Search

In this work we explore the applicability of unsupervised machine learning algorithms to the task of finding radio transients. Facilities such as the Square Kilometre Array (SKA) will provide huge volumes of data in which to detect rare transients; the challenge for astronomers is how to find them. We demonstrate the effectiveness of anomaly detection algorithms using 1.3 GHz light curves from the SKA precursor MeerKAT. We make use of three sets of descriptive parameters ('feature sets') as applied to two anomaly detection techniques in the Astronomaly package and analyse our performance by comparison with citizen science labels on the same dataset. By using transients found by volunteers as our ground truth, we demonstrate that anomaly detection techniques can recall over half of the radio transients in the 10 per cent of the data with the highest anomaly scores. We find that the choice of anomaly detection algorithm makes a minimal (sub-one per cent) level difference, but that feature set choice is crucial, especially when considering available resources for human inspection and/or follow-up. Active learning, where human labels are given for just 2 per cent of the data, improves recall by up to 10 percentage points, depending on the feature-model pair. The best performing feature-model pairs result in a factor of 5 times fewer sources requiring vetting by experts. This is the first effort to apply anomaly detection techniques to finding radio transients and shows great promise for application to other datasets, and as a real-time transient detection system for upcoming large surveys., Comment: Submitted to MNRAS, comments welcome! 17 pages, 9 Figures

In this short paper we outline the case for a small radio telescope array in the southern hemisphere with operations dedicated to rapid follow-up and monitoring of astrophysical transients. We argue that the science harvest from such a facility would be very large, using AMI-LA as an outstanding example of how such a programme is already being operated in the north with an enormous track record of success. A southern radio transients facility would in turn take pressure off the Square Kilometre Array and the other world class larger arrays with 10-100 times more collecting area, which will never have the programme time available to comprehensively pursue this science. We discuss comparisons with the development of transient surveys and follow up in optical astronomy, and also how single millimetre dishes can contribute to radio transients science in the south. This paper is not a funding proposal aimed at any particular body, but rather a concept and discussion piece, and the authors welcome comments and feedback., Comment: We welcome comments, thoughts, opinions and criticisms of our concept, anonymous or signed, via this google form: https://forms.gle/wHh31USPotNbPy6E6

We present the discovery of the radio afterglow of the short $\gamma$-ray burst (GRB) 210726A, localized to a galaxy at a photometric redshift of $z\sim 2.4$. While radio observations commenced $\lesssim 1~$day after the burst, no radio emission was detected until $\sim11~$days. The radio afterglow subsequently brightened by a factor of $\sim 3$ in the span of a week, followed by a rapid decay (a "radio flare"). We find that a forward shock afterglow model cannot self-consistently describe the multi-wavelength X-ray and radio data, and underpredicts the flux of the radio flare by a factor of $\approx 5$. We find that the addition of substantial energy injection, which increases the isotropic kinetic energy of the burst by a factor of $\approx 4$, or a reverse shock from a shell collision are viable solutions to match the broad-band behavior. At $z\sim 2.4$, GRB 210726A is among the highest redshift short GRBs discovered to date as well as the most luminous in radio and X-rays. Combining and comparing all previous radio afterglow observations of short GRBs, we find that the majority of published radio searches conclude by $\lesssim 10~$days after the burst, potentially missing these late rising, luminous radio afterglows., Comment: 29 pages, 10 figures, accepted to ApJ

Magnetic fields are extremely rare in close, hot binaries, with only 1.5\% of such systems known to contain a magnetic star. The eccentric $\epsilon$ Lupi system stands out in this population as the only close binary in which both stars are known to be magnetic. We report the discovery of strong, variable radio emission from $\epsilon$ Lupi using the upgraded Giant Metrewave Radio Telescope (uGMRT) and the MeerKAT radio telescope.The light curve exhibits striking, unique characteristics including sharp, high-amplitude pulses that repeat with the orbital period, with the brightest enhancement occurring near periastron. The characteristics of the light curve point to variable levels of magnetic reconnection throughout the orbital cycle, making $\epsilon$ Lupi the first known high-mass, main sequence binary embedded in an interacting magnetosphere. We also present a previously unreported enhancement in the X-ray light curve obtained from archival XMM-Newton data. The stability of the components' fossil magnetic fields, the firm characterization of their relatively simple configurations, and the short orbital period of the system make $\epsilon$ Lupi an ideal target to study the physics of magnetospheric interactions. This system may thus help us to illuminate the exotic plasma physics of other magnetically interacting systems such as moon-planet, planet-star, and star-star systems including T Tauri binaries, RS CVn systems, and neutron star binaries., Comment: Accepted for publication in MNRAS, 16 pages, 12 figures

The newest generation of radio telescopes are able to survey large areas with high sensitivity and cadence, producing data volumes that require new methods to better understand the transient sky. Here we describe the results from the first citizen science project dedicated to commensal radio transients, using data from the MeerKAT telescope with weekly cadence. Bursts from Space: MeerKAT was launched late in 2021 and received ~89000 classifications from over 1000 volunteers in 3 months. Our volunteers discovered 142 new variable sources which, along with the known transients in our fields, allowed us to estimate that at least 2.1 per cent of radio sources are varying at 1.28 GHz at the sampled cadence and sensitivity, in line with previous work. We provide the full catalogue of these sources, the largest of candidate radio variables to date. Transient sources found with archival counterparts include a pulsar (B1845-01) and an OH maser star (OH 30.1-0.7), in addition to the recovery of known stellar flares and X-ray binary jets in our observations. Data from the MeerLICHT optical telescope, along with estimates of long time-scale variability induced by scintillation, imply that the majority of the new variables are active galactic nuclei. This tells us that citizen scientists can discover phenomena varying on time-scales from weeks to several years. The success both in terms of volunteer engagement and scientific merit warrants the continued development of the project, whilst we use the classifications from volunteers to develop machine learning techniques for finding transients., Comment: Accepted to MNRAS, 14 pages + an appendix containing our main data table

