M. Lloyd

Abell 41: shaping of a planetary nebula by a binary central star★

We present the first detailed spatiokinematical analysis and modelling of the planetary nebula Abell 41, which is known to contain the well-studied close-binary system MT Ser. This object represents an important test case in the study of the evolution of planetary nebulae with binary central stars as current evolutionary theories predict that the binary plane should be aligned perpendicular to the symmetry axis of the nebula. Deep narrow-band imaging in the light of [N II] 6584 A, [O III] 5007 A and [S II] 6717+ 6731 A, obtained using ACAM on the William Herschel Telescope, has been used to investigate the ionization structure of Abell 41. Long-slit observations of the Hα and [N II] 6584 A emission were obtained using the Manchester Echelle Spectrometer on the 2.1-m San Pedro M´ artir Telescope. These spectra, combined with the narrow-band imagery, were used to develop a spatiokinematical model of [N II] 6584 A emission from Abell 41. The best-fitting model reveals Abell 41 to have a waisted, bipolar structure with an expansion velocity of ∼40 km s −1 at the waist. The symmetry axis of the model nebula is within 5 ◦ of perpendicular to the orbital plane of the central binary system. This provides strong evidence that the close-binary system, MT Ser, has directly affected the shaping of its nebula, Abell 41. Although the theoretical link between bipolar planetary nebulae and binary central stars is long established, this nebula is only the second to have this link, between nebular symmetry axis and binary plane, proved observationally.

Hubble-type outflows of the high-excitation poly-polar planetary nebula NGC 6302 – from expansion proper motions

The outflowing proper motions of 15 knots in the dominant northwestern lobe of the high-excitation poly-polar planetary nebula NGC 6302 have been determined by comparing their positions relative to those of faint stars in an image taken at the San Pedro Martir Observatory in 2007 to those in a South African Astronomical Observatory archival plate obtained by Evans in 1956. The Hubble-type expansion of this lobe is now directly confirmed in a model-independent way from these measurements. Furthermore, an unambigous distance to NGC 6302 of 1.17 ± 0.14 kpc is now determined. Also, all the velocity vectors of the 15 knots (and two others) point back to the central source. An eruptive event from within the central torus ≈2200 yr previously must have created the high-speed lobes of NGC 6302.

SWIFT OBSERVATIONS OF THE 2006 OUTBURST OF THE RECURRENT NOVA RS OPHIUCHI. III. X-RAY SPECTRAL MODELING

Following the Swift X-ray observations of the 2006 outburst of the recurrent nova RS Ophiuchi, we developed hydrodynamical models of mass ejection from which the forward shock velocities were used to estimate the ejecta mass and velocity. In order to further constrain our model parameters, we present synthetic X-ray spectra from our hydrodynamical calculations, which we compare to the Swift data. An extensive set of simulations was carried out to find a model that best fits the spectra up to 100 days after outburst. We find a good fit at high energies but require additional absorption to match the low energy emission. We estimate the ejecta mass to be in the range (2-5) × 10–7 M ☉ and the ejection velocity to be greater than 6000 km s–1 (and probably closer to 10, 000 km s–1). We also find that estimates of shock velocity derived from gas temperatures via standard model fits to the X-ray spectra are much lower than those of the true shock velocities.

Spatio-kinematic modelling of Abell 65, a double-shelled planetary nebula with a binary central star

We present the first detailed spatio-kinematical analysis and modelling of the planetary nebula Abell 65, which is known to host a post-common envelope, binary, central star system. As such, this object is of great interest in studying the link between nebular morphology and central star binarity. [O III]5007 A and Hα+[N II]6584 A longslit spectra and imagery of Abell 65 were obtained with the Manchester Echelle Spectrometer on the 2.1-m telescope at the San Pedro Martir Observatory (MES-SPM). Further [O III]5007 A longslit spectra were obtained with the Ultraviolet and Visual Echelle Spectrograph on the Very Large Telescope (VLT-UVES). These data were used to develop a spatio-kinematical model for the [O III]5007 A emission from Abell 65. A ‘best-fitting’ model was found by comparing synthetic spectra and images rendered from the model to the data. The model comprises an outer shell and an inner shell, with kinematical ages of 15000 ± 5000 yr kpc−1 and 8000 ± 3000 yr kpc−1, respectively. Both shells have peanut-shaped bipolar structures with symmetry axes at inclinations of (55 ± 10)° (to the line of sight) for the outer shell and (68 ± 10)° for the inner shell. The near alignment between the nebular shells and the binary orbital inclination [of (68 ± 2)°] is strongly indicative that the binary is responsible for shaping the nebula. Abell 65 is one of a growing number of planetary nebulae (seven to date, including Abell 65 itself) for which observations and modelling support the shaping influence of a central binary.

Two rings but no fellowship: LoTr 1 and its relation to planetary nebulae possessing barium central stars.

