Observations of high rotational CO lines in post-asymptotic giant branch stars and planetary nebulae

Journal Article · Sat Feb 01 04:00:00 EST 1997 · Astrophysical Journal

DOI:https://doi.org/10.1086/303623· OSTI ID:503581

Justtanont, K ^[1]; Tielens, A G ^[1]; Skinner, C J ^[2]; Haas, M R ^[3]

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1. NASA Ames Research Center, Mail Stop 245-3, Moffett Field, California 94035-1000 (United States)
2. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218 (United States)
3. NASA Ames Research Center, Mail Stop 245-6, Mofflett Field, California 94035-1000 (United States)

We have observed bright emission in high rotational CO lines (J=13{endash}12, 17{endash}16, and 22{endash}21) in the post-AGB object GL 2688 and the planetary nebulae, GL 618 and NGC 7027. These stars represent different evolutionary stages, as reflected by their effective temperatures. The observations reveal copious amounts of warm, dense molecular gas (n{approximately}10{sup 7}cm{sup {minus}3}; T{approximately}10{sup 3}K), implying that the AGB is terminated by a short-lived phase of high mass-loss rate. We investigate heating mechanisms for these objects. For NGC 7027, UV photons from the central star produce a photodissociation region and the gas cools via CO rotational transitions, as well as via fine-structure atomic lines. A shock is thought to heat the gas in GL 2688, which cools mainly via the [OI] 63 {mu}m line and molecular rotational lines. For GL 618, both mechanisms may coexist. {copyright} {ital 1997} {ital The American Astronomical Society}

• OSTI ID: 503581
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 476; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
CARBON MONOXIDE
DISSOCIATION
GIANT STARS
INFRARED SPECTRA
PLANETARY NEBULAE
RADIATION FLUX
ROTATIONAL STATES
SHOCK WAVES