We present the first sub-arcsecond localised Fast Radio Burst (FRB) detected using MeerKAT. FRB 20210405I was detected in the incoherent beam using the MeerTRAP pipeline on 2021 April 05 with a signal to noise ratio of 140.8 and a dispersion measure of 565.17 pc cm$^{-3}$. It was detected while MeerTRAP was observing commensally with the ThunderKAT large survey project, and was sufficiently bright that we could use the ThunderKAT 8s images to localise the FRB. Two different models of the dispersion measure in the Milky Way and halo suggest that the source is either right at the edge of the Galaxy, or outside. This highlights the uncertainty in the Milky Way dispersion measure models, particularly in the Galactic Plane, and the uncertainty of Milky Way halo models. Further investigation and modelling of these uncertainties will be facilitated by future detections and localisations of nearby FRBs. We use the combined localisation, dispersion measure, scattering, specific luminosity and chance coincidence probability information to find that the origin is most likely extra-galactic and identify the likely host galaxy of the FRB: 2MASS J1701249$-$4932475. Using SALT spectroscopy and archival observations of the field, we find that the host is a disk/spiral galaxy at a redshift of $z=0.066$., Comment: 15 pages, 4 tables, 10 figures. Accepted to MNRAS

We report low-frequency radio observations of the 2021 outburst of the recurrent nova RS Ophiuchi. These observations include the lowest frequency observations of this system to date. Detailed light curves are obtained by MeerKAT at 0.82 and 1.28 GHz and LOFAR at 54 and 154 MHz. These low-frequency detections allow us to put stringent constraints on the brightness temperature that clearly favour a non-thermal emission mechanism. The radio emission is interpreted and modelled as synchrotron emission from the shock interaction between the nova ejecta and the circumbinary medium. The light curve shows a plateauing behaviour after the first peak, which can be explained by either a non-uniform density of the circumbinary medium or a second emission component. Allowing for a second component in the light-curve modelling captures the steep decay at late times. Furthermore, extrapolating this model to 15 yr after the outburst shows that the radio emission might not fully disappear between outbursts. Further modelling of the light curves indicates a red giant mass-loss rate of $\sim 5 \cdot 10^{-8}~{\rm M_\odot~yr^{-1}}$. The spectrum cannot be modelled in detail at this stage, as there are likely at least four emission components. Radio emission from stellar wind or synchrotron jets is ruled out as the possible origin of the radio emission. Finally, we suggest a strategy for future observations that would advance our understanding of the physical properties of RS Ophiuchi., Comment: Published in MNRAS

We present radio observations of the symbiotic recurrent nova V3890 Sagitarii following the 2019 August eruption obtained with the MeerKAT radio telescope at 1.28 GHz and Karl G. Janksy Very Large Array (VLA) at 1.26 to 5 GHz. The radio light curves span from day 1 to 540 days after eruption and are dominated by synchrotron emission produced by the expanding nova ejecta interacting with the dense wind from an evolved companion in the binary system. The radio emission is detected early on (day 6) and increases rapidly to a peak on day 15. The radio luminosity increases due to a decrease in the opacity of the circumstellar material in front of the shocked material and fades as the density of the surrounding medium decreases and the velocity of the shock decelerates. Modelling the light curve provides an estimated mass-loss rate of $M_{\textrm {wind}} \approx 10^{-8} {\textrm {M}}_\odot~{\textrm {yr}}^{-1}$ from the red giant star and ejecta mass in the range of $M_{\textrm {ej}}=10^{-5}-10^{-6}~{\textrm {M}}_\odot$from the surface of the white dwarf. V3890 Sgr likely hosts a massive white dwarf similar to other symbiotic recurrent novae, thus considered a candidate for supernovae type Ia (SNe Ia) progenitor. However, its radio flux densities compared to upper limits for SNe Ia have ruled it out as a progenitor for SN 2011fe.

The radio-emitting neutron star population encompasses objects with spin periods ranging from milliseconds to tens of seconds. As they age and spin more slowly, their radio emission is expected to cease. We present the discovery of an ultra-long period radio-emitting neutron star, J0901-4046, with spin properties distinct from the known spin and magnetic-decay powered neutron stars. With a spin-period of 75.88 s, a characteristic age of 5.3 Myr, and a narrow pulse duty-cycle, it is uncertain how radio emission is generated and challenges our current understanding of how these systems evolve. The radio emission has unique spectro-temporal properties such as quasi-periodicity and partial nulling that provide important clues to the emission mechanism. Detecting similar sources is observationally challenging, which implies a larger undetected population. Our discovery establishes the existence of ultra-long period neutron stars, suggesting a possible connection to the evolution of highly magnetized neutron stars, ultra-long period magnetars, and fast radio bursts, Comment: Published in Nature Astronomy - https://www.nature.com/articles/s41550-022-01688-x

SXP 15.6 is a recently established Be star X-ray binary system (BeXRB) in the Small Magellanic Cloud (SMC). Like many such systems the variable X-ray emission is driven by the underlying behaviour of the mass donor Be star. It is shown here that the neutron star in this system is exceptionally close to spin equilibrium averaged over several years, with the angular momentum gain from mass transfer being almost exactly balanced by radiative losses. This makes SXP 15.6 exceptional compared to all other known members of its class in the SMC, all of whom exhibit much higher spin period changes. In this paper we report on X-ray observations of the brightest known outburst from this system. These observations are supported by contemporaneous optical and radio observations, as well as several years of historical data., Comment: 9 pages, 10 figures

We report on the detection of MKT J174641.0$-$321404, a new radio transient found in untargeted searches of wide-field MeerKAT radio images centred on the black hole X-ray binary H1743$-$322. MKT J174641.0$-$321404 is highly variable at 1.3 GHz and was detected three times during 11 observations of the field in late 2018, reaching a maximum flux density of 590 $\pm$ 60 $\mu$Jy. We associate this radio transient with a high proper motion, M dwarf star SCR~1746$-$3214 12 pc away from the Sun. Multiwavelength observations of this M dwarf indicate flaring activity across the electromagnetic spectrum, consistent with emission expected from dMe stars, and providing upper limits on quiescent brightness in both the radio and X-ray regimes. \textit{TESS} photometry reveals a rotational period for SCR~1746$-$3214 of $0.2292 \pm 0.0025$ days, which at its estimated radius makes the star a rapid rotator, comparable to other low mass systems. Dedicated spectroscopic follow up confirms the star as a mid-late spectral M dwarf with clear magnetic activity indicated by strong H$\alpha$ emission. This transient's serendipitous discovery by MeerKAT, along with multiwavelength characterisation, make it a prime demonstration of both the capabilities of the current generation of radio interferometers and the value of simultaneous observations by optical facilities such as MeerLICHT. Our results build upon the literature of of M dwarfs' flaring behaviour, particularly relevant to the habitability of their planetary systems., Comment: Accepted to MNRAS, 11 pages, 9 figures

