arXiv subjects

Brent Miszalski

Publications and source records attributed to Brent Miszalski.

50 records · Page 3Linked to original sources

arXiv2012

An Interacting Binary System Powers Precessing Outflows of an Evolved Star

Stars are generally spherical, yet their gaseous envelopes often appear non-spherical when ejected near the end of their lives. This quirk is most notable during the planetary nebula phase when these envelopes become ionized. Interactions among stars in a binary system are suspected to cause the asymmetry. In particular, a precessing accretion disk around a companion is believed to launch point-symmetric jets, as seen in the prototype Fleming 1. Our discovery of a post common-envelope binary nucleus in Fleming 1 confirms that this scenario is highly favorable. Similar binary interactions are therefore likely to explain these kinds of outflows in a large variety of systems.

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arXiv2012

A carbon dwarf wearing a Necklace: first proof of accretion in a post-common-envelope binary central star of a planetary nebula with jets

The formation of collimated outflows or jets in planetary nebulae (PNe) is not well understood. There is no evidence for active accretion disks in PNe making it difficult to decide which of several proposed jet formation scenarios may be correct. A handful of wide binary central stars of PNe are known to have accreted carbon and slow neutron capture (s-process) enhanced material, the immediate progenitors of barium stars, however no close binary analogues are known to have passed through a common-envelope (CE) phase. Here we present spectroscopy of The Necklace taken near lightcurve minimum that for the first time reveals a carbon-rich (C/O > 1) companion, a carbon dwarf, in a post-CE central star. As unevolved stars do not produce carbon, the chemical enhancement of the secondary can only be explained by accretion from the primary. Accretion most likely happened prior to the CE phase via wind accretion as not enough material can be accreted during the short CE phase. The pair of jets in The Necklace, which are observed to be older than the PN, are therefore likely to have been launched from an accretion disk around the companion during this early accretion phase. This discovery adds significant weight to the emerging scenario that jets in post-CE PNe are primarily launched by an accretion disk around a main-sequence companion before the CE phase.

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arXiv2012

IC4663: the first unambiguous [WN] Wolf-Rayet central star of a planetary nebula

Several [WC]-type central stars of planetary nebulae (PNe) are known to mimic the spectroscopic appearance of massive carbon-rich or WC-type Wolf-Rayet stars. In stark contrast, no [WN]-type central stars have yet been identified as clear-cut analogues of the common nitrogen-rich or WN-type Wolf-Rayet stars. We have identified the [WN3] central star of IC4663 to be the first unambiguous example in PNe. The low luminosity nucleus and an asymptotic giant branch (AGB) halo surrounding the main nebula prove the bona-fide PN nature of IC4663. Model atmosphere analysis reveals the [WN3] star to have an exotic chemical composition of helium (95%), hydrogen (<2%), nitrogen (0.8%), neon (0.2%) and oxygen (0.05%) by mass. Such an extreme helium-dominated composition cannot be predicted by current evolutionary scenarios for hydrogen deficient [WC]-type central stars. Only with the discovery of IC4663 and its unusual composition can we now connect [WN] central stars to the O(He) central stars in a second H-deficient and He-rich evolutionary sequence, [WN]->O(He), that exists in parallel to the carbon-rich [WC]->PG1159 sequence. This suggests a simpler mechanism, perhaps a binary merger, can better explain H-deficiency in PNe and potentially other H-deficient/He-rich stars. In this respect IC4663 is the best supported case for a possible merged binary central star of a PN.

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arXiv2012

The enigmatic central star of the planetary nebula PRTM 1

The central star of the planetary nebula PRTM 1 (PN G243.8-37.1) was previously found to be variable by M. Pena and colleagues. As part of a larger programme aimed towards finding post common-envelope binary central stars we have monitored the central star of PRTM 1 spectroscopically and photometrically for signs of variability. Over a period of ~3 months we find minimal radial velocity (<10 km/s) and photometric (< 0.2 mag) variability. The data suggest a close binary nucleus can be ruled out at all but the lowest orbital inclinations, especially considering the spherical morphology of the nebula which we reveal for the first time. Although the current data strongly support the single star hypothesis, the true nature of the central star of PRTM 1 remains enigmatic and will require further radial velocity monitoring at higher resolution to rule out a close binary. If in the odd case that it is a close binary, it would be the first such case in a spherical planetary nebula, in contradiction to current thinking.

