Speaker
Description
Usually, X-ray binary (XRB) outbursts are first detected by X-ray all-sky monitors like MAXI. Only after this are observations with more sensitive multi-wavelength telescopes triggered. This causes a gap in the coverage of the rise of the outbursts, limiting our knowledge of their early stages. Therefore, the best approach to better understand the accretion process in XRBs is to combine X-ray observations with regular optical band monitoring. According to the disc-instability model (DIM), XRBs experience an earlier optical brightening than in X-rays at the beginning of the outburst. In this talk, we show that, with our regular monitoring of ~50 XRBs with the Faulkes Telescopes/Las Cumbres Observatory (LCO), we are detecting the optical brightening of XRBs typically ~11 days before the outbursts are detected in X-rays with MAXI. In addition, we show that outbursts rise at shorter optical wavelengths before rising at longer wavelengths. This seems to occur as the ionizing heating wave propagates through the disk at the onset of the outburst. In addition, we present our real-time data analysis pipeline, the "X-ray Binary New Early Warning System” (XB-NEWS), which we use to detect and announce new XRB outbursts within days of their first optical detection. This allows the community to trigger multi-wavelength campaigns at the very beginning of outbursts, constraining the physical mechanisms triggering them.