The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a radio interferometer array currently in development, with an initial 256-element array to be deployed at the South African Radio Astronomy Observatory (SARAO) Square Kilometer Array (SKA) site in South Africa. Each of the 6m, $f/0.23$ dishes will be instrumented with dual-polarisation feeds operating over a frequency range of 400-800 MHz. Through intensity mapping of the 21 cm emission line of neutral hydrogen, HIRAX will provide a cosmological survey of the distribution of large-scale structure over the redshift range of $0.775 < z < 2.55$ over $\sim$15,000 square degrees of the southern sky. The statistical power of such a survey is sufficient to produce $\sim$7 percent constraints on the dark energy equation of state parameter when combined with measurements from the Planck satellite. Additionally, HIRAX will provide a highly competitive platform for radio transient and HI absorber science while enabling a multitude of cross-correlation studies. In this paper, we describe the science goals of the experiment, overview of the design and status of the sub-components of the telescope system, and describe the expected performance of the initial 256-element array as well as the planned future expansion to the final, 1024-element array., Comment: 24 pages, 6 figures. Updated to match published version

We report the discovery of a highly-polarized, highly-variable, steep-spectrum radio source, ASKAP J173608.2-321635, located $\sim$4\,deg from the Galactic center in the Galactic plane. The source was detected six times between 2020 January and 2020 September as part of the Australian Square Kilometre Array Pathfinder Variables and Slow Transients (ASKAP VAST) survey at 888\,MHz. It exhibited a high degree ($\sim 25$\%) of circular polarization when it was visible. We monitored the source with the MeerKAT telescope from 2020 November to 2021 February on a 2--4 week cadence. The source was not detected with MeerKAT before 2021 February 07 when it appeared and reached a peak flux density of 5.6\,mJy. The source was still highly circularly polarized, but also showed up to 80\% linear polarization, and then faded rapidly with a timescale of one day. The rotation measure of the source varied significantly, from $-11.8\pm0.8$\,rad\,m$^{-2}$ to $-64.0\pm1.5$\,rad\,m$^{-2}$, over three days. No X-ray counterpart was found in follow-up \textit{Swift} or \textit{Chandra} observations about a week after the first MeerKAT detection, with upper limits of $\sim 5.0\times10^{31}$\,erg\,s$^{-1}$ (0.3--8\,keV, assuming a distance $\sim10$ kpc). No counterpart is seen in new or archival near-infrared observations down to $J=20.8$\,mag. We discuss possible identifications for ASKAP J173608.2-321635 including a low-mass star/substellar object with extremely low infrared luminosity, a pulsar with scatter-broadened pulses, a transient magnetar, or a Galactic Center Radio Transient: none of these fully explains the observations, which suggests that ASKAP J173608.2-321635 may represent part of a new class of objects being discovered through radio imaging surveys., Comment: 22 pages, 15 figures, Accepted by ApJ

Astronomers require efficient automated detection and classification pipelines when conducting large-scale surveys of the (optical) sky for variable and transient sources. Such pipelines are fundamentally important, as they permit rapid follow-up and analysis of those detections most likely to be of scientific value. We therefore present a deep learning pipeline based on the convolutional neural network architecture called $\texttt{MeerCRAB}$. It is designed to filter out the so called 'bogus' detections from true astrophysical sources in the transient detection pipeline of the MeerLICHT telescope. Optical candidates are described using a variety of 2D images and numerical features extracted from those images. The relationship between the input images and the target classes is unclear, since the ground truth is poorly defined and often the subject of debate. This makes it difficult to determine which source of information should be used to train a classification algorithm. We therefore used two methods for labelling our data (i) thresholding and (ii) latent class model approaches. We deployed variants of $\texttt{MeerCRAB}$ that employed different network architectures trained using different combinations of input images and training set choices, based on classification labels provided by volunteers. The deepest network worked best with an accuracy of 99.5$\%$ and Matthews correlation coefficient (MCC) value of 0.989. The best model was integrated to the MeerLICHT transient vetting pipeline, enabling the accurate and efficient classification of detected transients that allows researchers to select the most promising candidates for their research goals., Comment: 15 pages, 13 figures, Accepted for publication in Experimental Astronomy and appeared in the 3rd Workshop on Machine Learning and the Physical Sciences, NeurIPS 2020

We report on the Swift/XRT Deep Galactic Plane Survey discovery and multi-wavelength follow-up observations of a new intermediate polar Cataclysmic Variable, Swift J183920.1-045350. A 449.7 s spin period is found in Xmm-Newton and NuSTAR data, accompanied by a 459.9 s optical period that is most likely the synodic, or beat period, produced from a 5.6 h orbital period. The orbital period is seen with moderate significance in independent long-baseline optical photometry observations with ZTF and SAAO. We find that the source X-ray pulsed fraction decreases with increasing energy. The X-ray spectra are consistent with the presence of an Fe emission line complex with both local and interstellar absorption. In the optical spectra, strong H$\alpha{}$, H I, He I and He II emission lines are observed, all common features in magnetic CVs. The source properties are thus typical of known intermediate polars, with the exception of its estimated distance of 2.26$^{+1.93}_{-0.83}$ kpc, which is larger than typical, extending the reach of the CV population in our Galaxy., Comment: 20 pages, 9 figures

We present the results of a weekly monitoring of the new black hole candidate X-ray binary MAXI J1631-472 carried out with the MeerKAT radio interferometer, the Neil Gehrels Swift Observatory, and the Monitor of All-sky X-ray Image (MAXI) instrument, during its 2018-2019 outburst. The source exhibits a number of X-ray states, in particular both high- and low-luminosity hard states bracketed by extended soft states. Radio flaring is observed shortly after a transition from hard/intermediate states to the soft state. This is broadly in agreement with existing empirical models, but its extended duration hints at multiple unresolved flares and/or jet-ISM interactions. In the hard state radio:X-ray plane, the source is revealed to be 'radio quiet' at high luminosities, but to rejoin the `standard' track at lower luminosities, an increasingly commonly-observed pattern of behaviour., Comment: Accepted for publication in MNRAS

