Search Publications
4C +39.29 - extended emission around a powerful type 2 quasar
Fabian, A. C.; Gandhi, P.; Crawford, C. S.
We present new X-ray and optical spectroscopy of a type 2 quasar candidate selected from a follow-up programme of hard, optically dim, serendipitous Chandra sources. The source is confirmed to be a type 2 quasar at z = 0.536 with an intrinsic 2-10 keV luminosity L2-10 = 5 × 1044h-20.7 erg s-1,…
Seasonal evolution of Titan's dark polar hood: midsummer disappearance observed by the Hubble Space Telescope
Lorenz, Ralph D.; Lemmon, Mark T.; Smith, Peter H.
Titan, Saturn's largest moon, has a dense organic-laden atmosphere that displays dramatic seasonal variations in composition and appearance. Here we document the evolution of the dark polar hood, first seen in 1980 by Voyager 1 around the north pole, and report quantitative measurements of the hood's disappearance from the south pole in 2002-2003 …
Hubble Space Telescope observations of SV Cam - I. The importance of unresolved star-spot distributions in light-curve fitting
Donati, J. -F.; Jeffers, S. V.; Collier Cameron, A. +1 more
We have used maximum entropy eclipse-mapping to recover images of the visual surface brightness distribution of the primary component of the RS CVn eclipsing binary SV Cam, using high-precision photometry data obtained during three primary eclipses with Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope (HST). These were augmen…
Challenging the identification of nitride dust in extreme carbon star spectra
Speck, A. K.; Pitman, K. M.; Hofmeister, A. M.
Nitride dust is predicted to form in small amounts around carbon stars, but the most likely candidate species such as aluminium nitride (AlN) have not yet been detected. Recently, α-Si3N4 was inferred to be the main carrier of the 8.5-12.5 µm absorption band(s) of an extreme carbon star (AFGL 5625), based on comparison …
Disc precession in the M31 dipping X-ray binary Bo 158?
Kolb, U.; Osborne, J. P.; Barnard, R. +3 more
We present results from three XMM-Newton observations of the M31 low mass X-ray binary (LMXB) XMMU J004314.4+410726.3 (Bo 158), spaced over 3d in 2004 July. Bo 158 was the first dipping LMXB to be discovered in M31. Periodic intensity dips were previously seen to occur on a 2.78-h period, due to absorption in material that is raised out of the pla…
The anatomy of a quadruply imaged gravitational lens system
Blandford, R. D.; Suyu, S. H.
The key to using a strong gravitational lens system to measure the Hubble constant is to obtain an accurate model of the lens potential. In this paper, we investigate the properties of gravitational lens B1608+656, a quadruply imaged lens system with an extended source intensity distribution. Our analysis is valid for generic quadruply lensed syst…
Radio and X-ray observations of an exceptional radio flare in the extreme z = 4.72 blazar GBB1428+4217
Fabian, A. C.; Worsley, M. A.; Pooley, G. G. +1 more
We report on the extreme behaviour of the high-redshift blazar GBB1428+4217 at z = 4.72. A continued programme of radio measurements has revealed an exceptional flare in the light curve, with the 15.2-GHz flux density rising by a factor of ~3 from ~140 to ~430 mJy in a rest-frame time-scale of only ~4 months - much larger than any previous flares …
The messy environment of Mrk 6
Schurch, N. J.; Warwick, R. S.; Griffiths, R. E.
In recent years it has become clear that understanding the absorption present in active galactic nuclei (AGN) is essential given its bearing on unification models. We present the most recent XMM-Newton observation of Mrk 6, with the goal of understanding the nature and origin of the complex absorption intrinsic to this source. X-ray spectral fitti…
Kinematics of O-B5 giants
Branham, Richard L.
To study the kinematics of O-B5 giant stars (luminosity class III), 290 non-Gould belt stars with proper motions taken from the Hipparcos catalogue are used, of which 107 have radial velocities taken from other sources. Semidefinite programming solves for the kinematical parameters and the coefficients of the velocity ellipsoid. The condition that…
The colour-magnitude relations of ClJ1226.9+3332, a massive cluster of galaxies at z = 0.89
Ebeling, H.; Jones, L. R.; Donovan, D. +2 more
The colour-magnitude relations (CMRs) of one of the most massive (~1015Msolar), high-redshift (z = 0.89) clusters of galaxies known have been studied. Photometry has been measured in the V, R, I, z, F606W, F814W, J and K bands to a depth of K ~ 20.5 = K* + 2.5 and spectroscopy confirms 27 K-band selected galaxies as members o…