Radio Study of the complex supernova remnant CTB80

CASTELLETTI G., DUBNER G.; GOLAP K., GOSS W.M.

Miramare, Trieste, Italia, 5 al 16 de julio

Workshop; Workshop on "Theoretical Plasma Physics"; 2004

the Abdus Salam International Centre for Theoretical Physics

Supernova remnants (SNRs) are the only astronomical objects that can join the two extremes of the life cycle of stars through  their interaction with the interstellar medium (ISM). They supply huge amounts of energy, accelerate cosmic rays, and represent almost the only way to feed the ISM with the heavy elements processed in the hot interior of the stars. The Galactic supernova remnant CTB 80 is a nonthermal radio source with a combined morphology in the radio band that not fit standard classifications. This source, located at a distance of ~ 2 kpc, has a large angular size (over 1 degree from the northern extreme to the southernmost limit). It is generally faint, except for the central region called the ´´plateau" (~ 8´ X 4´ in size), where three extended arms overlap. It is  one of the very few  known SNR associated with a fast pulsar (PSR B1951+32) (period ~ 40 ms), that is interacting with the rest of the remnant forming a bright radio nebula around it. This compact region (~ 45´´), called the ´´core´´, is placed on the western end of the plateau region. The three outer arms, about 30´ long each, point to the north, east and southwest of the plateau. Over a large part of the remnant there is a high degree of linear polarization, which rises up to 10% - 15% on the central component. New high resolution observations of CTB 80 in its full extent have been carried out, for the first time, at 240 MHz (beam ~ 20´´) and at 618 MHz (beam ~ 8´´) using the Giant Metrewave Radio Telescope (Pune, India), and at 324 MHz  (beam ~ 65´´) and at 1380 MHz (beam ~ 80´´) using the Very Large Array (USA). A variety  of faint features and interesting multifrequency correlations were identified  in the asymmetric arms of CTB 80. In addition, these new image have disclosed previously unknown structures in the central region. Based on the present observations, an analysis of the spatial variations of the radio spectral index reveals signatures of the interaction of the pulsar with the surrounding plasma. In the bright ´´core´´ negula, the images show a distortion in the morphology toward the west; this feature corresponds to the direction in which the pulsar escapes form the SNR with a velocity of ~ 240 km/s.