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1.
We present [N  ii ] and H α images and high-resolution long-slit spectra of the planetary nebula IC 4846, which reveal, for the first time, its complex structure and the existence of collimated outflows. The object consists of a moderately elongated shell, two (and probably three) pairs of collimated bipolar outflows at different orientations, and an attached circular shell. One of the collimated pairs is constituted by two curved, extended filaments the properties of which indicate a high-velocity, bipolar precessing jet. A difference of ≃10 km s−1 is found between the systemic velocity of the precessing jets and the centroid velocity of the nebula, as recently reported for Hu 2-1. We propose that this difference is as a result of orbital motion of the ejection source in a binary central star. The orbital separation of 30 au and period 100 yr estimated for the binary are similar to those in Hu 2-1, linking the central stars of both planetary nebulae to interacting binaries. Extraordinary similarities also exist between IC 4846 and the bewildering planetary nebula NGC 6543, suggesting a similar formation history for both objects.  相似文献   

2.
We present Hα, [N  II ]6583 and 6-cm continuum images of the emission line nebula K 3-35. The optical images reveal an extended nebula (size ≃ 11 × 9 arcsec2 in [N  II ]) in which most of the emission originates in a very narrow (width 0.7–1.3 arcsec) S-shaped region which extends almost all along the nebula (≃ 7 arcsec). The 6-cm continuum emission also arises in this narrow region, which is characterized by an exceedingly high point-symmetry and systematic and continuous changes of the orientation with respect to the nebular centre. The properties of the narrow region suggest that it represents a system of precessing bipolar jet-like components. Two low-excitation, compact bipolar knots near the tips of the jet-like components are observed in the deduced [N  II ]/Hα image ratio. These knots may be generated by the interaction of the collimated outflows with surrounding material. A comparison of the optical and radio images shows the existence of differential extinction within the nebula. Maximum extinction is observed in a disc-like region which traces the equator of the elliptical shell previously observed at 20-cm continuum. All available data strongly suggest that K 3-35 is a very young planetary nebula in which we could be observing the first stages of the formation of collimated outflows and point-symmetric structures typically observed in planetary nebulae. The properties of the jet-like components in K 3-35 are in good agreement with models of binary central stars in which highly collimated outflows originate either from a precessing accretion disc or via magnetic collimation in a precessing star.  相似文献   

3.
We present a detailed kinematical analysis of the young compact hourglass-shaped planetary nebula Hb 12. We performed optical imaging and long-slit spectroscopy of Hb 12 using the Manchester echelle spectrometer with the 2.1-m San Pedro Mártir telescope. We reveal, for the first time, the presence of end caps (or knots) aligned with the bipolar lobes of the planetary nebula shell in a deep [N  ii ]λ6584 image of Hb 12. We measured from our spectroscopy radial velocities of  ∼120 km s−1  for these knots.
We have derived the inclination angle of the hourglass-shaped nebular shell to be ∼65° to the line of sight. It has been suggested that Hb 12's central star system is an eclipsing binary which would imply a binary inclination of at least 80°. However, if the central binary has been the major shaping influence on the nebula, then both nebula and binary would be expected to share a common inclination angle.
Finally, we report the discovery of high-velocity knots with Hubble-type velocities, close to the core of Hb 12, observed in Hα and oriented in the same direction as the end caps. Very different velocities and kinematical ages were calculated for the outer and inner knots showing that they may originate from different outburst events.  相似文献   

4.
We present high-resolution echelle and long-slit spectra and broad-band ( R , I ) images of the very young planetary nebula K 3-35. Several emission lines are identified, including the He  ii  4686 line and strong [N  ii ]6548, 6583 and [O  iii ]4959, 5007 emissions [ I ([N  ii ])/ I (H α )≃5.5, I ([O  iii ])/ I (H β )≃30]. A systemic velocity V LSR≃10±2 km s−1 for K 3-35 is obtained from the optical emission lines. Two different kinematic components are identified in the nebula. One of them is probably related to the elliptical envelope previously observed. The second component exhibits systematic changes of the radial velocity with position, and a relatively small velocity width. This component may be attributed to the precessing jet-like outflows previously identified. The R and I images and the deduced R − I colour map strongly support the existence of a dense, partially neutral disc-like region in the equatorial plane of the nebula, which probably represents an equatorial density enhancement in a previously ejected slow wind. Diagnostic diagrams for line intensity ratios in K 3-35 and collimated components of other planetary nebulae suggest that the emission spectrum of this kind of structure is a combination of radiative and shock excitation, in agreement with recent models of shocks in a strongly photoionized medium.  相似文献   

