Angular diameter of IRC +10011 at 2.2, 10, and 20 microns.

The size of the long-period variable IRC + 10011 at 2.2, 10, and 20 has been measured by means of lunar occultations. At 10 and 20 the bulk of the radiation comes from an optically thick dust region about 0' 1 in diameter. At 2.2 the dominant source of radiation is the central Mira star, but the inner part of the dust shell is also visible. Sabject headings: circumstellar shells - infrared sources - long-period variables - lunar occultation