Near-infrared observations of candidate extrinsic S stars
Yunnan Observatory, National Observatories, CAS, Kunming 650011, PR China
2 Joint Laboratory for Optical Astronomy, CAS, Beijing 100012, PR China
Corresponding author: X.-H. Wang, firstname.lastname@example.org
Accepted: 30 January 2002
Photometric observations in the near infrared for 161 S stars, including 18 Tc-rich (intrinsic) stars, 19 Tc-deficient (extrinsic) ones and 124 candidates for Tc-deficient S stars, are presented in this paper. Based on some further investigations into the infrared properties of both Tc-rich and Tc-deficient S stars, 104 candidates are identified as very likely Tc-deficient S stars. The large number of infrared-selected Tc-deficient S stars provides a convenient way to study the physical properties and the evolutionary status of this species of S stars.
Key words: stars: AGB and post-AGB / stars: evolution / stars: circumstellar matter / infrared: stars
© ESO, 2002