On the superluminous variable stars in the Large Magellanic Cloud.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the superluminous variable stars in the Large Magellanic Cloud. Shapley, Harlow ; Nail, Virginia Mckibben ; Tifft, William G. Abstract The supergiant red variable stars in the Small Magellanic Cloud have been reported in Harvard Rep4nt No. 346, 1951. The survey of stars of top luminosity and of recognized variability in that system was carried down to the fifteenth apparent magnitude. The brightest variables at maximum have absolute magnitudes around -5; of the twenty brightest, sixteen are Cepheids and four are irregular red variables. The brightest long-period variables of the Small Cloud have absolute photographic magnitudes around -3.0. For both Clouds the elimination of superposed stars of the various variable and non-variable classes was accomplished through the study of stars of many comparison fields in similar galactic latitudes. Our complete survey of variables of the Large Magellanic Cloud has been taken at this time only to apparent magnitude 13.1, absolute magnitude -4.3 and brighter. We have dealt, therefore, only with the superlative luminosities. A considerable number of non-variable stars of classes 0, B, and P Cygni are found among these highest luminosities; but the only variable stars, aside from S Doradus, that are certainly Cloud members, and have maximum apparent magnitudes 13.0 and brighter, are eighteen Cepheids and a few red irregulars. The brightest long-period variables in the field of the Large Cloud are possibly all superposed. The following results appear of some significance in analyzing the Large Cloud: I. The superluminous variables show no tendency to follow the highest star concentration, such as is found in the axis and the rich clusterings. Some member variables are actually more than 40 from the Cloud center. 2. If the magnitudes at maximum are used for both Cepheids and long period variables, a joining of the two period-luminosity curves is indicated, thus suggesting that some of the long- period variables may be members. The results are not inconsistent with the work of Wilson and Merrill on the long period variables of the galactic system. 3. Assuming the average color index + 1.5 at maximum for these variables, and comparing them directly with Betelgeuse of absolute visual magnitude - 3.9 and radius of two astronomical units, we obtain the remarkably great linear dimensions given in the following tabulation, which contains also the periods, various photometric BRIGHTEST CEPHEIBS IN THE LARGE MAGELLANIC CLOUD Max. Star P mag. Range M R Dist. HV2882* I7I~.82 12.3 2.8 -5.0 6.6 4?o HV 883* 134.1 12.7 1.7 -4.6 5.5 2.2 HV2447 118.6394 12.6 1.0 -4.7 ~.8 0.5 HV8039* 108.93 12.8 2.2 -4.5 5.3 4.5 HV5497* 98.86 12.3 1.3 -5.0 6.6 3.3 HV2369* 48.267 12.0 2.2 -5.3 7.7 1.6 HV 953 47.82607 12.5 1.4 -4.8 6.2 0.7 HV 900 47.52 13.0 1.5 -4.3 5.0 2.2 HV2257 39.26 12.8 2.1 -4.5 5.3 2.8 HV 909 37.585 12.9 1.3 -4.4 5.1 2.4 HV2294* 36.536 12.1 2.0 -5.2 7.2 2.4 HV 873* 34.344 12.6 2.4 -4.7 ~.8 3.6 HVIoo2 30.43 12.0 2.4 -5.3 7.7 2.0 InnesVII* 28.3607 13.0 2.2 -4.3 5.0 3.9 HV2251 28.0 12.5 2.0 -4.8 6.2 2.8 HV 902 26.39 13.0 1.6 -4.3 5.0 2.5 Innes53* 24.242 13.0 o.8 -4.3 5.0 3.6 HV 886* 23.958 13.0 1.6 -4.3 5.0 3.0 data, and the distances of the variables from the geometrical center of the Cloud. The first variable in the tabulation, with the period 171.82 days and range 2.8 magnitudes, may be a superposed long period variable of our galactic system. Forthcoming radial velocity measurements will clarify its membership. 4. The aniplitudes of these long period Cepheids are large, averaging 1.8 magnitudes. Such amplitudes are found frequently for galactic Cepheids of similar periods. The light curves and periods of the stars marked with asterisks have been derived specially for this investigation. Harvard College Observatory, Cambridge, Mass. Publication: The Astronomical Journal Pub Date: 1951 DOI: 10.1086/106621 Bibcode: 1951AJ.....56R.139S full text sources ADS |