[Show abstract][Hide abstract] ABSTRACT: 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.
[OIII]5007A and H-alpha+[NII]6584A 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 [OIII]5007A 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 [OIII]5007A emission from Abell 65. A
"best-fit" 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 deg (to the line-of-sight) for the
outer shell and 68 +/- 10 deg for the inner shell. The near-alignment between
the nebular shells and the binary orbital inclination (of 68 +/- 2 deg) 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.
Monthly Notices of the Royal Astronomical Society 06/2013; 434(2). DOI:10.1093/mnras/stt1109 · 5.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have selected a group of 100 evolved planetary nebulae (PNe) and study
their kinematics based upon spatially-resolved, long-slit, echelle
spectroscopy. The data have been drawn from the San Pedro M\'artir Kinematic
Catalogue of PNe (L\'opez et al. 2012). The aim is to characterize in detail
the global kinematics of PNe at advanced stages of evolution with the largest
sample of homogenous data used to date for this purpose. The results reveal two
groups that share kinematics, morphology, and photo-ionization characteristics
of the nebular shell and central star luminosities at the different late stages
under study.The typical flow velocities we measure are usually larger than seen
in earlier evolutionary stages, with the largest velocities occurring in
objects with very weak or absent [N II] \lambda 6584 line emission, by all
indications the least evolved objects in our sample. The most evolved objects
expand more slowly. This apparent deceleration during the final stage of PNe
evolution is predicted by hydrodynamical models, but other explanations are
also possible. These results provide a template for comparison with the
predictions of theoretical models.
The Astrophysical Journal 05/2013; 771(2). DOI:10.1088/0004-637X/771/2/114 · 6.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present an extensive, long-slit, high-resolution coverage of the complex
planetary nebula (PN), NGC 7026. We acquired ten spectra using the Manchester
Echelle Spectrometer at San Pedro Martir Observatory in Baja California,
Mexico, and each shows exquisite detail, revealing the intricate structure of
this object. Incorporating these spectra into the 3-dimensional visualization
and kinematic program, SHAPE, and using HST images of NGC 7026, we have
produced a detailed structural and kinematic model of this PN. NGC 7026
exhibits remarkable symmetry consisting of three lobe-pairs and four sets of
knots, all symmetrical about the nucleus and displaying a conical outflow.
Comparing the 3-D structure of this nebula to recent, XMM-Newton X-ray
observations, we investigate the extended X-ray emission in relation to the
nebular structure. We find that the X-ray emission, while confined to the
closed, northern lobes of this PN, shows an abrupt termination in the middle of
the SE lobe, which our long slit data shows to be open. This is where the
shocked, fast wind seems to be escaping the interior of the nebula and the
X-ray emission rapidly cools in this region.
The Astronomical Journal 10/2012; 145(3). DOI:10.1088/0004-6256/145/3/57 · 4.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We study the line widths in the [O III]λ5007 and Hα lines for two groups of planetary nebulae in the Milky Way bulge based upon spectroscopy obtained at the Observatorio Astronómico Nacional in the Sierra San Pedro Mártir (OAN-SPM) using the Manchester Echelle Spectrograph. The first sample includes objects early in their evolution, having high Hβ luminosities, but [O III]λ5007/Hβ < 3. The second sample comprises objects late in their evolution, with He II λ4686/Hβ>0.5. These planetary nebulae represent evolutionary phases preceding and following those of the objects studied by Richer et al. in 2008. Our sample of planetary nebulae with weak [O III]λ5007 has a line width distribution similar to that of the expansion velocities of the envelopes of asymptotic giant branch stars and shifted to systematically lower values as compared to the less evolved objects studied by Richer et al. The sample with strong He II λ4686 has a line width distribution indistinguishable from that of the more evolved objects from Richer et al., but a distribution in angular size that is systematically larger and so they are clearly more evolved. These data and those of Richer et al. form a homogeneous sample from a single Galactic population of planetary nebulae, from the earliest evolutionary stages until the cessation of nuclear burning in the central star. They confirm the long-standing predictions of hydrodynamical models of planetary nebulae, where the kinematics of the nebular shell are driven by the evolution of the central star.
The Astrophysical Journal 05/2010; 716(1):857. DOI:10.1088/0004-637X/716/1/857 · 6.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Hubble Space Telescope (HST) has revealed the existence of multiple, regularly spaced, and faint concentric shells around some planetary nebulae. Here we present two- (and a half) dimensional magnetohydrodynamic numerical simulations of the effects of a solar-like magnetic cycle, with periodic polarity inversions, in the slow wind of an asymptotic giant branch (AGB) star. The stellar wind is modeled with a steady mass-loss at constant velocity. This simple version of a solar-like cycle, without mass-loss variations, is able to reproduce many properties of the observed concentric rings. The shells are formed by pressure oscillations, which drive compressions in the magnetized wind. These pressure oscillations are due to periodic variations in the field intensity. The periodicity of the shells, then, is simply a half of the magnetic cycle since each shell is formed when the magnetic pressure goes to zero during the polarity inversion. As a consequence of the steady mass-loss rate, the density of the shells scales as r-2, and their surface brightness has a steeper drop-off, as observed in the shells of NGC 6543, the best documented case of these HST rings. Deviations from sphericity can be generated by changing the strength of the magnetic field. For sufficiently strong fields, a series of symmetric and equidistant blobs are formed at the polar axis, resembling the ones observed in He 2-90. These blobs are originated by magnetic collimation within the expanding AGB wind.
