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Narrowband Mid-Infrared Images and Models of the H II Complex G34.3+0.2
We present mid-infrared images of the ultracompact H II region complexG34.3+0.2 taken on the IRTF through a 1.8% circular variable filterwheel at 8.0, 9.7, 11.2, 12.8, and 13.2 μm and through a 6.8% filterat 20.6 μm. Infrared emission was detected at the radio components A,C (the ``cometary'' component), and D. In addition, two new sources ofemission were found south of C at 20.6 μm we assign them names of Eand F. Infrared emission was not detected at B, and C does not have thefamous cometary shape that is observed in radio continuum emission.Photometric flux densities and source sizes are determined for A, C, andE. Radiative transfer models are then presented to match the observeddust emission for these sources. Based on the observations and models,an overview of the complex is suggested in which C is an approximatelyspherical centrally heated source that was not formed from material inthe adjacent ultracompact molecular core. C is not a blister source, andit is not colliding with the molecular core.
| The X-Ray Emission of A-Type Stars
From X-ray images in the ROSAT public archives, we determine soft X-rayfluxes, or flux upper limits, for 74 A-type stars, which have beenobserved during deep integrations with the PSPC. Nine supposedly single,late A stars (0.20 < B-V < 0.35) are found to coincide with X-raysources. The X-ray luminosities we infer for these stars range fromlevels comparable to the Active Sun, at log L_x ~27.6, to much brighteremission levels similar to those observed for active late-type binarysystems, near log L_x ~30.1. Another 10 sources are identified withearly A stars (0.0 < B-V < 0.2). Five of these are confirmeddouble stars, the rest are ostensibly single. The maximum luminosity wedetect in the early A stars, log L_x = 30.1, is 3.5 orders of magnitudebrighter than the X-ray upper limits for the nondetected stars.Additional study, including radial velocity monitoring and/or opticalinterferometry, will be needed to determine whether the putativelysingle X-ray emitting stars are in fact single, or whether theiremission is produced entirely or in part by unknown or unresolved binarycompanions. The level of X-ray emission associated with chemicallynormal, single A stars thus far appears to be uncorrelated with anyobvious stellar property, including the rotation rate, which is known togreatly influence the dynamo activity and the X-ray emission levels oflower mass stars. (SECTION: Stars)
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Observation and Astrometry data
| Constellation: | わし座 |
| Right ascension: | 18h53m27.94s |
| Declination: | +00°52'13.0" |
| Apparent magnitude: | 7.981 |
| Distance: | 303.03 parsecs |
| Proper motion RA: | -3.4 |
| Proper motion Dec: | -2 |
| B-T magnitude: | 8.114 |
| V-T magnitude: | 7.992 |
Catalogs and designations:
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