BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:P. Saikia: Lorentz factors of compact jets in black hole X-ray bin aries DTSTART;VALUE=DATE-TIME:20190604T163000Z DTEND;VALUE=DATE-TIME:20190604T164000Z DTSTAMP;VALUE=DATE-TIME:20200526T182544Z DESCRIPTION:Speakers: Payaswini Saikia (Nyuad)\nCompact\, continuously lau nched jets in black hole X-ray binaries (BHXBs) produce radio to optical –infrared (OIR) synchrotron emission. These jets are launched in the har d X-ray state\, and are quenched in the soft state. They are not spatially resolved except in a few cases using VLBI radio observations. One of the basic properties of these jets is the bulk Lorentz factor\, which defines how fast and how relativistic these jets are. The bulk Lorentz factor is n otoriously difficult to measure\, with to date only weak constraints for a few BHXBs. Here\, we adopt simple models to constrain the Lorentz factor of the compact jets in several BHXBs using the amplitude of the jet fade a nd recovery at infrared (IR) wavelengths over state transitions. We invest igate why some BHXBs have prominent IR excesses and some do not\, quantifi ed by the amplitude of the IR quenching or recovery over the transition fr om/to the hard state. Using the amplitude of the IR fade/recovery\, known orbital parameters and simple analytical models\, we constrain for the fir st time the Lorentz factor of compact jets in several BHXBs. We also find that the very high amplitude IR fade/recovery seen repeatedly in GX 339– 4 requires a much lower inclination angle than previously expected. Our re sults are strongly supportive of the IR excess being produced by synchrotr on emission in a relativistic outflow\, and demonstrates how useful OIR mo nitoring of BHXB is for studying jet properties.\n\nhttps://indico.in2p3.f r/event/17572/contributions/72664/ LOCATION:Cargèse Amphitheatre URL: END:VEVENT END:VCALENDAR