Near-infrared observations of the carbon stars TU Geminorum and SS Virginis at milliarcsecond resolution

Abstract

Aims.High-angular resolution investigations of carbon stars.
Methods. Milliarcsecond resolution observations in the near infrared K band by the method of lunar occultations are presented for the carbon stars TU Gem and SS Vir.
Results. Although a companion to TU Gem is known from the Tycho catalogue, we were not able to detect it so we place limits on its K-band brightness. For both stars, we determined accurate values of the angular diameters at the phase of the observation, namely 8.37 ± 0.07 mas and 4.62±0.15 mas for SS Vir and TU Gem. Using distance estimates from the literature, we found that the two stars have radii of about 500 R_⊙ and 250 R_⊙, respectively. We also computed their effective temperatures.
Conclusions. The result for SS Vir (2445 ± 40 K) is in good agreement with estimates, but in the case of TU Gem our value of 3160 ± 110 K requires reconsidering currently available models.