Discovery of a Rare Late-Type, Low-mass Wolf-Rayet Star in the LMC

Bruce Margon, Catherine Manea, Robert Williams, Howard E. Bond, J. Xavier Prochaska, Michał K. Szymański, Nidia Morrell

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Abstract

We report the serendipitous discovery of an object, UVQS J060819.93-715737.4, with a spectrum dominated by extremely intense, narrow C ii emission lines. The spectrum is similar to those of the very rare, late-Type [WC11] low-mass Wolf-Rayet stars. Despite the recognition of these stars as a distinct class decades ago, there remains barely a handful of Galactic members, all of which are also planetary-nebula central stars. Although no obvious surrounding nebulosity is present in J0608, [O ii], [N ii], and [S ii] emission suggest the presence of an inconspicuous, low-excitation nebula. There is low-Amplitude incoherent photometric variability on timescales of days to years, as well as numerous prominent P Cygni profiles, implying mass loss. There are indications of a binary companion. The star is located on the outskirts of the LMC, and the observed radial velocity (∼+250 km s-1) and proper motion strongly suggest membership. If indeed an LMC member, this is the first extragalactic late [WC] star, and the first with an accurately determined luminosity, as the Galactic examples are too distant for precise parallax determinations. A high-quality, broad-coverage spectrum of the prototype of the late [WC] class, CPD-56° 8032, is also presented. We discuss different excitation mechanisms capable of producing the great strength of the C ii emission. Numerous autoionizing levels of C ii are definitely populated by processes other than dielectronic recombination. Despite the spectacular emission spectra, observational selection makes objects such as these difficult to discover. Members of the [WC11] class may in fact be considerably more common than the handful of previously known late [WC] stars.

Original languageEnglish (US)
Article number54
JournalAstrophysical Journal
Volume888
Issue number2
DOIs
StatePublished - Jan 10 2020

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All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Margon, B., Manea, C., Williams, R., Bond, H. E., Prochaska, J. X., Szymański, M. K., & Morrell, N. (2020). Discovery of a Rare Late-Type, Low-mass Wolf-Rayet Star in the LMC. Astrophysical Journal, 888(2), [54]. https://doi.org/10.3847/1538-4357/ab5e78