Abstract:Context. The mechanisms that form extreme bipolar planetary nebulae remain unclear. Aims. The physical properties, structure, and dynamics of the bipolar planetary nebula, MyCn 18, are investigated in detail with the aim of understanding the shaping mechanism and evolutionary history of this object. Methods. VLT infrared images, VLT ISAAC infrared spectra, and long-slit optical Echelle spectra are used to investigate MyCn 18. Morpho-kinematic modelling was used to firmly constrain the structure and kinematics … Show more
“…Uncertainties in each radial velocity measurement are 1σ uncertainties determined from the standard error in the fit centroid provided by the fitting routine. The average nebular radial velocity of −72.78 ± 0.10 km s −1 agrees well with −71 km s −1 measured from spatio-kinematic modeling (Clyne et al 2014). Figure 3.The observed N iii λ4634.14 Å profiles (black lines) were fit with a model composed of a Voigt function and a straight line (red lines).…”
Section: Discussionsupporting
confidence: 86%
“…Included in our survey is the young planetary nebula MyCn 18 (PN G307.5−04.9, Mayall & Cannon 1940), also known as the Etched Hourglass Nebula. The bipolar appearance of MyCn 18 (Figure 1; Sahai et al 1999) is the result of an eponymous hourglass-shaped nebula inclined 38° to the line of sight (Dayal et al 2000; O’Connor et al 2000; Clyne et al 2014). MyCn 18 exhibits several features for which binary interactions are the preferred formation mechanism, yet no evidence has been found supporting the presence of a binary companion.…”
Section: Introductionmentioning
confidence: 99%
“…MyCn 18 has often been compared against bipolar nebulae around low and high mass evolved stars. It is particularly notable for its intriguing nested hourglass structure (Sahai et al 1999; Clyne et al 2014) that closely resembles the nebular remnant of SN 1987A (e.g. Burrows et al 1995; Sugerman et al 2005), the symbiotic nebula Hen 2-104 (Corradi & Schwarz 1993; Corradi et al 2001; Santander-García et al 2008; Clyne et al 2015), and Hb 12 which may be a young PN or possibly a symbiotic nebula (Hsia, Ip, & Li 2006; Kwok & Hsia 2007; Vaytet et al 2009; Clark et al 2014).…”
The shaping of various morphological features of planetary nebulae (PNe) is increasingly linked to the role of binary central stars. Identifying a binary within a PN offers a powerful tool with which to directly investigate the formation mechanisms behind these features. The Etched Hourglass Nebula, MyCn 18, is the archetype for several binary-linked morphological features, yet it has no identified binary nucleus. It has the fastest jets seen in a PN of 630 km s −1 , a central star position offset from the nebula centre, and a bipolar nebula with a very narrow waist. Here we report on the Southern African Large Telescope (SALT) High Resolution Spectrograph (HRS) detection of radial velocity variability in the nucleus of MyCn 18 with an orbital period of 18.15 ± 0.04 days and a semi-amplitude of 11.0 ± 0.3 km s −1 . Adopting an orbital inclination of 38 ± 5 deg and a primary mass of 0.6 ± 0.1 M yields a secondary mass of 0.19 ± 0.05 M corresponding to an M5V companion. The detached nature of the binary rules out a classical nova (CN) as the origin of the jets or the offset central star as hypothesised in the literature. Furthermore, scenarios that produce the offset central star during the AGB and that form narrow waist bipolar nebulae result in orbital separations 80-800 times larger than observed in MyCn 18. The inner hourglass and jets may have formed from part of the common envelope ejecta that remained bound to the binary system in a circumbinary disk, whereas the offset central star position may best be explained by proper motion. Detailed simulations of MyCn 18 are encouraged that are compatible with the binary nucleus to further investigate its complex formation history.
“…Uncertainties in each radial velocity measurement are 1σ uncertainties determined from the standard error in the fit centroid provided by the fitting routine. The average nebular radial velocity of −72.78 ± 0.10 km s −1 agrees well with −71 km s −1 measured from spatio-kinematic modeling (Clyne et al 2014). Figure 3.The observed N iii λ4634.14 Å profiles (black lines) were fit with a model composed of a Voigt function and a straight line (red lines).…”
Section: Discussionsupporting
confidence: 86%
“…Included in our survey is the young planetary nebula MyCn 18 (PN G307.5−04.9, Mayall & Cannon 1940), also known as the Etched Hourglass Nebula. The bipolar appearance of MyCn 18 (Figure 1; Sahai et al 1999) is the result of an eponymous hourglass-shaped nebula inclined 38° to the line of sight (Dayal et al 2000; O’Connor et al 2000; Clyne et al 2014). MyCn 18 exhibits several features for which binary interactions are the preferred formation mechanism, yet no evidence has been found supporting the presence of a binary companion.…”
Section: Introductionmentioning
confidence: 99%
“…MyCn 18 has often been compared against bipolar nebulae around low and high mass evolved stars. It is particularly notable for its intriguing nested hourglass structure (Sahai et al 1999; Clyne et al 2014) that closely resembles the nebular remnant of SN 1987A (e.g. Burrows et al 1995; Sugerman et al 2005), the symbiotic nebula Hen 2-104 (Corradi & Schwarz 1993; Corradi et al 2001; Santander-García et al 2008; Clyne et al 2015), and Hb 12 which may be a young PN or possibly a symbiotic nebula (Hsia, Ip, & Li 2006; Kwok & Hsia 2007; Vaytet et al 2009; Clark et al 2014).…”
The shaping of various morphological features of planetary nebulae (PNe) is increasingly linked to the role of binary central stars. Identifying a binary within a PN offers a powerful tool with which to directly investigate the formation mechanisms behind these features. The Etched Hourglass Nebula, MyCn 18, is the archetype for several binary-linked morphological features, yet it has no identified binary nucleus. It has the fastest jets seen in a PN of 630 km s −1 , a central star position offset from the nebula centre, and a bipolar nebula with a very narrow waist. Here we report on the Southern African Large Telescope (SALT) High Resolution Spectrograph (HRS) detection of radial velocity variability in the nucleus of MyCn 18 with an orbital period of 18.15 ± 0.04 days and a semi-amplitude of 11.0 ± 0.3 km s −1 . Adopting an orbital inclination of 38 ± 5 deg and a primary mass of 0.6 ± 0.1 M yields a secondary mass of 0.19 ± 0.05 M corresponding to an M5V companion. The detached nature of the binary rules out a classical nova (CN) as the origin of the jets or the offset central star as hypothesised in the literature. Furthermore, scenarios that produce the offset central star during the AGB and that form narrow waist bipolar nebulae result in orbital separations 80-800 times larger than observed in MyCn 18. The inner hourglass and jets may have formed from part of the common envelope ejecta that remained bound to the binary system in a circumbinary disk, whereas the offset central star position may best be explained by proper motion. Detailed simulations of MyCn 18 are encouraged that are compatible with the binary nucleus to further investigate its complex formation history.