5.
We have undertaken echelle spectroscopy and narrow-band line imaging of the bipolar planetary nebula M 1-8. This has permitted us to map the outflow in [N  ii ]λλ 6548+6583 Å, Hα, and in the v = 1–0 S(1) transition of H2 at λ 2.122 μm. It has also permitted us to acquire high-resolution spectra for [N  ii ]λ 6583 Å, Hα and He  ii λ 6560 Å. Our observations support the results of a previous 2MASS analysis by two of the authors (J. P. Phillips and G. Ramos-Larios), and confirm that there is strong H2 emission outside of the ionized zone, as well as along the major axis of the outflow. Finally, we have investigated the spatial structure of the outflow in low and high excitation lines, and noted evidence for strong ionization stratification within the envelope of the source. We also note that major axis spectra show asymmetries attributable to outflow along the lobes, oriented at an angle i ∼ 35°–40° to the line of sight. Asymmetries along the minor axis, by contrast, appear to be associated with the central collimating disc, and may be interpretable in terms of asymmetries in disc structure, or rotation at an angular velocity of Ω∼ 1.4 10−12 rad s−1. If the disc arises due to common-envelope evolution, then it seems that angular momentum constraints must be relatively tight, and can only be satisfied given fairly extreme physical assumptions (such as low disc mass, high primary star mass, a low distance to the source and so forth).  相似文献   

6.
Narrow-band H α and [N  ii ] images and high-dispersion spatially resolved echelle spectroscopy of the planetary nebula NGC 6891 are presented. These observations show a great wealth of structures. The bright central nebula is surrounded by an attached shell and a detached outer halo. Both the inner and intermediate shells can be described as ellipsoids with similar major to minor axial ratios, but different spatial orientations. The kinematical ages of the intermediate shell and halo are 4800 and 28 000 yr, respectively. The intershell time lapse is in good agreement with the evolutionary interpulse time lapse. A highly collimated outflow is observed to protrude from the tips of the major axis of the inner nebula and impact on the outer edge of the intermediate shell. Kinematics and excitation of this outflow provide conclusive evidence that it is deflected during the interaction with the outer edge of the intermediate shell. At the same time, both the kinematics and the morphology of the intermediate shell appear to be affected by this interaction.  相似文献   

7.
We propose a scheme to classify planetary nebulae (PNe) according to their departure from axisymmetric structure. We consider only departure along and near the equatorial plane, i.e. between the two sides perpendicular to the symmetry axis of the nebula. We consider six types of departure from axisymmetry: (1) PNe where the central star is not at the centre of the nebula; (2) PNe having one side brighter than the other; (3) PNe having unequal size or shape of the two sides; (4) PNe where the symmetry axis is bent, e.g. the two lobes in a bipolar PN are bent toward the same side; (5) PNe where the main departure from axisymmetry is in the outer regions, e.g. an outer arc; and (6) PNe that show no departure from axisymmetry, i.e. any departure, if it exists, is on scales smaller than the scale of blobs, filaments and other irregularities in the nebula. PNe that possess more than one type of departure are classified by the most prominent type. We discuss the connection between departure types and the physical mechanisms that may cause them, mainly resulting from the influence of a stellar binary companion. We find that ∼50 per cent of all PNe in the analysed sample possess large-scale departure from axisymmetry. This number is larger than that expected from the influence of binary companions, namely ∼25–30 per cent. We argue that this discrepancy comes from many PNe where the departure from axisymmetry, mainly unequal size, shape or intensity, results from the presence of long-lived and large (hot or cool) spots on the surface of their asymptotic giant branch progenitors. Such spots locally enhance the mass-loss rate, leading to a departure from axisymmetry, mainly near the equator, in the descendent PN.  相似文献   

