Hostname: page-component-cd9895bd7-lnqnp Total loading time: 0 Render date: 2024-12-26T19:00:57.695Z Has data issue: false hasContentIssue false
  • English
  • Français

The origin and pulsations of extreme helium stars†

Published online by Cambridge University Press:  18 February 2014

C. Simon Jeffery
C. Simon Jeffery*
Affiliation:
Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, UK
Rights & Permissions [Opens in a new window]

Abstract

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.

Stars consume hydrogen in their interiors but, generally speaking, their surfaces continue to contain some 70% hydrogen (by mass) throughout their lives. Nevertheless, many types of star can be found with hydrogen-deficient surfaces, in some cases with as little as one hydrogen atom in 10 000. Amongst these, the luminous B- and A-type extreme helium stars are genuinely rare; only ~15 are known within a very substantial volume of the Galaxy.

Evidence from surface composition suggests a connection to the cooler R CrB variables and some of the hotter helium-rich subdwarf O stars. Arguments currently favour an origin in the merger of two white dwarfs; thus there are also connections with AM CVn variables and Type Ia supernovae. Pulsations in many extreme helium stars provide an opportune window into their interiors. These pulsations have unusual properties, some being “strange” modes, and others being driven by Z-bump opacities. They have the potential to deliver distance-independent masses and to provide a unique view of pulsation physics.

We review the evolutionary origin and pulsations of these stars, and introduce recent progress and continuing challenges.

Keywords

stars: early-typestars: chemically-peculiarstars: supergiantsstars: white dwarfsstars: evolutionstars: oscillationsstars: variable: otherstars: individual: V652 HerFQ Aqr
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S301: Precision Asteroseismology , August 2013 , pp. 297 - 304
Copyright
Copyright © International Astronomical Union 2014 

Footnotes

†

The full version of this paper, including additional sections on the asteroarchæology and origin of EHes, is available online at ArXiv: 1311.1635.

