New Evidence for Mass-Loss from δ Cephei Based on HI 21-cm Line Observations

Details New Evidence for Mass-Loss from δ Cephei Based on HI 21-cm Line Observations New Evidence for Mass-Loss from δ Cephei Based on HI 21-cm Line Observations

May 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21832206m&link_type=abstract

American Astronomical Society, AAS Meeting #218, #322.06; Bulletin of the American Astronomical Society, Vol. 43, 2011

Astronomy and Astrophysics

Astronomy

2

Scientific paper

Our recent Spitzer Space Telescope observations of the classical Cepheid archetype δ Cep revealed an extended ( 21,000 AU) dusty nebula surrounding this star and its hot companion HD213307 (Marengo et al. 2010, ApJ, 725, 2392). At far infrared wavelengths, the emission resembles a bow shock aligned with the direction of space motion of the star. These observations strongly suggest that δ Cep is currently undergoing mass-loss through a stellar wind. To further investigate the nature of this probable mass-loss, we have used the Very Large Array (VLA) to search for 21-cm emission from neutral atomic hydrogen that may originate directly in the stellar wind and/or be swept up from the interstellar medium. Our VLA data reveal a spatially extended nebula of atomic hydrogen 10' ( 0.8 pc) across surrounding the position of δ Cep. Although a portion of the HI line profile is strongly contaminated by Galactic emission along the line-of-sight, the emission detected within the uncontaminated portion of our band is consistent with circumstellar material originating in an optically thin wind with an outflow velocity of 40 km/s. A portion of the detected HI emission also appears to be swept into a wake trailing the star's space motion. We will discuss the implications of these observations for Cepheid evolution and for resolving the so-called "Cepheid mass discrepancy". This work is supported by grant AST-1009644 from the National Science Foundation.

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