Managementof postoperative nausea and vomiting

Knapp, Robert M.

doi:10.1017/cbo9780511842306.056

Cited by 5 publications

(14 citation statements)

References 19 publications

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“…(The difference in these ratios is probably due to the fast wind being confined to the inner regions of the CRL 618 circumstellar envelope while the envelope produced by the steady wind is more extended and is partly resolved). CSO observations of AFGL 2688 give ratios of about ∼0.12 and 0.24 , and of V Hya ∼0.07 and 0.06 (Knapp, Jorissen and Young 1997).…”

Section: Acknowledgementsmentioning

confidence: 94%

“…evolving away from the AGB. There is evidence that the formation of fast winds occurs after that of slow winds, and that these fast winds are bipolar (Morris et al 1987;Cernicharo et al 1989;Gammie et al 1989;Bachiller et al 1991;Neri et al 1992;Young et al 1992;Jaminet et al 1992;Bujarrabal et al 1994;Alcolea et al 1996;Knapp, Jorissen and Young 1997).…”

Section: Acknowledgementsmentioning

confidence: 99%

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Multiple Molecular Winds in Evolved Stars. I. A Survey of CO(2–1) and CO(3–2) Emission from 45 Nearby Asymptotic Giant Branch Stars

Knapp

Lee

Jorissen

1998

ASTROPHYS J SUPPL S

161

256

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This paper describes observations of a new phenomenon in evolved mass-losing AGB stars: the presence of two winds with different expansion velocities. CO(2-1) and CO(3-2) line emission was observed for 45 AGB stars at high velocity resolution and double winds found in 20% of the sample. Highly asymmetric lines were found in six other stars. The data tentatively suggest that double winds occur when the star undergoes a change (pulsational mode, chemical composition) and that the very narrow components represent the onset of a new phase of mass loss.the interstellar radiation field (Morris 1980;Mamon, Glassgold and Huggins 1988;Kastner 1992;Groenewegen 1994). This model predicts simple line shapes; optically thick emission lines are parabolic while optically thin lines are flat-topped, and the full width of the line at zero power is twice the terminal outflow speed of the wind.While this model (hereafter called the "steady wind") gives a decent first order representation of most circumstellar shells, recent, more detailed observations have found many shells which deviate from this simple description:1. Bipolar outflows. The shells around many mass-losing stars (e.g. VY CMa, AFGL 2688, and OH231.8+4.2) show flattened, bipolar structure on scales of ∼ 10 16 cm (e.g. Olofsson 1997a).2. Very fast molecular winds. The highest steady wind outflow speeds, up to

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Section: Acknowledgementsmentioning

confidence: 94%

Section: Acknowledgementsmentioning

confidence: 99%

Multiple Molecular Winds in Evolved Stars. I. A Survey of CO(2–1) and CO(3–2) Emission from 45 Nearby Asymptotic Giant Branch Stars

Knapp

Lee

Jorissen

1998

ASTROPHYS J SUPPL S

161

256

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“…The carbon star V Hya has bright CO emission, weak CS emission and a very unusual CO line shape, with two horns and a Voigt-like line profile, quite different from the parabolic, steep sided line profile seen from almost all other AGB envelopes. In addition, the star has a fast molecular wind with an outflow velocity of at least 200 km s −1 (Knapp et al 1997).…”

Section: Hyamentioning

confidence: 99%

“…The distance to V Hya can be estimated at 380 pc assuming a standard absolute K magnitude, consistent with the upper limit to the Hipparcos parallax, 0.16±1.29 mas, Perryman et al (1997). The velocity and spatial structure of the CO emission from the V Hya envelope is complex (Kahane et al 1996;Knapp et al 1997). The CS(5-4) and (7-6) lines have relatively simple shapes, and the line widths suggest an outflow velocity of 15 km s −1 , consistent with the width of the weak, tentatively detected CI line (Table 2, Figure 1).…”

