Broad Hα Wings in Nebulae around Evolved Stars and in Young Planetary Nebulae

Arrieta, A.; Torres-Peimbert, S.

doi:10.1086/374922

Cited by 46 publications

(56 citation statements)

References 26 publications

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“…Note, however, that the FWZIs of such features are significantly smaller than those measured in the Arrieta & Torres-Peimbert (2003) sample and smaller than the H wings themselves.…”

Section: Broad H Emission Wingscontrasting

confidence: 58%

“…In these two objects, which happen to display H wings with similar widths and shapes, Raman scattering can be ruled out as the main line broadening mechanism. Arrieta & Torres-Peimbert (2003) found the same disagreement between the observed and predicted Raman profile for IRAS 20462+3416, which was also in their sample, concluding that a strong stellar wind is the most probable mechanism for line broadening in this case. We have searched for other emission features produced by Raman scattering in our spectra.…”

Section: Broad H Emission Wingsmentioning

confidence: 61%

“…In this scenario, Ly photons with a given velocity width are converted to optical photons that fill the H wing region. The conclusion of Arrieta & Torres-Peimbert (2003) is mainly supported by (1) the fit of the H -wing profile to a /k À2 law; (2) the presence of other Raman features produced in emission; and (3) the presence of a significant neutral hydrogen component. Criteria (1)Y(3) are to be satisfied for the line wings to be attributable to Raman scattering.…”

Section: Broad H Emission Wingsmentioning

confidence: 90%

“…The yet unclear origin of the very extended H wings, which are also observed in a number of PNs, has been discussed by Arrieta & Torres-Peimbert (2003). These authors consider several possible mechanisms for line broadening and conclude that Raman scattering of photons with wavelength close to Ly by neutral hydrogen is the most probable one in 12 of the 13 objects in their sample.…”

Section: Broad H Emission Wingsmentioning

confidence: 97%

“…As suggested by Arrieta & Torres-Peimbert (2003), further investigation of the effect of Raman scattering producing the line wings could be obtained by measuring the widths of UV lines produced in the same region as the Ly photons. This is because the width of the scattered H is proportional to the initial width of the Ly line, the Raman-scattering broadening factor being of k H /k Ly ¼ 6:4.…”

Section: Broad H Emission Wingsmentioning

confidence: 99%

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Echelle Long‐Slit Optical Spectroscopy of Evolved Stars

Contreras

Sahai²,

Paz

et al. 2008

Astrophysical Journal Supplement Series, The

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We present echelle long-slit optical spectra of a sample of objects evolving off the asymptotic giant branch (AGB), most of them in the preplanetary nebula ( PPN ) phase, obtained with the ESI and MIKE spectrographs at the 10 m Keck II and 6.5 m Magellan-I telescopes, respectively. The total wavelength range covered with ESI (MIKE) is $3900Y10900 8 ($3600Y7200 8). In this paper, we focus our analysis mainly on the H profiles. Prominent H emission is detected in half of the objects, most of which show broad H wings (with total widths of up to $4000 km s À1 ). In the majority of the H -emission sources, fast, post-AGB winds are revealed by P-Cygni profiles. In $37% of the objects H is observed in absorption. In almost all cases, the absorption profile is partially filled with emission, leading to complex, structured profiles that are interpreted as an indication of incipient post-AGB mass loss. The rest of the objects ($13%) are H nondetections. We investigate correlations between the H profile and different stellar and envelope parameters. All sources in which H is seen mainly in absorption have F-G type central stars, whereas sources with intense H emission span a larger range of spectral types from O to G, with a relative maximum around B, and also including very late C types. Shocks may be an important excitation/ionization agent of the close stellar surroundings for objects with late type central stars. Sources with pure emission or P Cygni H profiles have larger J À K color excess than objects with H mainly in absorption, which suggests the presence of warm dust near the star in the former. The two classes of profile sources also segregate in the IRAS color-color diagram in a way that intense H -emitters have dust grains with a larger range of temperatures. Spectral classification of the central stars in our sample is presented. For a subsample (13 objects), the stellar luminosity has been derived from the analysis of the O i 7771Y7775 8 infrared triplet. The location in the HR diagram of most of these targets, which represent $30% of the whole sample, is consistent with relatively high final (and, presumably, initial) masses in the range M f $ 0:6 Y0:9 M (M i $ 3Y 8 M ).