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arXiv2012

Discovery of New Faint Northern Galactic Planetary Nebulae

We present the discovery of 6 nebular objects made by amateur astronomers. Four of these discoveries are clearly planetary nebulae (PNe), one is a possible PN, and another is a likely H II region. The bipolar nebula Ou4 presents the largest angular extent ever found : over one degree on the sky! We consider various scenarios that could explain such a nebula. Ou4 could be one of the nearest PNe known, though its possible PN nature will need confirmation.

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arXiv2011

Ongoing surveys for close binary central stars and wider implications

Binary central stars have long been invoked to explain the vexing shapes of planetary nebulae (PNe) despite there being scant direct evidence to support this hypothesis. Modern large-scale surveys and improved observing strategies have allowed us to significantly boost the number of known close binary central stars and estimate at least 20% of PNe have close binary nuclei that passed through a common-envelope (CE) phase. The larger sample of post-CE nebulae appears to have a high proportion of bipolar nebulae, low-ionisation structures (especially in SN1987A-like rings) and polar outflows or jets. These trends are guiding our target selection in ongoing multi-epoch spectroscopic and photometric surveys for new binaries. Multiple new discoveries are being uncovered that further strengthen the connection between post-CE trends and close binaries. These ongoing surveys also have wider implications for understanding CE evolution, low-ionisation structure and jet formation, spectral classification of central stars, asymptotic giant branch (AGB) nucleosynthesis and dust obscuration events in PNe.

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arXiv2011

When asymmetric cosmic bubbles betray a difficult marriage: the study of binary central stars of Planetary Nebulae

Planetary Nebulae represent a powerful window into the evolution of low-intermediate mass stars that have undergone extensive mass-loss. The nebula manifests itself in an extremely wide variety of shapes, but exactly how the mass lost is shaped into such a diverse range of morphologies is still highly uncertain despite over thirty years of vigorous debate. Binaries have long been thought to offer a solution to this vexing problem. Now, thanks to recent surveys and improved observing strategies, it appears clearly that a binary channel, in particular common-envelope (CE) evolution, is responsible for a large fraction of planetary nebulae. Moreover, as planetary nebulae are just "fresh out of the oven" compared to other post-CE systems, they provide invaluable contributions to the study of common-envelope evolution and to the formation of jets in binary systems. Our studies have also started to identify strong links between binarity and morphology, including a high proportion of bipolar nebulae and rings of low ionisation filaments resembling SN 1987A. Equally important are the newly found binary CSPN with intermediate periods, which appear linked to chemically peculiar stars whose composition was modified by binary evolution. Their study may also reveal much information on mass and angular momentum transfer processes in binary stars. Here we show examples of four PNe for which we have discovered their binary nature, including the discovery of a rare case of a barium-rich cool central star.

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arXiv2011

Improved prospects for the detection of new Large Magellanic Cloud planetary nebulae

The Large Magellanic Cloud (LMC) contains the nearest large extragalactic population of planetary nebulae (PNe). A shallow viewing angle and low interstellar reddening towards the LMC potentially means a larger, more complete flux-limited population can be assembled than for any other galaxy. These advantages appear to be reflected by the small gap between the catalogued ($\sim$700 PNe) and estimated ($1000\pm250$ PNe) population size. With more detailed multi-wavelength studies the catalogued number of LMC PNe may fall, potentially widening this gap. We demonstrate here that the gap can be further bridged with improved optical and near-infrared imaging surveys. We present three [O III]-selected PNe discovered from ESO WFI observations of the 30 Doradus region and one serendipitous discovery from near-infrared Vista Magellanic Cloud (VMC) survey observations. The WFI PNe have resolved [O III] and H$α$ nebulae that verify their PN nature and their [O III] fluxes place them 6--7 mag ($m_{5007}=20$--21 mag) fainter than the bright-end of the planetary nebula luminosity function (PNLF). Their faintness, small angular size and surrounding complex emission-line background explains why previous H$α$ surveys of the region did not select them. We estimate there may be as many as 50--75 similar PNe awaiting discovery in the central $5\times5$ degrees of the LMC. The VMC survey routinely detects PNe as red resolved nebulae that may allow some of this expected population to be recovered without traditional narrow-band imaging surveys. We demonstrate this potential with the first new VMC-selected PN which has a rare Wolf-Rayet [WC9]--[WC11] central star.

