PROMINENCE AND PLAGE ACTIVITY IN THE RECENTLY DISCOVERED LATE-TYPE RAPID ROTATOR, RE-1816+541

The rapidly-rotating, chromospherically active late-type star RE 1816541 has shown signs of intense magnetic activity in various forms. Tim e-series of high resolution spec tra have been obtained during three n ights and several important events were detected. Observations contain ed several chromospheric lines, allowing us investigate simultaneously the response of the chromosphere at different heights. A detailed ana lysis of the Ha line behaviour, in particular, has revealed prominence clouds and plage-like regions in this star. Rapid rotation favours de tection and further investigation of these features. Prominence clouds are seen to lie below the co-rotation radius. A bright plage-like reg ion was well resolved on the first night. The feature disappeared temp orarily during meridian crossing, coinciding with the passage of a clo ud. Complete obscuration of the plage by the cloud proves that the emi ssion feature is located on or near the stellar surface, whereas the c loud is at larger height and is seen in projection onto it. A very lar ge flare was also detected during the observations, having strong effe cts in all the chromospheric lines selected for study.