The Luminous Blue Variable RMC 127 as Seen with ALMA and ATCA
- Millennium Institute of Astrophysics (MAS), Nuncio Monseñor Sótero Sanz 100, Providencia, Santiago (Chile)
- INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123, Catania Italy (Italy)
- Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago, 8320000 (Chile)
- European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago (Chile)
- National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
- Infrared Processing Analysis Center, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125 (United States)
- Space Telescope Science Institute, Space Telescope Science Institute 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- INAF-Istituto di Radioastronomia, via Gobetti 101, I-40129, Bologna (Italy)
We present ALMA and ATCA observations of the luminous blue variable RMC 127. The radio maps show for the first time the core of the nebula and evidence that the nebula is strongly asymmetric with a Z-pattern shape. Hints of this morphology are also visible in the archival Hubble Space Telescope Hα image, which overall resembles the radio emission. The emission mechanism in the outer nebula is optically thin free–free in the radio. At high frequencies, a component of point-source emission appears at the position of the star, up to the ALMA frequencies. The rising flux density distribution (S{sub ν}∼ν{sup 0.78±0.05}) of this object suggests thermal emission from the ionized stellar wind and indicates a departure from spherical symmetry with n{sub e}(r)∝r{sup −2}. We examine different scenarios to explain this excess of thermal emission from the wind and show that this can arise from a bipolar outflow, supporting the suggestion by other authors that the stellar wind of RMC 127 is aspherical. We fit the data with two collimated ionized wind models, and we find that the mass-loss rate can be a factor of two or more smaller than in the spherical case. We also fit the photometry obtained by IR space telescopes and deduce that the mid- to far-IR emission must arise from extended, cool (∼80 K) dust within the outer ionized nebula. Finally, we discuss two possible scenarios for the nebular morphology: the canonical single-star expanding shell geometry and a precessing jet model assuming the presence of a companion star.
- OSTI ID:
- 22872652
- Journal Information:
- Astrophysical Journal, Vol. 841, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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