F. van Wyk
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View article: Photometry of blazars using the Las Cumbres Observatory robotic telescope network
Photometry of blazars using the Las Cumbres Observatory robotic telescope network Open
We present an analysis of the photometry of nine of the brightest blazars using the 0.4m robotic telescopes of the Las Cumbres Observatory global network. Observations were carried out in four filters (B, V and Sloan g and r) with a typica…
View article: 1E 0502-667: An AGN without narrow lines?
1E 0502-667: An AGN without narrow lines? Open
1E 0502-667 is a comparatively nearby Seyfert 1 galaxy discovered 40 years ago during follow-up observations of X-ray sources in the direction of the Large Magellanic Cloud. Despite its early identification as an AGN, only a few studies ha…
View article: The GW Vir Instability Strip in Light of New Observations of PG 1159 Stars: Discovery of Pulsations in the Central Star of A72 and Variability of RX J0122.9–7521
The GW Vir Instability Strip in Light of New Observations of PG 1159 Stars: Discovery of Pulsations in the Central Star of A72 and Variability of RX J0122.9–7521 Open
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 stars, a median noise level in Fourier amplitude spectra of 0.…
View article: 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
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 Open
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 stars, a median noise level in Fourier amplitude spectra of 0.…
View article: RX J0818.2+0122 - an AGN with an unusually broad Keplerian rotator line profile
RX J0818.2+0122 - an AGN with an unusually broad Keplerian rotator line profile Open
We investigate low resolution spectra and the Balmer line profile in particular of the Active Galactic Nucleus associated with the X-ray source RX J0818.2+0122, and also compare this to an archival Gemini spectrum recorded seven years earl…
View article: The Missing Link? Discovery of Pulsations in the Nitrogen-rich PG 1159 Star PG 1144+005
The Missing Link? Discovery of Pulsations in the Nitrogen-rich PG 1159 Star PG 1144+005 Open
Up to 98% of all single stars will eventually become white dwarfs—stars that link the history and future evolution of the Galaxy, and whose previous evolution is engraved in their interiors. Those interiors can be studied using asteroseism…
View article: The optical and X-ray properties of a sample of Seyfert galaxies that have undergone significant spectral change
The optical and X-ray properties of a sample of Seyfert galaxies that have undergone significant spectral change Open
This paper presents the initial findings of a study of the optical spectra of two sets of data for about 50 Seyfert galaxies taken 20 years apart. We compared the spectra for the different epochs and identify some objects where significant…
View article: The post-maximum behaviour of the changing-look Seyfert galaxy NGC 1566
The post-maximum behaviour of the changing-look Seyfert galaxy NGC 1566 Open
We present results of the long-term multiwavelength study of optical, UV, and X-ray variability of the nearby changing-look (CL) Seyfert NGC 1566 observed with the Swift Observatory and the MASTER Global Robotic Network from 2007 to 2019. …
View article: DISCOVERY OF MORE CHANGING LOOK EVENTS IN NGC 1566
DISCOVERY OF MORE CHANGING LOOK EVENTS IN NGC 1566 Open
We summarize a study of optical, UV and X-ray light curves of the nearby changing look active galactic nucleus in the galaxy NGC 1566 obtained with the Neil Gehrels Swift Observatory and the MASTER Global Robotic Network over the period 20…
View article: New changing look case in NGC 1566
New changing look case in NGC 1566 Open
We present a study of optical, UV and X-ray light curves of the nearby changing look active galactic nucleus in the galaxy NGC 1566 obtained with the Neil Gehrels Swift Observatory and the MASTER Global Robotic Network over the period 2007…
View article: New changing look case in NGC 1566
New changing look case in NGC 1566 Open
We present a study of optical, UV and X-ray light curves of the nearby\nchanging look active galactic nucleus in the galaxy NGC 1566 obtained with the\nNeil Gehrels Swift Observatory and the MASTER Global Robotic Network over the\nperiod 2…