TY - JOUR
T1 - Circumstellar CO J = 3 → 2 detected around the evolving metal-poor ([Fe/H] ≈ –1.15 dex) AGB star RU Vulpeculae
AU - Mcdonald, Iain
AU - Uttenthaler, S.
AU - Zijlstra, Albert
AU - Richards, Anita
AU - Lagadec, Eric
PY - 2019/10/23
Y1 - 2019/10/23
N2 - We report the first detection of CO J = 3 → 2 around a truly metal-poor evolved star. RU Vulpeculae is modelled to have Teff ≈ 3620 K, L ≈ 3128 ± 516 L⊙, log(g) = 0.0 ± 0.2 dex and [Fe/H] = –1.3 to –1.0 dex, and is modelled to have recently undergone a thermal pulse. Its infrared flux has approximately doubled over 35 years. ALMA observations show the 3→2 line is narrow (half-width ∼1.8–3.5 km s−1). The 2→1 line is much weaker: it is not confidently detected. Spectral-energy-distribution fit- ting indicates very little circumstellar absorption, despite its substantial mid-infrared emission. A VISIR mid-infrared spectrum shows features typical of previously observed metal-poor stars, dominated by a substantial infrared excess but with weak silicate and (possibly) Al2O3 emission. A lack of resolved emission, combined with weak 2→1 emission, indicates the dense circumstellar material is truncated at large radii. We suggest that rapid dust condensation is occurring, but with an aspherical geometry (e.g., a disc or clumps) that does not obscure the star. We compare with T UMi, a similar star which is currently losing its dust.
AB - We report the first detection of CO J = 3 → 2 around a truly metal-poor evolved star. RU Vulpeculae is modelled to have Teff ≈ 3620 K, L ≈ 3128 ± 516 L⊙, log(g) = 0.0 ± 0.2 dex and [Fe/H] = –1.3 to –1.0 dex, and is modelled to have recently undergone a thermal pulse. Its infrared flux has approximately doubled over 35 years. ALMA observations show the 3→2 line is narrow (half-width ∼1.8–3.5 km s−1). The 2→1 line is much weaker: it is not confidently detected. Spectral-energy-distribution fit- ting indicates very little circumstellar absorption, despite its substantial mid-infrared emission. A VISIR mid-infrared spectrum shows features typical of previously observed metal-poor stars, dominated by a substantial infrared excess but with weak silicate and (possibly) Al2O3 emission. A lack of resolved emission, combined with weak 2→1 emission, indicates the dense circumstellar material is truncated at large radii. We suggest that rapid dust condensation is occurring, but with an aspherical geometry (e.g., a disc or clumps) that does not obscure the star. We compare with T UMi, a similar star which is currently losing its dust.
KW - stars: mass-loss
KW - circumstellar matter
KW - infrared: stars
KW - stars: winds, outflows
KW - stars: AGB and post-AGB
M3 - Article
SN - 1365-2966
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
ER -