Radio-continuum detections of Galactic Planetary Nebulae I. MASH PNe detected in large-scale radio surveys

We present an updated and newly compiled radio-continuum data-base for MASH PNe detected in the extant large scale "blind" radio-continuum surveys (NVSS, SUMSS/MGPS-2 and PMN) and, for a small number of MASH PNe, observed and detected in targeted radio-continuum observations. We found radio counterparts for approximately 250 MASH PNe. In comparison with the percentage of previously known Galactic PNe detected in the NVSS and MGPS-2 radio-continuum surveys and according to their position on the flux density-angular diameter and the radio brightness temperature evolutionary diagrams we conclude, unsurprisingly, that the MASH sample presents the radio-faint end of the known Galactic PNe population. Also, we present radio-continuum spectral properties of a small sub-sample of MASH PNe located in the strip between declinations -30arcdeg and -40arcdeg, that are detected in both the NVSS and MGPS-2 radio surveys.Comment: 13 figures and 7 tables, accepted for publication in MNRA

The binary fraction of planetary nebula central stars I. A high-precision, I-band excess search

In an attempt to determine how many planetary nebulae derive from binary interactions, we have started a project to measure their unbiased binary fraction. This number, when compared to the binary fraction of the presumed parent population can give a first handle on the origin of planetary nebulae. By detecting 27 bona fide central stars in the I band we have found that 30% of our sample have an I band excess between one and a few sigmas, possibly denoting companions brighter than M3-4V and with separations smaller than approximately 1000 AU. By accounting for the undetectable companions, we determine a de-biased binary fraction of 67-78% for all companions at all separations. We compare this number to a main sequence binary fraction of (50+/-4)% determined for spectral types F6V-G2V, appropriate if the progenitors of today's PN central star population is indeed the F6V-G2V stars. The error on our estimate could be between 10 and 30%. We conclude that the central star binary fraction may be larger than expected from the putative parent population. Using the more sensitive J band of a subset of 11 central stars, the binary fraction is 54% for companions brighter than approximately M5-6V and with separations smaller than about 900 AU. De-biassing this number we obtain a binary fraction of 100-107%. The two numbers should be the same and the discrepancy is likely due to small number statistics. We also present an accurately vetted compilation of observed main sequence star magnitudes, colours and masses, which can serve as a reference for future studies. We also present synthetic colours of hot stars as a function of temperature (20-170kK) and gravity (log g= 6-8) for Solar and PG1159 compositions.Comment: 22 pages, 6 figures, 12 tables, accepted by MNRA

The planetary nebula Abell 48 and its [WN4] central star

We have conducted a multi-wavelength study of the planetary nebula Abell 48 and give a revised classification of its nucleus as a hydrogen-deficient star of type [WN4]. The surrounding nebula has a morphology typical of PNe and importantly, is not enriched in nitrogen, and thus not the 'peeled atmosphere' of a massive star. Indeed, no WN4 star is known to be surrounded by such a compact nebula. The ionized mass of the nebula is also a powerful discriminant between the low-mass PN and high-mass WR ejecta interpretations. The ionized mass would be impossibly high if a distance corresponding to a Pop I star was adopted, but at a distance of 2 kpc, the mass is quite typical of moderately evolved PNe. At this distance, the ionizing star then has a luminosity of ~5000 Lsolar, again rather typical for a PN central star. We give a brief discussion of the implications of this discovery for the late-stage evolution of intermediate-mass stars.Comment: EUROWD12 Proceeding

The Girl Who Cares For Me

https://digitalcommons.library.umaine.edu/mmb-vp/4205/thumbnail.jp

A Lie algebra attached to a projective variety

Each choice of a K\"ahler class on a compact complex manifold defines an action of the Lie algebra \slt on its total complex cohomology. If a nonempty set of such K\"ahler classes is given, then we prove that the corresponding \slt-copies generate a semisimple Lie algebra. We investigate the formal properties of the resulting representation and we work things out explicitly in the case of complex tori, hyperk\"ahler manifolds and flag varieties. We pay special attention to the cases where this leads to a Jordan algebra structure or a graded Frobenius algebra.Comment: AMSTeX v2.1, 46 page

Geobase Information System Impacts on Space Image Formats

As Geobase Information Systems increase in number, size and complexity, the format compatability of satellite remote sensing data becomes increasingly more important. Because of the vast and continually increasing quantity of data available from remote sensing systems the utility of these data is increasingly dependent on the degree to which their formats facilitate, or hinder, their incorporation into Geobase Information Systems. To merge satellite data into a geobase system requires that they both have a compatible geographic referencing system. Greater acceptance of satellite data by the user community will be facilitated if the data are in a form which most readily corresponds to existing geobase data structures. The conference addressed a number of specific topics and made recommendations

The Harbor of Love

https://digitalcommons.library.umaine.edu/mmb-vp/1407/thumbnail.jp

Testing the binary hypothesis for the formation and shaping of planetary nebulae

There is no quantitative theory to explain why a high 80% of all planetary nebulae are non-spherical. The Binary Hypothesis states that a companion to the progenitor of a central star of planetary nebula is required to shape the nebula and even for a planetary nebula to be formed at all. A way to test this hypothesis is to estimate the binary fraction of central stars of planetary nebulae and to compare it with that of the main sequence population. Preliminary results from photometric variability and the infrared excess techniques indicate that the binary fraction of central stars of planetary nebulae is higher than that of the main sequence, implying that PNe could preferentially form via a binary channel. This article briefly reviews these results and current studies aiming to refine the binary fraction.Comment: EUROWD12 Proceeding

Planetary nebulae : getting closer to an unbiased binary fraction

Why 80% of planetary nebulae are not spherical is not yet understood. The Binary Hypothesis states that a companion to the progenitor of the central star of a planetary nebula is required to shape the nebula and even for a planetary nebula to be formed at all. A way to test this hypothesis is to estimate the binary fraction of central stars of planetary nebula and to compare it with the main sequence population. Preliminary results from photometric variability and infrared excess techniques indicate that the binary fraction of central stars of planetary nebulae is higher than that of the putative main sequence progenitor population, implying that PNe could be preferentially formed via a binary channel. This article briefly reviews these results and future studies aiming to refine the binary fraction.Comment: SF2A 2012 proceeding

Haplotype analysis of the PPARgamma Pro12Ala and C1431T variants reveals opposing associations with body weight.

BACKGROUND: Variation at the PPARG locus may influence susceptibility to type 2 diabetes and related traits. The Pro12Ala polymorphism may modulate receptor activity and is associated with protection from type 2 diabetes. However, there have been inconsistent reports of its association with obesity. The silent C1431T polymorphism has not been as extensively studied, but the rare T allele has also been inconsistently linked to increases in weight. Both rare alleles are in linkage disequilibrium and the independent associations of these two polymorphisms have not been addressed. RESULTS: We have genotyped a large population with type 2 diabetes (n = 1107), two populations of non-diabetics from Glasgow (n = 186) and Dundee (n = 254) and also a healthy group undergoing physical training (n = 148) and investigated the association of genotype with body mass index. This analysis has demonstrated that the Ala12 and T1431 alleles are present together in approximately 70% of the carriers. By considering the other 30% of individuals with haplotypes that only carry one of these polymorphisms, we have demonstrated that the Ala12 allele is consistently associated with a lower BMI, whilst the T1431 allele is consistently associated with higher BMI. CONCLUSION: This study has therefore revealed an opposing interaction of these polymorphisms, which may help to explain previous inconsistencies in the association of PPARG polymorphisms and body weight