8.
Continuum-subtracted dereddened images in the light of several atomic lines show the presence of an extended bipolar nebula surrounding η Carinae with size ∼100×45 arcsec2 (1.3×0.5 pc2). This feature is best delineated in [O  iii ] 5007. The geometrical disposition and mass of the shell suggest that it was formed by mass ejections from η Carinae. The dynamic age of the nebula is ∼13 000/ V 7 yr, where V 7 is the mean expansion velocity in 100 km s−1, and its mass is between 5 and 10 M⊙. The nebula is photoionized and composed of unprocessed material. The major axes of the nebula and of the Homunculus are nearly perpendicular. We also report the discovery of elongated emission knots prominent in [N  ii ] located 64 to 100 arcsec away from η Carinae, which implies that they were ejected either centuries ago or at a more recent date but with extremely large velocities.  相似文献   

9.
With the Hamilton echelle spectrograph at the Lick Observatory, emission-rich spectral lines of the planetary nebula NGC 6543 were secured in the wavelength range from 3550 to 10 100 Å. We chose two bright regions, ∼8 arcsec east and ∼13 arcsec north of the central star, the physical conditions and chemical abundances of which may differ as a result of the different physical characteristics involving the mass ejection of different epochs. By combining Hamilton echelle observations with archive UV data secured with the International Ultraviolet Explorer ( IUE ), we obtain improved diagnostics and chemical compositions for the two observed regions. The diagnostic diagram gives the average value of T e=8000∼8300 K, and the electron number density near N e∼5000 cm−3 for most ions, while some low-excitation lines indicate much higher temperatures, i.e. T e∼10 000 K. With the construction of a photoionization model, we try to fit the observed spectra in a self-consistent way: thus, for most elements, we employ the same chemical abundances in the nebular shell; and we adopt an improved Sobolev approximation model atmosphere for the hydrogen-deficient Wolf–Rayet type central star. Within the observational errors, the chemical abundances do not seem to show any positional variation except for helium. The chemical abundances of NGC 6543 appear to be the same as in average planetary nebulae. The progenitor star may have been an object of one solar mass, most of the heavier elements of which were less plentiful than in the Sun.  相似文献   

10.
We examine the possibility of detecting signatures of surviving Uranus/Neptune-like planets inside planetary nebulae. Planets that are not too close to the stars (orbital separation larger than ∼5 au) are likely to survive the entire evolution of the star. As the star turns into a planetary nebula, it has a fast wind and strong ionizing radiation. The interaction of the radiation and wind with a planet may lead to the formation of a compact condensation or tail inside the planetary nebula, which emits strongly in H α , but not in [O  iii ]. The position of the condensation (or tail) will change over a time-scale of ∼10 yr. Such condensations might be detected with currently existing telescopes.  相似文献   

11.
I argue that the large-scale departure from axisymmetry of the η Carinae nebula can be explained by the binary star model of η Carinae. The companion diverts the wind blown by the primary star, by accreting from the wind and possibly by blowing its own collimated fast wind (CFW). The effect of these processes depends on the orbital separation, and hence on the orbital phase of the eccentric orbit. The variation of the mass outflow from the binary system with the orbital phase leads to a large-scale departure from axisymmetry along the equatorial plane, as is observed in η Carinae. I further speculate that such a companion may have accreted a large fraction of the mass that was expelled in the Great Eruption of 1850 and the Lesser Eruption of 1890. The accretion process was likely to form an accretion disc, with the formation of a CFW, or jets, on the two sides of the accretion disc. The CFW may have played a crucial role in the formation of the two lobes.  相似文献   

12.
High-resolution long-slit Hα spectra of the shell of the old nova DQ Herculis have been obtained with the William Herschel Telescope using the ISIS spectrograph. An equatorial expansion velocity of  370 ± 14   km s−1  is derived from the spectra which, in conjunction with a narrow-band Hα image of the remnant, allows a distance estimate of 525 ± 28 pc. An equatorial ring which exhibits enhanced [N  ii ] emission has also been detected and the inclination angle of the shell is found to be     with respect to the line of sight. The spectra also reveal tails extending from the clumps in the shell, which have a radial velocity increasing along their length. This suggests the presence of a stellar wind, collimated in the polar direction, which ablates fragments of material from the clumps and accelerates them into its stream up to a terminal velocity of the order of 800–900 km s−1.  相似文献   

