20 cm VLA Radio-Continuum Study of M31 - Images and Point Source Catalogues DR2: Extraction of a supernova remnant sample

We present Data Release 2 of the Point Source Catalogue created from a series of previously constructed radio-continuum images of M31 at lambda=20 cm (nu=1.4 GHz) from archived VLA observations. In total, we identify a collection of 916 unique discrete radio sources across the field of M31. Comparing these detected sources to those listed by Gelfand et al. (2004) at lambda=92 cm, the spectral index of 98 sources has been derived. The majority (73%) of these sources exhibit a spectral index of alpha <-0.6, indicating that their emission is predominantly non-thermal in nature, which is typical for background objects and Supernova Remnants (SNRs). Additionally, we investigate the presence of radio counterparts for some 156 SNRs and SNR candidates, finding a total of only 13 of these object in our images within a 5 arcsec search area. Auxiliary optical, radio and X-ray catalogs were cross referenced highlighting a small population of SNR and SNR candidates common to multi-frequency domains

Newly confirmed and high quality candidate Galactic SNRs uncovered from the AAO/UKST HAlpha survey

We present a catalogue of 18 new Galactic supernova remnants (SNRs) uncovered in the optical regime as filamentary emissions and extended nebulosities on images of the Anglo Australian Observatory/United Kingdom Schmidt Telescope (AAO/UKST) HAlpha survey of the southern Galactic plane. Our follow-up spectral observations confirmed classical optical SNR emission lines for these 18 structures via detection of very strong [SII] at 6717 and 6731A relative to HAlpha ([SII]/HAlpha> 0.5). Morphologically, 10 of these remnants have coherent, extended arc or shell structures, while the remaining objects are more irregular in form but clearly filamentary in nature, typical of optically detected SNRs. In 11 cases there was a clear if not complete match between the optical and radio structures with H filamentary structures registered inside and along the presumed radio borders. Additionally, ROSAT X-ray sources were detected inside the optical/radio borders of 11 of these new remnants and 3 may have an associated pulsar. The multi-wavelength imaging data and spectroscopy together present strong evidence to confirm identification of 18 new, mostly senile Galactic SNRs. This includes G288.7-6.3, G315.1+2.7 and G332.5-5.6, identified only as possible remnants from preliminary radio observations. We also confirm existence of radio quiet but optically active supernova remnants.Comment: In original form 21 pages, 29 figures Accepted for MNRA

SMC SMP 24: A newly radio-detected planetary nebula in the small magellanic cloud

In this paper we report new radio-continuum detection of an extragalactic PN: SMC SMP 24. We show the radio-continuum image of this PN and present the measured radio data. The newly reduced radio observations are consistent with the multi-wavelength data and derived parameters found in the literature. SMC SMP 24 appear to be a young and compact PN, optically thick at frequencies below 2 GHz.Comment: accepted for publication in Serbian Astronomical Journa

A ROSAT PSPC X-Ray Survey of the Small Magellanic Cloud

We present the results of a systematic search for point-like and moderately extended soft (0.1-2.4 keV) X-ray sources in a raster of nine pointings covering a field of 8.95 deg^2 and performed with the ROSAT PSPC between October 1991 and October 1993 in the direction of the Small Magellanic Cloud. We detect 248 objects which we include in the first version of our SMC catalogue of soft X-ray sources. We set up seven source classes defined by selections in the count rate, hardness ratio and source extent. We find five high luminosity super-soft sources (1E 0035.4-7230, 1E 0056.8-7146, RX J0048.4-7332, RX J0058.6-7146 and RX J0103-7254), one low-luminosity super-soft source RX J0059.6-7138 correlating with the planetary nebula L357, 51 candidate hard X-ray binaries including eight bright hard X-ray binary candidates, 19 supernova remnants, 19 candidate foreground stars and 53 candidate background active galactic nuclei (and quasars). We give a likely classification for ~60% of the catalogued sources. The total count rate of the detected point-like and moderately extended sources in our catalogue is 6.9+/-0.3 s^-1, comparable to the background subtracted total rate from the integrated field of ~6.1+/-0.1 s^-1.Comment: Accepted by A&AS, 13 pages, 2 Postscript figure

