IRTF Data Archive Program Information

# # Program information file # PROGRAM_ID 2023A026 PROGRAM_TITLE The ortho/para ammonia conundrum in VY CMa. Comparative studies using high-resolution TEXES observations of ammonia in the late-type stars NML Cyg and IRC+10216 PROGRAM_INV1 Guido W. Fuchs PROGRAM_INV2 Eileen Doering PROGRAM_INV3 Thomas K. Greathouse PROGRAM_INV4 Rohini S. Giles PROGRAM_INV5 John H. Lacy PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG We would like to solve a puzzle that arose from previous TEXES/IRTF and EXES/SOFIA observations where we investigated NH3 in the envelope of the massive late-type star VY CMa. Since a while, the unusually high ammonia abundances relative to hydrogen of more than 1E-6 in the circumstellar envelope of evolved stars, such as VY CMa, have been noticed and considered an enigma. Even equally puzzling is our recently discovered mismatch of ortho[o]- to para[p]-ammonia with o/p>1.5 in VY CMa and that of other stars like IK Tau [o/p>2] that we re-investigated from previous observations. In line with these findings are the results found in 2006, where NH3 emission data of Odin observations towards IRC+10216 hint towards an unusually high o/p ratio when compared with 24 GHz data. The question therefore arises what causes these unusual ratios, and are they specific to certain types of stars? Beside a detailed analysis of the NH3 spectrum in the circumstellar envelope [CSE] of VY CMa and other stars, further comparative studies are now planned to investigate other stellar environments. Among these are the CSE of the massive M-type star NML Cyg, as it is very similar to VY CMa, and the aforementioned carbon star IRC+10216. However, for both stars a small but important part of the NH3 spectrum at 10.7 mu and 11.2 mu is missing or incomplete. With this proposal, we would like to close this gap to be able to make an appropriate comparison. PROGRAM_ABSTRACT_END