|Physical properties of the dusty circumstellar envelopes of two bright classical Cepheids
|The recent discovery of circumstellar envelopes (CSEs) around Cepheids is an indication that many Cepheids, if not all, are surrounded by CSEs. The bright classical Cepheids RS Pup and delta Cephei are particularly interesting members of their famous class of variable stars, as they are known to be surrounded by large CSEs that can be resolved angularly by Herschel. The requested observations will probe the cold extensions of these nebulae, and will be the first observations of any Cepheid in this wavelength domain. The present proposal aims at characterizing the dust in the CSEs using Herschel-PACS and SPIRE imaging photometry. Our scientific goal is to understand the origin of the envelopes: were they formed through evolutionary mass-loss from the Cepheids or are they made of residual interstellar material pre-existing the formation of the Cepheid progenitor? This question is of critical importance both to understand the evolution of the Cepheids themselves (stellar physics) and for the future application of the period-luminosity relation in the thermal-IR domain with the James Webb Space Telescope (extragalactic distance scale). The formation mechanism of the large dusty nebula surrounding these Cepheids is currently unknown, but two hypotheses appear plausible: (A} - it is a result of evolutionary mass-loss from the star through stellar wind, possibly linked to pulsation, that condensed into dust at large distances from the star. (B) - it is a remnant of the interstellar medium from which RS,Pup formed, blown away by the stellar wind from the Cepheid. Our goal is to test these two hypotheses and characterize physically the cold dust in the envelopes (mass, temperature, distribution, composition).
|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 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
|Publisher And Registrant
|European Space Agency
|European Space Agency, 2012, OT1_pkervell_1, SPG v14.2.0. https://doi.org/10.5270/esa-5y92jcl