Publications (20)44.47 Total impact
-
Article: Possible detection of two giant extrasolar planets orbiting the eclipsing polar UZ Fornacis
[show abstract] [hide abstract]
ABSTRACT: We present new high-speed, multi-observatory, multi-instrument photometry of the eclipsing polar UZ For in order to measure precise mid-eclipse times with the aim of detecting any orbital period variations. When combined with published eclipse times and archival data spanning ~27 years, we detect departures from a linear and quadratic trend of ~60 s. The departures are strongly suggestive of two cyclic variations of 16(3) and 5.25(25) years. The two favoured mechanisms to drive the periodicities are either two giant extrasolar planets as companions to the binary (with minimum masses of 6.3(1.5)M(Jupiter) and 7.7(1.2)M(Jupiter)) or a magnetic cycle mechanism (e.g. Applegate's mechanism) of the secondary star. Applegate's mechanism would require the entire radiant energy output of the secondary and would therefore seem to be the least likely of the two, barring any further refinements in the effect of magnetic fieilds (e.g. those of Lanza et al.). The two planet model can provide realistic solutions but it does not quite capture all of the eclipse times measurements. A highly eccentric orbit for the outer planet would fit the data nicely, but we find that such a solution would be unstable. It is also possible that the periodicities are driven by some combination of both mechanisms. Further observations of this system are encouraged.06/2011; -
Article: Determining the extragalactic extinction law with SALT – II. Additional sample★
[show abstract] [hide abstract]
ABSTRACT: We present new results from an ongoing programme to study the dust extragalactic extinction law in E/S0 galaxies with dust lanes with the Southern African Large Telescope (SALT) during its performance verification phase. The wavelength dependence of the dust extinction for seven galaxies is derived in six spectral bands ranging from the near-ultraviolet atmospheric cut-off to the near-infrared. The derivation of an extinction law is performed by fitting model galaxies to the unextinguished parts of the image in each spectral band, and subtracting from these the actual images. We compare our results with the derived extinction law in the Galaxy and find them to run parallel to the Galactic extinction curve with a mean total-to-selective extinction value of RV= 2.71 ± 0.43. We use total optical extinction values to estimate the dust mass for each galaxy, compare these with dust masses derived from IRAS measurements, and find them to range from 104 to 107 M⊙. We study the case of the well-known dust-lane galaxy NGC 2685 for which Hubble Space Telescope/Wide Field Planetary Camera 2 (HST/WFPC2) data are available to test the dust distribution on different scales. Our results imply a scale-free dust distribution across the dust lanes, at least within ∼1 arcsec (∼60 pc) regions.Monthly Notices of the Royal Astronomical Society 11/2010; 409(2):727 - 736. · 4.90 Impact Factor -
Article: Polarized QPOs from the INTEGRAL polar IGRJ14536-5522 (=Swift J1453.4-5524)
[show abstract] [hide abstract]
ABSTRACT: We report optical spectroscopy and high speed photometry and polarimetry of the INTEGRAL source IGRJ14536-5522 (=Swift J1453.4-5524). The photometry, polarimetry and spectroscopy are modulated on an orbital period of 3.1564(1) hours. Orbital circularly polarized modulations are seen from 0 to -18 per cent, unambiguously identifying IGRJ14536-5522 as a polar. Some of the high speed photometric data show modulations that are consistent with quasi-periodic oscillations (QPOs) on the order of 5-6 minutes. Furthermore, for the first time, we detect the (5-6) minute QPOs in the circular polarimetry. We discuss the possible origins of these QPOs. We also include details of HIPPO, a new high-speed photo-polarimeter used for some of our observations. Comment: Accepted for publication by MNRAS. The paper contains 7 figures and 1 table11/2009; -
Article: Determining the extragalactic extinction law with SALT★
[show abstract] [hide abstract]
