Excited OH 4.7-GHz masers associated with IRAS far-infrared sources - II

A sample of 85 far-infrared sources selected from the IRAS Point Source Catalog has been searched for maser emission from excited OH in the $$^2\Pi_{1/2} J=1/2$$ state, in the three transitions at 4765, 4750 and 4660 MHz. Four new detections were made at 4765 MHz, including one source where ground-state OH maser emission has not been reported. One new detection was made at 4660 MHz. This source OH 351.78-0.54 is remarkable in that it was detected only at 4660 MHz, and not at 4765 or 4750 MHz. Positions were measured for the new detections and for six previously known 4.7-GHz maser sources. In some cases the excited OH 4.7-GHz positions are significantly different from the positions of previously known ground-state OH 18-cm masers. The 4.7-GHz sources are among the brighter far-infrared sources in the IRAS sample. In most cases they are also OH 18-cm masers. There is a strong association between OH 4.7-GHz emission and OH 18-cm maser emission in the 1720-MHz transition. More than half of the 4.7-GHz masers that were examined for variability showed strong variations on a time-scale of a year.