arXiv subjects

Warren A. Reid

Publications and source records attributed to Warren A. Reid.

22 records · Page 2Linked to original sources

arXiv2007

The Unusual Variability of the Large Magellanic Cloud Planetary Nebula RPJ 053059-683542

We present images and light curves of the bipolar Planetary Nebula RPJ 053059-683542 that was discovered in the Reid-Parker AAO/UKST H-alpha survey of the Large Magellanic Cloud (LMC). The emission from this object appears entirely nebular, with the central star apparently obscured by a central band of absorption that bisects the nebula. The light curves, which were derived from images from the SuperMACHO project at CTIO, showed significant, spatially resolved variability over the period 2002 January through 2005 December. Remarkably, the emission from the two bright lobes of the nebula vary either independently, or similarly but with a phase lag of at least one year. The optical spectra show a low level of nebular excitation, and only modest N enrichment. Infrared photometry from the 2MASS and SAGE surveys indicates the presence of a significant quantity of dust. The available data imply that the central star has a close binary companion, and that the system has undergone some kind of outburst event that caused the nebular emission to first brighten and then fade. Further monitoring, high-resolution imaging, and detailed IR polarimetry and spectroscopy would uncover the nature of this nebula and the unseen ionizing source.

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arXiv2006

A New Population of Planetary Nebulae Discovered in the Large Magellanic Cloud (II): Complete PN Catalogue

This paper presents accurate homogeneous positions, velocities and other pertinent properties for 460 newly discovered and 169 previously known planetary nebulae (PNe) in the central 25 sq deg bar region of the Large Magellanic Cloud (LMC). Candidate emission sources were discovered using a deep, high resolution H-alpha map of the LMC obtained by median stacking a dozen 2 hour H-alpha exposures taken with the UK Schmidt Telescope (UKST). Our spectroscopic followup of more than 2,000 compact (ie. <20 arcsec) H-alpha emission candidates uncovered has tripled the number of PNe in this area. All of the 169 previously known PNe within this region have also been independently recovered and included in this paper to create a homogeneous data set. Of the newly discovered PNe, we classify 291 as "true", 54 as "likely" and 115 as "possible" based on the strength of photometric and spectroscopic evidence. Radial velocities have been measured using both weighted averaging of emission lines and cross-correlation techniques against high quality templates. Based on the median comparison of the two systems, we define a measurement error of pm4 km/s. A new velocity map of the central 25 sq deg of the LMC, based on results from the combined new and previously known PNe, is presented, indicating an averaged heliocentric velocity differential of 65 km/s perpendicular to the line of nodes for the entire PN population across our survey area. Averaged velocities of our PNe and molecular hydrogen (from the literature) across 37 x 37 arcmin sub areas are compared.

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arXiv2005

A New Population of Planetary Nebulae Discovered in the Large Magellanic Cloud (I): Preliminary Sample

We report our initial discovery of 73 new planetary nebulae (PNe) in the Large Magellanic Cloud (LMC) following confirmatory 2dF spectroscopy on the Anglo-Australian Telescope (AAT). Preliminary candidate sources come from a 10 per cent sub-area of our new deep, high resolution H-alpha map of the central 25 deg. square of the LMC obtained with the UK Schmidt Telescope (UKST). The depth of the high resolution map was extended to Requiv~22 for H-alpha (4.5 x 10-17 ergs cm-2 s-1 Ang-1) by a process of multi-exposure median co-addition of a dozen 2-hour H-alpha exposures. The resulting map is at least 1-magnitude deeper than the best wide-field narrow-band LMC images currently available. This depth, combined with our selection technique, has also led to the discovery of extended AGB halos around many new and previously known LMC PNe for the first time. Once complete, our new survey is expected to triple the LMC PN population and have significant implications for the LMC PN luminosity function, kinematics, abundance gradients chemical evolution and, via study of the AGB halos, the initial to final mass relation for low to intermediate mass stars.

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arXiv2004

H-alpha Stacked Images Reveal Large Numbers of PNe in the LMC

Our new, deep, high resolution H-alpha and matching R-band UKST multi-exposure stack of the central 25 sq. degrees of the LMC promises to provide an unprecedented homogeneous sample of >1,000 new PNe. Our preliminary 2dF spectroscopy on the AAT has vindicated our selection process and confirmed 136 new PNe and 57 emission-line stars out of a sample of 263 candidate sources within an initial 2.5 sq. deg. area. To date approximately one third of the entire LMC has been scanned for candidates (~7.5 sq.deg.). More than 750 new emission sources have been catalogued so far along with independent re-identification of all known and possible PNe found from other surveys. Once our image analysis is complete, we plan comprehensive spectroscopic follow-up of the whole sample, not only to confirm our PN candidates but also to derive nebula temperatures and densities which, with the aid of photoionization modeling, will yield stellar parameters which are vital for constructing H-R diagrams for these objects. A prime objective of the survey is to produce a Luminosity Function which will be the most accurate and comprehensive ever derived in terms of numbers, magnitude range and evolutionary state; offering significant new insights into the LMC's evolutionary history. The observation and measurement of our newly discovered AGB halos around 60% of these PN will also assist in determining the initial- to final-mass ratios for this phase of stellar evolution.

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