The Astrophysical Journal 12/2008; 560(2):928. DOI:10.1086/323072 · 6.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper explores the effects of post-asymptotic giant branch (AGB) winds driven solely by magnetic pressure from the stellar surface. It is found that winds can reach high speeds under this assumption and lead to the formation of highly collimated proto-planetary nebulae. Bipolar knotty jets with periodic features and constant velocity are well reproduced by the models. Several wind models with terminal velocities from a few tens of km s-1 up to 103 km s-1 are calculated, yielding outflows with linear momenta in the range 1036-1040 g cm s-1, and kinetic energies in the range 1042-1047 ergs. These results are in accord with recent observations of proto-planetary nebulae that have pointed out serious energy and momentum deficits if radiation pressure is considered as the only driver for these outflows. Our models strengthen the notion that the large mass loss rates of post-AGB stars, together with the short transition times from the late AGB to the planetary nebula stage, could be directly linked with the generation of strong magnetic fields during this transition stage.
The Astrophysical Journal 12/2008; 618(2):919. DOI:10.1086/426110 · 6.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present a systematic study of line widths in the [O III] λ5007 and Hα lines for a sample of 86 planetary nebulae in the Milky Way bulge based on spectroscopy obtained at the Observatorio Astronómico Nacional in the Sierra San Pedro Mártir (OAN-SPM) using the Manchester Echelle Spectrograph. The planetary nebulae were selected with the intention of simulating samples of bright extragalactic planetary nebulae. We separate the planetary nebulae into two samples containing cooler and hotter central stars, defined by the absence or presence, respectively, of the He II λ6560 line in the Hα spectra. This division separates samples of younger and more evolved planetary nebulae. The sample of planetary nebulae with hotter central stars has systematically larger line widths, larger radii, lower electron densities, and lower Hβ luminosities. The distributions of these parameters in the two samples all differ at significance levels exceeding 99%. These differences are all in agreement with the expectations from hydrodynamical models, but for the first time confirmed for a homogeneous and statistically significant sample of Galactic planetary nebulae. We interpret these differences as evidence for the acceleration of the nebular shells during the early evolution of these intrinsically bright planetary nebulae. As is the case for planetary nebulae in the Magellanic Clouds, the acceleration of the nebular shells appears to be the direct result of the evolution of the central stars.
The Astrophysical Journal 12/2008; 689(1):203. DOI:10.1086/592737 · 6.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present a powerful new tool to disentangle the 3-D geometry and kinematic structure of gaseous nebulae. The method consists of combining commercially available digital animation software to simulate the 3-D structure and expansion pattern of the nebula with a dedicated, purpose built rendering software and graphical user interface that produce the final images and long slit spectra which are compared to the real data.
Proceedings of the International Astronomical Union 04/2006; 234:517-518. DOI:10.1017/S1743921306004029
[Show abstract][Hide abstract] ABSTRACT: We present a powerful new tool to analyse and disentangle the 3-D geometry and kinematic structure of gaseous nebulae. The method consists in combining commercially available digital animation software to simulate the 3-D structure and expansion pattern of the nebula with a dedicated, purpose-built rendering software that produces the final images and long slit spectra which are compared to the real data. We show results for the complex planetary nebulae NGC 6369 and Abell 30 based on long slit spectra obtained at the San Pedro Mártir Observatory.
Revista mexicana de astronomía y astrofísica 01/2006; · 1.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Presentamos una nueva herramienta para desenredar la geometráa 3-D y la estructura cinemática de nebulosas gaseosas. El método consiste en combinar software comercial para animación digital para simular la estructura 3-D y el modo de expansión de la nebulosa junto con un software de representación gráfica de imagenes y per les de línea dise~nado especialmente para el propósito.
[Show abstract][Hide abstract] ABSTRACT: We present a powerful new tool to disentangle the 3-D geometry and
kinematic structure of gaseous nebulae. The method consists of combining
commercially available digital animation software to simulate the 3-D
structure and expansion pattern of the nebula with a dedicated, purpose
built rendering software that produces the final images and long slit
spectra which are compared to the real data. In this contribution we
show results for the complex planetary nebula NGC369 based on long slit
spectra obtained at the San Pedro Mártir observatory.
[Show abstract][Hide abstract] ABSTRACT: We present an alternative model for the formation of fast low-ionization emission regions (FLIERs) in planetary nebulae that is able to account for many of their attendant characteristics and circumvent the problems on the collimation/formation mechanisms found in previous studies. In this model, the section of the stellar wind flowing along the symmetry axis carries less mechanical momentum than at higher latitudes, and temporarily develops a concave or inverted shock geometry. The shocked ambient material is thus refracted towards the symmetry axis, instead of away from it, and accumulates in the concave section. The reverse is true for the outflowing stellar wind, which in the reverse shock is refracted away from the axis. It surrounds the stagnation region of the bow-shock and confines the trapped ambient gas. The latter has time to cool and is then compressed into a dense "stagnation knot" or "stagnation jet". In the presence of a variable stellar wind these features may eventually overrun the expanding nebular shell and appear as detached FLIERs. We present representative two and three-dimensional hydrodynamic simulations of the formation and early evolution of stagnation knots and jets and compare their dynamical properties with those of FLIERs in planetary nebulae. Subject Headings: hydrodynamics - ISM: jets and outflows - ISM: kinematics and dynamics - planetary nebulae: FLIERs and stagnation knots Comment: accepted for publication in The Astrophysical Journal
The Astrophysical Journal 04/2001; 556(2). DOI:10.1086/321592 · 6.28 Impact Factor