1994A&A...289L...7M

Direct images taken in 1988 and 1993 and spectra of the bipolar reflection nebula RNO 138 are presented. The images show that the illuminating star of the nebula, RNO 138S, for the first time visible in the 1993 image, has brightened by ≥-1.2 mag sometime between 1988 and 1993. The spectrum presents absorption lines, including strong LiI 6708, weak Hα emission with a possible blueshifted P Cygni absorption and no emission lines. At present, an EXor-type outburst can be excluded as an explanation for the brightening of RNO 138S and the data are not completely compatible with a FUor-type outburst.