ESO 149-G003 is a close-by, isolated dwarf irregular galaxy. Previous observations with the ATCA indicated the presence of anomalous neutral hydrogen (HI) deviating from the kinematics of a regularly rotating disc. We conducted follow-up observations with the MeerKAT radio telescope during the 16-dish Early Science programme as well as with the MeerLICHT optical telescope. Our more sensitive radio observations confirm the presence of anomalous gas in ESO 149-G003, and further confirm the formerly tentative detection of an extraplanar HI component in the galaxy. Employing a simple tilted-ring model, in which the kinematics is determined with only four parameters but including morphological asymmetries, we reproduce the galaxy's morphology, which shows a high degree of asymmetry. By comparing our model with the observed HI, we find that in our model we cannot account for a significant (but not dominant) fraction of the gas. From the differences between our model and the observed data cube we estimate that at least 7%-8% of the HI in the galaxy exhibits anomalous kinematics, while we estimate a minimum mass fraction of less than 1% for the morphologically confirmed extraplanar component. We investigate a number of global scaling relations and find that, besides being gas-dominated with a neutral gas-to-stellar mass ratio of 1.7, the galaxy does not show any obvious global peculiarities. Given its isolation, as confirmed by optical observations, we conclude that the galaxy is likely currently acquiring neutral gas. It is either re-accreting gas expelled from the galaxy or accreting pristine intergalactic material., Comment: 16 pages, 14 figures, MNRAS, Accepted 2020 December 2, in original form 2019 September 18

We report detailed follow-up observations of 8 cataclysmic variable stars (CVs) that are apparently AM Her stars, also called polars. For all, we either determine orbital periods for the first time, or improve on existing determinations. The seven for which we have spectra show the high-amplitude radial velocity curves and prominent HeII 4686 emission lines characteristic of strongly magnetic CVs, and their periods, which range from 81 to 219 minutes, are also typical for AM Her stars. Two objects from the Gaia-alerts index, Gaia18aot and Gaia18aya, are newly identified as CVs. Another, RX J0636.3+6554, eclipses deeply, while CSS080228:081210+040352 shows a sharp dip that is apparently a partial eclipse. The spectrum of Gaia18aya has a cyclotron harmonic near 5500 Angstroms that constrains the surface field to about 49 Megagauss or greater., Comment: Astronomical Journal, in press

Cosmic neutrinos provide a unique window into the otherwise-hidden mechanism of particle acceleration in astrophysical objects. A flux of high-energy neutrinos was discovered in 2013, and the IceCube Collaboration recently reported the likely association of one high-energy neutrino with a flare from the relativistic jet of an active galaxy pointed towards the Earth. However a combined analysis of many similar active galaxies revealed no excess from the broader population, leaving the vast majority of the cosmic neutrino flux unexplained. Here we present the likely association of a radio-emitting tidal disruption event, AT2019dsg, with a second high-energy neutrino. AT2019dsg was identified as part of our systematic search for optical counterparts to high-energy neutrinos with the Zwicky Transient Facility. The probability of finding any coincident radio-emitting tidal disruption event by chance is 0.5%, while the probability of finding one as bright in bolometric energy flux as AT2019dsg is 0.2%. Our electromagnetic observations can be explained through a multi-zone model, with radio analysis revealing a central engine, embedded in a UV photosphere, that powers an extended synchrotron-emitting outflow. This provides an ideal site for PeV neutrino production. Assuming that the association is genuine, our observations suggest that tidal disruption events with mildly-relativistic outflows contribute to the cosmic neutrino flux., Comment: Title and text modified during journal review. Version accepted for publication in Nature Astronomy

We present phase-resolved spectroscopy, photometry and circular spectropolarimetry of the eclipsing polar UZ Fornacis. Doppler tomography of the strongest emission lines using the inside-out projection revealed the presence of three emission regions: from the irradiated face of the secondary star, the ballistic stream and the threading region, and the magnetically confined accretion stream. The total intensity spectrum shows broad emission features and a continuum that rises in the blue. The circularly polarized spectrum shows the presence of three cyclotron emission harmonics at $\sim$4500 \AA{}, 6000 \AA{} and 7700 \AA{}, corresponding to harmonic numbers 4, 3, and 2, respectively. These features are dominant before the eclipse and disappear after the eclipse. The harmonics are consistent with a magnetic field strength of $\sim$57 MG. We also present phase-resolved circular and linear photopolarimetry to complement the spectropolarimetry around the times of eclipse. MeerKAT radio observations show a faint source which has a peak flux density of 30.7 $\pm$ 5.4 $\mu$Jy/beam at 1.28 GHz at the position of UZ For., Comment: Accepted on MNRAS

We report spectroscopy and photometry of the cataclysmic variable stars ASASSN-14ho and V1062 Cyg. Both are dwarf novae with spectra dominated by their secondary stars, which we classify as approxomately K4 and M0.5, respectively. Their orbital periods, determined mostly from the secondary stars' radial velociites, proved to be nearly identical, respectively 350.14 +- 0.15 and 348.25 +- 0.60 min. The H-alpha emission line in V1062 Cyg displays a relatively sharp emission component that tracks the secondary's motion, which may arise on the irradiated face of the secondary; tihs is not often seen and may indicate an unusually strong flux of ionizing radiation. Both systems exhibit double-peaked orbital modulation consistent with ellipsoidal variation from the changing aspect of the secondary. We model these variations to constrain the orbital inclination i, and estimate approximate component masses based oni and the secondary velocity amplitude K2.

We present new time-resolved photometry of 74 cataclysmic variables (CVs), 47 of which are eclipsing. 13 of these eclipsing systems are newly discovered. For all 47 eclipsing systems we show high cadence (1-20 seconds) light curves obtained with the high-speed cameras ultracam and ultraspec. We provide new or refined ephemerides, and supply mid-eclipse times for all observed eclipses. We assess the potential for light curve modelling of all 47 eclipsing systems to determine their system parameters, finding 20 systems which appear to be suitable for future study., Comment: 33 pages (incl 17 pages appendices), 37 figures (incl 25 in appendices), accepted on 22nd November 2016 for publication in MNRAS

We present 8--12\,GHz radio light curves of five dwarf nova (DN) type Cataclysmic Variable stars (CVs) in outburst (RX And, U Gem and Z Cam), or superoutburst (SU UMa and YZ Cnc), increasing the number of radio-detected DN by a factor of two. The observed radio emission was variable on time-scales of minutes to days, and we argue that it is likely to be synchrotron emission. This sample shows no correlation between the radio luminosity and optical luminosity, orbital period, CV class, or outburst type; however higher-cadence observations are necessary to test this, as the measured luminosity is dependent on the timing of the observations in these variable objects. The observations show that the previously detected radio emission from SS Cyg is not unique in type, luminosity (in the plateau phase of the outburst), or variability time-scales. Our results prove that DN, as a class, are radio emitters in outburst., Comment: Accepted to MNRAS. 14 pages, 6 figures

