Search Publications
On the nature of a secondary main-sequence turn-off in the rich LMC cluster NGC 1868
de Grijs, R.; Santiago, B.; Castro, R. +1 more
Evidence for a second main-sequence turn-off in a deep colour-magnitude diagram (CMD) of NGC 1868 is presented. The data were obtained with Hubble Space Telescope (HST) WFPC2 and reach down to m555~= 25 mag. Besides the usual τ~= 0.8 Gyr turn-off found in previous analyses, another possible turn-off is seen at m555~= 21 mag (…
Sub-arcsecond atomic hydrogen absorption in the Seyfert galaxies NGC 7674 and NGC 7469
Beswick, R. J.; Pedlar, A.; McDonald, A. R.
Neutral hydrogen has been studied on sub-arcsecond scales in two Seyfert galaxies, NGC 7469 and NGC 7674. The 1.4-GHz continuum emission from these sources agree with higher frequency measurements and shows linear, triple source in NGC 7674 and a compact source surrounded by a weak ring of radio emission in NGC 7469. In both of these sources we de…
The anomalous ultraviolet light curves and IUE spectra of β Lyrae revisited
Linnell, A. P.
Recent studies of β Lyrae have proposed several possible models to explain the anomalous ultraviolet light curves of that mass-transfer binary system. This paper subjects four proposed models to tests involving a comparison of system synthetic spectra with the observed spectra and a comparison of synthetic light curves, based on synthetic photomet…
Observations of Hipparcos short-period red giant stars
Koen, Chris; van Wyk, Francois; Laney, Dave
Optical UBV(RI)C and infrared JHK photometry is presented of a small sample of giant stars with short periods in the Hipparcos catalogue. Observations were limited, but were sufficient to rule out most of the Hipparcos periods. Radial velocity measurement were also made for a few stars, over six successive nights. Low-level variability …
On the kinematic deconvolution of the local neighbourhood luminosity function
Siebert, A.; Pichon, C.; Bienaymé, O.
A method for inverting the statistical star counts equation, including proper motions, is presented; in order to break the degeneracy in that equation, it uses the supplementary constraints required by dynamical consistency. The inversion gives access to both the kinematics and the luminosity function of each population in three régimes: the singu…
Contribution to the search for binaries among Am stars - III. HD 7119: a double-lined spectroscopic binary and a triple system
Udry, S.; Ginestet, N.; Prieur, J. -L. +1 more
Radial velocity observations of HD 7119 with the CORAVEL instrument at Observatoire de Haute-Provence are reported. Known as an Amδδ Del metallic-line star, HD 7119 was included in our spectroscopic survey of Am-type stars, the purpose of which was to determine the frequency of binaries in this stellar family. This object is found to be a double-l…
The galaxy population of Cl1601+42 at
Fransson, Claes; Dahlén, Tomas; Näslund, Magnus
Photometric redshifts are used to determine the rest-frame luminosity function (LF) of both early- and late-type galaxies to for the cluster Cl1601+42 at . The total LF shows a steep faint-end slope , indicating the existence of a population of numerous dwarf galaxies. Luminous galaxies, with are mostly red, early-type galaxies, with a LF best des…
Overpressured emission-line clouds in the haloes of powerful radio galaxies
Tadhunter, C. N.; Robinson, T. G.; Dyson, J. E.
We present accurate measurements of the physical conditions in five powerful radio galaxies, as derived from deep, long-slit spectroscopic observations. All five objects show prominent extended line emission, and have X-ray luminosities similar to those of isolated elliptical galaxies. The data are high enough quality that the electron density and…
The origin of [FeII] emission in NGC4151
Chapman, Scott; Lee, David; Turner, James E. H. +5 more
The centre of NGC4151 has been observed in the J band with the SMIRFS integral field unit (IFU) on the UK Infrared Telescope. A map of [FeII] emission is derived, and compared with the distributions of the optical narrow-line region and radio jet. We conclude that, because the [FeII] emission is associated more closely with the visible narrow-line…
Time-resolved ultraviolet spectroscopy of the compact interacting binary QU Car
Long, K. S.; Drew, J. E.; Hartley, L. E.
We present Hubble Space Telescope STIS (1160-1700 Å) echelle spectra of the cataclysmic variable (CV) star QU Car, at three epochs. In catalogues this binary is classified as a nova-like variable. QU Car was observed three times in time-tag mode for 2300, 2600 and 2600 s, allowing us to study the spectral time evolution on time-scales down to ~10 …