Section: Hyamentioning

confidence: 99%

Atomic Carbon in the Envelopes of Carbon‐rich Post–Asymptotic Giant Branch Stars

Knapp

Crosas

Ivezić

2000

ApJ

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Atomic carbon has been detected in the envelopes of three carbon-rich evolved stars: HD 44179 (=AFGL 915, the 'Red Rectangle'); HD 56126; and, tentatively, the carbon star V Hya. This brings to seven the number of evolved star envelopes in which CI has been detected. Upper limits were found for several other stars, including R CrB. CI was not detected in several oxygen rich post asymptotic giant branch (AGB) stars (OH231.8+4.2, for example), although it is detected in their carbon-rich analogues. Two trends are evident in the data. First, circumstellar envelopes with detectable CI are overwhelmingly carbon rich, suggesting that much of the CI is produced by the dissociation of molecules other than CO. Second, the more evolved the envelope away from the AGB, the higher is the CI/CO ratio. The oxygen-rich supergiant star α Ori remains the only oxygen rich star with a wind containing detectable CI.These data suggest an evolutionary sequence for the CI/CO ratio in cool circumstellar envelopes. This ratio is small (a few %) while the star is on the AGB, and the CI is located in the outer envelope and produced by photodissociation. The ratio increases to about 0.5 as the star evolves away from the AGB because of the dissociation of CO and other carbon-bearing molecules by shocks caused by the fast winds which appear at the end of evolution on the AGB. Finally, the ratio becomes >> 1 as the central star becomes hot enough to photodissociate CO.

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“…Lloyd Evans (1991) obtained optical spectra in the blue-violet range and found emission lines indicating outflow velocities up to about 160 km s −1 . High signal-to-noise millimeter-wave CO J=2-1 and 3-2 line profiles showed wide wings, implying that the high-speed (200 km s −1 ) outflow was fairly massive (Knapp et al 1997). Mmwave interferometry of the CO lines by Hirano et al (2004) with ∼ 3 − 4 resolution showed that the highvelocity outflow is bipolar, blobby and highly collimated (see also Kahane et al 1996).…”

Section: Introductionmentioning

confidence: 96%

High-Speed Bullet Ejections During the Agb-to-Planetary Nebula Transition: HST Observations of the Carbon Star, v Hydrae

Sahai

Scibelli

Morris

2016

ApJ

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The well-studied carbon star, V Hya, showing evidence for high-speed, collimated outflows and dense equatorial structures, is a key object in the study of the poorly understood transition of AGB stars into aspherical planetary nebulae. Using the STIS instrument onboard HST, we have obtained high spatial-resolution long-slit optical spectra of V Hya that show high-velocity emission in [SII] and [FeII] lines. Our dataset, spanning three epochs spaced apart by a year during each of two periods (in 2002-2004 and 2011-2013), shows that V Hya ejects high-speed (∼ 200 − 250 km s −1 ) bullets once every ∼8.5 yr. The ejection axis flip-flops around a roughly eastern direction, both in and perpendicular to the sky-plane, and the radial velocities of the ejecta also vary in concert between low and high values. We propose a model in which the bullet ejection is associated with the periastron passage of a binary companion in an eccentric orbit around V Hya with an orbital period of ∼8.5 yr. The flip-flop phenomenon is likely the result of collimated ejection from an accretion disk (produced by gravitational capture of material from the primary) that is warped and precessing, and/or that has a magnetic field that is misaligned with that of the companion or the primary star. We show how a previously observed 17-year period in V Hya's light-cycle can also be explained in our model. Additionally, we describe how the model proposed here can be extended to account for multipolar nebulae.

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Managementof postoperative nausea and vomiting

Cited by 5 publications

References 19 publications

Multiple Molecular Winds in Evolved Stars. I. A Survey of CO(2–1) and CO(3–2) Emission from 45 Nearby Asymptotic Giant Branch Stars

Multiple Molecular Winds in Evolved Stars. I. A Survey of CO(2–1) and CO(3–2) Emission from 45 Nearby Asymptotic Giant Branch Stars

Atomic Carbon in the Envelopes of Carbon‐rich Post–Asymptotic Giant Branch Stars

High-Speed Bullet Ejections During the Agb-to-Planetary Nebula Transition: HST Observations of the Carbon Star, v Hydrae

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