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

Hillen, M.; Winckel, H. Van; Menu, J.; Manick, R.; Debosscher, J.; Min, M.; Wit, W. J. de; Verhoelst, Tijl; Kamath, D.; Waters, L. B. F. M.

doi:10.1051/0004-6361/201629161

Cited by 39 publications

(69 citation statements)

References 97 publications

(151 reference statements)

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“…This is in line with the fact that Giridhar et al (1994) derived a spectroscopic effective temperature of 6700 K, which is much hotter than typical RV Tau stars (Kiss et al 2007). AR Pup and its post-AGB disk was observed interferometrically by Hillen et al (2017), who noted that for this star, the total infrared luminosity dominates over the dereddened optical fluxes, which is indicative of the disk close to edge-on. The least is known for the OGLE star, for which only the very red colour (V − I ≈ 3.3 mag) is listed in the catalogues, which could indicate both high interstellar reddening and instrinsically red colour.…”

Section: Discussionmentioning

confidence: 98%

Amplitude variations of modulated RV Tauri stars support the dust obscuration model of the RVb phenomenon

Kiss

Bódi

2017

A&A

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Context. RV Tauri-type variables are pulsating post-AGB stars that evolve rapidly through the instability strip after leaving the Asymptotic Giant Branch. Their light variability is dominated by radial pulsations. Members of the RVb subclass show an additional variability in form of a long-term modulation of the mean brightness, for which the most popular theories all assume binarity and some kind of circumstellar dust. Here we address if the amplitude modulations are consistent with the dust obscuration model. Aims. We measure and interpret the overall changes of the mean amplitude of the pulsations along the RVb variability. Methods. We compiled long-term photometric data for RVb-type stars, including visual observations of the American Association of Variable Star Observers, ground-based CCD photometry from the OGLE and ASAS projects and ultra-precise space photometry of one star, DF Cygni, from the Kepler space telescope. After converting all the observations to flux units, we measure the cycle-to-cycle variations of the pulsation amplitude and correlate them to the actual mean fluxes. Results. We find a surprisingly uniform correlation between the pulsation amplitude and the mean flux: they scale linearly with each other for a wide range of fluxes and amplitudes. It means that the pulsation amplitude actually remains constant when measured relative to the system flux level. The apparent amplitude decrease in the faint states has long been noted in the literature but it was always claimed to be difficult to explain with the actual models of the RVb phenomenon. Here we show that when fluxes are used instead of magnitudes, the amplitude attenuation is naturally explained by periodic obscuration from a large opaque screen, one most likely corresponding to a circumbinary dusty disk that surrounds the whole system.

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Section: Discussionmentioning

confidence: 98%

Amplitude variations of modulated RV Tauri stars support the dust obscuration model of the RVb phenomenon

Kiss

Bódi

2017

A&A

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“…It is now well established that these specific features in the SED indicate the presence of a stable compact disc in the system (e.g. Hillen et al 2017;Kluska et al 2018, and references therein). This type of SEDs are called disc-type SEDs.…”

