UIR-band emission from M supergiants

We have obtained 10−μm spectra of 16 M supergiants, 15 of them in the h and χ Per association. All of the stars exhibit silicate emission features, but in addition seven of the stars show narrow UIR (unidentified infrared) band emission features, at 11.3 μm⁠, 8.65 μm and other wavelengths, which are normally associated with carbon-rich media. Not only are these the coolest objects to have been found to exhibit UIR-band emission, but the outflows from these classical oxygen-rich stars should form only O-rich particles according to equilibrium condensation theory. We interpret our results in terms of the non-equilibrium chemistry model by Beck et al., whereby chromospheric UV radiation can liberate some atomic carbon via the photodissociation of CO molecules, enabling the formation of carbon-rich species as well as silicates. Such a chromospheric UV radiation field could also provide the photons needed to excite the observed UIR-band emission

Silicate and hydrocarbon emission from Galactic M supergiants

Following our discovery of unidentified infrared (UIR) band emission in a number of M supergiants in h and χ Per, we have obtained 10-μm spectra of a sample of 60 galactic M supergiants. Only three new sources, V1749 Cyg, UW Aql and IRC+40 427, appear to show the UIR bands; the others show the expected silicate emission or a featureless continuum. The occurrence of UIR-band emission in M supergiants is therefore much higher in the h and χ Per cluster than in the Galaxy as a whole. Possible explanations for the origin and distribution of UIR bands in oxygen-rich supergiants are discussed. We use our spectra to derive mass-loss rates ranging from 10−8 to 10−4 M⊙ yr−1 for the new sample, based on the power emitted in the silicate feature. The relationship between mass-loss rate and luminosity for M supergiants is discussed, and correlations are explored between their mid-infrared emission properties

Optical, infrared and millimetre-wave properties of Vega-like systems - III. Models with thermally spiking grains

Vega-like stars are main-sequence stars that exhibit excess IR emission due to circumstellar dust grains which are probably distributed in discs. We have recently published an obser- vational data base for a large sample of candidate Vega-like systems, comprising optical, near- IR and mm/submm-wave photometry, and mid-IR spectra. In a previous paper we presented radiative transfer models of eight sources from our sample that had low fractional excess luminosities. Here we present models of a further eight sources, all with large fractional excess luminosities dominated by excess emission at near-IR wavelengths. It was found that no single distribution of dust grains at thermal equilibrium in a disc could simultaneously match the excess emission at near-IR and longer wavelengths. We attempted to model the near-IR emission as due to thermally spiking small grains, which can temporarily attain the high temperatures required to produce excess near-IR emission. A near-IR spectrum of SAO 186777 shows the 3.3-μm UIR emission band, confirming our earlier detection of UIR emission at longer wavelengths, and suggesting that small carbonaceous particles are responsible for some of the near-IR emission. The thermally spiking models were only partially successful and many of the sources required the presence of grains emitting in thermal equilibrium at ∼ 1000- 1500 K. These grains must either be located very close to the stars (<1 au), or else be powered by accretion luminosity. Calculations of the optical depths of the model discs suggest the discs are optically thick at visual wavelengths; optically thick modelling of these sources is desirable. The discs are optically thin at mm wavelengths, allowing us to confirm the presence of large grains in the discs. The stars presented in this paper may well be younger than the prototype Vega-like stars

CO emission from shock and PDR in C-rich PN and post-AGB objects

The LWS full grating scans of the PN, NGC 7027, and post-AGB objects, GL618 and GL2688 reveal a forest of lines which are identified as CO rotational lines. These lines are used as diagnostics for warm gas around these objects. For NGC 7027 and GL 618, the hot central star is the source of the ionizing photons, creating a PDR. GL2688 is a cooler post-AGB star with evidence of a fast wind which results in shock heated gas. From the CO observations, we can estimate the density of the molecular layer. In agreement with earlier work, we found that the molecular layer is warm (T~ 350-600 K) and dense (n~ 107 cm-3). This may have implications on mass loss during the last stage of the evolution before stars evolve off the AGB

The Dust Disk around the Vega-Excess Star SAO 26804

We present multiwaveband observations of the K2 Vega-excess star SAO 26804 (= HD 233517). These include James Clerk Maxwell Telescope millimeter-wave photometry, plus spectra in the 8-13 microns and 18-24 microns atmospheric windows, an image at a wavelength of 10 microns through a broadband N filter and near-IR (JHKLL'M) photometry all taken at the United Kingdom Infrared Telescope. The source is resolved at 10 microns, and we can confirm with these observations that the IR excess seen in IRAS observations of this source is associated with the optical star. The image is consistent with the dust being confined to a disk with Full Width at Half Maximum (FWHM) 1.5 sec on the major axis, with an inclination angle of less than 30 deg away from edge-on. This represents the first confirmation that the dust in a Vega-excess star other than beta Pic is confined to a disk geometry. We present models of the source which show that many of the properties of the disk and the dust in it are similar to those which we have previously derived for the disk around SAO 179815, but that there are some very small grains in the disk around the star which give around SAO 179815, but that there are some very small grains in the disk around the star which give rise to a very prominent and narrow silicate dust feature at 9.7 microns and to so-called unidentified infrared bands in the 10 micron region. The larger grains are composed of a mixture of amorphous carbon and silicate with an abundance ratio consistent with an interstellar origin. The total mass of dust in the disk is 3.0 x 10-7 solar mass. Finally, our model suggests that there may be a substantial UV and/or soft X-ray flux from SAO 26804, consistent with it being a very young and rather active star

Novel insights into maladaptive behaviours in Prader-Willi syndrome: serendipitous findings from an open trial of vagus nerve stimulation.

