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

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.