Other
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21542702f&link_type=abstract
American Astronomical Society, AAS Meeting #215, #427.02; Bulletin of the American Astronomical Society, Vol. 42, p.342
Other
Scientific paper
Only a quarter of a complete sample of IRAS color selected sources exhibit 1612 MHz OH masers. In addition, these sources show a distinct blue MIR cutoff. We employed the radiative transfer code DUSTY to check for any correlation between the 53 μm flux, which powers the maser, and the star's effective temperature, optical spectral type, mass loss rate and its history. We found that none of these parameters has much of an effect: rather the pumping rate is sensitive to details of the optical depth in lines involved with the 53 μm pumping route. However, the characteristics of a grid of models created using DUSTY, when compared with the sample sources in a near-infrared (NIR) v MIR plot, show that the NIR color is sensitive to the immediate mass loss rate while the MIR color references the longer-term mass loss rate. We conclude from these comparisons that (1) mass loss from low mass stars is not in general strongly modulated, as the locus of objects closely follows that expected from continuous mass-loss; and (2) the temperature of the hottest dust in the circumstellar shell is much cooler in objects without masers, which suggests that their dust shells have a different dust composition. In addition, when cross-referencing information from other catalogs, we find that the great majority of objects without masers are semi-regular or L type variable stars, while most of those with masers are Mira variables and/or have M-type spectra. This leads to the selection of a list of high priority targets in which 1612 MHz masers may turn on again in future epochs with the goal of exploring the possibility that the presence and intensity of maser activity may be a recurrent and variable phenomenon. This work was funded by the NSF through the NAIC REU program.
Faesi Christopher
Lewis Murray B.
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