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A photometric and spectroscopic study of the brightest northern Cepheids - III. A high-resolution view of Cepheid atmospheres
Vinkó, József; Kiss, László L.
We present new high-resolution spectroscopic observations (λ/Δλ~40000) of 18 bright northern Cepheids carried out at the David Dunlap Observatory in 1997. The measurements mainly extend those presented in Paper I of this series, adding three more stars (AW Per, SV Vul, T Mon). The spectra were obtained in the yellow-red spectral region in the inte…
The hyperluminous infrared quasar 3C 318 and its implications for interpreting submm detections of high-redshift radio galaxies
Willott, Chris J.; Rawlings, Steve; Jarvis, Matt J.
We present near-infrared spectroscopy and imaging of the compact steep-spectrum radio source 3C 318, which shows it to be a quasar at redshift z=1.574 (the z=0.752 value previously reported is incorrect). 3C 318 is an IRAS, ISO and SCUBA source so its new redshift makes it the most intrinsically luminous far-infrared (FIR) source in the 3C catalog…
A study of interstellar Nai D absorption lines towards the Lupus molecular clouds
Crawford, I. A.
Intermediate-resolution (60000<=R<=120000) observations of interstellar Nai lines towards 29 stars in the general direction of the Lupus molecular clouds (330°<~l<~350° 0°<~b<~25°) are presented. Previously published spectra towards an additional seven stars are also included. Based on the Hipparcos distances to these stars, and …
Time evolution of galactic warps in prolate haloes
Ideta, M.; Hozumi, S.; Tsuchiya, T. +1 more
A recent observation with the Hipparcos satellite and some numerical simulations imply that the interaction between an oblate halo and a disc is inappropriate for the persistence of galactic warps. Following on from this, we have compared the time evolution of galactic warps in a prolate halo with that in an oblate halo. The haloes were approximat…
Progress on a model for β Lyrae
Linnell, A. P.
It is generally accepted that β Lyrae is a massive mass-transfer system in which the more massive gainer is embedded in a thick accretion disc. No detailed, quantitative accretion disc model of the system, which fits both the available photometric and spectroscopic data, has been published. This paper considers a thick accretion disc model. An emp…
Dynamic-range limitations of intensified CCD photon-counting detectors
Fordham, J. L. A.; Moorhead, C. F.; Galbraith, R. F.
The bright limit to the dynamic range of intensified CCD photon-counting detectors is governed by coincidence losses. In this paper a theoretical analysis of the loss mechanisms is carried out and verified using laboratory data. For applications where the input source is stable, such as star field imaging from space, the theoretical dynamic-range …
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…