A Spitzer Study of 21 and 30 Micron Emission in Several Galactic Carbon-rich Proto-Planetary Nebulae - Astrophysics > Solar and Stellar AstrophysicsReport as inadecuate




A Spitzer Study of 21 and 30 Micron Emission in Several Galactic Carbon-rich Proto-Planetary Nebulae - Astrophysics > Solar and Stellar Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: We have carried out mid-infrared spectroscopy of seven Galacticproto-planetary nebulae PPNs using the Spitzer Space Telescope. They wereobserved from 10-36 microns at relatively high spectral resolution, R~600. Thesample was chosen because they all gave some evidence in the visible of acarbon-rich chemistry. All seven of the sources show the broad, unidentified 21micron emission feature; three of them are new detections IRAS 06530-0213,07430+1115, and 19477+2401 and the others are observed at higher S-N than inprevious spectra. These have the same shape and central wavelength 20.1microns as found in the ISO spectra of the brighter PPNs. The 30 micronfeature was seen in all seven objects. However, it is not resolved into twoseparate features 26 and 33 microns as was claimed on the basis of ISOspectra, which presumably suffered from the noisy detector bands in thisregion. All showed the infrared aromatic bands AIB at 11.3, 12.4, and 13.3microns. Five of these also appear to have the C2H2 molecular band at 13.7microns, one in absorption and four in emission. This is extremely rare, withonly one other evolved star, IRC+10216, in which C2H2 emission has beenobserved. Four also possessed a broad, unidentified emission feature at 15.8microns that may possibly be related to the 21 micron feature. Model fits weremade to the spectral energy distributions for these PPNs to determineproperties of the detached circumstellar envelopes. The 21 micron feature hasbeen seen in all Galactic carbon-rich PPNs observed, and thus its carrierappears to be a common component of the outflow around these objects.



Author: Bruce J. Hrivnak, Kevin Volk, Sun Kwok

Source: https://arxiv.org/



DOWNLOAD PDF




Related documents