Hostname: page-component-78c5997874-ndw9j Total loading time: 0 Render date: 2024-11-05T14:48:57.577Z Has data issue: false hasContentIssue false

Some Progress and Problems in the Upper Left of the HR Diagram

Published online by Cambridge University Press:  14 August 2015

Nolan R. Walborn*
Affiliation:
Cerro Tololo Inter-American Observatory∗

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The MK system of spectral classification does not include luminosity classes for types earlier than 09. Subsequent work with higher dispersions has allowed a luminosity classification for early O stars to be proposed. One of the principal criteria at types 09-B0 is the selective, negative luminosity effect in the Hell 4686 Å absorption line; a similar effect was found in the NIII 4634-4640-4642 Å absorption lines at 09-B0. These particular lines weaken markedly with increasing luminosity, while other HeII lines maintain a constant ratio to HeI (by definition), and other NIII lines strengthen considerably. These anomalous lines are the same ones which selectively appear in emission in Of stars, and the derived luminosity classification for earlier types is based upon the hypothesis that the negative absorption effect at 09-B0 is due to emission filling by the same mechanism producing the Of phenomenon, and that hence the latter may also be identified as a luminosity effect (Walborn 1971). One observes strong 4686 Å absorption and often weak 4640 Å emission [denoted ((f))] on the main sequence to the earliest types. As luminosity increases at a given spectral type, the HeII absorption weakens while the NIII emission increases [denoted (f)] and finally the most luminous stars have both 4686 and 4640 Å strongly in emission [denoted f]. A sequence of spectra all with types very near 07, but showing the marked changes with luminosity class in 4686 and 4640 Å, is illustrated by Walborn (1973). These effects show good agreement with other spectroscopic luminosity criteria such as SiIV absorption (Conti and Alschuler 1971) and Balmer-line strength (Crawford 1975, Morrison 1975), which are however less sensitive at the earliest types.

Type
Part I: Fundamentals of the HR Diagram
Copyright
Copyright © Reidel 1978 

References

Baschek, B., Kodaira, K. and Scholz, M. (1972). Astrophys. Lett. 12, 227.Google Scholar
Bohannan, B. and Conti, P.S. (1976). Astrophys. J. 204, 797.Google Scholar
Bolton, C.T. and Rogers, G.L. (1977). preprint.Google Scholar
Bond, H.E. and Levato, H. (1976). Publ. Astron. Soc. Pacific 88, 905.Google Scholar
Catchpole, R.M. and Feast, M.W. (1970). Observatory 90, 136.Google Scholar
Conti, P.S. (1973a). Astrophys. J. 179, 161.CrossRefGoogle Scholar
Conti, P.S. (1973b). Astrophys. J. 179, 181.Google Scholar
Conti, P.S. and Alschuler, W.R. (1971). Astrophys. J. 170, 325.CrossRefGoogle Scholar
Conti, P.S. and Burnichon, M.L. (1975). Astron. Astrophys. 38, 467.Google Scholar
Conti, P.S., Garmany, C.D. and Hutchings, J.B. (1977). Astrophys. J. 215, 561.CrossRefGoogle Scholar
Conti, P.S. and Leep, E.M. (1974). Astrophys. J. 193, 113.Google Scholar
Crawford, D.L. (1975). Publ. Astron. Soc. Pacific 87, 481.Google Scholar
Dearborn, D.S.P. and Eggleton, P.P. (1977). Astrophys. J. 213, 448.CrossRefGoogle Scholar
Dubois, P., Jaschek, M. and Jaschek, C. (1977). Astron. Astrophys. 60, 205.Google Scholar
Feast, M.W. (1976). Mon. Not. R. Astron. Soc. 174, 9P.Google Scholar
Groote, D. and Hunger, K. (1977). Astron. Astrophys. 56, 129.Google Scholar
Heap, S.R. (1977). Astrophys. J. 215, 609.Google Scholar
Hesser, J.E., Moreno, H. and Ugarte, P. P. (1977). Astrophys. J. Lett. 216, L31.CrossRefGoogle Scholar
Hutchings, J.B. (1975). Astrophys. J. 200, 122.Google Scholar
Hutchings, J.B., Crampton, D., Cowley, A.P. and Osmer, P.S. (1977). Astrophys. J. 217, 186.Google Scholar
Kemp, J.C. and Herman, L. C. (1977). Astrophys. J. 218, 770.Google Scholar
Massey, P. and Conti, P.S. (1977). Astrophys. J. 218, 431.CrossRefGoogle Scholar
Mihalas, D. and Hummer, D.G. (1973). Astrophys. J. 179, 827.Google Scholar
Mihalas, D., Hummer, D.G. and Conti, P.S. (1972). Astrophys. J. Lett. 175, L99.CrossRefGoogle Scholar
Montmerle, T. and Michaud, G. (1976). Astrophys. J. Supp. 31, 489.Google Scholar
Morrison, N.D. (1975). Astrophys. J. 200, 113.CrossRefGoogle Scholar
Osmer, P.S. (1973). Astrophys. J. Lett. 184, L127.Google Scholar
Osmer, P.S. and Peterson, D.M. (1974). Astrophys. J. 187, 117.CrossRefGoogle Scholar
Pedersen, H. and Thomsen, B. (1977). Astron. Astrophys. Supp. 30, 11.Google Scholar
Pismis, P. (1974). Revista Mexicana Astron. Astrof. 1, 45.Google Scholar
Przybylski, A. (1972). Mon. Not. R. Astron. Soc. 159, 155.CrossRefGoogle Scholar
Shore, S.N. and Bolton, C.T. (1977). preprint.Google Scholar
Stothers, R. (1976). Astrophys. J. 209, 800.CrossRefGoogle Scholar
Stothers, R. and Chin, C. (1977). Astrophys. J. 211, 189.Google Scholar
Thackeray, A.D. (1977). Mon. Not. R. Astron. Soc. 180, 95.CrossRefGoogle Scholar
Walborn, N.R. (1971). Astrophys. J. Suppl. 23, 257.Google Scholar
Walborn, N.R. (1972). Astron. J. 77, 312.Google Scholar
Walborn, N.R. (1973). Astron. J. 78, 1067.CrossRefGoogle Scholar
Walborn, N.R. (1974). Astrophys. J. 189, 269.Google Scholar
Walborn, N.R. (1976). Astrophys. J. 205, 419.Google Scholar
Walborn, N.R. (1977). Astrophys. J. 215, 53.Google Scholar
Walborn, N.R. and Hesser, J.E. (1976). Astrophys. J. Lett. 205, L87.CrossRefGoogle Scholar