The color dependent morphology of the post-AGB star HD 161796

Min, M.; Jeffers, S. V.; Cánovas, H.; Rodenhuis, M.; Keller, Christoph U.; Waters, L. B. F. M.

doi:10.1051/0004-6361/201219967

Cited by 18 publications

(19 citation statements)

References 31 publications

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“…The red plusses show the IR photometric data, pointing to the presence of a compact disc (Hillen et al 2014). The bottom panel shows the SED of HD 161796, the solid line represents the photosphere, the black crosses the dereddened measurements, while the red crosses show the IR data, pointing to the presence of an expanding dusty shell (Min et al 2013). …”

Section: Reference Samplementioning

confidence: 99%

TheWISEview of RV Tauri stars

Gezer

Winckel

Bozkurt

et al. 2015

Mon. Not. R. Astron. Soc.

128

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We present a detailed study based on infrared photometry of all Galactic RV Tauri stars from the General Catalogue of Variable Stars (GCVS). RV Tauri stars are the brightest among the population II Cepheids. They are thought to evolve away from the asymptotic giant branch (AGB) towards the white dwarf domain. IRAS detected several RV Tauri stars because of their large IR excesses and it was found that they occupy a specific region in theWe used the all sky survey of WISE to extend these studies and compare the infrared properties of all RV Tauri stars in the GCVS with a selected sample of post-AGB objects with the goal to place the RV Tauri pulsators in the context of post-AGB evolution. Moreover, we correlated the IR properties of both the RV Tauri stars and the comparison sample with other observables like binarity and the presence of a photospheric chemical anomaly called depletion. We find that Galactic RV Tauri stars display a range of infrared properties and we differentiate between disc sources, objects with no IR excess and objects for which the spectral energy distribution (SED) is uncertain. We obtain a clear correlation between disc sources and binarity. RV Tauri stars with a variable mean magnitude are exclusively found among the disc sources. We also find evidence for disc evolution among the binaries. Furthermore our studies show that the presence of a disc seems to be a necessary but not sufficient condition for the depletion process to become efficient.

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Section: Reference Samplementioning

confidence: 99%

TheWISEview of RV Tauri stars

Gezer

Winckel

Bozkurt

et al. 2015

Mon. Not. R. Astron. Soc.

128

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“…We performed a preliminary SED analyses to classify the LMC post-AGB and post-RGB candidates into shell-and disc-souces, based on the visual inspection of the position of the peak of their dust excess. In shell-sources, the dust emission peaks at wavelengths greater than 10µm (as shown by radiative transfer models of the well known expanding shell source HD161796, where the peak of the dust SED is at around 30µm, see Min et al 2013, for details). On the other hand, for disc-sources the peak of the dust SED lies around 10 µm and in some cases even bluer (de Ruyter et al 2006;Gielen et al 2011a).…”

Section: Classification Of Spectral Energy Distributionsmentioning

confidence: 96%

Optically visible post-AGB stars, post-RGB stars and young stellar objects in the Large Magellanic Cloud

Kamath¹,

Wood²,

Winckel³

2015

Mon. Not. R. Astron. Soc.

125

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We have carried out a search for optically visible post-Asymptotic Giant Branch (post-AGB) stars in the Large Magellanic Cloud (LMC). First, we selected candidates with a mid-IR excess and then obtained their optical spectra. We disentangled contaminants with unique spectra such as M-stars, C-stars, planetary nebulae, quasi-stellar objects and background galaxies. Subsequently, we performed a detailed spectroscopic analysis of the remaining candidates to estimate their stellar parameters such as effective temperature, surface gravity (log g), metallicity ([Fe/H]), reddening and their luminosities. This resulted in a sample of 35 likely post-AGB candidates with late-G to late-A spectral types, low log g, and [Fe/H] < −0.5. Furthermore, our study confirmed the existence of the dusty post-Red Giant Branch (post-RGB) stars, discovered previously in our SMC survey, by revealing 119 such objects in the LMC. These objects have mid-IR excesses and stellar parameters (T eff , log g, [Fe/H]) similar to those of post-AGB stars except that their luminosities (< 2500 L ), and hence masses and radii, are lower. These post-RGB stars are likely to be products of binary interaction on the RGB. The post-AGB and post-RGB objects show SED properties similar to the Galactic post-AGB stars, where some have a surrounding circumstellar shell, while some others have a surrounding stable disc similar to the Galactic post-AGB binaries. This study also resulted in a new sample of 162 young stellar objects, identified based on a robust log g criterion. Other interesting outcomes include objects with an UV continuum and an emission line spectrum; luminous supergiants; hot main-sequence stars; and 15 B[e] star candidates, 12 of which are newly discovered in this study.

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“…With the advent of high contrast imaging polarimeters, such as NaCo/VLT (Lenzen et al 2003), HiCiao/Subaru (Tamura et al 2006), GPI/Gemini South (Macintosh et al 2008), and SPHERE/VLT (Beuzit et al 2008), polarized differential imaging (PDI) has become a standard tool to directly image and analyze the dusty circumstellar environments around young and evolved stars (e.g., Canovas et al 2012Canovas et al , 2015aJeffers et al 2012Jeffers et al , 2014Garufi et al 2013;Min et al 2013). In disks, PDI have proven powerful to show a variety of features like spiral arms, bright inner rings and/or disk asymmetries revealing complex morphologies.…”

Section: Introductionmentioning

confidence: 99%

Nonazimuthal linear polarization in protoplanetary disks

Cánovas

Ménard

Boer

et al. 2015

A&A

Self Cite

102

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Several studies discussing imaging polarimetry observations of protoplanetary disks use the so-called radial Stokes parameters Q φ and U φ to discuss the results. This approach has the advantage of providing a direct measure of the noise in the polarized images under the assumption that the polarization is only azimuthal, i.e., perpendicular to the direction toward the illuminating source. However, a detailed study of the validity of this assumption is currently missing. We aim to test whether departures from azimuthal polarization can naturally be produced by scattering processes in optically thick protoplanetary disks at near infrared wavelengths. We use the radiative transfer code MCFOST to create a generic model of a transition disk using different grain size distributions and dust masses. From these models we generate synthetic polarized images at 2.2 µm. We find that even for moderate inclinations (e.g., i = 40 • ), multiple scattering alone can produce significant (up to ∼4.5% of the Q φ image, peak-to-peak) nonazimuthal polarization reflected in the U φ images. We also find that different grain populations can naturally produce radial polarization (i.e., negative values in the Q φ images). Despite the simplifications of the models, our results suggest that caution is recommended when interpreting polarized images by only analyzing the Q φ and U φ images. We find that there can be astrophysical signal in the U φ images and negative values in the Q φ images, which indicate departures from azimuthal polarization. If significant signal is detected in the U φ images, we recommend checking the standard Q and U images to look for departures from azimuthal polarization. On the positive side, signal in the U φ images once all instrumental and data-reduction artifacts have been corrected for means that there is more information to be extracted regarding the dust population and particle density.

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The color dependent morphology of the post-AGB star HD 161796

Cited by 18 publications

References 31 publications

TheWISEview of RV Tauri stars

TheWISEview of RV Tauri stars

Optically visible post-AGB stars, post-RGB stars and young stellar objects in the Large Magellanic Cloud

Nonazimuthal linear polarization in protoplanetary disks

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