Rapid Optical Flaring in MXB 1735-444 and an Optical Burst from GX 17+2

The results of high-speed white-light photometry of five low-mass X-ray binaries (LMXB), including MXB 1735-444 (V926 Sco), are reported. It is found that MXB 1735-444 was in a previously unreported state. It showed rapid optical flaring on time scales of 10 s or less to about 20 minutes over the course of a 2 hr observation. During the bursts, the optical luminosity increased by up to a factor of five; the average optical luminosity of MXB 1735-444 was about 2 x 10 to the 34th ergs/s at these times. Qualitatively similar long type II X-ray bursts have been observed from the rapid burster, MXB 1730-335, and long X-ray bursts of undetermined type have been observed from GX 17+2 (4U 1813-14). The detection of an optical burst from the source GX 17+2 is also reported. Optical bursts have not been previously reported in this object. 21 references.