Radio-continuum study of Large Magellanic Cloud Supernova Remnant J0509-6731

We present a detailed study of Australia Telescope Compact Array (ATCA) observations ($\lambda$ = 20, 13, 6 & 3~cm) of supernova remnant (SNR) J0509--6731 in the Large Magellanic Cloud (LMC). The remnant has a ring morphology with brightened regions towards the south-western limb. We also find a second brightened inner ring which is only seen in the radio-continuum. The SNR is almost circular, with a diameter ranging from 7 to 8~pc, and a steep radio spectral index between 36 and 3~cm of $\alpha=-0.73\pm0.02$, which is characteristic of younger SNRs. We also report detection of radially orientated polarisation across the remnant at 6~cm, with a mean fractional polarisation level of $P\cong$~(26~$\pm$~13)%. We find the magnetic field ($\sim$168~$\mu$G) and $\Sigma - D$ ($\Sigma =$ $1.1\times 10^{-19}$~W m$^{-2}$~Hz$^{-1}$~sr$^{-1}$ , $D=$ 7.35~pc) to be consistent with other young remnants

Multiwavelength appearance of Vela Jr.: Is it up to expectations?

Vela Jr. is one of the youngest and likely nearest among the known galactic supernova remnants (SNRs). Discovered in 1997 it has been studied since then at quite a few wavelengths, that spread over almost 20 decades in energy. Here we present and discuss Vela Jr. properties revealed by these multiwavelength observations, and confront them with the SNR model expectations. Questions that remained unanswered at the time of publication of the paper of Iyudin et al. (2005), e.g. what is the nature of the SNR's proposed central compact source CXOU J085201.4-461753, and why is the ISM absorption column density apparently associated with RX J0852.0-4622 much greater than the typical column of the Vela SNR, can be addressed using the latest radio and X-ray observations of Vela Jr.. These, and other related questions are addressed in the following.Comment: 8 pages, 7 figures. Accepted for publication in ESA SP-622, Proceedings of the 6th INTEGRAL Workshop held in Moscow, Russia, July 02-08, 200

Radio-continuum detections of Galactic Planetary Nebulae I. MASH PNe detected in large-scale radio surveys

We present an updated and newly compiled radio-continuum data-base for MASH PNe detected in the extant large scale "blind" radio-continuum surveys (NVSS, SUMSS/MGPS-2 and PMN) and, for a small number of MASH PNe, observed and detected in targeted radio-continuum observations. We found radio counterparts for approximately 250 MASH PNe. In comparison with the percentage of previously known Galactic PNe detected in the NVSS and MGPS-2 radio-continuum surveys and according to their position on the flux density-angular diameter and the radio brightness temperature evolutionary diagrams we conclude, unsurprisingly, that the MASH sample presents the radio-faint end of the known Galactic PNe population. Also, we present radio-continuum spectral properties of a small sub-sample of MASH PNe located in the strip between declinations -30arcdeg and -40arcdeg, that are detected in both the NVSS and MGPS-2 radio surveys.Comment: 13 figures and 7 tables, accepted for publication in MNRA

A digital video system for observing and recording occultations

Stellar occultations by asteroids and outer solar system bodies can offer ground based observers with modest telescopes and camera equipment the opportunity to probe the shape, size, atmosphere and attendant moons or rings of these distant objects. The essential requirements of the camera and recording equipment are: good quantum efficiency and low noise, minimal dead time between images, good horological faithfulness of the image time stamps, robustness of the recording to unexpected failure, and low cost. We describe the Astronomical Digital Video occultation observing and recording System (ADVS) which attempts to fulfil these requirements and compare the system with other reported camera and recorder systems. Five systems have been built, deployed and tested over the past three years, and we report on three representative occultation observations: one being a 9 +/-1.5 second occultation of the trans-Neptunian object 28978 Ixion (mv=15.2) at 3 seconds per frame, one being a 1.51 +/-0.017 second occultation of Deimos, the 12~km diameter satellite of Mars, at 30 frames per second, and one being a 11.04 +/-0.4 second occultation, recorded at 7.5 frames per second, of the main belt asteroid, 361 Havnia, representing a low magnitude drop (Dmv = 0.4) occultation.Comment: 9 pages, 5 figures, 3 tables, accepted to Publications of the Astronomical Society of Australia (PASA