Evolution of the Dust/Gas Environment around Herbig Ae/Be Stars

• Published in: The Astrophysical journal 2011-06, Vol.734 (1), p.22-jQuery1323907606770='48'
• Main Authors: Liu, Tie, Zhang, Huawei, Wu, Yuefang, Qin, Sheng-Li, Miller, Martin
• Format: Article
• Language: English
• Subjects: Age; Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON 13; CARBON COMPOUNDS; CARBON ISOTOPES; CARBON MONOXIDE; CARBON OXIDES; CHALCOGENIDES; CORRELATIONS; DENSITY; Disks; DUSTS; Earth, ocean, space; ELEMENTS; EMISSION; ENERGY SPECTRA; Envelopes; EVEN-ODD NUCLEI; EVOLUTION; Exact sciences and technology; HYDROGEN; Infrared; ISOTOPES; LIGHT NUCLEI; LINE WIDTHS; MASS; NONMETALS; NUCLEI; OXIDES; OXYGEN COMPOUNDS; PHYSICAL PROPERTIES; SPECTRA; Spectral energy distribution; STABLE ISOTOPES; STAR EVOLUTION; STARS
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/734/1/22

Using the KOSMA 3 m telescope, 54 Herbig Ae/Be (HAe/Be) stars were surveyed in CO and 13CO emission lines. The properties of the stars and their circumstellar environments were studied by fitting spectral energy distributions (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 X 1021 cm--2 for stars younger than 106 yr, while this drops to 2.5 X 1021 cm--2 for those older than 106 yr. No significant difference is found among the SEDs of HAe and HBe stars of the same age. Infrared excess decreases with age, envelope masses and envelope accretion rates decease with age after 105 yr, the average disk mass of the sample is 3.3 X 10--2 M , the disk accretion rate decreases more slowly than the envelope accretion rate, and a strong correlation between the CO line intensity and the envelope mass is found.