OmegaWhite is a wide-field, high cadence, synoptic survey targeting fields in the southern Galactic plane, with the aim of discovering short period variable stars. Our strategy is to take a series of 39 s exposures in the g band of a 1 square degree of sky lasting 2 h using the OmegaCAM wide field imager on the VLT Survey Telescope (VST). We give an overview of the initial 4 years of data which covers 134 square degrees and includes 12.3 million light curves. As the fields overlap with the VLT Survey Telescope Halpha Photometric Survey of the Galactic plane and Bulge (VPHAS+), we currently have $ugriH\alpha$ photometry for ~1/3 of our fields. We find that a significant fraction of the light curves have been affected by the diffraction spikes of bright stars sweeping across stars within a few dozen of pixels over the two hour observing time interval due to the alt-az nature of the VST. We select candidate variable stars using a variety of variability statistics, followed by a manual verification stage. We present samples of several classes of short period variables, including: an ultra compact binary, a DQ white dwarf, a compact object with evidence of a 100 min rotation period, three CVs, one eclipsing binary with an 85 min period, a symbiotic binary which shows evidence of a 31 min photometric period, and a large sample of candidate delta Sct type stars including one with a 9.3 min period. Our overall goal is to cover 400 square degrees, and this study indicates we will find many more interesting short period variable stars as a result., Comment: Accepted for publication in MNRAS. Figures 5 and A1 have been compressed to lower resolution. Full resolution images will be published in MNRAS and also here http://star.arm.ac.uk/~rto/MNRAS-Toma-OW-accepted.pdf

The Outburst Catalogue contains a wide variety of observational properties for 722 dwarf nova-type (DN) cataclysmic variables (CVs) and 309 CVs of other types from the Catalina Real-time Transient Survey. In particular, it includes the apparent outburst and quiescent V-band magnitudes, duty cycles, limits on the recurrence time, upper- and lower-limits on the distance and absolute quiescent magnitudes, colour information, orbital parameters, and X-ray counterparts. These properties were determined by means of a classification script presented in this paper. The DN in the catalogue show a correlation between the outburst duty cycle and the orbital period (and outburst recurrence time), as well as between the quiescent absolute magnitude and the orbital period (and duty cycle). This is the largest sample of dwarf nova properties collected to date. Besides serving as a useful reference for individual systems and a means of selecting objects for targeted studies, it will prove valuable for statistical studies that aim to shed light on the formation and evolution of cataclysmic variables., Comment: Accepted for publication in MNRAS

We report on the discovery of an eclipsing dwarf nova (DN) inside the peculiar, bilobed nebula Te 11. Modelling of high-speed photometry of the eclipse finds the accreting white dwarf to have a mass 1.18 M$_\odot$ and temperature 13 kK. The donor spectral type of M2.5 results in a distance of 330 pc, colocated with Barnard's loop at the edge of the Orion-Eridanus superbubble. The perplexing morphology and observed bow shock of the slowly-expanding nebula may be explained by strong interactions with the dense interstellar medium in this region. We match the DN to the historic nova of 483 CE in Orion and postulate that the nebula is the remnant of this eruption. This connection supports the millennia time scale of the post-nova transition from high to low mass-transfer rates. Te 11 constitutes an important benchmark system for CV and nova studies as the only eclipsing binary out of just three DNe with nova shells., Comment: Accepted for publication in MNRAS. 8 pages, 7 figures, 3 tables

The thermal radio emission of novae during outburst enables us to derive fundamental quantities such as the ejected mass, kinetic energy, and density profile of the ejecta. Recent observations with newly-upgraded facilities such as the VLA and e-MERLIN are just beginning to reveal the incredibly complex processes of mass ejection in novae (ejections appear to often proceed in multiple phases and over prolonged timescales). Symbiotic stars can also exhibit outbursts, which are sometimes accompanied by the expulsion of material in jets. However, unlike novae, the long-term thermal radio emission of symbiotics originates in the wind of the giant secondary star, which is irradiated by the hot white dwarf. The effect of the white dwarf on the giant's wind is strongly time variable, and the physical mechanism driving these variations remains a mystery (possibilities include accretion instabilities and time-variable nuclear burning on the white dwarf's surface). The exquisite sensitivity of SKA1 will enable us to survey novae throughout the Galaxy, unveiling statistically complete populations. With SKA2 it will be possible to carry out similar studies in the Magellanic Clouds. This will enable high-quality tests of the theory behind accretion and mass loss from accreting white dwarfs, with significant implications for determining their possible role as Type Ia supernova progenitors. Observations with SKA1-MID in particular, over a broad range of frequencies, but with emphasis on the higher frequencies, will provide an unparalleled view of the physical processes driving mass ejection and resulting in the diversity of novae, whilst also determining the accretion processes and rates in symbiotic stars., Comment: 13 pages, 3 figures, in proceedings of "Advancing Astrophysics with the Square Kilometre Array", PoS(AASKA14)116, in press

Radio observations of novae in outburst are of particular interest due to the physical parameters that may be retrieved from fitting the radio light curves. Most models that have fitted previous data assumed spherical symmetry however, it is becoming more and more clear that this is not the case. We explore morpho-kinematical techniques to retrieve the free-free radio light curves of non-spherical models and explore the effects of a non-spherical outburst on the physical parameters. In particular, we find that we may have been over estimating the ejected masses in the outburst of non-spherical novae., Comment: 4 pages, 2 figures, to appear in Stella Novae: Past and Future Decades, P. A. Woudt & V. A. R. M. Ribeiro (eds), ASPCS 490

Current studies of the peculiar velocity flow field in the Local Universe are limited by either the lack of detection or accurate photometry for galaxies at low Galactic latitudes. The contribution to the dynamics of the Local Group of the largely unknown mass distribution in this 'Zone of Avoidance' remains controversial. We present here the results of a pilot project to obtain deep near infrared (NIR) observations of galaxies detected in the systematic Parkes deep HI survey of the ZoA - 578 galaxies with recession velocities out to 6000 km/s were observed with the 1.4m InfraRed Survey Facility SIRIUS camera providing J, H and K_s imaging ~2 mag deeper than 2MASS. After star-subtraction, the resulting isophotal magnitudes and inclinations of ZoA galaxies are of sufficient accuracy (magnitude errors under 0.1 mag even at high extinction) to ultimately be used to determine cosmic flow fields "in" the ZoA via the NIR Tully-Fisher relation. We further used the observed NIR colours to assess the ratio of the true extinction to the DIRBE/IRAS extinction deep into the dust layers of the Milky Way. The derived ratio was found to be 0.87 across the HIZOA survey region with no significant variation with Galactic latitude or longitude. This value is in excellent agreement with the completely independently derived factor of 0.86 by Schlafly & Finkbeiner based on Sloan data far away from the Milky Way., Comment: 18 pages, 15 figures, accepted for publication in MNRAS

