Multiple Coaxial Rings in the Bipolar Nebula Hubble 12

Abstract

A series of two-dimensional rings along a common axis aligned with the bipolar lobes is found in the planetary nebula Hb 12. The rings have separations of about 0.3 00 , which can be translated into physical separations of $1000 AU, or time separations of the order of 50 yr. We suggest that the existence of the rings is a manifestation of the interaction between a time-variable, collimated fast outflow with the circumstellar envelope created by the stellar wind of an asymptotic giant branch star. Comparison of Hb 12 with other bipolar nebulae with hourglass structures such as Hen 2-104, MyCn 18, and SN 1987A suggests that the nebula of Hb 12 may represent the inner nebula of a much larger bipolar structures, and we propose to search for such outer structures with a wide-field infrared camera. Subject headingg s: binaries: symbiotic -planetary nebulae: general -planetary nebulae: individual (Hubble 12) -stars: AGB and post-AGB

A DETAILED STUDY OF THE STRUCTURE OF THE NESTED PLANETARY NEBULA, Hb 12, THE MATRYOSHKA NEBULA

“…There is practically no molecular hydrogen emission from the lobes; instead, what looks like a ring of emission is detected from −30 km s −1 to 60 km s −1 . This emission corresponds to the arcs described by Hora et al (2000) and Kwok & Hsia (2007). The emission from these arcs is relatively bright in the central velocity channels corresponding to 0 km s −1 and 30 km s −1 and fainter in the contiguous outer channels at −30 km s −1 and 60 km s −1 .…”

“…Hora et al (2000) had suggested from the F160W and F212N NICMOS/HST images that Hb 12 could be a PN with multiple nested bipolar bubbles. The possible existence of this larger bipolar structure was speculated by Kwok & Hsia (2007) in relation to the equatorial arcs. The mosaic of images in Figure 3 and the NIFS data now confirm that the nested filaments or arcs correspond to an expanding and tilted equatorial structure that is part of this remarkably larger, outer, bipolar system that replicates the inner one, like a Russian Matryioshka doll.…”

“…The inner regions are dominated by UV-excited, fluorescent, H 2 emission (Dinerstein et al 1988) and shockexcited [Fe ii] emission has been detected within 10 of the core in the polar regions (Welch et al 1999). Hubble Space Telescope (HST) NICMOS images reveal a series of nested equatorial arcs (Hora et al 2000;Kwok & Hsia 2007) surrounding the core of the hourglass. Hsia et al (2006) suggested that Hb 12 has a binary nucleus, but this has not been confirmed by others (DeMarco 2009).…”

Planetary Nebulae: Observational Properties, Mimics and Diagnostics

“…This latter object may possibly be a symbiotic outflow. Hb 12 is another interesting case, with properties intermediate between symbiotics and PN (Kwok & Hsia 2007;Vaytet et al 2009). Schmeja & Kimeswenger (2001) have used DENIS near-IR colour-colour plots to differentiate symbiotic stars (including those with resolved outflows) from compact PN.…”

CRYSTALLINE SILICATES IN EVOLVED STARS. I.SPITZER/INFRARED SPECTROGRAPH SPECTROSCOPY OF IRAS 16456–3542, 18354–0638, AND 23239+5754

“…It has long been suspected to be a binary. Also known as Hubble 12 at a distance of ∼3 kpc (Kingsburgh & Barlow 1992), this PN, in particular its multiple coaxial rings in the whole-scale bipolar structure, has been well studied in the literature (see, e.g., Kwok & Hsia 2007, and references therein). The shape of this object reveals that it is probably at a very early PN phase, with a kinematic age of ∼300 years (Miranda & Solf 1989).…”