ABSTRACT: We present CCD imaging observations of early-type galaxies with dark lanes obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. The observations were performed in six spectral bands that span the spectral range from the near-ultraviolet atmospheric cut-off to the near-infrared. We derive the extinction law by the extragalactic dust in the dark lanes in the spectral range 1.11 < λ−1 < 2.94 μm−1 by fitting model galaxies to the unextinguished parts of the image, and subtracting from these the actual images. This procedure allows the derivation, with reasonably high signal-to-noise ratio, of the extinction in each spectral band we used for each resolution element of the image. We also introduce an alternative method to derive the extinction values by comparing various colour-index maps under the assumption of negligible intrinsic colour gradients in these galaxies. We than compare the results obtained using these two methods.We compare the total-to-selective extinction derived for these galaxies with previously obtained results and with similar extinction values of Milky Way dust to derive conclusions about the properties of extragalactic dust in different objects and conditions.We find that the extinction curves run parallel to the Galactic extinction curve, which implies that the properties of dust in the extragalactic environment are similar to those of the Milky Way, despite our original expectations. The ratio of the total V-band extinction to the selective extinction between the V and B bands is derived for each galaxy with an average of 2.82 ± 0.38, compared to a canonical value of 3.1 for the Milky Way. The similar values imply that galaxies with well-defined dark lanes have characteristic dust grain sizes similar to those of Galactic dust. We use total optical extinction values to estimate the dust mass for each galaxy, compare these with dust masses derived from IRAS measurements, and find them in the range 104–107 M⊙.Monthly Notices of the Royal Astronomical Society 10/2008; 390(3):969 - 984. · 4.90 Impact Factor -
Article: Determining the extragalactic extinction law with SALT
[show abstract] [hide abstract]
ABSTRACT: We present CCD imaging observations of early-type galaxies with dark lanes obtained with the Southern African Large Telescope (SALT) during its performance-verification phase. We derive the extinction law by the extragalactic dust in the dark lanes in the spectral range 1.11mu m^{-1} < lambda^{-1} < 2.94 mu m^{-1} by fitting model galaxies to the unextinguished parts of the image, and subtracting from these the actual images. We find that the extinction curves run parallel to the Galactic extinction curve, which implies that the properties of dust in the extragalactic enviroment are similar to those of the Milky Way. The ratio of the total V band extinction to the selective extinction between the V and B bands is derived for each galaxy with an average of 2.82+-0.38, compared to a canonical value of 3.1 for the Milky Way. The similar values imply that galaxies with well-defined dark lanes have characteristic dust grain sizes similar to those of Galactic dust. Comment: 20 pages, 15 figures and 4 tables. Accepted for publication in MNRAS08/2008; -
Article: The polar ring galaxy AM1934−563 revisited★
[show abstract] [hide abstract]
ABSTRACT: We report long-slit spectroscopic observations of the dust-lane polar ring galaxy AM1934−563 obtained with the Southern African Large Telescope (SALT) during its performance verification phase. The observations target the spectral region of the Hα, [N ii] and [S ii] emission lines, but also show deep Na i absorption lines, that we interpret as being produced by stars in the galaxy. We derive rotation curves along the major axis of the galaxy that extend out to about 8 kpc from the centre for both the gaseous and the stellar components, using the emission and absorption lines. We derive similar rotation curves along the major axis of the polar ring and point out differences between these and the ones of the main galaxy.We identify a small diffuse object visible only in Hα emission and with a low velocity dispersion as a dwarf H ii galaxy and argue that it is probably metal poor. Its velocity indicates that it is a fourth member of the galaxy group in which AM1934−563 belongs.We discuss the observations in the context of the proposal that the object is the result of tidal mater transfer from a major neighbour galaxy and point out some observational discrepancies from this explanation. We argue that an alternative scenario that could better fit the observations may be the slow accretion of cold intergalactic gas, focused by a dense filament of galaxies in which this object is embedded.Given the pattern of rotation we found, with the asymptotic rotation of the gas in the ring being slower than that in the disc while both components have approximately the same extent, we point out that AM1934−563 may be a galaxy in which a dark matter halo is flattened along the galactic disc and the first object in which this predicted behaviour of polar ring galaxies in dark matter haloes is fulfilled.Monthly Notices of the Royal Astronomical Society 12/2007; 382(4):1809 - 1822. · 4.90 Impact Factor -
Article: Photometric and polarimetric observations of the eclipsing polar SDSS J205017.84‐053626.8
[show abstract] [hide abstract]
