KVN MONITORING OBSERVATIONS TOWARD THE RECENT OUTBURST SYMBIOTIC STAR V407 CYGNI

Abstract

Simultaneous time monitoring observations of H₂O and SiO maser lines were performed toward the D-type symbiotic binary system V407 Cyg with the Korean VLBI Network single dish radio telescope. These monitoring observations were carried out from March 2, 2010 (optical phase ∅ = 0.0), 8 days before the nova outburst on March 10, 2010 to June 5, 2014 ( = 2.13). Eight days before the nova outburst, we detected the SiO v = 1, 2, J = 1–0 maser lines which exhibited values of 0.51 K (~ 6.70 Jy) and 0.71 K ( 9.30 Jy), respectively, while after the outburst we could not detect them on April 2 (∅ = 0.04), May 5 ( = 0.09), May 8 (∅ = 0.09), or on June 5, 2010 ( ∅ = 0.13) within the upper limits of our KVN observations. After restarting our monitoring observations, we detected SiO v = 2, J = 1–0 masers starting on October 20, 2011 (∅ = 0.83) and detected SiO v = 1, J = 1–0 masers starting on December 22, 2011 (∅ = 0.92). These results provide clear evidence of the interaction between the shock from the nova outburst and the SiO maser regions of the Mira envelope. The peak emission of SiO v = 1, 2, J = 1–0 masers always occurred at blueshifted velocities with respect to the stellar velocity except for that of SiO v = 1 at one epoch. These phenomena may be related to the redistribution of SiO maser regions after the outburst. The peak velocity variations of SiO masers associated with stellar pulsation phases show an increasing blueshifted trend during our monitoring interval after the outburst.