Search Publications
The ultraviolet to X-ray continua of BL Lac objects.
Warwick, R. S.; George, I. M.; McHardy, I. M.
We present the results from EXOSAT observations of three X-ray bright BL Lacertae objects, Mrk 501, 1218+304 and MRK 180. All three sources have soft power-law X-ray spectra with low-energy cut-offs consistent with absorption in the line-of-sight gas column density through our own galaxy. The three objects also exhibit significant spectral variabi…
Magnesium abundances in planetary nebulae and interstellar absorptionof MG II lambda 2800 A.
Middlemass, D.
High-resolution IUE images have provided line profiles of emission cut by interstellar absorption in the magnesium II lines λλ 2795, 2802 Å in nine objects. The underlying emission has been reconstructed in seven of these and estimates of the ratio of intrinsic to observed emission ranging from 1.5 to 23 have been obtained. Photoionization models …
Effective temperatures and radii of Small Magellanic Cloud supergiants.
Nandy, K.; Houziaux, L.; Thompson, G. I. +1 more
The effective temperatures and radii of Small Magellanic Cloud supergiants are found by comparison with models. The methods used parallel those used previously by ourselves for the Large Cloud and by Underhill and co-workers for the Galaxy. No significant difference is found among these galaxies in this respect. A new analysis of the SMC extinctio…
A relation between UV excess and the interstellar medium in elliptical galaxies ?
Sparks, W. B.; Collier Cameron, A.
We have obtained IUE spectra of the nuclear region of the dust-lane elliptical galaxy NGC 7196, with the intention of investigating a possible relationship between UV excess and the presence of a cool interstellar medium component in elliptical galaxies. This galaxy has a smooth, compact major-axis dust lane and no known nuclear activity. Excess U…
Rapid soft X-ray variability in a newly discovered active galaxy : EXO 1128+691.
Bedford, D. K.; Vilhu, O.; Petrov, P.
A previously unknown active galaxy has been discovered, and has been tentatively identified as a Seyfert type 1. 1t is possibly a member of the UMa I cluster. The X-ray emission differs from that for 'normal' Seyferts in that it is very soft and also shows rapid variability (~15 min to 2 hr). Assuming the galactic value N_H_~1.5x10^20^ cm^-2^ for …
Serendipitous discovery of an AGN showing rapid X-ray variability.
Barstow, M. A.; Stanger, V. J.
A serendipitous X-ray source, discovered by EXOSAT in the field of the hot, helium-rich degenerate star PG1159-035, has been identified with the 15.1-mag galaxy ZWG 013.024. The object is classified as Seyfert 1 and has a redshift of 0.019, implying a distance of 117 Mpc. ZWG 013.024 has an unusually soft medium-energy (0.5-6 keV) X-ray spectrum (…
HD 38451 : J.R. Hind's star that changed colour.
Sneden, Christopher; Warner, Brian
In 1851, John Russell Hind announced that a star previously observed by him to be very red had become bluish white in color. It is shown that this star, HD 38451, is a ninth magnitude shell star which presumably was ejecting a shell when Hind first observed it. From high dispersion coude spectra, low dispersion IUE spectra, and ground-based photom…