ABSTRACT: Photometric and polarimetric observations of the eclipsing polar (AM Herculis system) Sloan Digital Sky Survey 2050-05 are reported, in which both sets of data are found to be modulated on a period of ∼94.2 min. This is the first detection of polarization in this system, unambiguously confirming its identification. Circular polarization variations are seen from ∼−10 to +4 per cent, consistent with a ‘two-pole’ accretor. Both accreting poles are self-occulted by the white dwarf during parts of the orbit. The photopolarimetry from different epochs shows the system to be in different states. During the epochs showing a higher state the polarimetry suggests accretion occurs preferentially near the pole displaying positive circular polarization, and vice versa during the epoch showing a lower state. From the eclipses we estimate some of the system's parameters.Monthly Notices of the Royal Astronomical Society 07/2006; 371(2):727 - 731. · 4.90 Impact Factor -
Article: XMM Spectroscopy of the Transient Supersoft Source RX J0513.9-6951: probing the dynamic white dwarf photosphere
[show abstract] [hide abstract]
ABSTRACT: The highly luminous (> 10^37 erg s^-1) supersoft X-ray sources (SSS) are believed to be Eddington limited accreting white dwarfs undergoing surface hydrogen burning. The current paradigm for SSS involves thermally unstable mass transfer from a 1-2 solar mass companion. However this model has never been directly confirmed and yet is crucial for the evolution of cataclysmic variables in general, and for the establishment of SSS as progenitors of type Ia supernovae in particular. The key SSS is RX J0513.9-6951 which has recurrent X-ray outbursts every 100-200 d (lasting for ~40 d) during which the optical declines by 1 mag. We present the first XMM-Newton observations of RX J0513.9-6951 through one of its optical low states. Our results show that as the optical low state progresses the temperature and the X-ray luminosity decrease, behaviour that is anti-correlated with the optical and UV emission. We find that as the optical (and UV) intensity recover the radius implied by the spectral fits increases. The high resolution spectra show evidence of deep absorption features which vary during the optical low state. Our results are consistent with the predictions of the white dwarf photospheric contraction model proposed by Southwell et al. 1996. Comment: 14 pages, 8 figures, 4 tables, accepted for publication in MNRAS09/2005; -
Article: Astronomical Telescopes and Instrumentation
[show abstract] [hide abstract]
ABSTRACT: This paper describes the science drivers and first generation instrumentation capabilities of the Southern African Large Telescope (SALT), due to begin science operations in late 2004/early 2005. First generation instruments are confined to the visible spectrum, but optimized for UV performance, with capability to ~320 nm. Instrumentation will have access to a circular 8 arcmin diameter science field, with guidance objects outside of this region (< 5 arcmin off-axis). Although SALT will have active mirror control to optimize image quality, the mirror array will not be phased (in it's first light configuration), so adaptive optics is not planned initially and instruments will be optimized to the median seeing conditions (0.9 arcsec FWHM). The telescope design, based on the Hobby-Eberly Telescope (HET), also necessitates a queue-scheduled observing approach, which is ideal for time resolved studies of astrophysical phenomena on timescales of >days. Time resolved studies are an important aspect of the overall SALT science drivers. Special efforts are being made to ensure high time resolution capability by employing frame transfer CCDs on two of the first-light instruments, the imaging spectrograph (PFIS/IMPALAS) and imaging camera (SALTICAM). Time resolutions of ~50 ms for spectroscopy, with zero dead-time, are planned. Instrument capabilities, which include polarimetry, Fabry-Perot imaging spectroscopy and high resolution fibre-fed spectroscopy (HRS/CELESTIA), will ensure that the major science goals of SALT's partners are realized.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.01/2003; -
Article: Astronomical Telescopes and Instrumentation
[show abstract] [hide abstract]
ABSTRACT: SALT, although similar to the Hobby-Eberly Telescope (HET - the prototype for a fixed altitude optical analog of the Arecibo radio telescope), has some significant differences in the optical design. This paper gives an overall description of the SALT optics and a description of the analyses done in order to develop an optical error budget, which satisfies the overall requirements for total image quality. An optical prescription for SALT is presented, including an optical model of the telescope with a segmented primary mirror (PM) array. The design of the spherical aberration corrector (SAC) is summarised, with particular reference to the effects of non-axisymmetric distortion. The concepts for an atmospheric dispersion corrector (ADC), and guidance and focusing (GF) systems, are also discussed. Finally, the primary mirror alignment system (PMAS) concept is presented and the difficulty in controlling the Global Radius of Curvature (GRoC) discussed.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.01/2003; -
