2020/06/08 by B. Margon, Bruce Margon, Philip Massey +3
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Large Magellanic Cloud #Line (geometry) #Luminosity #Physics #Spectral line #Stars #Stellar, planetary, and galactic studies #White dwarf #astro-ph.GA #astro-ph.SR
paper · pdf · doi:10.3847/1538-4357/ab9abe
Accepted for publication in the Astrophysical Journal, 2020
arxiv created 2020/06/08 · openalex publication_date 2020/07/01 · arxiv updated 2020/08/05 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract We present a narrowband imaging survey of the Large Magellanic Cloud (LMC), designed to isolate the C ii λλ 7231, 7236 emission lines in objects as faint as m λ 7400 ∼ 18. The work is motivated by the recent serendipitous discovery in the LMC of the first confirmed extragalactic [WC11] star, whose spectrum is dominated by C ii emission, and the realization that the number of such objects is currently largely unconstrained. The survey, which imaged ∼50 deg 2 using on-band and off-band filters, will significantly increase the total census of these rare stars. In addition, each new LMC [WC] star has a known luminosity, a quantity quite uncertain in the Galactic sample. Multiple known C ii emitters were easily recovered, validating the survey design. We find 38 new C ii emission candidates; spectroscopy of the complete sample will be needed to ascertain their nature. In a preliminary spectroscopic reconnaissance, we observed three candidates, finding C ii emission in each. One is a new [WC11]. Another shows both the narrow C ii emission lines characteristic of a [WC11], but also broad emission of C iv , O v , and He ii characteristic of a much hotter [WC4] star; we speculate that this is a binary [WC]. The third object shows weak C ii emission, but the spectrum is dominated by a dense thicket of strong absorption lines, including numerous O ii transitions. We conclude it is likely an unusual hot, hydrogen-poor post-AGB star, possibly in transition from [WC] to white dwarf. Even lacking a complete spectroscopic program, we can infer that late [WC] stars do not dominate the central stars of LMC planetary nebulae, and that the detected C ii emitters are largely of an old population.