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“…Note, however, that the FWZIs of such features are significantly smaller than those measured in the Arrieta & Torres-Peimbert (2003) sample and smaller than the H wings themselves.…”

Section: Broad H Emission Wingscontrasting

confidence: 58%

Section: Broad H Emission Wingsmentioning

confidence: 61%

Section: Broad H Emission Wingsmentioning

confidence: 90%

Section: Broad H Emission Wingsmentioning

confidence: 97%

Section: Broad H Emission Wingsmentioning

confidence: 99%

See 3 more Smart Citations

Echelle Long‐Slit Optical Spectroscopy of Evolved Stars

Contreras

Sahai²,

Paz

et al. 2008

Astrophysical Journal Supplement Series, The

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Understanding the immediate progenitors of planetary nebulae

Sahai¹,

Morris²,

Contreras³

et al. 2011

Proc. IAU

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Abstract. Pre-Planetary Nebulae (PPNe) are believed to represent a relatively short, intermediate evolutionary phase in the evolution of AGB stars to Planetary Nebulae (PNe). Our unbiased, high-resolution imaging surveys with HST of young PNe and PPNe show very strong morphological similarities between these classes, enabling us to extend our morphological scheme for PPN classification to young PNe, preserving virtually all of the primary and secondary descriptors, and adding a few new ones. These morphological surveys show that the primary shaping of PNe begins during the PPNe and/or late-AGB phase, and the key to understanding the shaping process lies in the study of these PNe progenitors. Here we present results from two recent studies of PNe progenitors: (i) Hα emission with very broad wings and P-Cygni profiles as probes of the region where the fast post-AGB outflows that do the shaping are most likely launched from, and (ii) equatorial waists with large-sized dust grains and large masses.

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Polarization of the broad Hα wing in symbiotic stars

Yoo

Bak

Lee

2002

Monthly Notices of the Royal Astronomical Society

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In many symbiotic stars there appear broad wings around Hα, of which the formation mechanisms proposed thus far include a fast outflow, motion of the inner accretion disc, electron scattering and Raman scattering of Lyβ. We adopt a Monte Carlo technique to simulate the Raman scattering of ultraviolet photons that are converted into optical photons around Hα, forming broad wings, and compute its polarization. Noting that many symbiotic stars exhibit a bipolar nebular morphology and polarization flip in the red‐wing part of the Raman‐scattered O vi features, we assume that the neutral scattering region is composed of two components. The first component is a static cylindrical shell with finite thickness; and the second component is a finite slab that is moving away with velocity vp= 100 km s−1 along the symmetry axis of the first component. The cylindrical shell component yields polarization in the direction parallel to the cylinder axis. The strongest polarization is obtained in the limit where the height of the cylinder approaches zero and the scattering region effectively becomes a circular ring. As the height of the cylinder increases, the resultant polarization decreases and becomes negligible in the limit of the infinite cylinder. The polarization near the line centre is weaker than in the far‐wing regions because of the large Rayleigh scattering numbers arising from the large scattering cross‐sections near the line centre. The receding polar scattering component produces strong polarization in the direction perpendicular to the cylinder axis. In the presence of a Lyβ emission‐line component with an equivalent width ∼ 0.5 Å, the polarized flux exhibits a local maximum at λ= 6578 Å that corresponds to a recession velocity 6.4vp relative to Hα. When both of the scattering components co‐exist, the polarization is characterized by weak parallel polarization near the line centre and strong perpendicular polarization in the red part. We discuss the observational implications of our computation.

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Broad Hα Wings in Nebulae around Evolved Stars and in Young Planetary Nebulae

Cited by 46 publications

References 26 publications

Echelle Long‐Slit Optical Spectroscopy of Evolved Stars

Echelle Long‐Slit Optical Spectroscopy of Evolved Stars

Understanding the immediate progenitors of planetary nebulae

Polarization of the broad Hα wing in symbiotic stars

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