its spectrum above 2 keV has a photon index Gamma =2.3 much steeper than that of a ``normal'' Seyfert 1 galaxy. A broad spectral feature is observed around 6.0 keV (+/-1 keV) that can be fitted by a relativistic emission pr…
Analysis of colour-magnitude diagrams of rich LMC clusters: NGC 1831
Santiago, B. X.; Kerber, L. O.; Valls-Gabaud, D. +1 more
We present the analysis of a deep colour-magnitude diagram (CMD) of NGC 1831, a rich star cluster in the LMC. The data were obtained with HST/WFPC2 in the F555W ( ~ V) and F814W ( ~ I) filters, reaching m555 ~ 25. We discuss and apply a method of correcting the CMD for sampling incompleteness and field star contamination. Efficient use …
HST, VLT, and NTT imaging search for wide companions to bona-fide and candidate brown dwarfs in the Cha I dark cloud
Neuhäuser, R.; Comerón, F.; Brandner, W. +2 more
We present results from a deep imaging search for companions around the young bona-fide and candidate brown dwarfs Cha Hα 1 to 12 in the Cha I dark cloud, performed with HST WFPC2 (R, I, Hα ), VLT FORS1 (VRI), and NTT SofI (JHKs). We find 16 faint companion candidates around five primaries with separations between 1.5'' and 7…
The Phoenix galaxy: UGC 4203 re-birth from its ashes?
Perola, G. C.; Fiore, F.; Guainazzi, M. +1 more
We report on a dramatic transition between a Compton-thick, reflection-dominated state and a Compton-thin state in the Seyfert 2 galaxy UGC 4203, discovered by comparing a recent (May 2001) XMM-Newton observation with ASCA observations performed about six years earlier. This transition can be explained either as a change in the column density of t…
Discovery of complex narrow X-ray absorption features from the low-mass X-ray binary GX 13+1 with XMM-Newton
Parmar, A. N.; Sidoli, L.; Oosterbroek, T. +1 more
We report the detection of a complex of narrow X-ray absorption features from the low-mass X-ray binary GX 13+1 during 3 XMM-Newton observations in 2000 March and April. The features are consistent with being due to resonant scattering of the Kalpha and Kbeta lines of He- and H-like iron (Fe XXV and Fe XXVI) and H-like calcium (Ca XX) Kalpha . Onl…
The circumstellar dust shell of the post-AGB star HD 161796
Waters, L. B. F. M.; Dominik, C.; Barlow, M. J. +3 more
We have modeled the complete optical to millimeter spectrum of the Post-Asymptotic Giant Branch (Post-AGB) star HD 161796 and its circumstellar dust shell. A full 2-200 mu m spectrum taken with the Infrared Space Observatory was used to constrain the dust properties. A good fit is achieved using only 4 dust components: amorphous silicates, the cry…
ISOCAM observations of the Ursa Major cirrus:. Evidence for large abundance variations of small dust grains
Miville-Deschênes, M. -A.; Boulanger, F.; Falgarone, E. +1 more
We present mid-IR imaging observations of a high Galactic latitude cirrus obtained with the ISO camera ISOCAM at 6'' angular resolution. The observations were done with two filters LW2 (5-8.5 mu m) and LW3 (12-18 mu m) that measure respectively the aromatic carbon bands and the underlying continuum emission from small dust particles. Three 0.05 sq…
The mineral composition and spatial distribution of the dust ejecta of NGC 6302
Waters, L. B. F. M.; Molster, F. J.; Kemper, F. +1 more
We have analysed the full ISO spectrum of the planetary nebula
Statistics of galaxy warps in the HDF North and South
Battaner, E.; Combes, F.; Jiménez-Vicente, J. +1 more
We present a statistical study of the presence of galaxy warps in the Hubble deep fields. Among a complete sample of 45 edge-on galaxies above a diameter of 1\farcs3, we find 5 galaxies to be certainly warped and 6 galaxies as good candidates. In addition, 4 galaxies reveal a characteristic U-warp. Compared to statistical studies of local warps, a…
An inverse method to interpret colour-magnitude diagrams
Bienaymé, O.; Egret, D.; Vergely, J. -L. +1 more
An inverse method is developed to determine the star formation history, the age-metallicity relation, and the IMF slope from a colour-magnitude diagram. The method is applied to the Hipparcos HR diagram. We found that the thin disk of our Galaxy shows a peak of stellar formation 1.6 Gyr ago. The stars close to the Sun have a solar metallicity and …