NSV 11154 Is a New R Coronae Borealis Star

NSV 11154 has been confirmed as a new member of the rare hydrogen-deficient R Coronae Borealis (RCB) stars based on new photometric and spectroscopic data. Using new photometry, as well as archival plates from the Harvard archive, we have constructed the historical light curve of NSV 11154 from 1896 to the present. The light curve shows the sudden, deep, irregularly spaced declines characteristic of RCB stars. The visible spectrum is typical of a cool (Teff ≲ 5000 K) RCB star, showing no hydrogen lines, strong C2 Swan bands, and no evidence of 13C. In addition, the star shows small pulsations that are typical of an RCB star and an infrared excess due to circumstellar dust, with a temperature of ∼800 K. The distance to NSV 11154 is estimated to be ∼14.5 kpc. RCB stars are very rare in the Galaxy, so each additional star is important to population studies leading to a better understanding the origins of these mysterious stars. Among the known sample of RCB stars, NSV 11154 is unusual in that it lies well above the Galactic plane (5 kpc) and away from the Galactic center, which suggests that its parent population is neither thick disk nor bulge.