Article: Superhumps in Cataclysmic Binaries. XXIII. V442 Ophiuchi and RX J1643.7+3402
[show abstract] [hide abstract]
ABSTRACT: We report the results of long observing campaigns on two novalike variables: V442 Ophiuchi and RX J1643.7+3402. These stars have high-excitation spectra, complex line profiles signifying mass loss at particular orbital phases, and similar orbital periods (respectively 0.12433 and 0.12056 d). They are well-credentialed members of the SW Sex class of cataclysmic variables. Their light curves are also quite complex. V442 Oph shows periodic signals with periods of 0.12090(8) and 4.37(15) days, and RX J1643.7+3402 shows similar signals at 0.11696(8) d and 4.05(12) d. We interpret these short and long periods respectively as a "negative superhump" and the wobble period of the accretion disk. The superhump could then possibly arise from the heating of the secondary (and structures fixed in the orbital frame) by inner-disk radiation, which reaches the secondary relatively unimpeded since the disk is not coplanar. At higher frequencies, both stars show another type of variability: quasi-periodic oscillations (QPOs) with a period near 1000 seconds. Underlying these strong signals of low stability may be weak signals of higher stability. Similar QPOs, and negative superhumps, are quite common features in SW Sex stars. Both can in principle be explained by ascribing strong magnetism to the white dwarf member of the binary; and we suggest that SW Sex stars are borderline AM Herculis binaries, usually drowned by a high accretion rate. This would provide an ancestor channel for AM Hers, whose origin is still mysterious. Comment: PDF, 41 pages, 4 tables, 16 figures; accepted, in press, to appear December 2002, PASP; more info at http://cba.phys.columbia.edu/11/2002; -
Article: Millihertz Optical/UV Oscillations in 4U 1626-67: Evidence for a Warped Accretion Disk
[show abstract] [hide abstract]
ABSTRACT: We have detected large-amplitude 0.3-1.2 mHz quasi-periodic oscillations (QPOs) from the low-mass X-ray binary pulsar 4U 1626-67/KZ TrA, using UV photometry from HST and ground-based optical photometry. These 1 mHz QPOs, which have coherence (Nu/DeltaNu)=8, are entirely distinct from the 130 mHz pulsar spin frequency, a previously known 48 mHz QPO, and the 42 min binary period (independently confirmed here). Unlike the 48 mHz and 130 mHz oscillations which are present in both the optical/UV and the X-ray emission, the 1 mHz QPOs are not detected in simultaneous observations with RXTE. The rms amplitude of the mHz QPO decreases from 15% in the far UV to 3% in the optical, while the upper limit on a corresponding X-ray QPO is as low as 0.8%. We suggest that the mHz oscillations are due to warping of the inner accretion disk. We also report the detection of coherent upper and lower sidebands of the 130 mHz optical pulsations, with unequal amplitude and a spacing of 1.93 mHz around the main pulsation. The origin of these sidebands remains unclear. Comment: 7 pages (including figs). Revised, accepted for publication in ApJ06/2001; -
Article: Astronomical Telescopes and Instrumentation
[show abstract] [hide abstract]
ABSTRACT: We review the characteristics of SALT and discuss the major science drivers, both of which will decide the choice of a fist-light instrument package. Current science drivers call for instrumentation similar to that of the Hobby-Eberly Telescope, on which SLAT is closely modeled, with fiber-fed and direct spectroscopy in the visible/near-IR being the major observational mode delivering the best astrophysical returns. The suite will include multi-object spectroscopic capability over a continuous wavelength range of at least 400 nm to 1300 nm, with possible extended capabilities to the blue and near-IR. Factors which will decide these limits are discussed, which include mirror coatings and fiber transmission. Other specific science drivers, which may influence instrument choice or design, include photometry, imaging spectroscopy and spectropolarimetry. Possibility exist for different or novel approaches to instrument designs. Together with potential enhancements of the telescope design, these will have some impact on instrument choice. The nature of the first light instrument suite is currently under discussion and will probably be decided by late-2000.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.08/2000; -
