For more information:
Miszalski, B., Crowther, P. A., De Marco, O., Köppen, J., Moffat, A.F.J., Acker, A., and Hillwig, T. C.,
“IC 4663: the first unambiguous [WN] Wolf-Rayet
central star of a planetary nebula,” Monthly Notices
of the Royal Astronomical Society, 423: 934, 2012
Crowther, P. A., Morris, P. W., and Smith, J. D., “An
Ultraviolet to Mid-Infrared Study of the Physical
and Wind Properties of HD 164270 (WC9) and
Comparison to BD +30 3639 ([WC9]),” Astrophysical Journal, 636: 1033, 2006
Crowther, P. A., “Physical Properties of Wolf-Rayet
stars,” Annual Review of Astronomy & Astrophysics,
45: 177, 2007
Miszalski, B., “Ongoing surveys for close binary
central stars and wider implications,” IAU Symposium 283, in press (arXiv:1110.1831), 2012
Figure 4.
Atmospheric compositions (by mass) of a
[WN3] star (IC 4663),
an O(He) star (K 1-27),
a [WC11] star (PM
1-188), and a PG 1159
star (PG 1159-035,
the prototype of the
class), from our study
and Werner and
Herwig (2006). Note
the similarity between
the [WN3] and O(He),
and the [WC11] and
PG 1159, compositions. The carbon-rich
[WC]→PG 1159 evolutionary sequence
is well established,
but only with IC 4663
are we able to newly
propose the heliumrich equivalent
[WN]→O(He). Only
the main subset of
elements are used to
illustrate the similarity between the two
separate groups.
20
nature found in most [WC] atmospheres, it has
never reproduced the extreme helium-rich nature of O(He) stars or IC 4663. This suggests another explanation is required to produce [WN]
central stars and their O(He) progeny.
At present it is unclear what this mechanism
may be. Binary interactions may be the most
promising avenue for investigation, especially
considering the rapidly growing evidence for
binarity in the central stars of planetary nebulae (Miszalski, IAU Symposium 283, in press,
2012; and references therein). Lack of radial
velocity variability in IC 4663 suggests it is not
a binary system, but it may have been in the
past. One possible explanation for the formation of R Coronae Borealis stars, which share
a similar hydrogen-deficient and helium-rich
composition to IC 4663, involves a merger of
two white dwarfs. There may also be some
follow-on evolutionary ties to helium-rich novae and cataclysmic variables.
Whatever the reason behind the unusual
composition of IC 4663, solving this puzzle
will certainly require new ideas enriched by
the prospect of future [WN] discoveries. We
look forward to further developments in this
exciting field of study.
GeminiFocus
Rauch, T., Dreizler, S., and Wolff, B., “Spectral analysis of O(He)-type post-AGB stars,” Astronomy and
Astrophysics, 338: 651, 1998
Smith, L. F., and Aller, L. H., “A Detailed Comparison
of the Spectra of a Planetary Nucleus and a WolfRayet Star,” Astrophysical Journal, 164: 275, 1971
Werner, K., and Herwig, F., “The Elemental Abundances in Bare Planetary Nebula Central Stars and
the Shell Burning in AGB Stars,” Publications of the
Astronomical Society of the Pacific, 118: 183, 2006
Brent Miszalski is a SALT research fellow at the South
African Astronomical Observatory and Southern African Large Telescope (SALT). He can be reached at:
[email protected]
Paul Crowther is a professor within the Department
of Physics and Astronomy at the University of Sheffield. He can be reached at:
[email protected]
Anthony Moffat is an emeritus professor in the
Départment de physique of the Université de Montréal and a member of the Centre de recherche
d’astrophysique du Québec. He can be reached at:
[email protected]
We acknowledge the contribution of our co-authors
in this work, Orsola De Marco, Joachim Köppen, Agnès Acker, and Todd Hillwig.
June2012