The Unusual Hydrocarbon Emission from the Early Carbon Star HD 100764: The Connection between Aromatics and Aliphatics

Sloan, G. C.; Jura, M.; Duley, W. W.; Kraemer, K. E.; Bernard─Salas, J.; Forrest, W. J.; Sargent, B.; Li, A.; Barry, D. J.; Bohac, C. J.; Watson, D. M.; Houck, J. R.

doi:10.1086/519236

Cited by 173 publications

(280 citation statements)

References 57 publications

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“…The intimate structures of the carriers of these different classes of AIBs are still unknown, although they are probably built on a polyaromatic skeleton spanning sizes from large molecules to small nanograins (Leger & Puget 1984;Allamandola et al 1985;Goto et al 2007;Sloan et al 2007;Pino et al 2008;Tielens 2008;Joblin & Tielens 2011;Li & Draine 2012;Carpentier et al 2012;Yang et al 2013).…”

Section: General Overviewmentioning

confidence: 99%

VUV spectroscopy of carbon dust analogs: contribution to interstellar extinction

Gavilan

Alata

et al. 2016

A&A

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Context.A full spectral characterization of carbonaceous dust analogs is necessary to understand their potential as carriers of observed astronomical spectral signatures such as the ubiquitous UV bump at 217.5 nm and the far-ultraviolet (FUV) rise common to interstellar extinction curves. Aims. Our goal is to study the spectral properties of carbonaceous dust analogs from the FUV to the mid-infrared (MIR) domain. We seek in particular to understand the spectra of these materials in the FUV range, for which laboratory studies are scarce. Methods. We produced analogs to carbonaceous interstellar dust encountered in various phases of the interstellar medium: amorphous hydrogenated carbons (a-C:H), for carbonaceous dust observed in the diffuse interstellar medium, and soot particles, for the polyaromatic component. Analogs to a-C:H dust were produced using a radio-frequency plasma reactor at low pressures, and soot nanoparticles films were produced in an ethylene (C 2 H 4 ) flame. We measured transmission spectra of these thin films (thickness <100 nm) in the far-ultraviolet (190−250 nm) and in the vacuum-ultraviolet (VUV; 50−190 nm) regions using the APEX chamber at the DISCO beam line of the SOLEIL synchrotron radiation facility. These were also characterized through infrared microscopy at the SMIS beam line. Results. We successfully measured the transmission spectra of these analogs from λ = 1 μm to 50 nm. From these, we extracted the laboratory optical constants via Kramers-Kronig inversion. We used these constants for comparison to existing interstellar extinction curves. Conclusions. We extend the spectral measurements of these types of carbonaceous analogs into the VUV and link the spectral features in this range to the 3.4 μm band. We suggest that these two materials might contribute to different classes of interstellar extinction curves.

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Section: General Overviewmentioning

confidence: 99%

VUV spectroscopy of carbon dust analogs: contribution to interstellar extinction

Gavilan

Alata

et al. 2016

A&A

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“…Two young objects, the T Tauri star SU Aur (Furlan et al 2006) and the Herbig Ae/Be source HD 135344 (Sloan et al 2005), also show PAH spectra of class C, although in HD 135344 the PAH features seem to be somewhat more in between B and C. This source is also slightly hotter than other class C sources. A comparison of the PAH features in all these sources is given by Sloan et al (2007). They find that all the known class-C spectra are excited by relatively cool stars of spectral type F or later and argue that the hydrocarbons in these sources have not been exposed to much ultraviolet radiation.…”

Section: Pah Featuresmentioning

confidence: 99%

“…Whether these can be attributed to PAHs remains uncertain. The PAH spectrum of EP Lyr can be classified as class C. EP Lyr is a high amplitudevariable with an effective temperature around 7000 K, which is on the hot end of the other class-C emitters (see Sloan et al 2007).…”

Section: Pah Featuresmentioning

confidence: 99%

Analysis of the infrared spectra of the peculiar post-AGB stars EP Lyrae and HD 52961

Gielen¹,

Winckel²,

Matsuura

et al. 2009

A&A

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Aims. We aim to study in detail the peculiar mineralogy and structure of the circumstellar environment of two binary post-AGB stars, EP Lyr and HD 52961. Both stars were selected from a larger sample of evolved disc sources observed with Spitzer and show unique solid-state and gas features in their infrared spectra. Moreover, they show a very small infrared excess in comparison with the other sample stars. Methods. The different dust and gas species are identified on the basis of high-resolution Spitzer-IRS spectra. We fit the full spectrum to constrain grain sizes and temperature distributions in the discs. This, combined with our broad-band spectral energy distribution and interferometric measurements, allows us to study the physical structure of the disc, using a self-consistent 2D radiative-transfer disc model. Results. We find that both stars have strong emission features due to CO 2 gas, dominated by 12 C 16 O 2 , but with clear 13 C 16 O 2 and even 16 O 12 C 18 O isotopic signatures. Crystalline silicates are apparent in both sources but proved very hard to model. EP Lyr also shows evidence of mixed chemistry, with emission features of the rare class-C PAHs. Whether these PAHs reside in the oxygen-rich disc or in a carbon-rich outflow is still unclear. With the strongly processed silicates, the mixed chemistry and the low 12 C/ 13 C ratio, EP Lyr resembles some silicate J-type stars, although the depleted photosphere makes nucleosynthetic signatures difficult to probe. We find that the disc environment of both sources is, to a first approximation, well modelled with a passive disc, but additional physics such as grain settling, radial dust distributions, and an outflow component must be included to explain the details of the observed spectral energy distributions in both stars.

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“…Buss et al (1991) report an 8 μm feature in some carbon stars such as HD 38218 but their spectra also show a broad SiC feature at 11.3 μm, much wider than the weak narrow one that we observed. Sloan et al (2007) show spectra of a number of C stars and one of them-HD 100764-displays three very weak emission features centered at 6.35, 8.1, and 11.4 μm, tantalizingly close to V2362 Cyg's. They attribute these to PAHs, whose peak wavelength of the features shifts as a function of effective temperature of the exciting star.…”

Section: Dustmentioning

confidence: 99%

NOVA V2362 CYGNI (NOVA CYGNI 2006):SPITZER,SWIFT, AND GROUND-BASED SPECTRAL EVOLUTION

Lynch

Woodward

Gehrz

et al. 2008

The Astronomical Journal

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Nova V2362 Cygni has undergone a number of very unusual changes. Ground-based spectroscopy initially revealed a normal sequence of events: the object faded and its near-infrared emission lines gradually shifted to higher excitation conditions until about day 100 when the optical fading reversed and the object slowly brightened. This was accompanied by a rise in the Swift X-ray telescope flux and a sudden shift in excitation of the visible and IR spectrum back to low levels. The new lower excitation spectrum revealed broad line widths and many P-Cygni profiles, all indicative of the ejection of a second shell. Eventually, dust formed, the X-ray brightnessapparently unaffected by dust formation-peaked and then declined, and the object faded at all wavelengths. The Spitzer dust spectra revealed a number of solid-state emission features that, at this time, are not identified.

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The Unusual Hydrocarbon Emission from the Early Carbon Star HD 100764: The Connection between Aromatics and Aliphatics

Cited by 173 publications

References 57 publications

VUV spectroscopy of carbon dust analogs: contribution to interstellar extinction

VUV spectroscopy of carbon dust analogs: contribution to interstellar extinction

Analysis of the infrared spectra of the peculiar post-AGB stars EP Lyrae and HD 52961

NOVA V2362 CYGNI (NOVA CYGNI 2006):SPITZER,SWIFT, AND GROUND-BASED SPECTRAL EVOLUTION

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