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| Paper: |
Hubble Space Telescope Imaging and Grism Spectroscopy of the
Binary Nucleus of the Planetary Nebula EGB 6 |
| Volume: |
469, 18th European White Dwarf Workshop (EUROWD12) |
| Page: |
391 |
| Authors: |
Liebert, J.; Bond, H. E.; Dufour, P.; Ciardullo, R. |
| Abstract: |
EGB 6 is a large, very old, low-surface-brightness planetary nebula.
The central star (also cataloged as PG 0950+139) is a very hot DAOZ
white dwarf with an apparent M dwarf companion detected initially in
the near-infrared. The binary nucleus is juxtaposed with an unusual,
compact, extremely dense emission nebula, unresolved in ground-based
images. The electron density of ne = 2.2×106 cm–3 is
measured because of the quenching (collisional deexcitation) of
[O III], [O II], [N II] and [S II] lines. The HST imaging and
grism spectroscopy show that the binary system is resolved with a
separation of 0.″166, or a projected 108 AU at the estimated
distance of 650 pc, and that the compact emission nebula coincides
with the cool (likely) dM star rather than the hot white dwarf.
Moreover, a striking mid-infrared excess has recently been measured in
Spitzer/MIPS and IRAC bands, indicating dust shells of 500 K and
150 K, by K. Su, Y.-H. Chu, and collaborators (cf. Su et al. 2011). |
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