The Poetics of Commemoration

Goeres, Erin Michelle

doi:10.1093/acprof:oso/9780198745747.001.0001

Cited by 8 publications

(5 citation statements)

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“…The only other HDC PN to show evidence for a dust disk is M2-29 which experienced a remarkable dust obscuration event in its lightcurve (Hajduk et al 2008;Gesicki et al 2010;Miszalski et al 2011a). Miszalski et al (2011a) applied a simple R Coronae Borealis star model (Goeres & Sedlmayr 1992) to the M2-29 lightcurve to determine that the dust responsible for these events forms at ∼70 AU from the WD. This separation is comparable to the distance of the M-dwarf companion from the WD in EGB6.…”

Section: Planetary Nebulae With High Density Coresmentioning

confidence: 99%

Symbiotic stars and other Hα emission-line stars towards the Galactic bulge★

Miszalski

Mikołajewska

Udalski

2013

Monthly Notices of the Royal Astronomical Society

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Symbiotic stars are interacting binaries with the longest orbital periods and their multi-component structure makes them rich astrophysical laboratories. The accretion of a high mass loss rate red giant wind on to a white dwarf (WD) makes them promising Type Ia supernovae (SNe Ia) progenitors. Systematic surveys for new Galactic symbiotic stars are critical to identify new promising SNe Ia progenitors (e.g. RS Oph) and to better estimate the total population size to compare against SNe Ia rates. Central to the latter objective is building a complete census of symbiotic stars towards the Galactic Bulge. Here we report on the results of a systematic survey of Hα emission line stars covering 35 deg 2 . It is distinguished by the combination of deep optical spectroscopy and long-term lightcurves that improve the certainty of our classifications. A total of 20 bona-fide symbiotic stars are found (13 S-types, 6 D-types and 1 D ′ -type), 35% of which show the symbiotic specific Raman-scattered OVI emission bands, as well as 15 possible symbiotic stars that require further study (6 S-types and 9 D-types). Lightcurves show a diverse range of variability including stellar pulsations (semi-regular and Mira), orbital variations and slow changes due to dust. Orbital periods are determined for 5 S-types and Mira pulsation periods for 3 D-types. The most significant D-type found is H1-45 and its carbon Mira with a pulsation period of 408.6 days, corresponding to an estimated period-luminosity relation distance of ∼6.2 ± 1.4 kpc and M K = −8.06 ± 0.12 mag. If H1-45 belongs to the Galactic Bulge, then it would be the first bona-fide luminous carbon star to be identified in the Galactic Bulge population. The lack of luminous carbon stars in the Bulge is a longstanding unsolved problem. A possible explanation for H1-45 may be that the carbon enhancement was accreted from the progenitor of the WD companion. A wide variety of unusual emission line stars were also identified. These include central stars of PNe (one [WC10-11] Wolf-Rayet and 5 with high density cores), 2 novae, 2 WN6 Wolf-Rayet stars, 2 possible Be stars, a B[e] star with a bipolar outflow, an ultracompact HII region and a dMe flare star. Dust obscuration events were found in two central stars of PNe, increasing the known cases to 5, as well as one WN6 star. There is considerable scope to uncover several more symbiotic stars towards the Bulge, many of which are currently misclassified as PNe, provided that deep spectroscopy is combined with optical and near-infrared lightcurves.

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Section: Planetary Nebulae With High Density Coresmentioning

confidence: 99%

Symbiotic stars and other Hα emission-line stars towards the Galactic bulge★

Miszalski

Mikołajewska

Udalski

2013

Monthly Notices of the Royal Astronomical Society

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“…The formation process of fullerenes in space is still uncertain and several mechanisms have been proposed in the literature as the most suitable ones: i) the formation in H-poor environments (Goeres & Sedlmayr 1992); ii) high-and low-temperature formation in C-rich environments (Jäger et al 2009;Fulvio et al 2017); iii) photochemical processing of hydrogenated amorphous carbon grains (HACs; García-Hernández et al 2010); and iv) photochemical processing of large PAHs (Berné & Tielens 2012). Hydrogenated species cannot be produced by the first two mechanisms, which is very difficult to reconcile with the astronomical evidence.…”

