Results from follow up observations are presented for two BL Lac objects, namely ON 231 and OQ 530. Previous EVN images of ON 231 at 1.6 GHz and 5 GHz showed new relevant features: a two-sided jet structure and a low brightness extension South-East of the main jet. The new EVN image obtained from observations done 2.3 years later at 5 GHz confirms the previous finding and, moreover, shows significant changes in the structure of the jet. Images obtained with the EVN at 5 GHz at two epochs separated by 2.3 years are also analysed for OQ 530. The comparison shows large changes in the flux density of the core component and suggests an apparent superluminal motion of the components along the straight jet. The BL Lac objects ON 231 and OQ 530 were selected because of their long term optical trends. Their optical behaviour will be briefly discussed in connection with the changes in the radio structure.
Structure changes in two BL Lac Objects: ON 231 and OQ 530
TOSTI, Gino;
2002
Abstract
Results from follow up observations are presented for two BL Lac objects, namely ON 231 and OQ 530. Previous EVN images of ON 231 at 1.6 GHz and 5 GHz showed new relevant features: a two-sided jet structure and a low brightness extension South-East of the main jet. The new EVN image obtained from observations done 2.3 years later at 5 GHz confirms the previous finding and, moreover, shows significant changes in the structure of the jet. Images obtained with the EVN at 5 GHz at two epochs separated by 2.3 years are also analysed for OQ 530. The comparison shows large changes in the flux density of the core component and suggests an apparent superluminal motion of the components along the straight jet. The BL Lac objects ON 231 and OQ 530 were selected because of their long term optical trends. Their optical behaviour will be briefly discussed in connection with the changes in the radio structure.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
