A VLA 3.6 centimeter survey of N-type carbon stars

The results are presented of a VLA-continuum survey of 7 N-type carbon stars at 3.6 cm. Evidence exists for hot plasma around such stars; the IUE satellite detected emission lines of singly ionized metals in the optically brightest carbon stars, which in solar-type stars indicate the existence of a chromosphere. In the past, these emission lines were used to constrain the lower portion of the archetypical chromospheric model of N-type carbon stars, that of TX Psc. Five of the survey stars are semiregular (1 SRa and 4 SRb) variables and two are irregular (Lb) variables. Upper limits of about 0.07 mJy are set of the SRb and Lb variables and the lone SRa (V Hya) was detected with a flux of 0.22 mJy. The upper limits for the six stars that are not detected indicate that the temperature in their winds is less than 10,000 K. Various scenarios for the emission from V Hya are proposed, and it is suggested that the radio continuum is shock-related (either due to pulsation or the suspected bipolar jet) and not due to a supposed accretion disk around an unseen companion.