arXiv subjects

J. Meaburn

Publications and source records attributed to J. Meaburn.

At least 37 records · Page 2Linked to original sources

arXiv2007

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

The ouflowing proper motions of fifteen 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 unambiguous distance to NGC 6302 of 1.17 +/- 0.14 kpc is now determined. Also all the velocity vectors of the fifteen knots (and two others) point back to the central source. An eruptive event from within the central torus, approximately 2200 years previously must have created the high speed lobes of NGC 6302.

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arXiv2007

Optical line profiles of the Helix planetary nebula (NGC 7293) to large radii

New, very long (25'), cuts of spatially resolved profiles of the Halpha and [N II] optical emission lines have been obtained over the face of the Helix planetary nebula, NGC 7293. These directions were chosen to supplement previous similar, though shorter, cuts as well as crossing interesting phenomena in this nebular envelope. In particular one new cut crosses the extremes of the proposed CO J=2-1 emitting outer "torus" shown by Huggins and his co-workers to be nearly orthogonal to its inner counterpart. The second new cut crosses the extensive outer filamentary arcs on either side of the bright nebular core. It is shown that NGC 7293 is composed of multiple bipolar outflows along different axes. Hubble-type outflows over a dynamical timescale of 11,000 years are shown to be occurring for all the phenomena from the smallest He II emitting core out to the largest outer filamentary structure. All must then have been ejected over a short timescale but with a range of ejection velocities

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arXiv2007

Deep optical observations of the interaction of the SS 433 microquasar jet with the W 50 radio continuum shell

Four mosaics of deep, continuum-subtracted, CCD images have been obtained over the extensive galactic radio continuum shell, W 50, which surrounds the remarkable stellar system SS 433. Two of these mosaics in the Halpha+[N II] and [O III] 5007 A emission lines respectively cover a field of ~2.3 x 2.5 degr^2 which contains all of W 50 but at a low angular resolution of 5 arcsec. The third and fourth mosaics cover the eastern (in [O III] 5007 A) and western (in Halpha+[N II]) filamentary nebulosity respectively but at an angular resolution of 1 arcsec. These observations are supplemented by new low dispersion spectra and longslit, spatially resolved echelle spectra. The [O III] 5007 A images show for the first time the distribution of this emission in both the eastern and western filaments while new Halpha+[N II] emission features are also found in both of these regions. Approaching flows of faintly emitting material from the bright eastern filaments of up 100 km/s in radial velocity are detected. The present observations also suggest that the heliocentric systemic radial velocity of the whole system is 56+-2 km/s. Furthermore, very deep imagery and high resolution spectroscopy of a small part of the northern radio ridge of W 50 has revealed for the first time the very faint optical nebulosity associated with this edge. It is suggested that patchy foreground dust along the ~5 kpc sightline is inhibiting the detection of all of the optical nebulosity associated with W 50. The interaction of the microquasar jets of SS 433 with the W 50 shell is discussed.

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arXiv2006

Proof of polar ejection fom the close-binary core of the planetary nebula Abell 63

We present the first detailed kinematical analysis of the planetary nebula Abell 63, which is known to contain the eclipsing close-binary nucleus UU Sge. Abell 63 provides an important test case in investigating the role of close-binary central stars on the evolution of planetary nebulae. Longslit observations were obtained using the Manchester echelle spectrometer combined with the 2.1-m San Pedro Martir Telescope. The spectra reveal that the central bright rim of Abell 63 has a tube-like structure. A deep image shows collimated lobes extending from the nebula, which are shown to be high-velocity outflows. The kinematic ages of the nebular rim and the extended lobes are calculated to be 8400+/-500 years and 12900+/-2800 years, respectively, which suggests that the lobes were formed at an earlier stage than the nebular rim. This is consistent with expectations that disk-generated jets form immediately after the common envelope phase. A morphological-kinematical model of the central nebula is presented and the best-fit model is found to have the same inclination as the orbital plane of the central binary system; this is the first proof that a close-binary system directly affects the shaping of its nebula. A Hubble-type flow is well-established in the morphological-kinematical modelling of the observed line profiles and imagery. Two possible formation models for the elongated lobes of Abell 63 are considered (1) a low-density, pressure-driven jet excavates a cavity in the remnant AGB envelope; (2) high-density bullets form the lobes in a single ballistic ejection event.

