NEW EVIDENCE FOR MASS LOSS FROM {delta} CEPHEI FROM H I 21 cm LINE OBSERVATIONS

Journal Article · Sun Jan 01 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/744/1/53· OSTI ID:22004335

Matthews, L D ^[1]; Marengo, M ^[2]; Evans, N R ^[3]; Bono, G ^[4]

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1. Massachusetts Institute of Technology, Haystack Observatory, Off Route 40, Westford, MA 01886 (United States)
2. Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)
3. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
4. Department of Physics, Universita di Roma Tor Vergata, via Della Ricerca Scientifica 1, 00133 Roma (Italy)

Recently published Spitzer Space Telescope observations of the classical Cepheid archetype {delta} Cephei revealed an extended dusty nebula surrounding this star and its hot companion HD 213307. At far-infrared wavelengths, the emission resembles a bow shock aligned with the direction of space motion of the star, indicating that {delta} Cephei is undergoing mass loss through a stellar wind. Here we report H I 21 cm line observations with the Very Large Array (VLA) to search for neutral atomic hydrogen associated with this wind. Our VLA data reveal a spatially extended H I nebula ({approx}13' or 1 pc across) surrounding the position of {delta} Cephei. The nebula has a head-tail morphology, consistent with circumstellar ejecta shaped by the interaction between a stellar wind and the interstellar medium (ISM). We directly measure a mass of circumstellar atomic hydrogen M{sub H{sub i}}{approx}0.07 M{sub sun}, although the total H I mass may be larger, depending on the fraction of circumstellar material that is hidden by Galactic contamination within our band or that is present on angular scales too large to be detected by the VLA. It appears that the bulk of the circumstellar gas has originated directly from the star, although it may be augmented by material swept from the surrounding ISM. The H I data are consistent with a stellar wind with an outflow velocity V{sub o} = 35.6 {+-} 1.2 km s{sup -1} and a mass-loss rate of M-dot {approx}(1.0{+-}0.8) Multiplication-Sign 10{sup -6} M{sub sun} yr{sup -1}. We have computed theoretical evolutionary tracks that include mass loss across the instability strip and show that a mass-loss rate of this magnitude, sustained over the preceding Cepheid lifetime of {delta} Cephei, could be sufficient to resolve a significant fraction of the discrepancy between the pulsation and evolutionary masses for this star.

• OSTI ID: 22004335
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 744; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CEPHEIDS
CONTAMINATION
HYDROGEN
MORPHOLOGY
NEBULAE
PULSATIONS
SHOCK WAVES
STELLAR WINDS
TELESCOPES