“…O'Connor et al (2000), Soker & Kashi (2012) and Clyne et al (2014) suggested the possibility that MyCn 18 might have been a SySt, however, it is clearly placed in the PNe regime of the optical diagnostic diagram (Fig. 7).…”
Section: The Optical Pne Versus Systs Diagrammentioning
Context. Complex bipolar shapes can be generated either as a planetary nebula or a symbiotic system. The origin of the material ionised by the white dwarf is very different in these two scenarios, and it complicates the understanding of the morphologies of planetary nebulae. Aims. The physical properties, structure, and dynamics of the bipolar nebulae, M 2−9, Mz 3, and Hen 2−104, are investigated in detail with the aim of understanding their nature, shaping mechanisms, and evolutionary history. Both a morpho-kinematic study and a spectroscopic analysis, can be used to more accurately determine the kinematics and nature of each nebula. Methods. Long-slit optical echelle spectra are used to investigate the morpho-kinematics of M 2−9, Mz 3, and Hen 2−104. The morpho-kinematic modelling software SHAPE is used to constrain both the morphology and kinematics of each nebula by means of detailed 3D models. Near-infrared (NIR) data, as well as optical, spectra are used to separate Galactic symbiotic-type nebulae from genuine planetary nebulae by means of a 2MASS J−H/H−Ks diagram and a λ4363/Hγ vs. λ5007/Hβ diagnostic diagram, respectively. Results. The best-fitted 3D models for M 2−9, Mz 3, and Hen 2−104 provide invaluable kinematical information on the expansion velocity of its nebular components by means of synthetic spectra. The observed spectra match up very well with the synthetic spectra for each model, thus showing that each model is tightly constrained both morphologically and kinematically. Kinematical ages of the different structures of M 2−9 and Mz 3 have also been determined. Both diagnostic diagrams show M 2−9 and Hen 2−104 to fall well within the category of having a symbiotic source, whereas Mz 3 borders the region of symbiotic and young planetary nebulae in the optical diagram but is located firmly in the symbiotic region of the NIR colour−colour diagram. The optical diagnostic diagram is shown to successfully separate the two types of nebulae, however, the NIR colour−colour diagram is not as accurate in separating these objects. Conclusions. The morphology, kinematics, and evolutionary history of M 2−9, Mz 3, and Hen 2−104 are better understood using the interactive 3D modelling tool . The expansion velocities of the components for each nebula are better constrained and fitted with a vector field to reveal their direction of motion. The optical and NIR diagnostic diagrams used are important techniques for separating Galactic symbiotic-type nebulae from genuine planetary nebulae.
“…The parameters of the model are then interactively adjusted until a satisfactory solution is obtained (e.g. Akras and Steffen 2012;Akras and López 2012;Clyne et al 2014;Clyne et al 2015). Our model of Abell 14 was constructed using the image and kinematic data from the [N ii] λ6584 line due to its lower thermal broadening compared to that of the Hα line (thermal width of the Hα and [N ii] lines at 10,000 K are 21.4 km s −1 and 5.8 km s −1 , respectively).…”
Abell 14 is a poorly studied object despite being considered a born again planetary nebula. We performed a detailed study of its 3D morphology and ionization structure using the shape and mocassin codes. We found that Abell 14 is a highly evolved, bipolar nebula with a kinematical age of ∼19,400 yr for a distance of 4 kpc. The high He abundance, and N/O ratio indicate a progenitor of 5 M ⊙ that has experienced the third dredge-up and hot bottom burning phases. The stellar parameters of the central source reveal a star at a highly evolved stage near to the white dwarf cooling track, being inconsistent with the born again scenario. The nebula shows unexpectedly strong [N i] λ5200 and [O i] λ6300 emission lines indicating possible shock interactions. Abell 14 appears to be a member of a small group of highly evolved, extreme Type-I PNe. The members of this group lie at the lower-left corner of the PNe regime on the [N ii]/Hα vs. [S ii]/Hα diagnostic diagram, where shock-excited regions/objects are also placed. The low luminosity of their central stars, in conjunction with the large physical size of the nebulae, result in a very low photo-ionization rate, which can make any contribution of shock interaction easily perceptible, even for small velocities.
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