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arXiv2011

PHR1315-6555: a bipolar planetary nebula in the compact Hyades-age open cluster ESO96-SC04

We present a detailed study of a bipolar, possible Type I planetary nebula (PN), PHR1315-6555 (PN G305.3-03.1), that was discovered as part of the Macquarie/AAO/Strasbourg H-alpha planetary nebula project (MASH) and that we considered at the time was an excellent candidate for membership of the distant, compact, intermediate-age open cluster, ESO 96-SC04. The strong evidence for this association is presented here making this the only known example of a PN physically associated with a Galactic open cluster. Cluster membership is extremely important as it allows for very precise estimates of the fundamental properties of the PN as the cluster is at a known distance. The PN was discovered by one of us (QAP) during systematic MASH searches for new Galactic PNe of the AAO/UKST H-alpha survey and had been missed in earlier broadband surveys, including specific CCD studies of the host cluster. We present original discovery images and CTIO 4m MOSAIC-II camera follow-up narrow-band images that reveal its bipolar morphology. We also present: (i) low-resolution optical spectra that spectroscopically confirm the PN; (ii) accurate radial velocities of the PN and cluster stars from high resolution spectroscopy which show they are consistent; and (iii) a reliable, independent distance estimate to the PN using a robust PN distance indicator which agrees with the published cluster distance to within the errors. We also provide preliminary estimates of basic PN properties and abundance estimates from deeper spectra that show it to be of possible Type I chemistry. This is also consistent its estimated turn-off mass. Taken together these findings present a powerful case for clear physical association between the PN and host cluster. Results for this association will be of considerable interest to specialists across differing astrophysical disciplines, including PNe, white dwarfs, and open clusters.

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arXiv2011

Newly Discovered Wolf-Rayet and Weak Emission-Line Central Stars of Planetary Nebulae

We present spectra of 32 previously unpublished confirmed and candidate Wolf-Rayet ([WR]) and weak emission-line (WELS) central stars of planetary nebulae (CSPNe). Eighteen stars have been discovered in the Macquarie/AAO/Strasbourg H-Alpha (MASH) PN survey sample, and we have also uncovered 14 confirmed and candidate [WR]s and WELS among the CSPNe of previously known PNe. Spectral classifications have been undertaken using both the Acker & Neiner and Crowther, De Marco & Barlow schemes. Twenty-two members in this sample are identified as probable [WR]s; the remaining 10 appear to be WELS. Observations undertaken as part of the MASH spectroscopic survey have now increased the number of known [WR]s by ~30 per cent. This will permit a better analysis of [WR] subclass distribution, metallicity effects, and evolutionary sequences in these uncommon objects.

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arXiv2010

Planetary Nebulae towards the Galactic bulge. I. [OIII] fluxes

We present [OIII]λ5007 fluxes and angular diameters for 435 Planetary Nebulae (PN) in the central 10' x 10' region towards the Galactic bulge. Our sample is taken from the new discoveries of the MASH PN surveys as well as previously known PN. This sample accounts for 80% of known PN in this region. Fluxes and diameters are measured from narrow-band imaging with the MOSAIC-II camera on the 4-m Blanco telescope at the Cerro-Tololo Inter-American Observatory. This is the largest (~60 square degrees), uniform [OIII]λ5007 survey of the inner Galactic bulge ever undertaken. 104 of the objects have measured [OIII]λ5007, [OIII]λ4959, Hα or Hβ fluxes from the literature, which we use to undertake a detailed comparison to demonstrate the integrity of our new fluxes. Our independent measurements are in excellent agreement with the very best literature sources over two orders of magnitude, while maintaining good consistency over five orders of magnitude. The excellent resolution and sensitivity of our data allows not only for a robust set of homogenous PN fluxes, but provides greater detail into their intricate, otherwise undetermined [OIII]λ5007 morphologies. These new, extensive measurements significantly increase the sample of reliable [OIII]λ5007 fluxes for Galactic bulge PN making it a valuable resource and a prelude to the construction of our new Galactic bulge Planetary Nebula luminosity function (Paper II).

