A dataset provided by the European Space Agency

Name OT1_rsahai_4
Title Searching for Interrupted Mass-Loss in AGB stars: A Herschel Survey
URL

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DOI 10.5270/esa-h4qxrm6
Author sahai, r.
Description Although the massive winds of AGB stars are reasonably well understood as resulting from radiation pressure on dust grains, our knowledge of how the mass-loss rates change as stars ascend the AGB is very poor. A small number of carbon-rich AGB stars have been found with detached circumstellar shells that imply that their mass-loss rates dropped dramatically a few thousand years ago. This decrease has been hypothesised to result from a He-shell flash which is believed to occur periodically in these stars; the nucleosynthesis of carbon in this flash, and its subsequent dredge-up to the stellar surface, converts oxygen-rich stars to carbon-rich ones. We propose to use Herschel.s unprecedented far-IR sensitivity and angular resolution to make a systematic search for signatures of interrupted mass-loss such as detached shells in a list of 21 targets which includes C-rich, O-rich and S-type stars (C-O~1) to test this hypothesis. Our list has been constructed using the IRAS point-source catalog to identify objects which have "60-micron excesses": their 60 to 25 micron flux ratio is > 0.4 and thus significantly larger than the average ratio for AGB stars. This excess implies the presence of a cold, extended dust shell, and relatively little hot dust close to the star, as compared to the average mass-losing AGB star. The morphology of detached shells provides a clear indication as to its origin (circular rings due to interrupted mass-loss, paraboloidal bow-shock shaoes due to interaction of the AGB wind with the ISM): hence our proposed PACS observations will thus be able to distinguish between detached shells due to interrupted mass-loss and ISM interactions.
Publication
Instrument PACS_PacsPhoto_largeScan
Temporal Coverage 2011-04-19T21:38:35Z/2012-04-13T02:34:17Z
Version SPG v14.2.0
Mission Description Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 ┬Ám range, bridging the gap between earlier infrared space missions and groundbased facilities.
Creator Contact https://support.cosmos.esa.int/herschel/
Date Published 2012-10-13T02:09:19Z
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, 2012-10-13T02:09:19Z, OT1_rsahai_4, SPG v14.2.0. https://doi.org/10.5270/esa-h4qxrm6