Article: Rapid Oscillations in Cataclysmic Variables. XIV. Orbital and Spin Ephemerides of FO Aquarii
[show abstract] [hide abstract]
ABSTRACT: We report on 17 years of photometry of FO Aquarii, a cataclysmic variable with a rapidly rotating, magnetic white dwarf. We give ephemerides for its variations at the 4.8 hr binary period and the 21 minute spin period. The orbital period is constant at 0.2020596(1) day. The spin period decreases on a timescale of 10^6 yr, but with additional wiggles on timescales of years to decades. The observed alternation between spin-down and spin-up suggests that the star is near its equilibrium spin period, an important prediction of the theory of magnetic cataclysmic variables.Publications of the Astronomical Society of the Pacific 03/1998; 110:415-419. · 3.58 Impact Factor -
Article: Optical identifications of southern rosat EUV and soft X-ray sources
[show abstract] [hide abstract]
ABSTRACT: This paper discusses the first all-sky surveys of cosmic extreme ultra-violet and soft X-ray sources, discovered by ROSAT. Details of the surveys are presented, with comparisons made to previous selected surveys in the X-ray regime. The subsequent optical identification programs are described, and the major results summarized. We then discuss the main classes of EUV emitters: active chromosphere stars and hot white dwarfs, and describe the importance of EUV observations in understanding the astrophysics of these objects. Many bright, and relatively nearby, sources have been identified as hitherto unrecognized active stars, representing the extremes in chromospheric and coronal activity, be it binary or age related. Many new hot DA white dwarfs have also been indentified, and the most exciting result in this area is the discovery that significant traces of heavier elements (e.g. C, N, O, Si, Fe and Al) exist in their atmospheres, substantially increasing their EUV opacities. The importance of hot white dwarfs as standard candles in probing the local interstellar medium is also discussed. Miscellaneous counterparts (AGN, PNN, O-B stars and CVs) that make up the rest of the sample of EUV sources are also briefly mentioned. We finish with a discussion of the on-going ROSAT Galactic Plane Survey (RGPS) identification program.Astrophysics and Space Science 07/1995; 230(1):117-130. · 1.69 Impact Factor -
Article: RX J1712.6-2414: a polarized intermediate polar from the ROSAT Galactic Plane Survey
[show abstract] [hide abstract]
ABSTRACT: We report the discovery of a new intermediate polar, RX J1712.6-2414, discovered during the ROSAT Galactic Plane Survey optical identification programme. Photometric and polarimetric observations establish that the system exhibits two periodicities at 1003 and 927s (or aliases thereof) in the two data sets respectively. This makes RX J1712.6-2414 only the third IP to have a positive detection of circular polarization, and the second for which periodic variations have been detected. Furthermore, the degree of polarization is the largest yet observed in an IP: up to -5 per cent in the I band, and with a semi-amplitude of ~1 per cent in the V, R and I bands. The extensive photometric observations, spanning 3yr, show a convincing 1003-s or 1027-s period, although the amplitude of this signal varies markedly from non-detection to a ~15 per cent semi-amplitude. Detectability of the photometric signal in RX J1712.6-2414 appears to be anticorrelated with its brightness. Low-amplitude (K~10 km s^-1) periodic radial velocity variations at the 1003-s photometric period are observed in at least two nights of data. These variations are particularly pronounced for the HeII lambda4686-A line, where the amplitude is as much as 20 km s^-1. Interpretation of the 927-s polarimetric and 1003-s photometric periods as the spin and synodic (beat) periods, respectively, implies an orbital period of 3.41h, or an alias of this. However, no photometric, and more significantly no radial velocity variations are seen at these or any nearby periods, with an upper limit of ~10 km s^-1. This may be evidence that RX J1712.6-2414 is a low-inclination system, which is supported by the negative sign of the circular polarization over the entire spin cycle, implying that only one accreting pole is observable. We interpret the synodic photometric and radial velocity variations as evidence for discless accretion in RX J1712.6-2414, or at least direct accretion on to the white dwarf's magnetosphere, either directly by the accretion stream, or via disc overflow. Analysis of the ROSAT sky survey data for RX J1712.6-2414 shows that the source had a mean PSPC count rate of 0.52 count s^-1, although the total exposure time was only 302s. The X-ray spectrum is consistent with moderately absorbed (N_H~10^21 cm^-2) and reasonably hard (kT>~1 keV) thermal bremsstrahlung, which implies an L_x/L_opt ratio of ~0.1. These properties are consistent with an intermediate polar model for RX J1712.6-2414, probably involving discless accretion.Monthly Notices of the Royal Astronomical Society 07/1995; 275:1028-1048. · 4.90 Impact Factor -
