Revisiting the optical interferometry observations of HR 4049

Menut, Jean-Luc; Chesneau, O.; Bakker, E.; López, B.; Perrin, G.; Leinert, Christoph; Quirrenbach, A.

doi:10.1051/0004-6361:200810403

Cited by 4 publications

(4 citation statements)

References 18 publications

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“…This indicates that the PAH emission region is fully resolved by the interferometer, even on the short baseline of 15 m. We estimated a lower limit to the extent of the PAH emission region of 100 mas (64 AU at 640 pc). In line with Menut et al (2009), we conclude that the PAH emission region is not only situated in the disk, although a contribution from the disk is still possible.…”

Section: Pah Emissionsupporting

confidence: 86%

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Amorphous carbon in the disk around the post-AGB binary HR 4049

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Lombaert

et al. 2013

A&A

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Context. Infrared spectroscopy has been extensively used to determine the mineralogy of circumstellar dust. The identification of dust species with featureless opacities, however, is still ambiguous. Here we present a method to lift the degeneracy using the combination of infrared spectroscopy and interferometry. Aims. The binary post-AGB star HR 4049 is surrounded by a circumbinary disk viewed at a high inclination angle. Apart from gaseous emission lines and molecular emission bands of polycyclic aromatic hydrocarbons (PAH), diamonds, and fullerenes, the 2-25 μm infrared spectrum is featureless. The goal of the paper is to identify the dust species responsible for the smooth spectrum. Methods. We gathered high-angular-resolution measurements in the near-and mid-infrared with the VLTI interferometric instruments AMBER and MIDI. The data set is expanded with archival Geneva optical photometry, ISO-SWS and Spitzer-IRS infrared spectroscopy, and VISIR N-band images and spectroscopy. We computed a grid of radiative-transfer models of the circumbinary disk of HR 4049 using the radiative-transfer code MCMax. We searched for models that provide good fits simultaneously to all available observations. Results. We find that the variable optical extinction towards the primary star is consistent with the presence of very small (0.01 μm) iron-bearing dust grains or amorphous carbon grains. The combination of the interferometric constraint on the disk extent and the shape of the infrared spectrum points to amorphous carbon as the dominant source of opacity in the circumbinary disk of HR 4049. The disk is optically thick to the stellar radiation in the radial direction. At infrared wavelengths it is optically thin. The PAH emission is spatially resolved in the VISIR data and emanates from a region with an extent of several hundreds of AU, with a projected photocenter displacement of several tens of AU from the disk center. The PAHs most likely reside in a bipolar outflow. Conclusions. Dust species with featureless opacity curves, such as metallic iron and amorphous carbon, can be identified by combining infrared spectroscopy and high-angular-resolution measurements. In essence, this is because the temperatures of the dust species are notably different at the same physical distance to the star.

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Section: Pah Emissionsupporting

confidence: 86%

“…Menut et al (2009) analyzed early MIDI observations of HR 4049. They find that the emission region of the PAH 7.7, 8.6, and 11.3 μm features is more extended than that of the underlying continuum.…”

Section: Pah Emissionmentioning

confidence: 99%

Amorphous carbon in the disk around the post-AGB binary HR 4049

Acke

Degroote

Lombaert

et al. 2013

A&A

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“…Dominik et al 2003;Menut et al 2009;Malek & Cami 2014). Apart from a compact disk with a very small temperature range (Dominik et al 2003), a large-scale outflow has been resolved in this source by spatially extended emission of the mid-IR Polycyclic Aromatic Hydrocarbon (PAH) features (e.g.…”

Section: Hr4049 (Nr 7)mentioning

confidence: 99%

A mid-IR interferometric survey with MIDI/VLTI: resolving the second-generation protoplanetary disks around post-AGB binaries

Hillen

Winckel

et al. 2017

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Aims. We present a mid-IR interferometric survey of the circumstellar environment of a specific class of post-asymptotic giant branch (post-AGB) binaries. For this class the presence of a compact dusty disk has been postulated on the basis of various spatially unresolved measurements. The aim is to determine the angular extent of the N-band emission directly and to resolve the compact circumstellar structures. Methods. Our interferometric survey was performed with the MIDI instrument on the VLTI. In total 19 different systems were observed using variable baseline configurations. Combining all the visibilities at a single wavelength at 10.7 µm, we fitted two parametric models to the data: a uniform disk and a ring model mimicking a temperature gradient. We compared our observables of the whole sample, with synthetic data computed from a grid of radiative transfer models of passively irradiated disks in hydrostatic equilibrium. These models are computed with a Monte Carlo code that has been widely applied to describe the structure of protoplanetary disks around young stellar objects (YSO). Results. The spatially resolved observations show that the majority of our targets cluster closely together in the distance-independent size-colour diagram, and have extremely compact N-band emission regions. The typical uniform disk diameter of the N-band emission region is ∼40 mas, which corresponds to a typical brightness temperature of 400-600 K. The resolved objects display very similar characteristics in the interferometric observables and in the spectral energy distributions. Therefore, the physical properties of the disks around our targets must be similar. Our results are discussed in the light of recently published sample studies of YSOs to compare quantitatively the secondary discs around post-AGB stars to the ones around YSOs. Conclusions. Our high-angular-resolution survey further confirms the disk nature of the circumstellar structures present around wide post-AGB binaries. The grid of protoplanetary disk models covers very well the observed objects. Much like for young stars, the spatially resolved N-band emission region is determined by the hot inner rim of the disk. Continued comparisons between post-AGB and protoplanetary disks will help to understand grain growth and disk evolution processes, and to constrain planet formation theories. These second-generation disks are an important missing ingredient in binary evolution theory of intermediate-mass stars.

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“…Sofar, it is not clear whether the PAH carriers reside in the circumbinary disc, or in bipolar lobes created by a more recent mass-loss event, as observed in HR 4049 (Johnson et al 1999;Dominik et al 2003;Antoniucci et al 2005;Hinkle et al 2007;Menut et al 2009) and in the Red Rectangle (Men'shchikov et al 2002;Cohen et al 2004). For HR 4049, Johnson et al (1999) found that the optical polarisation seems to vary with orbital phase, suggesting that the polarisation in the optical is due to scattering in the circumbinary disc.…”

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

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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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Revisiting the optical interferometry observations of HR 4049

Cited by 4 publications

References 18 publications

Amorphous carbon in the disk around the post-AGB binary HR 4049

Amorphous carbon in the disk around the post-AGB binary HR 4049

A mid-IR interferometric survey with MIDI/VLTI: resolving the second-generation protoplanetary disks around post-AGB binaries

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

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