The Be shell star beta1 Monocerotis.

Abstract

view Abstract Citations (3) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Be shell star beta1 Monocerotis. McLaughlin, Dean B. Abstract Among the bright Be stars on the Michigan program, excluding the binary Persei, p1 Monocerotis is unique in being both a "shell" star and a conspicuous V/R variable. It is, therefore, of special interest to compare its changes with those of V/R variables that have weak absorption. Although emission is very strong at Hp, strong at H , and conspicuous at H , all absorption lines give accordant velocities except Hp and occasionally H . With these excluded, the velocities since 1924 show smooth variation with a rough period of 12.5 years and range 9 to 43 km/sec. Maxima occurred in 1933 and 1945. HP ranges about 55 km/sec, probably due in part to "crowding" by the stronger emlsslon. Such crowding is evidently absent even at H which agrees with higher Balmer lines. Deviations of H are always negative and are attributed to blending with X3889 Hei. Differences between the two observed cycles show that large effects other than those of orbital motion are present. From 1905 to 1914 the velocity was constant, about $23 km/sec, and V/R constant at 1.0. It is concluded that recent variations are due wholly to the shell, and not to orbital motion. The ratio V/R, the absorption velocity, and emission velocity from the mean of the outer edges are closely correlated in the same manner as in 25 Orionis5 and Aquarii.2 The entire emission oscillates with the absorption, which remains nearly central. Minimum and maximum velocity are associated with minimum and maxomum V/R. The outer emission edge toward the red has much larger amplitude than the absorption, the violet edge a lesser amplitude, the mean about equal to that of the absorption and in the same sense. The shell absorption faded from 1938 through 1941 and recovered from 1942 to 1945. Its near disappearance late in 1941 occurred with V/R = I, and radial velocity near the mean, both increasing. Absorption was well below normal strength in 1928, at a phase corresponding to the decrease. Such change may be a normal event of the cycle, and should be watched for within the next few years. Interpretation of variations in terms of motions in a shell or ring would require total displacements of several astronomical units. However, rotational widening of the emission shows that it must originate wholly within about 0.3 astronomical units of the star, for any reasonable stellar mass. I.Dodson, Ap. J. 84, s8o, 1936. 2.McLaughlin, Pub. Obs. Univ. Michigan 4, 37, 1931; Ap. J. 77, 221, 1933. Observatory, University of Michigan, Ann Arbor, Mich. Publication: The Astronomical Journal Pub Date: 1951 DOI: 10.1086/106585 Bibcode: 1951AJ.....56Q..44M full text sources ADS | data products SIMBAD (5)