We present ground-based optical and near infrared photometric observations and Hubble Space Telescope COS spectroscopic observations of the old nova V842 Cen (Nova Cen 1986). Analysis of the optical light curves reveals a peak at 56.5 +/- 0.3s with an amplitude of 8.9 +/- 4.2 mma, which is consistent with the rotation of a magnetic white dwarf primary in V842 Cen that was detected earlier by Woudt et al., and led to its classification as an intermediate polar.However, our UV lightcurve created from the COS time-tag spectra does not show this periodicity. Our synthetic spectral analysis of an HST COS spectrum rules out a hot white dwarf photosphere as the source of the FUV flux. The best-fitting model to the COS spectrum is a full optically thick accretion disk with no magnetic truncation, a low disk inclination angle, low accretion rate and a distance less than half the published distance that was determined on the basis of interstellar sodium D line strengths.Truncated accretion disks with truncation radii of 3Rwd and 5Rwd yielded unsatisfactory agreement with the COS data. The accretion rate is unexpectedly low for a classical nova only 24 years after the explosion when the accretion rate is expected to be high and the white dwarf should still be very hot, especially if irradiation of the donor star took place. Our low accretion rate is consistent with low accretion rates derived from X-ray and ground-based optical data., Comment: The Astrophysical Journal, 2013, in press

High speed photometric observations of the spectroscopically-discovered PG 1159 star SDSS J034917.41-005917.9 in 2007 and 2009 reveal a suite of pulsation frequencies in the range of 1038 - 3323 microHz with amplitudes between 3.5 and 18.6 mmag. SDSS J034917.41-005917.9 is therefore a member of the GW Vir class of pulsating pre-white dwarfs. We have identified 10 independent pulsation frequencies that can be fitted by an asymptotic model with a constant period spacing of 23.61 +/- 0.21 s, presumably associated with a sequence of l = 1 modes. The highest amplitude peak in the suite of frequencies shows evidence for a triplet structure, with a frequency separation of 14.4 microHz. Five of the identified frequencies do not fit the l = 1 sequence, but are, however, well-modeled by an independent asymptotic sequence with a constant period spacing of 11.66 +/- 0.13 s. It is unclear to which l mode these frequencies belong., Comment: Accepted for publication in MNRAS; 5 pages, 6 figures and 4 tables

We present high speed photometric observations of 20 faint cataclysmic variables, selected from the Sloan Digital Sky Survey and Catalina catalogues. Measurements are given of 15 new directly measured orbital periods, including four eclipsing dwarf novae (SDSS0904+03, CSS0826-00, CSS1404-10 and CSS1626-12), two new polars (CSS0810+00 and CSS1503-22) and two dwarf novae with superhumps in quiescence (CSS0322+02 and CSS0826-00). Whilst most of the dwarf novae presented here have periods below 2 h, SDSS0805+07 and SSS0617-36 have relatively long orbital periods of 5.489 and 3.440 h, respectively. The double humped orbital modulations observed in SSS0221-26, CSS0345-01, CSS1300+11 and CSS1443-17 are typical of low mass transfer rate dwarf novae. The white dwarf primary of SDSS0919+08 is confirmed to have non-radial oscillations and quasi-periodic oscillations were observed in the short-period dwarf nova CSS1028-08 during outburst. We further report the detection of a new nova-like variable (SDSS1519+06). The frequency distribution of orbital periods of CVs in the Catalina survey has a high peak near ~80 min orbital period, independently confirming that found by Gaensicke et al (2009) from SDSS sources. We also observe a marked correlation between the median in the orbital period distribution and the outburst class, in the sense that dwarf novae with a single observed outburst (over the 5-year baseline of the CRTS coverage) occur predominantly at shortest orbital period., Comment: 17 pages, 38 figures, accepted for publication in MNRAS

Current studies of the peculiar velocity flow field in the Local Universe are limited by the lack of detection of galaxies behind the Milky Way. The contribution of the largely unknown mass distribution in this "Zone of Avoidance" (ZoA) to the dynamics of the Local group remains contraversial. We have undertaken a near infrared (NIR) survey of HI detected galaxies in the ZoA. The photomety derived here will be used in the NIR Tully-Fisher (TF) relation to derive the peculiar velocities of this sample of galaxies in the ZoA., Comment: To appear in "Ten years of Infrared Survey Facility and the Future", eds. T. Nagayama, S. Sato, and K. Wakamatsu

We have observed 8 faint cataclysmic variable stars photometrically. The nova-like Car2 was extensively sampled but showed little variability. V1040 Cen was observed near the end of a dwarf nova outburst and possessed dwarf nova and quasi-periodic oscillations. Ha 075648 has strong large amplitude flickering and a possible orbital modulation at 3.49 h. The correct identification for the nova remnant IL Nor (Nova Nor 1893) has been established. HS Pup (Nova Pup 1963) has a possible orbital period of 3.244 h. SDSS J2048-06 is a low mass transfer dwarf nova that in quiescence shows slow variations at 7.67 h (though poorly sampled with our observations) and an orbital modulation at 87.26 min. The dwarf nova CSS 081419-005022 has an orbital period of 1.796 h and the eclipsing dwarf nova CSS 112634-100210 has an orbital period of 1.8581 h., Comment: 7 pages, 15 figures. Accepted for publication in MNRAS

Galaxies behind the Milky Way suffer size reduction and dimming due to their obscuration by dust in the disk of our Galaxy. The degree of obscuration is wavelength dependent. It decreases towards longer wavelengths. Compared to the optical, the Near InfraRed (NIR) $K_s$ band extinction is only $\approx10%$ that of the $B$ band. This makes NIR surveys well suited for galaxy surveys close to the Galactic Plane where extinction is severe. While Galactic obscuration is less prominent in the NIR it is not negligible. In this paper we derive empirical relations to correct isophotal radii and magnitudes of galaxies observed in the NIR for foreground absorption. We simulate extinction in the $J$, $H$ and $K_s$ bands on 64 (unobscured) galaxies from the 2MASS Large Galaxy Atlas \citep{jarrett}. We propose two methods for the extinction correction, the first is optimized to provide the most accurate correction and the second provides a convenient statistical correction that works adequately in lower extinction regions. The optimized correction utilizes the galaxy surface brightness, either the disk central surface brightness, $\mu_0$, or the combined disk plus bulge central surface brightness, elliptical and disk/spiral Hubble types. A detailed comparison between the different methods and their accuracy is provided., Comment: 9 pages, 8 figures and 8 tables. Accepted by the MNRAS: Accepted 2009 September 18. Received 2009 September 18; in original form 2009 July 15