References

Bartolini, C., Bonifazi, A., Fusi Pecci, F., et al. 1982, Ap&SS, 83, 287Google Scholar
Berger, J. & Greenstein, J. L. 1963, PASP, 75, 336Google Scholar
Fadeyev, Y. A. & Lynas-Gray, A. E. 1996, MNRAS, 280, 427CrossRefGoogle Scholar
Gautschy, A. & Glatzel, W. 1990, MNRAS, 245, 597Google Scholar
Grauer, A. D., Drilling, J. S., & Schönberner, D. 1984, A&A, 133, 285Google Scholar
Guzik, J. A., Peterson, B. R., Cox, A. N., & Bradley, P. A. 2006, MemSAIt, 77, 131Google Scholar
Hill, P. W., Kilkenny, D., Schönberner, D., & Walker, H. J. 1981, MNRAS, 197, 81Google Scholar
Hill, P. W., Lynas-Gray, A. E., & Kilkenny, D. 1984, MNRAS, 207, 823Google Scholar
Jeffery, C. S. 1984, MNRAS, 210, 731Google Scholar
Jeffery, C. S. 2008a, ASP-CS, 391, 3Google Scholar
Jeffery, C. S. 2008b, ASP-CS, 391, 53Google Scholar
Jeffery, C. S. 2008c, IBVS, 5817Google Scholar
Jeffery, C. S. 2013, arXiv: 1311.1635Google Scholar
Jeffery, C. S. & Hill, P. W. 1986, MNRAS, 221, 975CrossRefGoogle Scholar
Jeffery, C. S. & Lynas-Gray, A. E. 1990, MNRAS, 242, 6Google Scholar
Jeffery, C. S., Malaney, R. A. 1985, MNRAS, 213, 61PGoogle Scholar
Jeffery, C. S. & Saio, H. 1999, MNRAS, 308, 221Google Scholar
Jeffery, C. S. & Saio, H. 2013, MNRAS, 435, 885Google Scholar
Jeffery, C. S., Skillen, I., Hill, P. W., Kilkenny, D., Malaney, R. A., & Morrison, K. 1985, MNRAS, 217, 701CrossRefGoogle Scholar
Jeffery, C. S., Drilling, J. S., & Heber, U. 1987, MNRAS, 226, 317Google Scholar
Jeffery, C. S., Hill, P. W., & Morrison, K. 1986, in: Hunger, K., Schönberner, D., Rao, N. Kameswara (eds.), Hydrogen-Deficient Stars and Related Objects, Proc. IAU Colloqium No. 87, Astrophysics and Space Sci. Library, Vol. 128 (Dordrecht: D. Reidel Publishing Co.) p. 95Google Scholar
Jeffery, C. S., Hill, P. W., & Heber, U. 1999, A&A, 346, 491Google Scholar
Jeffery, C. S., Starling, R. L. C., Hill, P. W., & Pollacco, D. 2001a, MNRAS, 321, 111Google Scholar
Jeffery, C. S., Woolf, V. M., & Pollacco, D. L. 2001b, A&A, 376, 497Google Scholar
Jeffery, C. S., Shibahashi, H., Kurtz, D., Elkin, V., Montañés-Rodríguez, P., & Saio, H. 2013a, in: Shibahashi, H., Lynas-Gray, A. E. (eds.), Progress in Physics of the Sun and Stars: A New Era in Helio- and Asteroseismology, ASP-CS, in pressGoogle Scholar
Jeffery, C. S., Shibahashi, H., Kurtz, D., Elkin, V., Montañés- Rodríguez, P., & Saio, H. 2013b, in: Van Grootel, V., Green, E., Fontaine, G., Charpinet, S. (eds.), Hot Subdwarf Stars and Related Objects, ASP-CS, in pressGoogle Scholar
Kilkenny, D. & Koen, C. 1995, MNRAS, 275, 327CrossRefGoogle Scholar
Kilkenny, D. & Lynas-Gray, A. E. 1982, MNRAS, 198, 873Google Scholar
Kilkenny, D., Lawson, W. A., Marang, F., Roberts, G., & van Wyk, F., 1999, MNRAS, 305, 103Google Scholar
Kilkenny, D., Crause, L. A., & van Wyk, F. 2005, MNRAS, 361, 559Google Scholar
Landolt, A. U. 1975, ApJ, 196, 789Google Scholar
Lawson, W. A. & Kilkenny, D. 1998, Observatory, 118, 1Google Scholar
Lawson, W. A., Kilkenny, D., van Wyk, F., Marang, F., Pollard, K., & Ryder, S. D. 1993, MNRAS, 265, 351CrossRefGoogle Scholar
Lynas-Gray, A. E., Schönberner, D., Hill, P. W., & Heber, U. 1984, MNRAS, 209, 387Google Scholar
Lynas-Gray, A. E., Kilkenny, D., Skillen, I., & Jeffery, C. S. 1987, MNRAS, 227, 1073Google Scholar
Montañés Rodríguez, P. & Jeffery, C. S. 2002, MNRAS, 384, 433Google Scholar
Morrison, K. 1987, MNRAS, 224, 1083Google Scholar
Morrison, K. & Willingale, G. P. H. 1987, MNRAS, 228, 819Google Scholar
Percy, J. R. & Fu, R. 2012, Journal AAVSO, 40, 900Google Scholar
Pigott, E. & Englefield, H. C. 1797, Phil. Trans. Ser. I, 87, 133Google Scholar
Popper, D. M. 1942, PASP, 54, 160Google Scholar
Rogers, F. J. & Iglesias, C. A. 1992, ApJS, 79, 507Google Scholar
Saio, H. 1993, MNRAS, 260, 465Google Scholar
Saio, H. 1995, MNRAS, 277, 1393Google Scholar
Saio, H. & Jeffery, C. S. 1988, ApJ, 328, 714Google Scholar
Saio, H. & Jeffery, C. S. 2000, MNRAS, 313, 671Google Scholar
Saio, H., Baker, N. H., & Gautschy, A. 1998, MNRAS, 294, 622CrossRefGoogle Scholar
Schönberner, D. 1975, A&A, 44, 383Google Scholar
Walker, H. J. & Hill, P. W. 1985, A&AS, 61, 303Google Scholar
Wood, P. R. 1976, MNRAS, 174, 531Google Scholar
Wright, D. J., Lynas-Gray, A. E., Kilkenny, D., et al. 2006, MNRAS, 369, 2049Google Scholar
Zhang, X. & Jeffery, C. S. 2012, MNRAS, 419, 452Google Scholar