THE SPECTRUM OF HR 2902 IN 1961

Abstract

HR 2902 (=Boss 1985), formerly listed as symbiotic star, has been listed as binary of the VV Cephei type by Bidelman1 who also listed the literature prior to 19S4. The appearance of the speo trum has been subject to changes. In 192 S Adams, Joy, and Humason described the spectrum as having double, bright components separated by strong absorption line in the Balmer series,2 feature not mentioned in the Henry Draper Catalogue. Several prominent bright lines of unknown origin were identified later in other stars by Merrill3 as belonging to [Fe π] . McLaughlin remarked that between 1934 and 1942, Hs was usually fairly weak, except in 1936.4 In 1940, Swings and Struve identified new [Fe n] multiplets in the ultraviolet region and described the higher members of the Balmer series as showing a bright line of appreciable width flanked on the red side by narrow deep absorption line and this structure superposed over broader line having Stark effect wings. 5 Later the same writers6»7 gave detailed identification of the emission lines in the ultraviolet region; the lines belong to Cm, [Cm], [Sn] λ 4068, and [Nin] besides the already mentioned Fen and [Fen]. It was found that in general the low excitation lines of Fe η were considerably strengthened with respect to the high excitation lines and that Fe π was weaker than [Fe π] , as in WY Geminorum, but to the contrary in symbiotic stars (cf. Ζ Andromedae). From 1946 on,4»8 spectacular change was observed: an absorption shell spectrum appeared consisting of H, Ca n, Ti n, and other elements characteristic of an extended atmosphere. The emission lines of Fe n strengthened, but [Fe π] remained without appreciable change. Hydrogen lines also became intensified. In 1948, McLaughlin stated that the spectrum closely resembled that of VV Cephei. From 1947 to 1950, Bosman-Crespin and Swensson9 found general weakening of the shell absorption lines while the strength of the emissions showed few variations. This star was observed by the writers as part of an observational program of symbiotic stars, and in March 1961, at the