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arXiv2006

A deep mosaic of [O III] 5007 A CCD images of the environment of the LBV star P Cygni

A mosaic of six, deep, CCD images in the light of the [O III] 5007 A nebular emission line has been obtained with the 1.3-m Skinakas (Crete) telescope of the filamentary nebulosity surrounding P Cygni. The [O III] 5007 A line discriminates against confusing galactic H II regions along the same sight-lines and the new mosaic did not include the 4.8 mag. central star; a source of artifacts in the previous lower angular resolution observations. New giant `lobes' and `shells' are found to be clustered around P Cygni which must be the relics of historic eruptions between 2400 and up to ~10^5 yr ago.

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arXiv2006

The tails in the Helix Nebula NGC 7293

We have examined a stream-source model for the production of the cometary tails observed in the Helix Nebula NGC 7293 in which a transonic or moderately supersonic stream of ionized gas overruns a source of ionized gas. Hydrodynamic calculations reveal velocity structures which are in good agreement with the observational data on tail velocities and are consistent with observations of the nebular structure. The results also are indicative of a stellar atmosphere origin for the cometary globules. Tail remnants persist for timescales long enough for their identification with faint striations visible in the nebula gas to be plausible.

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arXiv2006

The Dynamical Evolution of Planetary Nebulae After the Fast Wind

In this paper we explore the dynamics of ionization bounded planetary nebulae after the termination of the fast stellar wind. When the stellar wind becomes negligible, the hot, shocked bubble depressurizes and the thermal pressure of the photoionized region, at the inner edge of the swept-up shell, becomes dominant. At this stage the shell tends to fragment creating clumps with comet-like tails and long, photoionized trails in between, while the photoionized material expands back towards the central stars as a rarefaction wave. Once that the photoionized gas fills the inner cavity, it develops a kinematical pattern of increasing velocity from the center outwards with a typical range of velociti es starting from the systemic velocity to 50 Km/s at the edges. The Helix nebula is a clear example of a planetary nebula at this late evolutionary stage.

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arXiv2006

OH maser disc and outflow in the Orion-BN/KL region

MERLIN measurements of 1.6-GHz OH masers associated with Orion-BN/KL are presented, and the data are compared with data on other masers, molecular lines, compact radio continuum sources and infrared sources in the region. OH masers are detected over an area 30 arcsec in diameter, with the majority lying along an approximately E-W structure that extends for approx. 18~arcsec, encompassing the infrared sources IRc2, IRc6 and IRc7. Radial velocities range from -13 to +42 km/s. The system of OH masers shows a velocity gradient together with non-circular motions. The kinematics are modelled in terms of an expanding and rotating disc or torus. The rotation axis is found to be in the same direction as the molecular outflow. There is an inner cavity of radius approx 1300 au with no OH masers. The inner cavity, like the water `shell' masers and SiO masers, is centred on radio source I. Some of the OH masers occur in velocity-coherent strings or arcs that are longer than 5~arcsec (2250 au). One such feature, Stream A, is a linear structure at position angle approx 45 degree, lying between IRc2 and BN. We suggest that these masers trace shock fronts, and have appeared, like a vapour trail, 200 yr after the passage of the runaway star BN. The radio proper motions of BN, source I and source n project back to a region near the base of Stream A that is largely devoid of OH masers. The 1612-MHz masers are kinematically distinct from the other OH masers. They are also more widely distributed and appear to be associated with the outflow as traced by water masers and by the 2.12-micron emission from shocked H2 The magnetic field traced by the OH masers ranges from 1.8 to 16.3 mG, with a possible reversal. No OH masers were found associated with even the most prominent proplyds within 10 arcsec of Theta1 Ori C.

