Einstein ring fingerprint around supermassive black holes illuminated by broad line region spectral lines
The study investigates how broad line region (BLR) spectral lines illuminate a supermassive black hole (SMBH), creating an Einstein ring signature in the spectrum. This method bypasses contamination from the inner accretion disk, allowing for precise measurement of SMBH mass using the ring's size and spectral peak separation, offering an independent mass measurement.