Detection of circumstellar dust shell around supergiant TV GEM from milliarcsecond resolution near infrared observations

Abstract

The M1 supergiant TV Gem has been observed at 2.2 µm by lunar occultation technique. The central star has been resolved from our observatins. We have also detected the circumstellar dust envelope around this star from our light curve. The detected circumstellar dust envelope has an radius of ~20 RH with star to shell flux ratio of ~35 at 2.2 µm. A simple radiative transfer dust shell model constrained by our occultation observations, 9.7 µm silicate emission feature strength and far IR excess seen in IRAS observations shows that the dust is probably restricted to two well separated dust shells - the inner shell is at a radial distance of ~20 RH and the outer one is at ~500 RH. Sporadic dust condensation in TV Gem is suggested, which might be a general phenomena in late type supergiants.