13.
We study the bending of jets in binary stellar systems. A compact companion accretes mass from the slow wind of the mass-losing primary star, forms an accretion disc and blows two opposite jets. These fast jets are bent by the slow wind. Disregarding the orbital motion, we find the dependence of the bending angle on the properties of the slow wind and the jets. Bending of jets is observed in planetary nebulae which are thought to be the descendants of interacting binary stars. For example, in some of these planetary nebulae, the two bubbles (lobes) which are inflated by the two opposite jets are displaced to the same side of the symmetry axis of the nebula. Similar displacements are observed in bubble pairs in the centre of some clusters and groups of galaxies. We compare the bending of jets in binary stellar systems with that in clusters of galaxies.  相似文献   

14.
High-resolution, spatially-resolved profiles of H α , He  ii λ 6560 and [O  iii ] λ 5007 and deep narrow-band CCD images in the H α and [O  iii ] λ 5007 emission lines have been obtained of the planetary nebula (PN) NGC 4361. In addition, VLA-DnC λ 3.6-cm continuum observations are presented. This material allows one to explore in unprecedented detail the morphology and kinematics of this PN. The morphology of this object is complex given the highly filamentary structure of the envelope, which is confirmed to possess a low mass. The halo has a high expansion velocity that yields incompatible kinematic and evolutionary ages, unless previous acceleration of the nebular expansion is considered. However, the most remarkable result from the present observations is the detection of a bipolar outflow in NGC 4361, which is unexpected in a PN with a Population II low-mass-core progenitor. It is shown that shocks resulting from the interaction of the bipolar outflow with the outer shell are able to provide an additional heating source in this nebula.  相似文献   

15.
To investigate the kinematics of the neutral material around the Gum nebula, emission from hydroxyl at 1667 MHz was observed at many positions over the region. Fitting models of expanding shells to these data together with previously published molecular line data shows that the diffuse molecular clouds and cometary globules form a single expanding shell centred on G261−2.5. The mean angular radius is 10.5° and its maximum radius is 14°. The models show that the distance range to the expansion centre is from 200 pc to 500 pc.
The path of the runaway O-star ζ Puppis passed within <0.5° of the expansion centre of the neutral shell ∼1.5 Myr ago. The supernova of the erstwhile binary companion of ζ Puppis is the probable origin of the Gum nebula and the swept up expanding neutral shell. The 500-pc distance to the supernova is adopted as the distance to the expansion centre of the neutral shell. At this distance the energy required to produce the observed expansion could have been met with a single supernova. The radii of the front and back faces of the shell are 130 and 70 pc respectively. The front face is expanding faster than the back face, at 14 and 8.5 km s−1 respectively.
The extent of the neutral shell matches the radio continuum and H α emission of the Gum nebula well. The photoionized gas in the nebula is probably primarily ionized by ζ Puppis, which is still within the neutral shell. No evidence was found for the IRAS -Vela shell as a separate expanding shell.  相似文献   

16.
12CO (1-0) observations of two Southern dark clouds (globules) associated with cometary nebulae GRV 8 (a biconical nebula) and GRV 16 (a conelike nebula) are presented. GRV 8 shows an outflow from the central part of the nebula (where in 2MASS images a star is located, which is perhaps responsible for this outflow); however, both lobes of the outflow are redshifted with a velocity of +1.95 km/s with respect to the molecular cloud. The two opposite redshifted lobes are a rather rare phenomenon that could be explained by the presence of a double star instead of a single one as the engine responsible for the outflow. The two lobes are almost parallel to the axis of symmetry of the biconical nebula. In the case of the conelike nebula GRV 16 we observe a bipolar outflow, where the eastern blueshifted lobe has a velocity of –4 km/s with respect to the molecular cloud, and the western redshifted one has a velocity +2.5 km/s. The outflow has a direction almost coinciding with the axis of symmetry of the conelike nebula. The star associated with the conelike nebula is responsible for this outflow.Published in Astrofizika, Vol. 48, No. 1, pp. 101–112 (February 2005).  相似文献   

