• T. Velusamy

      Articles written in Journal of Astrophysics and Astronomy

    • VLA observations of ‘Compact’ sources in CTB 80

      T. Velusamy M. R. Kundu

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      High resolution (3 arcsec-4 arcsec) maps of three compact sources in CTB 80, observed with the Very Large Array at 6 and 20 cm wavelengths are presented. The central core consists of a limb-brightened shell (of diameter 30 arcsec) superimposed on a diffuse emission of size 75 arcsec x 45 arcsec. The compact sources 1949 + 324 and 1952 + 332 located near the tips of the southwest and northeast ridges are rather remarkable and possibilities for these to be fragments ejected by the SN are examined. 1949 + 324 is fully resolved by the 4 arcsec beam and shows structure with multiple components oriented perpendicular to the ridge. 1950 + 326 is a background radio source.

    • WSRT observations of radio sources in the galactic plane near l =54°

      T. Velusamy W. M. Goss E. M. Arnal

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      A radio continuum map of a 1°5 X 1°5 region in the galactic plane nearl = 54° is presented at 49 cm with a resolution of 100 arcsec X 200 arcsec. The shell source G 54.4 - 0.3 has the characteristics of a supernova remnant while the second large ring structure G 53.9 + 0.3 is a Hn ring consisting of W 52 and several small-diameter thermal sources. One of the twelve small-diameter sources (G 54.73 + 0.61) has a spectral index⇏ -1.6.

    • Thick radio shell in supernova remnant DA 495 (G 65.7+ 1.2)?

      T. Velusamy R. H. Becker W. M. Goss D. J. Helfand

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      High resolution (11.7 to 64 arcsec) multifrequency radio observations of DA 495 (G 65.7 +1.2) at 20, 49 and 92 cm wavelengths with the VLA, WSRT and OSRT are presented. A map of infrared emission in the surrounding region is also presented. Although the remnant has a minimum near the centre, its brightness distribution does not show limb brightening. Hence it has characteristics of both shell-type SNRs and Crab-type SNR. Alternatively it has an unusually thick shell with inner and outer radii of 125 and 500 arcsec respectively. The volume emissivity within the shell decreases radially outward. Its integrated flux density spectrum is characteristic of a shell-type remnant. The role of the reverse shock in the formation of a thick shell is discussed. The association of the open star cluster NGC6834 with DA 495 is also noted. The parameters of twenty-nine small diameter sources detected around DA 495 are also presented. The radio source 1949 + 291 is associated with an IRAS source. 1948 + 292 may be a Crablike pulsar-driven synchrotron nebula. The radio spectrum of the planetary nebula NGC 6842 is optically thick at 49 cm.

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      Posted on January 27, 2016

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