142 citations · 661 across the 16 of their papers we have counts for
16 papers
The GW Vir instability strip in the light of new observations of PG 1159 stars. Discovery of pulsations in the central star of Abell 72 and variability of RX J0122.9-7521
Paulina Sowicka, Gerald Handler, David Jones +9
We present the results of new time series photometric observations of 29 pre-white dwarf stars of PG 1159 spectral type, carried out in the years 2014-2022. For the majority of sta…
South African night sky brightness during high aerosol epochs
Hartmut Winkler, Francois van Wyk, Fred Marang
Sky conditions in the remote, dry north-western interior of South Africa are now the subject of considerable interest in view of the imminent construction of numerous solar power p…
Near-Infrared Evidence for a Sudden Temperature Increase in Eta Carinae
Andrea Mehner, Kazunori Ishibashi, Patricia Whitelock +4
Aims. Eta Car's ultra-violet, optical, and X-ray light curves and its spectrum suggest a physical change in its stellar wind over the last decade. It was proposed that the mass-los…
The UBV(RI)c colors of the Sun
I. Ramirez, R. Michel, R. Sefako +6
Photometric data in the UBV(RI)c system have been acquired for 80 solar analog stars for which we have previously derived highly precise atmospheric parameters Teff, log g, and [Fe…
The Spitzer Spectroscopic Survey of S-type Stars
K. Smolders, P. Neyskens, J. A. D. L. Blommaert +28
S-type AGB stars are thought to be in the transitional phase between M-type and C-type AGB stars. Because of their peculiar chemical composition, one may expect a strong influence…
Recurrent dust formation by WR 48a on a 30-year timescale
Peredur M. Williams, Karel A. van der Hucht, Francois van Wyk +4
We present infrared photometry of the WC8 Wolf-Rayet system WR 48a observed with telescopes at ESO, the SAAO and the AAT between 1982 and 2011 which show a slow decline in dust emi…
The discovery of rapid oscillations in the magnetic Ap stars HD69013 and HD96237
V. G. Elkin, D. W. Kurtz, H. L. Worters +4
We report the detection of short period variations in the stars HD69013 and HD96237. These stars possess large overabundances of rare earth elements and global magnetic fields, thu…
Post-AGB stars with hot circumstellar dust: binarity of the low-amplitude pulsators
Hans Van Winckel, Tom Lloyd Evans, Maryline Briquet +28
While the first binary post-AGB stars were serendipitously discovered, the distinct characteristics of their Spectral Energy Distribution (SED) allowed us to launch a more systemat…
Asteroseismology of hybrid pulsators made possible: simultaneous MOST space photometry and ground-based spectroscopy of Gamma Peg
G. Handler
We have acquired simultaneous high-precision space photometry and radial velocities of the bright hybrid Beta Cep/SPB pulsator Gamma Peg. Frequency analyses reveal the presence of…
Asteroseismic analysis of the roAp star alpha Circini: 84 days of high-precision photometry from the WIRE satellite
H. Bruntt, D. W. Kurtz, M. S. Cunha +8
We present a detailed study of the pulsation of alpha Circini, the brightest of the rapidly oscillating Ap stars. We have obtained 84 days of high-precision photometry from four ru…
Resolving the 47 Tucanae Distance Problem
Susan M. Percival, Maurizio Salaris, Francois van Wyk +1
We present new B, V and I-band photometry for a sample of 43 local subdwarfs with HIPPARCOS parallax errors < 13%, in the metallicity range -1.0 < [Fe/H] < -0.3, which we use to pe…
A search for previously unrecognised metal-poor subdwarfs in the Hipparcos astrometric catalogue
I. Neill Reid, F. van Wyk, F. Marang +3
We have identified 317 stars included in the Hipparcos astrometric catalogue which have parallaxes measured to a precision of better than 15%, and whose location in the (M_V, (B-V)…
Time-series Spectroscopy of Pulsating sdB Stars: PG1605+072
S. J. O'Toole, T. R. Bedding, H. Kjeldsen +6
We report the detection of velocity variations in the pulsating sdB star, PG 1605+072. Oscillations are detected at the same frequencies found from photometry and have amplitudes o…
The fall and rise of V854 Centauri: long-term ultraviolet spectroscopy of a highly-active R Coronae Borealis star
W. A. Lawson
We examine long-term low-dispersion IUE, SWP and LWP spectroscopy of the R Coronae Borealis (RCB) star V854 Cen, obtained across the deep 1991, 1992-1993 and 1994 declines. We also…
Multiwavelength Monitoring of the BL Lacertae Object PKS 2155-304 in May 1994. I. The Ground-Based Campaign
J. E. Pesce, C. M. Urry, L. Maraschi +29
Optical, near-infrared, and radio observations of the BL Lac object PKS2155-304 were obtained simultaneously with a continuous UV/EUV/X-ray monitoring campaign in 1994 May. Further…
Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. VI. Variability of NGC 3783 from ground-based data
G. M. Stirpe
The Seyfert 1 galaxy NGC 3783 was intensely monitored between 1991 December and 1992 August. We present the results from the ground-based observations in the optical and near-IR, w…