BACKGROUND: We report striking and unanticipated improvements in maladaptive behaviours in Prader-Willi syndrome (PWS) during a trial of vagus nerve stimulation (VNS) initially designed to investigate effects on the overeating behaviour. PWS is a genetically determined neurodevelopmental disorder associated with mild-moderate intellectual disability (ID) and social and behavioural difficulties, alongside a characteristic and severe hyperphagia. METHODS: Three individuals with PWS underwent surgery to implant the VNS device. VNS was switched on 3 months post-implantation, with an initial 0.25 mA output current incrementally increased to a maximum of 1.5 mA as tolerated by each individual. Participants were followed up monthly. RESULTS: Vagal nerve stimulation in these individuals with PWS, within the stimulation parameters used here, was safe and acceptable. However, changes in eating behaviour were equivocal. Intriguingly, unanticipated, although consistent, beneficial effects were reported by two participants and their carers in maladaptive behaviour, temperament and social functioning. These improvements and associated effects on food-seeking behaviour, but not weight, indicate that VNS may have potential as a novel treatment for such behaviours. CONCLUSIONS: We propose that these changes are mediated through afferent and efferent vagal projections and their effects on specific neural networks and functioning of the autonomic nervous system and provide new insights into the mechanisms that underpin what are serious and common problems affecting people with IDs more generally.This study was funded by The Dunhill Medical Trust, Addenbrooke’s Charitable Trust, Isaac Newton Trust , and Prader-Willi Association UK. Funding bodies had no role in study design, data collection, data analysis, data interpretation, writing of the report or the decision to submit for publication. We are grateful to the NIHR Collaborations for Leadership in Applied Health Care Research and Care (CLAHRC) East of England for financial support to AJH and HAR and to the Health Foundation for support of AJH. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health.This is the final version of the article. It first appeared from Taylor & Francis via http://dx.doi.org/10.1111/jir.1220

Stellar winds from Massive Stars

We review the various techniques through which wind properties of massive stars - O stars, AB supergiants, Luminous Blue Variables (LBVs), Wolf-Rayet (WR) stars and cool supergiants - are derived. The wind momentum-luminosity relation (e.g. Kudritzki et al. 1999) provides a method of predicting mass-loss rates of O stars and blue supergiants which is superior to previous parameterizations. Assuming the theoretical sqrt(Z) metallicity dependence, Magellanic Cloud O star mass-loss rates are typically matched to within a factor of two for various calibrations. Stellar winds from LBVs are typically denser and slower than equivalent B supergiants, with exceptional mass-loss rates during giant eruptions Mdot=10^-3 .. 10^-1 Mo/yr (Drissen et al. 2001). Recent mass-loss rates for Galactic WR stars indicate a downward revision of 2-4 relative to previous calibrations due to clumping (e.g. Schmutz 1997), although evidence for a metallicity dependence remains inconclusive (Crowther 2000). Mass-loss properties of luminous (> 10^5 Lo) yellow and red supergiants from alternative techniques remain highly contradictory. Recent Galactic and LMC results for RSG reveal a large scatter such that typical mass-loss rates lie in the range 10^-6 .. 10^-4 Mo/yr, with a few cases exhibiting 10^-3 Mo/yr.Comment: 16 pages, 2 figures, Review paper to appear in Proc `The influence of binaries on stellar population studies', Brussels, Aug 2000 (D. Vanbeveren ed.), Kluwe

Association of Polymorphisms in Oxidative Stress Genes with Clinical Outcomes for Bladder Cancer Treated with Bacillus Calmette-Guérin

Genetic polymorphisms in oxidative stress pathway genes may contribute to carcinogenesis, disease recurrence, treatment response, and clinical outcomes. We applied a pathway-based approach to determine the effects of multiple single nucleotide polymorphisms (SNPs) within this pathway on clinical outcomes in non-muscle-invasive bladder cancer (NMIBC) patients treated with Bacillus Calmette-Guérin (BCG). We genotyped 276 SNPs in 38 genes and evaluated their associations with clinical outcomes in 421 NMIBC patients. Twenty-eight SNPs were associated with recurrence in the BCG-treated group (P<0.05). Six SNPs, including five in NEIL2 gene from the overall and BCG group remained significantly associated with recurrence after multiple comparison adjustments (q<0.1). Cumulative unfavorable genotype analysis showed that the risk of recurrence increased with increasing number of unfavorable genotypes. In the analysis of risk factors associated with progression to disease, rs3890995 in UNG, remained significant after adjustment for multiple comparison (q<0.1). These results support the hypothesis that genetic variations in host oxidative stress genes in NMIBC patients may affect response to therapy with BCG