Article: The pulsating DAV white dwarf BPM 31594 (VY Hor) - Evidence for non-linear mode coupling by direct resonance
[show abstract] [hide abstract]
ABSTRACT: Results of 300 hr of high-speed photometry of the pulsating DAV white dwarf BPM 31594 obtained during 1975-1979 are presented. The light curve exhibits nonsinusoidal pulses with a peak-to-peak range of 30 percent but with obvious modulation in amplitude and pulse shape. The mean amplitude spectrum shows that the dominant contributor to these oscillations is the principal frequency f = 1.62 mHz. Detailed frequency analysis shows that in most, but not all of the data, the frequency spectrum near f contains a rotationally split triplet along with another component very close by. Although the central component is present in all the data, the sidebands of the triplet are not always seen. The separation among the components of the triplet is 12.7 micro-Hz, implying a rotation period of about 0.9 d. The frequency of the central component is found to be stable on timescales of a few months or less; on longer timescales, significant variation which is not monotonic is found.Monthly Notices of the Royal Astronomical Society 08/1992; 258:415-438. · 4.90 Impact Factor -
Article: High-speed photometry and spectroscopy of the dwarf nova TY Piscis Austrini
[show abstract] [hide abstract]
ABSTRACT: High-speed photometry of TY PsA was obtained during quiescence, in a normal outburst, and in a superoutburst. Simultaneous spectroscopy was also obtained for four nights of the superoutburst. The photometry is used to derive an orbital period of 0.08400 + or - 0.00006 day and a superhump period of 0.08765 day. It is found that the observed spectroscopic properties may be explained if TY PsA develops a nonaxially symmetric accretion disk during superoutbursts. It is suggested that cool gas lying above the accretion disk of TY PsA is occasionally projected against the bright center of the disk. The results are similar to those of observations in the soft X-rays from SS Cyg by Cordova et al. (1983).Monthly Notices of the Royal Astronomical Society 04/1989; 238:73-96. · 4.90 Impact Factor -
Article: High-speed photometry of Z Chamaleontis during outbursts
[show abstract] [hide abstract]
ABSTRACT: High-speed white-light photometry of the dwarf nova Z Cha at time resolutions of 4 or 5 s is presented for six supermaxima and one ordinary maxima during the period 1973-1984. It is found that at early stages of the superoutburst, the source of the superhump light is partially eclipsed by the secondary star. Therefore the source of the this light is not a bright spot on the secondary. Synthetic light curves are computed to assist in locating the source of the superhump light and simulations are obtained by modulating the intensity of a bright ring at the outer edge of the disk at the superhump period. MEM deconvolution of eclipse light curves is used to discuss the structural changes that take place during a superoutburst. The observed light curve shows unusual dips at maximum light at phases 0.25 and 0.75. At the end of superoutburst, it is found that the disk has almost completely disappeared, leaving a central source whose size is only that of a few white dwarf radii.Monthly Notices of the Royal Astronomical Society 07/1988; 233:705-738. · 4.90 Impact Factor -
Article: A new two channel high-speed photo-polarimeter (HIPPO) for the SAAO
[show abstract] [hide abstract]
ABSTRACT: We report on the completion of a new 2 channel, HIgh speed Photo-POlarimeter (HIPPO) for the 1.9m optical telescope of the South African Astronomical Observatory. The instrument makes use of rapidly counter-rotating (10Hz), super-achromatic half- and quarter-waveplates, a fixed Glan-Thompson beamsplitter and two photo-multiplier tubes that record the modulated O and E beams. Each modulated beam permits an independent measurement of the polarisation and therefore simultaneous 2 filter observations. All Stokes parameters are recorded every 0.1sec and photometry every 1 millisecond. Post-binning of data is possible in order to improve the signal. This is ideal for measuring e.g. the rapid variability of the optical polarisation from magnetic Cataclysmic Variable stars. First light was obtained in February 2008.
Top co-authors
Top Journals
Institutions
-
2000–2010
-
South African Astronomical Observatory
Cape Town, Province of the Western Cape, South Africa
-
-
1988
-
University of Cape Town
- Department of Astronomy
Cape Town, Province of the Western Cape, South Africa
-
