Volume 626, June 2019
|Number of page(s)||13|
|Section||Stellar structure and evolution|
|Published online||24 June 2019|
A massive nebula around the luminous blue variable star RMC 143 revealed by ALMA⋆⋆⋆
European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago de Chile, Chile
2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, Garching bei München 85748, Germany
3 Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago 8320000, Chile
4 INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
5 Trinity College Dublin, The University of Dublin, College Green, Dublin, Ireland
6 Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA
7 Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
8 Infrared Processing Analysis Center, California Institute of Technology, 770 South Wilson Ave., Pasadena, CA 91125, USA
9 Millennium Institute of Astrophysics (MAS), Nuncio Monseñor Sótero Sanz 100, Providencia, Santiago, Chile
Accepted: 9 May 2019
The luminous blue variable (LBV) RMC 143 is located in the outskirts of the 30 Doradus complex, a region rich with interstellar material and hot luminous stars. We report the 3σ sub-millimetre detection of its circumstellar nebula with ALMA. The observed morphology in the sub-millimetre is different than previously observed with HST and ATCA in the optical and centimetre wavelength regimes. The spectral energy distribution (SED) of RMC 143 suggests that two emission mechanisms contribute to the sub-mm emission: optically thin bremsstrahlung and dust. Both the extinction map and the SED are consistent with a dusty massive nebula with a dust mass of 0.055 ± 0.018 M⊙ (assuming κ850 = 1.7 cm2 g−1). To date, RMC 143 has the most dusty LBV nebula observed in the Magellanic Clouds. We have also re-examined the LBV classification of RMC 143 based on VLT/X-shooter spectra obtained in 2015/16 and a review of the publication record. The radiative transfer code CMFGEN is used to derive its fundamental stellar parameters. We find an effective temperature of ∼8500 K, luminosity of log(L/L⊙) = 5.32, and a relatively high mass-loss rate of 1.0 × 10−5 M⊙ yr−1. The luminosity is much lower than previously thought, which implies that the current stellar mass of ∼8 M⊙ is comparable to its nebular mass of ∼5.5 M⊙ (from an assumed gas-to-dust ratio of 100), suggesting that the star has lost a large fraction of its initial mass in past LBV eruptions or binary interactions. While the star may have been hotter in the past, it is currently not hot enough to ionize its circumstellar nebula. We propose that the nebula is ionized externally by the hot stars in the 30 Doradus star-forming region.
Key words: stars: massive / stars: variables: S Doradus / stars: evolution / stars: individual: RMC143 / stars: mass-loss / dust / extinction
The ALMA and ATCA maps, and Tables 1 and 4, are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/626/A126
© ESO 2019
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