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Spectral energy distributions of FR I nuclei and the FR I/BL Lac unifying model
Capetti, A.; Chiaberge, M.; Celotti, A. +2 more
We consider archival ROSAT and Hubble Space Telescope (HST) observations of five FR I radio galaxies and isolate their nuclear emission from that of the host galaxy. This enables us to determine the spectral energy distributions (SEDs) of their nuclei spanning the region from the radio to the X-ray band. They cannot be described as single power la…
Hot dust in two hard Chandra X-ray sources
Fabian, A. C.; Gandhi, P.; Wilman, R. J.
The two brightest hard X-ray sources discovered serendipitously by Chandra in the field of the lensing cluster A2390 are found to have ISOCAM counterparts at 6.7 and 15µm. We use this fact, together with their non-detection by SCUBA at 850µm, as the basis for dusty radiative transfer modelling of their infrared spectral energy distribu…
On measuring low-degree p-mode frequency splitting with full-disc integrated data
Appourchaux, T.; Gough, D. O.; Sekii, T. +1 more
The standard method of measuring rotational splitting from solar full-disc oscillation data, based on maximum-likelihood fitting of multi-Lorentzian profiles to oscillation power spectra, systematically overestimates the splitting. One of the reasons is that the maximum likelihood estimators (MLE) become unbiased only asymptotically as the number …
On the existence of differences in luminosity between horizontal branch stars in globular clusters and in the field
Clementini, G.; Carretta, E.; Gratton, R. G.
The discrepancy between a long distance-scale derived from Hipparcos-based distances to globular clusters via main-sequence fitting to local subdwarfs, and a short distance-scale derived from the absolute magnitude of field RR Lyraes via statistical parallaxes and the Baade-Wesselink method could be accounted for whether an intrinsic difference of…
The outer atmosphere of α Tau - III. Inhomogeneities deduced from cold CO fluorescence
McMurry, A. D.; Jordan, C.
Ultraviolet spectra of α Tau obtained with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope show clusters of CO emission lines which are excited by the Oi (uv2) multiplet near 1304Å. Identifications of these fluorescent lines and their pumping routes are presented. The absolute intensities of the CO lines and their rat…
Adaptive optics near-infrared imaging of NGC 2992 - unveiling core structures related to radio figure-of-8 loops
Alonso-Herrero, Almudena; Morris, Simon L.; Chapman, Scott C. +1 more
We present near-infrared adaptive optics, Very Large Array (VLA) radio and Hubble Space Telescope (HST) optical imaging of the nearby Seyfert galaxy NGC 2992. Spiral structure and an extension to the west are traced down to the core region at the limiting resolution of our near-infrared images. A faint, diffuse loop of near-infrared and radio emis…
The infrared counterpart of the Z source GX 5-1
van der Klis, M.; Hambly, N. C.; Fender, R. P. +1 more
We have obtained UK Infrared Telescope infrared observations of the field of the bright Galactic Z source GX 5-1. From an astrometric plate solution tied to Tycho-ACT standards we have obtained accurate positions for the stars in our field which, combined with an accurate radio position, have allowed us to identify the probable infrared counterpar…
The evolution of iron-core white dwarfs
Althaus, L. G.; Panei, J. A.; Benvenuto, O. G.
Recent measurements by Hipparcos present observational evidence supporting the existence of some white dwarf (WD) stars with iron-rich core composition. In connection with this, the present paper is aimed at exploring the structure and evolution of iron-core WDs by means of a detailed and updated evolutionary code. In particular, we examined the e…
Far-infrared-loud quasars - I. Disturbed and quiescent quasars in the PG survey
Clements, D. L.
We use host galaxy imaging studies of the PG quasar survey to compare the far-infrared (FIR) properties of quasars with disturbed and undisturbed host galaxies. By using survival analysis, we show that the quasars with disturbed host galaxies, with morphologies classified from a homogeneous data set, have a 60-µm luminosity distribution that…
Imaging of the merging galaxy NGC 3597 and its population of protoglobular clusters
Forbes, Duncan A.; Hau, G. K. T.
We present wide field-of-view near-infrared imaging from the NTT and very deep optical imaging from the HST of the young merging galaxy NGC 3597. The morphology of the galaxy and the properties of the newly formed protoglobular clusters (PGCs) are examined. Our K-band data reveal the presence of a second nucleus, which provides further evidence th…