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Published June 2019 | Accepted Version + Published
Journal Article Open

A massive nebula around the luminous blue variable star RMC 143 revealed by ALMA

Abstract

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 κ_(850) = 1.7 cm^2g^(−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.

Additional Information

© 2019 ESO. Article published by EDP Sciences. Received 9 February 2019; Published online 24 June 2019; Accepted 9 May 2019. We thank the reviewer, Simon Clark, for their careful review of the manuscript and their constructive remarks. We wish to thank the staff at ALMA, ATCA and ESO who made these observations possible. We also thank Jorge Melnick for trying to find the photographic plates of his observations of RMC 143. CA acknowledges support from FONDECYT grant No. 3150463. Support to CA and GP was provided by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2013.1.00450.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan) and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. This paper also includes data collected: at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 096.D-0047(A); at the Australia Telescope Compact Array, which is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO. This work made use of PyAstronomy. This research has made use of the: International Variable Star Index (VSX) database, operated at AAVSO, Cambridge, Massachusetts, USA; VizieR catalogue access tool, CDS, Strasbourg, France. The original description of the VizieR service was published in A&AS 143, 23.

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Additional details

Created:
August 19, 2023
Modified:
October 20, 2023