With the KOSMA 3-m telescope, 54 Herbig Ae/Be stars were surveyed in CO and 13CO emission lines. The properties of the stars and their circumstellar environments are studied by fitting the SEDs. The mean line width of 13CO (2-1) lines of this sample is 1.87 km s−1. The average column density of H2 is found to be 4.9×1021 cm−2 for the stars younger than 106 yr, while drops to 2.5×1021 cm−2 for those older than 106 yr. No significant difference is found among the SEDs of Herbig Ae stars and Herbig Be stars at the same age. The infrared excess decreases with age. The envelope masses and the envelope accretion rates decease with age after 105 yr. The average disk mass of the sample is 3.3×10−2M\sun. The disk accretion rate decreases more slowly than the envelope accretion rate. A strong correlation between the CO line intensity and the envelope mass is found.
@article{arxiv.1105.5534,
title = {Evolution of the dust/gas environment around Herbig Ae/Be stars},
author = {Tie Liu and Huawei Zhang and Yuefang Wu and Sheng-Li Qin and Martin Miller},
journal= {arXiv preprint arXiv:1105.5534},
year = {2015}
}