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Angular diameter and effective temperature of a sample of 15M giants at 2.2µm from lunar occultation observations
Tej, Anandmayee; Chandrasekhar, T.
High angular resolution measurements of a sample of 15M giants at 2.2µm by the technique of lunar occultation are presented in this paper. We obtain angular diameters for 11 sources of which five are the first diameter measurements. For these resolved sources we have estimated the effective temperatures, which are consistent with previous ca…
High time-resolution spectroscopic imaging using intensified CCD detectors
Much, R.; Kawakami, H.; Fordham, J. L. A. +2 more
The micro-channel plate intensified CCD photon counting detector developed at University College London has been upgraded to allow time-resolved spectroscopic optical data to be acquired on periodical sources such as pulsars. First observing trials have been carried out, acquiring spectroscopic data on the Crab pulsar. The detector was phase locke…
Source of excitation of low-l solar p modes: characteristics and solar-cycle variations
Chaplin, W. J.; Elsworth, Y.; Appourchaux, T. +3 more
We investigate various properties of the excitation source that is responsible for driving the acoustic p-mode oscillations of the Sun. Current prejudice places this in the superadiabatic layer of the convection zone. We consider in detail how the precise nature of the resonant mode spectrum is modified: (i) as a result of the impact of different …
Using Hubble Space Telescope images to identify straight segments in galaxy nuclear spirals
Chernin, A. D.
This Letter reports the discovery of straight segments of nuclear spiral arms. Hubble Space Telescope images of Seyfert galaxies are used. The morphology of the straight features on scales of few hundred parsecs proves to be similar to the morphology of disc-wide polygonal spirals and rings. This suggests that the straight structures on both nucle…
Interstellar CO towards X Persei (HD 24534) - I. One-component model
Kaczmarczyk, Grzegorz
Data on molecular CO in absorbing gas towards X Per, from the International Ultraviolet Explorer (IUE) and the echelle mode of the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope, are reported. A statistical equilibrium model is used to recreate equivalent widths of CO bands and reproduce high-resolution GHRS spectra.…
The spectral variations of the O-type runaway supergiant HD 188209
Galeev, A.; Herrero, A.; Kaufer, A. +4 more
We report spectral time series of the late O-type runaway supergiant HD 188209. Radial velocity variations of photospheric absorption lines with a possible quasi-period of ~6.4d have been detected in high-resolution echelle spectra. Night-to-night variations in the position and strength of the central emission reversal of the Hα profile occurring …
Single Be stars as binary ejecta?
Rinehart, S. A.
Among the mechanisms suggested for the creation of discs around Be stars is interaction with binary companions. This idea has largely been dismissed, because the majority of Be stars have no observed companion. This difficulty can be circumvented if single Be stars are actually ejected from binary systems (owing, for instance, to the supernova of …
Bulk flow velocities in the solar corona
Simnett, G. M.; Lewis, D. J.
We present velocity estimates of bulk motions in the solar corona using data from the Large Angle Spectrometric Coronagraph (LASCO) aboard the Solar and Heliospheric Observatory spacecraft (SOHO). We describe a new technique which automatically provides a mass-weighted mean velocity profile in an entirely objective fashion without the need for ind…
The far-UV spectrum of T Tauri stars - I. The relevance of the IUE Newly Extracted Spectra
Huélamo, N.; Gómez de Castro, A. I.; Franqueira, M.
The far-UV spectrum of the T Tauri stars (TTSs) provides important clues about the structure of the stellar atmospheres, winds and accretion shocks. The IUE (International Ultraviolet Explorer) Final Archive contains the most complete data base for such studies. A new extraction system, the IUE Newly Extracted Spectra (ines), has been developed to…
Redshift distribution of Lyα lines and metal systems
Demiański, M.; Doroshkevich, A. G.; Turchaninov, V.
The observed redshift distribution of Lyα lines and metal systems is examined in order to discriminate and to trace the evolution of structure elements observed in the galaxy distribution, at small redshifts, and to test the theoretical description of structure evolution. We show that the expected evolution of a filamentary component of structure …