Section: Introductionmentioning

confidence: 99%

GTC/CanariCam Mid-IR Imaging of the Fullerene-rich Planetary Nebula IC 418: Searching for the Spatial Distribution of Fullerene-like Molecules

Díaz-Luis

García-Hernández

Manchado

et al. 2018

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We present seeing-limited narrow-band mid-IR GTC/CanariCam images of the spatially extended fullerenecontaining planetary nebula (PN) IC 418. The narrow-band images cover the C 60 fullerene band at 17.4 µm, the polycyclic aromatic hydrocarbon like (PAH-like) feature at 11.3 µm, the broad 9-13 µm feature, and their adjacent continua at 9.8 and 20.5 µm. We study the relative spatial distribution of these complex species, all detected in the Spitzer and Infrared Space Observatory (ISO) spectra of IC 418, with the aim of getting observational constraints to the formation process of fullerenes in H-rich circumstellar environments. A similar ring-like extended structure is seen in all narrow-band filters, except in the dust continuum emission at 9.8 µm, which peaks closer to the central star. The continuum-subtracted images display a clear ring-like extended structure for the carrier of the broad 9-13 µm emission, while the spatial distribution of the (PAH-like) 11.3 µm emission is not so well defined. Interestingly, a residual C 60 17.4 µm emission (at about 4-σ from the sky background) is seen when subtracting the dust continuum emission at 20.5 µm. This residual C 60 emission, if real, might have several interpretations; the most exciting being perhaps that other fullerene-based species like hydrogenated fullerenes with very low H-content may contribute to the observed 17.4 µm emission. We conclude that higher sensitivity mid-IR images and spatially resolved spectroscopic observations (especially in the Q-band) are necessary to get some clues about fullerene formation in PNe.

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“…molecule/dust formation at a radius of 20 R ⋆ from the star. The temperature of the gas in this region is observed to be < 1500 K (Goeres & Sedlmayr 1992). The effective temperature of RCB's range from 4,000-20,000 K, with mean values of 6000-8000 K for dust-forming sources (Lambert & Rao 1994).…”

Section: Casementioning

confidence: 90%

Is acetylene essential for carbon dust formation?

Dhanoa¹,

Rawlings²

2014

Monthly Notices of the Royal Astronomical Society

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We have carried out an investigation of the chemical evolution of gas in different carbonrich circumstellar environments. Previous studies have tended to invoke terrestrial flame chemistries, based on acetylene (C 2 H 2 ) combustion to model the formation of carbon dust, via Polycyclic Aromatic Hydrocarbons (PAHs). In this work we pay careful attention to the accurate calculation of the molecular photoreaction rate coefficients to ascertain whether there is a universal formation mechanism for carbon dust in strongly irradiated astrophysical environments. A large number of possible chemical channels may exist for the formation of PAHs, so we have concentrated on the viability of the formation of the smallest building block species, C 2 H 2 , in a variety of carbon-rich stellar outflows. C 2 H 2 is very sensitive to dissociation by UV radiation. This sensitivity is tested, using models of the time-dependent chemistry. We find that C 2 H 2 formation is sensitive to some of the physical parameters and that in some known sources of dust-formation it can never attain appreciable abundances. Therefore multiple (and currently ill-defined) dust-formation channels must exist.

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The Poetics of Commemoration

Cited by 8 publications

References 0 publications

Symbiotic stars and other Hα emission-line stars towards the Galactic bulge★

Symbiotic stars and other Hα emission-line stars towards the Galactic bulge★

GTC/CanariCam Mid-IR Imaging of the Fullerene-rich Planetary Nebula IC 418: Searching for the Spatial Distribution of Fullerene-like Molecules

Is acetylene essential for carbon dust formation?

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