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arXiv2005

The 'Hubble-type' outflows from the high excitation, poly-polar planetary nebula NGC 6302

Spatially resolved profiles of the Halpha and [NII] lines have been obtained at unprecendented signal--to--noise ratios over the outflowing lobes of the high--excitation, poly--polar planetary nebula NGC~6302. A deep image in the light of [NII]6584 A was also obtained of the extremities of the prominent north--western lobe. The Manchester Echelle spectrometer combined with the 2.1--m San Pedro Martir telescope (Mexico) was used for these observations. Firstly, an accurate value of the systemic heliocentric radial velocity of Vsys = -29.8 +/- 1 km/s has been established. Also, from `velocity ellipses' across its diameter from previous observations the parallel--sided north--western lobe is shown to have a circular section with a tilt of its axis to the plane of the sky of 12.8 deg. With this starting point the pv arrays of profiles have been very closely simulated, using the SHAPE code, with Hubble-type outflows. The faint extremities of the north--western outflow are shown to be expanding at 600 km/s. The prominent lobes of NGC~6302 have then been generated in an eruptive event with a dynamical age of 1900 y for the expansion proper-motion distance of 1.04 +/- 0.16 kpc as measured here by comparing a 1956 image with that taken in 2002. Kinematical evidence of a high--speed `skirt' around the nebular core, expanding nearly orthogonally to the lobes, is also presented as are the unusual motions at the western extremities of the NW lobe.

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arXiv2005

The kinematics of the large western knot in the halo of the young planetary nebula NGC 6543

A detailed analysis is presented of the dominant ionised knot in the halo of the planetary nebula NGC 6543. Observations were made at high spectral and spatial resolution of the [OIII] 5007 line using the Manchester echelle spectrometer combined with the 2.1-m San Pedro Martir Telescope. A 20-element multislit was stepped across the field to give almost complete spatial coverage of the knot and surrounding halo. The spectra reveal, for the first time, gas flows around the kinematically inert knot. The gas flows are found to have velocities comparable to the sound speed as gas is photo-evaporated off an ionised surface. No evidence is found of fast wind interaction with the knot and we find it likely that the fast wind is still contained in a pressure-driven bubble in the core of the nebula. This rules out the possibility of the knot having its origin in instabilities at the interface of the fast and AGB winds. We suggest that the knot is embedded in the slowly expanding Red Giant wind and that its surfaces are being continually photoionised by the central star.

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arXiv2005

The creation of the Helix planetary nebula (NGC 7293) by multiple events

A deep, continuum-subtracted, image of NGC 7293 has been obtained in the light of the Halpha+[N II] emission lines. New images of two filamentary halo stuctures have been obtained and the possible detection of a collimated outflow made. Spatially resolved, longslit profiles of the Halpha+[N II] lines have been observed across several of these features with the MES combined with the SPM 2.1m telescope; these are compared with the [N II]6584, [O III]5007, HeII 6560 and Halpha profiles obtained over the nebular core. The central HeII emission is originating in a ~0.34pc diameter spherical volume expanding at <=12km/s which is surrounded, and partially coincident with an [O III] emitting inner shell expanding at 12km/s. The bright helical structure surrounding this inner region is modelled as a bi-polar nebula with lobe expansions of 25km/s whose axis is tilted at 37deg to the sight line but with a toroidal waist itself expanding at 14 km/s. These observations are compared with the expectations of the interacting two winds model for the formation of PNe. Only after the fast wind has switched off could this global velocity structure be generated. Ablated flows must complicate any interpretation. It is suggested that the clumpy nature of much of the material could play a part in creating the radial `spokes' shown here to be apparently present close to the central star. These `spokes' could in fact be the persistant tails of cometary globules whose heads have now photo-evaporated completely. A halo arc projecting from the north-east of the bright core has a conterpart to the south-east. Anomolies in the position-velocity arrays of line profiles could suggest that these are part of an expanding disc not aligned with the central helical structure though expanding bi-polar lobes along a tilted axis are not ruled out.