LoTr 1 is a planetary nebula thought to contain an intermediate-period binary central star system (that is, a system with an orbital period, P, between 100 and, say, 1500 d). The system shows the signature of a K type, rapidly rotating giant and most likely constitutes an accretion-induced post-mass-transfer system similar to other PNe, such as LoTr 5, WeBo 1 and A70. Such systems represent rare opportunities to further the investigation into the formation of barium stars and intermediate-period post-asymptotic giant branch systems – a formation process still far from being understood. Here, we present the first detailed analyses of both the central star system and the surrounding nebula of LoTr 1 using a combination of spectra obtained with Very Large Telescope-Focal Reducer and low dispersion Spectrograph, Anglo-Australian Telescope-UCL Coude Echelle Spectrograph and New Technology Telescope-European Southern Observatory Multi-Mode Instrument, as well as SuperWASP (Wide Angle Search for Planets) photometry. We confirm the binary nature of the central star of LoTr 1 that consists of a K1 III giant and a hot white dwarf. The cool giant does not present any sign of s-process enhancement but is shown to have a rotation period of 6.4 d, which is a possible sign of mass accretion. LoTr 1 also presents broad double-peaked Hα emission lines, whose origin is still unclear. The nebula of LoTr 1 consists in two slightly elongated shells, with ages of 17 000 and 35 000 yr, respectively, and with different orientations. As such, LoTr 1 present a very different nebular morphology than A70 and WeBo 1, which may be an indication of difference in the mass-transfer episodes.

A long trail behind the planetary nebula HFG1 (PK 136+05) and its pre-cataclysmic binary central star V664 Cas

ABSTRACT A deep wide–field image in the light of the H α& [N II ] 6548& 6584A emission lines, of˚the planetary nebula HFG1 which surrounds the precataclysmic binary system V664 Cas, hasrevealed a tail of emission at least 20 ′ long, at a position angle of 316 ◦ . Evidence is presentedwhich suggests that this is an ≈ 10 5 y old trail of shocked material, left behind V664 Cas asit ejects matter whilst ploughing through its local interstellar media at anywhere between 29and 59 km s −1 depending on its distance from the Sun.Key words: stars: AGB – binaries: general – cataclysmic variables: ind ividual: V664 Cas –ISM: planetary nebulae: individual: HFG1 1 INTRODUCTIONHFG1 around what later was recognized to be a 13.7 mag precat-aclysmic binary star named V664 Cas (Bond, Fleming & Grauer1989; Acker & Stenholm 1990; Exter et al. 2005). Thisstellar closebinary system was found to have a period of 13.96 h and brightnessamplitude of 1 mag. Exter et al. (2005) give its distance D = 310to 950 pc but there is as yet no parallax measurement to determinethis with more certainty. Shimanskii et al. (2004) show that V664Cas is a precataclysmic variable with an orbital period of ≈ 0.58days and with the inclination of the rotation axis along a positionangle PA = 177 ± 5

VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18

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 of the source. A timescale analysis was used to determine the kinematical age of the nebula and its main components. Results. A spectroscopic study of MyCn 18’s central and offset region reveals the detailed make-up of its nebular composition. Molecular hydrogen, atomic helium, and Bracket gamma emission are detected from the central regions of MyCn 18. ISAAC spectra from a slit position along the narrow waist of the nebula demonstrate that the ionised gas resides closer to the centre of the nebula than the molecular emission. A final reconstructed 3D model of MyCn 18 was generated, which provides kinematical information on the expansion velocity of its nebular components by means of position-velocity (P-V) arrays. A kinematical age of the nebula and its components were obtained by the P-V arrays and timescale analysis. Conclusions. The structure and kinematics of MyCn 18 are better understood using an interactive 3D modelling tool called SHAPE. A dimensional and timescale analysis of MyCn 18’s major components provides a possible mechanism for the nebula’s asymmetry. The putative central star is somewhat offset from the geometric centre of the nebula, which is thought to be the result of a binary system. We speculate that the engulfing and destruction of an exoplanet during the asymptotic giant branch phase may have been a key event in shaping MyCn 18 and generating of its hypersonic knotty outflow.

The influence of binarity on the morpho-kinematics of planetary nebulae

The role of central star binarity in the shaping of planetary nebulae (PNe) has been the subject of much debate, with single stars believed to be incapable of producing the most highly collimated morphologies. However, observational support for binary-induced shaping has been sadly lacking. Here, we highlight the results of a continuing programme to spatio-kinematically model the morphologies of all PNe known to contain a close binary central star. Spatio-kinematical modelling is imperative for these objects, as it circumvents the degeneracy between morphology and orientation which can adversely affect determinations of morphology based on imaging alone. Furthermore, spatio-kinematical modelling accurately determines the orientation of the nebular shell, allowing the theoretically predicted perpendicular alignment, between nebular symmetry axis and binary orbital plane, to be tested. To date, every PN subjected to this investigation has displayed the predicted alignment, indicating that binarity has played an important role in the formation and evolution of these nebulae. The further results from this programme will be key, not only in determining whether binary interaction is responsible for shaping the studied PNe, but also in assessing the importance of binarity in the formation and evolution of all PNe in general.

The SPM kinematic catalogue of Galactic planetary nebulae

The San Pedro Martir kinematic catalogue of galactic planetary nebulae provides spatially resolved, long-slit, Echelle spectra for about 600 planetary nebulae, representing 55 observing runs and about 4000 individual integrations to date in this first release. The project is ongoing and will continue adding spectra to the database. The data are presented wavelength calibrated and corrected for heliocentric motion. This is the most extensive and homogeneous single source of data concerning the internal kinematics of the ionized nebular material in planetary nebulae. The catalogue is available through the world wide web at http://kincatpn.astrosen.unam.mx and an article will a full description of the catalogue will soon appear in the RevMexAA.