Hubble Space Telescope/NICMOS near-infrared imaging of the proto planetary nebula OH 231.8+4.2
| Autor: | Meakin, CA, Bieging, JH, Latter, WB, Hora, JL, Tielens, AGGM |
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| Přispěvatelé: | Kapteyn Astronomical Institute |
| Jazyk: | angličtina |
| Rok vydání: | 2003 |
| Předmět: |
OH231.8+4.2
Astrophysics::High Energy Astrophysical Phenomena Astrophysics::Cosmology and Extragalactic Astrophysics YOUNG STELLAR OBJECTS circumstellar matter planetary nebulae : individual (OH 231.8+4.2) MODEL SCATTERING ENVELOPES OH 231.8+4.2 MOLECULAR OUTFLOW BIPOLAR OUTFLOW LONG-SLIT SPECTROSCOPY JETS Astrophysics::Solar and Stellar Astrophysics Astrophysics::Earth and Planetary Astrophysics EMISSION OH/IR STARS Astrophysics::Galaxy Astrophysics stars : AGB and post-AGB infrared : stars |
| Zdroj: | Astrophysical Journal, 585(1), 482-493. IOP PUBLISHING LTD |
| ISSN: | 0004-637X |
| Popis: | We present observations of the bipolar nebula OH 231.8+4.2, made with the Hubble Space Telescope (HST) NICMOS camera, in three wide filter bands (F205W, F160W, and F110W). The images have excellent dynamic range after removal of low-level instrumental artifacts. In the F205W filter (lambda approximate to 2.04 mum), we achieve a peak/rms of greater than 8000 with an angular resolution of 0."20 (FWHM). The combination of high dynamic range and angular resolution confirms previous observations but also reveals new features in the near-IR morphology of the nebula, which at these wavelengths is dominated by scattered light. The northern (approaching) lobe shows well-defined, limb-brightened edges. The central jet splits into two laments and exhibits some curvature between the center of the nebula and the end of the northern lobe. The southern (receding) lobe has a diffuse, occulent appearance without a sharply defined central jet, in contrast to the northern lobe. A sharpened version of the F205W image shows indications of turbulent structures both in the northern lobe and jet and in the southern lobe. A faint cylindrical halo of scattered light shows a sharp increase in surface brightness inside a radius of similar to4" from the center, possibly resulting from a transition from a spherical wind to a disk- or torus-like mass ejection, on the same timescale as the formation of the collimated fast wind seen in CO and HCO(+) images. We calculate the extinction through the nebula from the measured near-IR colors and a silicate grain model. For a simple geometric model of a dense central disk, we estimate a disk mass (gas and dust) in the range 0.03-0.06 M., relatively insensitive to grain size. The circumstance of an asymptotic giant branch (AGB) star with a massive, highly collimated, high-velocity bipolar flow may be understood in terms of the model of Soker & Rappaport if the central star underwent a change in mass-loss properties from a (roughly) spherical AGB wind to equatorially enhanced mass loss beginning similar to(1-3) X 10(3) yr ago. Supposing the presence of a dwarf companion in a suitable orbit, the bipolar nebula then is a consequence of a strong increase in mass loss as the central star evolves close to the tip of the AGB and will soon evolve to higher T(eff) and appear as a more typical proto planetary nebula. |
| Databáze: | OpenAIRE |
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