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arXiv2005

The global kinematics of the Dumbbell planetary nebula (NGC 6853, M27, PN G060.8-03.6)

Spatially resolved profiles of the HeII 6560 A, Halpha and [N II] 6548 & 6584 A nebular emission lines have been obtained in two orthogonal long cuts over the Dumbbell planetary nebula. The central HeII 6560 A emitting volume of the bright dumbbell structure is shown to be particularly inert with an expansion velocity of <= 7 km/s. This is enveloped by an inner [O III] 5007 A emitting shell expanding at 13 km/s, an outer [O III] 5007 A shell expanding at 31 km/s which is on the inside of the outer [N II] 6584 A emitting shell expanding at 35 km/s. A new Halpha + [N II] 6548 & 6584 A continuum-subtracted image of the 15' diameter halo has also been compared with recent proper motion measurements of the central star and the present line profiles from the halo's inner edge. Interaction with the ambient interstellar medium is suggested. The bright [N II] 6584 A emitting shell must be running into this relatively inert halo with a differential velocity of >= 25 km/s. The present results are compared with currents models for the creation of planetary nebulae.

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arXiv2004

Rapid GRB Follow-up with the 2-m Robotic Liverpool Telescope

We present the capabilities of the 2-m robotic Liverpool Telescope (LT), owned and operated by Liverpool John Moores University and situated at ORM, La Palma. Robotic control and scheduling of the LT make it especially powerful for observations in time domain astrophysics including: (i) rapid response to Targets of Opportunity: Gamma Ray Bursts, novae, supernovae, comets; (ii) monitoring of variable objects on timescales from seconds to years, and (iii) observations simultaneous or coordinated with other facilities, both ground-based and from space. Following a GRB alert from the Gamma Ray Observatories HETE-2, INTEGRAL and Swift we implement a special over-ride mode which enables observations to commence in about a minute after the alert, including optical and near infrared imaging and spectroscopy. In particular, the combination of aperture, site, instrumentation and rapid response (aided by its rapid slew and fully-opening enclosure) makes the LT excellently suited to help solving the mystery of the origin of optically dark GRBs, for the investigation of short bursts (which currently do not have any confirmed optical counterparts) and for early optical spectroscopy of the GRB phenomenon in general. We briefly describe the LT's key position in the RoboNet-1.0 network of robotic telescopes.

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arXiv2004

The kinematics of the bi-lobal supernova remnant G 65.3+5.7 - Paper II

Further deep, narrow-band images in the light of [O III] 5007 A have been added to the previous mosaic of the faint galactic supernova remnant G 65.3+5.7. Additionally longslit spatially resolved [O III] 5007 A line profiles have been obtained at sample positions using the Manchester Echelle Spectrometer at the San Pedro Martir observatory. The remnant is shown to be predominantly bi-lobal with an EW axis for this structure. However, a faint additional northern lobe has now been revealed. Splitting of the profiles along the slit lengths, when extrapolated to the remnant's centre, although uncertain suggests that the expansion velocity of this remnant is between 124 and 187 km/s ie much lower than the 400 km/s previously predicted for the forward shock velocity from the X-ray emission. An expansion proper motion measurement of 2.1+-0.4 arcsec in 48 years for the remnant's filamentary edge in the light of Halpha+[N II] has also been made. When combined with an expansion velocity of ~155 km/s, a distance of ~800 pc to G 65.3+5.7 is derived. Several possibilities are considered for the large difference in the expansion velocity measured here and the 400 km/s shock velocity required to generate the X-ray emission. It is also suggested that the morphology of the remnant may be created by a tilt in the galactic magnetic field in this vicinity.