Little is known about the properties of extremely massive HI-galaxies. They are extremely scarce and are - according to hierarchical structure formation - only forming now (z < 1). The forthcoming deep HI SKA Pathfinders surveys will uncover many more of them. This will lead to a better understanding of their evolution and frequency, and the shape of the bright end of the HI mass function. The recently discovered galaxy HIZOA J0836-43 is one of the most HI-rich galaxies (M(HI)=7.5 x 10^10Msun - and the nearest of its kind. As such it is an ideal local probe of these elusive galaxies. Results from a detailed investigation in the near- (IRSF) and far-infrared (Spitzer) of this local HI-massive galaxy are presented. Unlike other giant HI galaxies, it is not of low surface brightness. The galaxy is found to be a luminous starbursting galaxy at an unexpected early stage of stellar mass building, more typical of star-forming galaxies at higher redshift (z~0.7). With regard to its environment, hence possible clues to its formation, the near infrared imaging survey finds HIZOAJ0836-43 to lie in a region underdense in L* galaxies - consistent with the observation that HI-massive galaxies are preferentially found in low density regions - in the presence, however, of an uncommonly large number of low stellar mass galaxies., Comment: To appear in "Panoramic Radio Astronomy: Wide-field 1-2 GHz research on galaxy evolution", Proceedings of Science

We have observed dwarf nova oscillations (DNOs) in OY Car during outburst, down through decline and beyond; its behaviour is similar to what we have previously seen in VW Hyi, making it only the second dwarf nova to have DNOs late in outburst that continue well into quiescence. There are also occasional examples of DNOs in deep quiescence, well away from outburst - they have properties similar to those during outburst, indicating similar physical causes and structures. We discuss the occurrence of DNOs in other dwarf novae and conclude that DNOs during quiescence are more common than often supposed and exhibit properties similar to those seen in outburst., Comment: Accepted for publication in MNRAS; paper contains 11 figures and 2 tables. This paper has become paper VII in the series

Photometric observations of V597 Pup made in 2008, 9.1 mag below maximum, 4 months after eruption, showed no certain orbital modulation but exhibited a quintuplet of oscillations centred on a period 261.9 s and uniform splitting at a frequency ~2.68 h^{-1}. One year later the system had fallen in brightness by a further 2.5 mag, showed deep eclipses with a period of 2.6687 h, and the 261.9 s modulation at a reduced amplitude. There is often power near the `subharmonic' at 524 s, showing that the shorter periods observed are actually first harmonics. V597 Pup is thus an intermediate polar and is in the `orbital period gap'. Furthermore it is the first to show a prominent secondary eclipse, caused by passage of the optically thick disc in front of the irradiated side of the secondary star., Comment: 7 pages, 12 figures. Accepted for publication in MNRAS

An overview is given of the properties of the various kinds of quasi-periodic luminosity modulations observed in cataclysmic variables (CVs). The two principal types, known in the CV literature as dwarf nova oscillations and quasi-periodic oscillations, have similarities to the high and low frequency quasi-periodic oscillations in X-Ray binaries. There is a further well observed class known as longer period dwarf nova oscillations. In CVs the observed interrelations between these oscillations suggests a model of magnetically controlled accretion onto a rapidly rotating equatorial belt of accreted gas. Non-radial oscillations of the central white dwarf are observed in some systems., Comment: 10 pages, 7 figures, to appear in `Cool discs, hot flows: The varying faces of accreting compact objects' (AIP Conf. Series)

Ultraviolet observations using the Solar Blind Channel on the Hubble Space Telescope provide light curves and low resolution spectra of three pulsating white dwarfs in the cataclysmic variables SDSS013132.39-090122.3, SDSSJ161033.64-010223.3 and SDSSJ220553.98+115553.7. The UV light curves show enhanced pulsation amplitudes over those from simultaneous and previous optical photometry, while the UV-optical spectra are fit with white dwarf temperatures near 15,000K. These temperatures place the accreting white dwarfs outside the instability zone for non-interacting DAV white dwarfs and show that the instability strip is complex for accreting white dwarfs., Comment: 28 pages, 11 figures

We present observations of dwarf nova oscillations (DNOs), longer period dwarf nova oscillations (lpDNOs), and quasi-periodic oscillations (QPOs) in 13 cataclysmic variable stars (CVs). In the six systems WW Cet, BP CrA, BR Lup, HP Nor, AG Hya, and V1193 Ori, rapid, quasi-coherent oscillations are detected for the first time. For the remainder of the systems discussed we have observed more classes of oscillations, in addition to the rapid oscillations they were already known to display, or previously unknown aspects of the behaviour of oscillations. The period of a QPO in RU Peg is seen to change by 84% over ten nights of the decline from outburst--the largest evolution of a QPO period observed to date. A period-luminosity relation similar to the relation that has long been known to apply to DNOs is found for lpDNOs in X Leo; this is the first clear case of lpDNO frequency scaling with accretion luminosity. WX Hyi and V893 Sco are added to the small list of dwarf novae that have shown oscillations in quiescence., Comment: 15 pages, 23 figures, to appear in MNRAS

We present new observations of the rapid oscillations in the dwarf nova VW Hyi, made late in outburst. These dwarf nova oscillations (DNOs) increase in period until they reach 33 s, when a transition to a strong 1st harmonic and weak fundamental takes place. After further period increase the 2nd harmonic appears; often all three components are present simultaneously. This 1:2:3 frequency suite is similar to what has been seen in some neutron star and black hole X-Ray binaries, but has not previously been seen in a cataclysmic variable. When studied in detail the fundamental and 2nd harmonic vary similarly in phase, but the 1st harmonic behaves independently, though keeping close to twice the frequency of the fundamental. The fundamental period of the DNOs, as directly observed or inferred from the harmonics, increases to ~100 s before the oscillation disappears as the star reaches quiescence. Its maximum period is close to that of the `longer period' DNOs observed in VW Hyi. The quasi-periodic oscillations (QPOs), which have fundamental periods 400 -- 1000 s, behave in the same way, showing 1st and 2nd harmonics at approximately the same times as the DNOs. We explore some possible models. One in which the existence of the 1st harmonic is due to transition from viewing a single accretion region to viewing two regions, and the rate of accretion onto the primary is modulated at the frequency of the 1st harmonic, as in the `beat frequency model', can generate the suite of DNO frequencies observed. But the behaviour of the QPOs is not yet understood., Comment: 16 pages, 13 figures; accepted for publication in MNRAS