17.
Sakurai's object (V4334 Sgr) is a planetary nebula nucleus which is undergoing its final helium shell flash. This is the first of these rare and important events to be observable with non-optical instruments. We report the first radio detection, using a short (2-h) observation with the Very Large Array (VLA) at 4.86 GHz. The radio emission structure is coincident with the 34-arcsec diameter planetary nebula seen in optical emission lines. We find a statistical distance ∼ 3.8 ± 0.6 kpc, with a range of 1.9 <  D  < 5.3 kpc, depending on the planetary nebula (PN) mass. While we have no direct evidence for a new (post-flash) stellar wind, we estimate an upper limit to the mass-loss rate due to any such wind of 1.7 × 10−7 M⊙ yr−1. The number of emitting knots in the radio-visible nebula indicates an electron density of ∼ 2 × 108 m−3 in those knots, and a total emitting ionized mass of ∼ 0.15 M⊙, at an assumed distance of 3.8 kpc. The radio flux density indicates an Hβ flux of ∼ 6 × 10−16 W m−2, suggesting an extinction E ( B  −  V ) ∼ 1.15, comparable with reddening estimates in the direction of V4334 Sgr.  相似文献   

18.
A local void and the accelerating Universe   总被引：1，自引：0，他引：1  
RCW 114 is a filamentary nebula of about 250 arcmin diameter. Based on its large diameter-to-filament-width ratio, the expansion velocity, distance and size of the shell, it has been suggested that RCW 114 is a supernova remnant in its momentum-conserving phase. Confirmation of this identification is important, as the large angular size and extensive optical emission of this object will allow for detailed study to improve our knowledge of supernova remnants and their interaction with the interstellar medium.
We have used the FLAIR instrument on the UK Schmidt Telescope to obtain optical spectra of several filaments in RCW 114. These confirm that the emission is being produced by the interaction of the shock wave of a supernova remnant with the surrounding interstellar medium. We also obtained narrow-band H α +[N  ii ] and [S  ii ] images to examine the spatial variation in ionization structure.  相似文献   

19.
We report the discovery of the first probable Galactic [WN] central star of a planetary nebula (CSPN). The planetary nebula candidate was found during our systematic scans of the AAO/UKST Hα Survey of the Milky Way. Subsequent confirmatory spectroscopy of the nebula and central star reveals the remarkable nature of this object. The nebular spectrum shows emission lines with large expansion velocities exceeding 150 km s−1, suggesting that perhaps the object is not a conventional planetary nebula. The central star itself is very red and is identified as being of the [WN] class, which makes it unique in the Galaxy. A large body of supplementary observational data supports the hypothesis that this object is indeed a planetary nebula and not a Population I Wolf–Rayet star with a ring nebula.  相似文献   

20.
We analyse the distribution of the interstellar matter in the environs of the Wolf-Rayet star LSS 3982 (= WR 85, WN6+OB?) linked to the optical ring nebula RCW 118. Our study is based on neutral hydrogen 21-cm line data belonging to the Southern Galactic Plane Survey (SGPS).
The analysis of the H  i data allowed the identification of a neutral hydrogen interstellar bubble related to WR 85 and the 25-arcmin-diameter ring nebula RCW 118. The H  i bubble was detected at a systemic velocity of −21.5 km s−1, corresponding to a kinematical distance of 2.8 ± 1.1 kpc, compatible with the stellar distance. The neutral structure is about 25 arcmin in radius or 21 ± 8 pc, and is expanding at 9 ± 2 km s−1. The associated ionized and neutral masses amount to  3000 M⊙  . The carbon monoxide (CO) emission distribution depicts a region lacking CO coincident in position and velocity with the H  i structure. The 9.3-arcmin-diameter inner optical nebula appears to be related to the approaching part of the neutral atomic shell. The H  i void and shell are the neutral gas counterparts of the optical bubble and have very probably originated in the action of the strong stellar wind of the central star during the O-type and WR phases on the surrounding interstellar medium. The H  i bubble appears to be in the momentum conserving stage.  相似文献   

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