AN INFRARED NEBULA ASSOCIATED WITH δ CEPHEI: EVIDENCE OF MASS LOSS?

We present the discovery of an infrared nebula around the Cepheid prototype delta Cephei and its hot companion HD 213307. Large-scale (similar to 2.1 x 10(4) AU) nebulosity is detected at 5.8, 8.0, 24, and 70 mu m. Surrounding the two stars, the 5.8 and 8.0 mu m emission is largely attributable to polycyclic aromatic hydrocarbon emission swept from the interstellar medium by a wind originating from delta Cephei and/or its companion. Stochastically heated small dust grains are the most likely source of the 24 and 70 mu m extended emission. The 70 mu m emission, in particular, resembles a bow shock aligned in the direction of the proper motion of delta Cephei. This discovery supports the hypothesis that delta Cephei may be currently losing mass, at a rate in the range of approximate to 5 x 10(-9) to 6 x 10(-8) M-circle dot yr(-1).