Contents of Dust envelopes around RV Tauri stars

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Accepted 1988 December 15. Received 1988 December 14; in original form 1988 October 11

Abstract:

In the IRAS [12]–[25], [25]–[60] colour–colour diagram, RV Tauri stars are found to populate cooler temperature regions (T < 600 K), distinctly different from those occupied by the oxygen and carbon Miras. The IRAS fluxes are consistent with the dust density in the envelope varying as the inverse square of the radial distance, implying that the grain formation processes in these objects are most probably continuous and not sporadic. It is found that the spectroscopic subgroups A and B are well separated in the far-infrared two-colour diagram, with group B objects having systematically cooler dust envelopes. We interpret this as being due to a difference in the nature of grains, including the chemical composition, in the two cases.