We report photometry of the helium-rich cataclysmic variable ES Ceti during 2001-2004. The star is roughly stable at V ~ 17.0 and has a light curve dominated by a single period of 620 s, which remains measurably constant over the 3 year baseline. The weight of evidence suggests that this is the true orbital period of the underlying binary, not a "superhump" as initially assumed. We report GALEX ultraviolet magnitudes, which establish a very blue flux distribution (F_nu ~ nu^1.3), and therefore a large bolometric correction. Other evidence (the very strong He II 4686 emission, and a ROSAT detection in soft X-rays) also indicates a strong EUV source, and comparison to helium-atmosphere models suggests a temperature of 130+-10 kK. For a distance of 350 pc, we estimate a luminosity of (0.8-1.7)x10^34 erg/s, yielding a mass accretion rate of (2-4)x10^-9 M_sol/yr onto an assumed 0.7 M_sol white dwarf. This appears to be about as expected for white dwarfs orbiting each other in a 10 minute binary, assuming that mass transfer is powered by gravitational radiation losses. We estimate mean accretion rates for other helium-rich cataclysmic variables, and find that they also follow the expected M-dot ~ P_o^-5 relation. There is some evidence (the lack of superhumps, and the small apparent size of the luminous region) that the mass transfer stream in ES Cet directly strikes the white dwarf, rather than circularizing to form an accretion disk., Comment: PDF, 26 pages, 3 tables, 9 figures; accepted, in press, to appear February 2005, PASP; more info at http://cba.phys.columbia.edu/

Nova Puppis 2000 (V445 Pup) has been proposed as the first example of a helium nova. Recent optical spectroscopy of V445 Pup at V=19.91 mag obtained with IMACS on the 6.5-m Magellan telescope, shows that the spectrum consists of HeI, [OI], [OII] and [OIII] emission lines and no hydrogen is present. The spectroscopy shows an expanding nova shell with blue- and redshifted velocity components around +/- 850 km/s and +/- 1600 km/s. Images taken with Magellan under very good seeing conditions (FWHM ~ 0.6") shows V445 Pup to be extended (full width at zero intensity ~ 1.9") and elongated (position angle ~ 150deg). We have followed the secular evolution of V445 Pup since the decline from (optical) maximum, at near-infrared wavelengths (J, H and Ks) using the Infrared Survey Facility (IRSF) at the Sutherland site of the South African Astronomical Observatory. We find that V445 Pup is still covered by a dense dust shell more than three years after its outburst., Comment: 2 pages, 1 figure. To appear in `The Astrophysics of Cataclysmic Variables and Related Objects', eds. J.M. Hameury and J.P. Lasota (ASP Conf. Ser.)

We describe some of the recent observations of Dwarf Nova Oscillations and Quasi-Periodic Oscillations in cataclysmic variable stars. The similarities to high frequency QPOs seen in X-Ray binaries make this an increasingly useful field to explore. Our principal new result is the discovery of 1:2:3 harmonic structure in the DNOs of VW Hyi late in outburst. Similar structure is seen in the QPOs of some black hole and neutron star X-Ray binaries. In VW Hyi there is a sudden frequency-doubling when the DNO period reaches ~39 s. This first harmonic increases in period to ~28 s at which point the second harmonic appears. Both harmonics continue with increasing period, together or separately, with an occasional appearance of the fundamental, until the latter reaches ~105 s, by which time VW Hyi has fallen to its quiescent magnitude. We also report the first extensive observations of DNOs in a dwarf nova (OY Car) in quiescence. These are lpDNOs (longer period DNOs) and show similar short time scale properties to the DNOs and lpDNOs seen in outburst., Comment: 10 pages, 7 figures. To appear in `The Astrophysics of Cataclysmic Variables and Related Objects', eds. J.M. Hameury and J.P. Lasota (ASP Conf.Ser.)

We compare some of the properties of rapid oscillations in cataclysmic variables and X-Ray binaries. In addition to the earlier recognition that both types possess the same correlation between high and low frequency quasi-periodic oscillations, we have now found that the dwarf nova VW Hyi in its late stages of outburst shows the 1:2:3 oscillations harmonics that are seen in some neutron star and black hole X-Ray binaries. We point out that the behaviour of the dwarf nova WZ Sge has some similarities to those of accreting millisecond pulsars., Comment: 10 pages, 4 figures (needs AIP style file). To appear in the conference proceedings of `Interacting Binaries: Accretion, Evolution & Outcomes' (Cefalu, July 4-10 2004)

This paper continues the series that identifies new cataclysmic variables found in the Sloan Digital Sky Survey. We present 36 cataclysmic variables and one possible symbiotic star from Sloan spectra obtained during 2002, of which 34 are new discoveries, 2 are known dwarf novae (BC UMa, KS UMa) and one is a known CV identified from the 2dF survey. The positions, colors and spectra of all 37 systems are presented, along with follow-up spectroscopic/photometric observations of 10 systems. As in the past 2 years of data, the new SDSS systems show a large variety of characteristics based on their inclination and magnetic fields, including 3 eclipsing systems, 4 with prominent He II emission, and 15 systems showing features of the underlying stars., Comment: 12 pages, 13 figures (some bitmapped, will print okay), AJ, in press, Oct issue

We present results of a search for galaxies around the highly obscured giant radio galaxy PKS1343-601 using the near-infrared DENIS survey. We compare our findings with surveys in the B-band, at the 21cm line emission, and with 2MASS. Recession velocities of galaxies in this area suggest a low-velocity-dispersion group or cluster of galaxies including an X-ray confirmed Seyfert 2. The colours of the galaxies have been used to examine the extinctions in this low-latitude area where IRAS/DIRBE estimates are unreliable. We find the true extinction to be roughly 15% lower than the IRAS/DIRBE extinctions., Comment: 10 pages, 5 figures. To appear in "Nearby Large-Scale Structures and the Zone of Avoidance", eds. A.P Fairall & P.A. Woudt, ASP Conf. Ser