Predicting Jets in Cygnus X-2
Abstract
We describe simultaneous radio and X-ray observations of Cygnus X-2 that captured the launching of relativistic jets. Observations with the e-EVN, revealed the switch-on of radio while Swift showed the source to be on the Horizontal Branch of the Z-track. The evolution of the jet images in radio showed the velocity to be 0.33c. We have also analysed 16 years of RXTE pointed and ASM data. The 16-year ASM lightcurve shows strong aperiodic variability having about 10 large intensity peaks per year. All pointed data were analysed and correlated with the ASM light curve allowing us to recognize important features of the Z-track in ASM data, such as the hard and soft apex. The aim was to be able to predict jet formation using such monitoring data. All available radio data were used to obtain a relation between radio flux and ASM count rate. This showed that jet launching takes place at the hard apex which is seen at count rates in the ASM more than 40 counts per second, regardless of position in the long-term variability. This threshold can be converted to the equivalent, much lower count rate in MAXI
- Publication:
-
The X-ray Universe 2014
- Pub Date:
- July 2014
- Bibcode:
- 2014xru..confE..34B