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Giants with infrared excess.
We have correlated optical and infrared catalogs in order to extract alarge sample of luminosity class III stars with known infrared fluxdensities. For a non-negligible fraction of G and K giants, afar-infrared excess emission was found, starting beyond 25μm. Anexplanation in terms of present-day mass loss thus becomes unlikely,since the dust should then be warmer and the excess emission less far inthe infrared. We believe that the far-infrared excesses of theseobjects, most likely first-ascent giants, are related to the Vegaphenomenon. The dusty disks around these stars, gradually cooled downduring their main-sequence phase, could be reheated once the star leavesthe main sequence and enters the luminous post-main-sequence phase. Thefairly large sample we constructed enables us to derive an estimationfor the occurrence of excesses. This fraction of G or K giants withfar-infrared excess appears to be distinctly smaller than amongmain-sequence stars. Since the higher radiation field of giants couldlead to a larger evaporation rate of the circumstellar debris, this factdoes not conflict with our hypothesis.
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Osservazione e dati astrometrici
| Costellazione: | Uccello del Paradiso |
| Ascensione retta: | 17h46m27.82s |
| Declinazione: | -78°16'35.3" |
| Magnitudine apparente: | 8.269 |
| Distanza: | 303.951 parsec |
| Moto proprio RA: | 22.6 |
| Moto proprio Dec: | -26.8 |
| B-T magnitude: | 9.708 |
| V-T magnitude: | 8.388 |
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