Modeling of the dust and gas outflows from OH 26.5+0.6: The superwind

Journal Article · Mon Jan 01 04:00:00 EST 1996 · Astrophysical Journal

DOI:https://doi.org/10.1086/176655· OSTI ID:279885

Justtanont, K ^[1]; Skinner, C J ^[2]; Tielens, A G ^[1]; Meixner, M ^[3]; Baas, F ^[4]

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1. NASA Ames Research Center, MS 245-3, Moffett Field, California 94035 (United States)
2. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218 (United States)
3. Astronomy Department, MC 221, 1002 W. Green Street, University of Illinois, Urbana, Illinois 61801 (United States)
4. Leiden Observatory, P.O. Box 9513, NL-2300, RA Leiden (The Netherlands)

We have observed the extreme OH/IR star, OH 26.5+0.6, in the infrared dust continuum and in the sub-millimeter rotational lines of CO. Mid-infrared images reveal the compact nature of the circumstellar shell ({lt}0{center_dot}{double_prime}5). A deep 9.7 {mu}m absorption feature and an absorption at 18 {mu}m show that the dust mass-loss rate is very high. However, the low antenna temperatures of CO {ital J}=1{minus}0 and 2{minus}1 lines suggest that the outer part of the circumstellar shell is much more tenuous. In order to resolve this discrepancy, we have observed the {ital J}=3{minus}2 and 4{minus}3 CO rotational transitions. We have developed a model for the circumstellar shell for OH 26.5+0.6 which is consistent with the infrared and submillimeter observations. The dust and gas data are well fitted by a two-shell model, consisting of a dense shell surrounded by a more tenuous shell. The former we identify with the superwind ({dot {ital M}}=5.5{times}10{sup {minus}4}{ital M}{sub {circle_dot}} yr{sup {minus}1}), and the latter we identify with mass loss on the asymptotic giant branch (AGB) ({dot {ital M}}=10{sup {minus}6}{ital M}{sub {circle_dot}} yr{sup {minus}1}). The transition between the two mass-loss phases is shown to be rather abrupt ({Delta}{ital t}{lt}150 yr). Depending on the mass of the progenitor, this superwind phase may be the last thermal pulse (for {ital M}{sub {asterisk}}{lt}1.5{ital M}{sub {circle_dot}}), or the first of a series of the superwind phases (for up to 8{ital M}{sub {circle_dot}}), punctuated by a period of low mass-loss rates, before the star evolves off the AGB. {copyright} {ital 1996 The American Astronomical Society.}

• Research Organization: Lawrence Livermore National Laboratory
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 279885
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 456; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
CARBON MONOXIDE
CIRCUMSTELLAR SHELLS
COSMIC DUST
ENERGY SPECTRA
GAS FLOW
GHZ RANGE 100-1000
GIANT STARS
IMAGES
INFRARED SPECTRA
MASS LOSS
MATHEMATICAL MODELS
OH-IR STARS
ROTATIONAL STATES
SHELLS
STELLAR WINDS