OH observations of selected I.R.A.S. sources from southern hemisphere

Abstract

In this paper, we report the results of observations of 53 objects taken from the IRAS point source catalog, with δ < -30°. These objects were studied in the 1612 MHz transition, as well as in the 1665 and 1667 MHz main lines of the OH radical. The observations were made at the Instituto Argentino de Radioastronomia with a 30 m antenna. The selection criteria applied to the objects place them among the stars of evolved type with cool circumstellar envelopes. We found 12 objects with maser radiation in emission and/or absorption. Six of them seem to be new detections previously unreported. Ten objects show double peak profiles in the satellite line, as is typical for OH/IR stars with expansion envelopes. An analysis of the global IRAS colour properties of the 53 selected objects does not show any significant difference between the sources detected at OH and those not detected. Further analysis of the data allow us to conclude that the excitation of the maser mechanism is produced by infrared pumping due to circumstellar dust, as is usual in these types of sources.