2MASS Discoveries of Cool, Dust‐enshrouded Carbon Stars out of the Galactic Plane1

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Abstract
Several very cool carbon stars have been found in or beyond the Galactic halo in the Two Micron All Sky Survey (2MASS). All appear to be N (C‐N) type asymptotic branch giants, much redder than most carbon stars found at high Galactic latitude at optical wavelengths. Three are heavily dust enshrouded, radiate primarily in the thermal infrared at temperatures of order 1000 K, and are IRAS sources. Low‐resolution red spectrophotometry with the Keck II and Palomar 5 m telescopes shows red to extremely red continua with CN absorption bands, similar to IRAS SSC 08546+1732, which is detected here (2MASSI J0857258+172052). One object, 2MASSI J0401097+182807, featured an overlying low‐excitation emission‐line spectrum with neutral alkalis (Ki, Rb i, and Cs i), which disappeared after 19 months. This is argued to be due to vigorous mass loss probably associated with Mira‐like pulsations. These initial results suggest that 2MASS can be used to define a useful sample at high Galactic latitude as tracers of the Galactic halo out to distances comparable to those of the Magellanic Clouds.

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