Section: Introductionmentioning

confidence: 94%

Orbital properties of binary post-AGB stars

Oomen

Winckel

Pols

et al. 2018

A&A

146

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Binary post-asymptotic giant branch (post-AGB) stars are thought to be the products of a strong but poorly understood interaction during the AGB phase. The aim of this contribution is to update the orbital elements of a sample of galactic post-AGB binaries observed in a long-term radial-velocity monitoring campaign by analysing these systems in a homogeneous way. Radial velocities are computed from high signal-to-noise spectra via a cross-correlation method. The radial-velocity curves are fitted by using both a least-squares algorithm and a Nelder–Mead simplex algorithm. We use a Monte Carlo method to compute uncertainties on the orbital elements. The resulting mass functions are used to derive a companion mass distribution by optimising the predicted to the observed cumulative mass-function distributions, after correcting for observational bias. As a result, we derive and update orbital elements for 33 galactic post-AGB binaries, among which 3 are new orbits. The orbital periods of the systems range from 100 to about 3000 days. Over 70% (23 out of 33) of our binaries have significant non-zero eccentricities ranging over all periods. Their orbits are non-circular even though the Roche-lobe radii are smaller than the maximum size of a typical AGB star and tidal circularisation should have been strong when the objects were on the AGB. We derive a distribution of companion masses that is peaked around 1.09 M⊙ with a standard deviation of 0.62 M⊙. The large spread in companion masses highlights the diversity of post-AGB binary systems. Post-AGB binaries are often chemically peculiar, showing in their photospheres the result of an accretion process of circumstellar gas devoid of refractory elements. We find that only post-AGB stars with high effective temperatures (> 5500 K) in wide orbits are depleted in refractory elements, suggesting that re-accretion of material from a circumbinary disc is an ongoing process. It appears, however, that depletion is inefficient for the closest orbits irrespective of the actual surface temperature.

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“…To date, disks have been well mapped only in three objects, the Red Rectangle, AC Her, and IW Car, by means of interferometric mm-wave maps of CO lines (Bujarrabal et al 2013b, 2015, 2017). These sources belong to a class of binary post-AGB stars surrounded by low-mass nebulae that show independent evidence of the presence of disks (e.g., Van Winckel 2003, de Ruyter et al 2006, Gezer et al 2015, Hillen et al 2016, 2017). Notably, they are characterized by spectral energy distributions (SEDs) with a significant near-infrared (NIR) excess, revealing the existence hot dust close to the stellar system.…”

Section: Introductionmentioning

confidence: 99%

High-resolution observations of IRAS 08544−4431

Bujarrabal

Castro-Carrizo

Winckel

et al. 2018

A&A

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Aims. In order to study the effects of rotating disks in the post-asymptotic giant branch (post-AGB) evolution, we observe a class of binary post-AGB stars that seem to be systematically surrounded by equatorial disks and slow outflows. Although the rotating dynamics had only been well identified in three cases, the study of such structures is thought to be fundamental to the understanding of the formation of disks in various phases of the late evolution of binary stars and the ejection of planetary nebulae from evolved stars. Methods. We present ALMA maps of 12 CO and 13 CO J=3−2 lines in the source IRAS 08544−4431, which belongs to the above mentioned class of objects. We analyzed the data by means of nebula models, which account for the expectedly composite source and can reproduce the data. From our modeling, we estimated the main nebula parameters, including the structure and dynamics and the density and temperature distributions. We discuss the uncertainties of the derived values and, in particular, their dependence on the distance. Results. Our observations reveal the presence of an equatorial disk in rotation; a low-velocity outflow is also found, probably formed of gas expelled from the disk. The main characteristics of our observations and modeling of IRAS 08544−4431 are similar to those of better studied objects, confirming our interpretation. The disk rotation indicates a total central mass of about 1.8 M , for a distance of 1100 pc. The disk is found to be relatively extended and has a typical diameter of ∼ 4 10 16 cm. The total nebular mass is ∼ 2 10 −2 M , of which ∼ 90% corresponds to the disk. Assuming that the outflow is due to mass loss from the disk, we derive a disk lifetime of ∼ 10000 yr. The disk angular momentum is found to be comparable to that of the binary system at present. Assuming that the disk angular momentum was transferred from the binary system, as expected, the high values of the disk angular momentum in this and other similar disks suggest that the size of the stellar orbits has significantly decreased as a consequence of disk formation.

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

Cited by 39 publications

References 97 publications

Amplitude variations of modulated RV Tauri stars support the dust obscuration model of the RVb phenomenon

Amplitude variations of modulated RV Tauri stars support the dust obscuration model of the RVb phenomenon

Orbital properties of binary post-AGB stars

High-resolution observations of IRAS 08544−4431

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