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arXiv2010

Multi-wavelength diagnostic properties of Galactic Planetary Nebulae detected by GLIMPSE-I

We uniformly analyze 136 optically detected PNe and candidates from the GLIMPSE-I survey in order to to develop robust, multi-wavelength, classification criteria to augment existing diagnostics and provide pure PN samples. PNe represent powerful astrophysical probes. They are important dynamical tracers, key sources of ISM chemical enrichment, windows into late stellar evolution, and potent cosmological yardsticks. But their utility depends on separating them unequivocally from the many nebular mimics which can strongly resemble bona fide PNe in traditional optical images and spectra. We merge new PNe from the carefully evaluated, homogeneous MASH-I and MASH-II surveys, which offer a wider evolutionary range of PNe than hitherto available, with previously known PNe classified by SIMBAD. Mid-infrared (MIR) measurements vitally complement optical data because they reveal other physical processes and morphologies via fine-structure lines, molecular bands and dust. MIR colour-colour planes, optical emission line ratios and radio fluxes show the unambiguous classification of PNe to be complex, requiring all available evidence. Statistical trends provide predictive value and we offer quantitative MIR criteria to determine whether an emission nebula is most likely to be a PN or one of the frequent contaminants such as compact HII regions or symbiotic systems. Prerequisites have been optical images and spectra but MIR morphology, colours, environment and a candidate's MIR/radio flux ratio provide a more rigorous classification. Our ultimate goal is to recognize PNe using only MIR and radio characteristics, enabling us to trawl for PNe effectively even in heavily obscured regions of the Galaxy.

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arXiv2007

Spitzer IRAC observations of newly-discovered planetary nebulae from the Macquarie-AAO-Strasbourg H-alpha Planetary Nebula Project

We compare H-alpha, radio continuum, and Spitzer Space Telescope (SST) images of 58 planetary nebulae (PNe) recently discovered by the Macquarie-AAO-Strasbo- urg H-alpha PN Project (MASH) of the SuperCOSMOS H-alpha Survey. Using InfraRed Array Camera (IRAC) data we define the IR colors of PNe and demonstrate good isolation between these colors and those of many other types of astronomical object. The only substantive contamination of PNe in the color-color plane we illustrate is due to YSOs. However, this ambiguity is readily resolved by the unique optical characteristics of PNe and their environs. We also examine the relationships between optical and MIR morphologies from 3.6 to 8.0um and explore the ratio of mid-infrared (MIR) to radio nebular fluxes, which is a valuable discriminant between thermal and nonthermal emission. MASH emphasizes late evolutionary stages of PNe compared with previous catalogs, enabling study of the changes in MIR and radio flux that attend the aging process. Spatially integrated MIR energy distributions were constructed for all MASH PNe observed by the GLIMPSE Legacy Project, using the H-alpha morphologies to establish the dimensions for the calculations of the Midcourse Space Experiment (MSX), IRAC, and radio continuum (from the Molonglo Observatory Synthesis Telescope and the Very Large Array) flux densities. The ratio of IRAC 8.0-um to MSX 8.3-um flux densities provides a measure of the absolute diffuse calibration of IRAC at 8.0 um. We independently confirm the aperture correction factor to be applied to IRAC at 8.0um to align it with the diffuse calibration of MSX. The result agrees with the recommendations of the Spitzer Science Center and with results from a parallel study of HII regions. These PNe probe the diffuse calibration of IRAC on a spatial scale of 9-77 arcsec.

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arXiv2006

Multi-Object Spectroscopy Field Configuration by Simulated Annealing

Multi-object spectroscopy (MOS) instruments, such as the Two-degree Field (2dF) facility of the Anglo-Australian Observatory (AAO), have facilitated large-scale redshift surveys. Yet despite their acclaim, instrument design has been suspected of introducing subtle selection effects into surveys. Investigation into these selection effects has been overshadowed by instrument complexity. We identify the field configuration algorithm (FCA) used to select targets for observation as mainly responsible for such effects. A FCA can imprint artificial structure on observed target distributions, which may accrue over large angular scales, potentially to the detriment of statistical analyses applied to such surveys. We present here a new FCA developed for 2dF that is based on simulated annealing (SA), a generic method commonly used to solve constrained optimisation problems. We generate synthetic fields and utilise mock 2dF volumes to contrast the behaviour of previous strategies with the SA FCA. The angular two-point correlation function and other sensitive techniques reveal that the new FCA achieves unprecedented sampling uniformity and target yield with improved target priority handling and observational flexibility over current FCAs. The SA FCA is generic enough to be used by current 2dF-like and potentially next-generation MOS instruments with little modification.

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