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arXiv2004

Candidates for giant lobes projecting from the LBV stars P Cygni and R 143

Deep, wide-field, continuum-subtracted, images in the light of the Halpha+[NII] 6548 & 6584 A and [O III] 5007 A nebular emission lines have been obtained of the environment of the Luminous Blue Variable (LBV) star P Cygni. A previously discovered, receding, nebulous filament along PA 50 deg has now been shown to extend up to 12' from this star. Furthermore, in the light of [O III] 5007 A, a southern counterpart is discovered as well as irregular filaments on the opposite side of P Cygni. Line profiles from this nebulous complex indicate that this extended nebulosity is similar to that associated with middle-aged supernova remnants. However, there are several indications that it has originated in P Cygni and is not just a chance superposition along the same sight-line. This possibility is explored here and comparison is made with a new image of the LBV star R 143 in the LMC from which similar filaments appear to project. The dynamical age of the P Cygni giant lobe of ~5x10^{4} yr is consistent with both the predicted and observed durations of the LBV phases of 50M stars after they have left the main sequence. Its irregular shape may have been determined by the cavity formed in the ambient gas by the energetic wind of the star, and shaped by a dense torus, when on the main sequence. The proper motion and radial velocity of P Cygni, with respect to its local environment, could explain the observed angular and kinematical shifts of the star compared with the giant lobe.

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arXiv2003

High speed outflows driven by the 30 Doradus starburst

Echelle spectroscopy has been carried out towards a sample region of the halo of the giant HII region 30 Doradus in the Large Magellanic Cloud. This new kinematical data is the amongst the most sensitive yet obtained for this nebula and reveals a wealth of faint, complex high speed features. These are interpreted in terms of localised shells due to individual stellar winds and supernova explosions, and collections of discrete knots of emission that still retain the velocity pattern of the giant shells from which they fragmented. The high speed velocity features may trace the base of the superwind that emanates from the 30 Doradus starburst, distributed around the super star cluster R136.

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arXiv2002

Kinematics of the Pencil Nebula (RCW 37) and its association with the young Vela supernova remnant RX J0852.0-4622

The association between the Pencil nebula (RCW 37, NGC 2736), the Vela X-ray fragment D/D' and the recently discovered new X-ray supernova remnant (RX J0852.0-4622) in Vela is investigated. Recently published Chandra images of D/D' are compared with optical images of RCW 37 and confirm the close association of the two objects. New optical line profiles of RCW 37 from an extended slit position passing through this unusual optical nebula are presented. They reveal a partial velocity ellipse with expansion velocities of around 120 km/s. Various scenarios for the origin of the nebula are considered and the evidence of a link with RX J0852.0-4622 is reviewed. A funnel of gas similar to those in the Crab and DEM34a SNRs is not ruled out but a more plausible explanation may be that a `wavy sheet' is responsible. We suggest that RX J0852.0-4622 is located within the older larger Vela SNR and that some of the X-ray gas from RX J0852.0-4622 has collided with the dense HI wall of the older remnant. This gives rise to the morphology and velocity structure of the optical emission and explains the unusual X-ray emission from this portion of the supernova remnant. If our hypothesis is correct, a distance prediction of 250 +/- 30 pc can be made, based on recent measurements of the distance to the old Vela SNR. This is at the lower end of the range of distances quoted in the literature would confirm unusual nature of this young nearby supernova remnant.

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arXiv2002

Two jets from the Orion (M42) `proplyds' - kinematics, morphologies and origins

A spatially unresolved velocity feature, with an approaching radial velocity of ~100 km/s with respect to the systemic radial velocity, in a position-velocity array of [O III] 5007 line profiles is identified as the kinematical counterpart of a jet from the proplyd LV 5 (158-323) in the core of the Orion Nebula. The only candidate in HST imagery for this jet appears to be a displaced, ionized knot. Also an elongated jet projects from the proplyd GMR 15 (161-307). Its receding radial velocity difference appears at ~80 km/s in the same position-velocity array. A `standard' model for jets from young, low mass stars invokes an accelerating, continuous flow outwards with an opening angle of a few degrees. Here an alternative explanation is suggested which may apply to some, if not all, of the proplyd jets. In this, a `bullet' of dense material is ejected which ploughs through dense circumstellar ambient gas. The decelerating tail of material ablated from the bullet's surface would be indistinguishable from a continuously emitted jet in current observations.

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