Images of the Extended Outer Regions of the Debris Ring Around Hr 4796 A

Thalmann, Christian; Janson, Markus; Buenzli, E.; Brandt, Timothy D.; Wisniewski, John P.; Moro‐Martín, Amaya; Usuda, Tomonori; Schneider, Glenn; Carson, J.; McElwain, Michael; Grady, C. A.; Goto, Miwa; Abe, Lyu; Brandner, W.; Dominik, C.; Egner, Sebastian; Feldt, M.; Fukue, T.; Golota, Taras; Guyon, Olivier; Hashimoto, Jun; Hayano, Yutaka; Hayashi, Masao; Hayashi, Saeko S.; Henning, Thomas; Hodapp, Klaus W.; Ishii, Miki; Iye, Masanori; Kandori, Ryo; Knapp, G. R.; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Kuzuhara, Masayuki; Matsuo, Taro; Miyama, Shoken M.; Morino, Jun-Ichi; Nishimura, Tetsuo; Pyo, Tae‐Soo; Serabyn, Eugene; Shimada, Hiroshi; Suzuki, Ryuji; Takahashi, Yasuhiro; Miki, Takami; Takato, Naruhisa; Terada, Hiroshi; Tomono, Daigo; Turner, Edwin L.; Watanabe, Makoto; Yamada, Tōru; Takami, Hideki; Tamura, Motohide

doi:10.1088/2041-8205/743/1/l6

Cited by 72 publications

(111 citation statements)

References 46 publications

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“…Nevertheless, they can be very efficient in emphasizing regions with strong gradients of similar spatial scales as point sources (rings for instance). In the past few years, several impressive results were obtained using ADI and revealed the very detailed structures within some debris disks (Buenzli et al 2010;Thalmann et al 2011;Lagrange et al 2012a,b). Self-subtraction is an important issue and is caused by the contribution of the disk itself to the building of the reference image to be subtracted from the data cube.…”

Section: Data Reduction and Resultsmentioning

confidence: 99%

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Morphology of the very inclined debris disk around HD 32297

Boccaletti

Augereau

Lagrange

et al. 2012

A&A

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Context. Direct imaging of circumstellar disks at high angular resolution is mandatory to provide morphological information that constrains their properties, in particular the spatial distribution of dust. For a long time, this challenging objective was, in most cases, only within the realm of space telescopes from the visible to the infrared. New techniques combining observing strategy and data processing now allow very high-contrast imaging with 8-m class ground-based telescopes (10 −4 to 10 −5 at ∼1 ) and complement space telescopes while improving angular resolution at near infrared wavelengths. Aims. We present the results of a program carried out at the VLT with NACO to image known debris disks with higher angular resolution in the near-infrared than ever before in order to study morphological properties and ultimately detect the signpost of planets. Methods. The observing method makes use of advanced techniques of adaptive optics, coronagraphy, and differential imaging, a combination designed to directly image exoplanets with the upcoming generation of "planet finders" such as GPI (Gemini Planet Imager) and SPHERE (Spectro-Polarimetric High contrast Exoplanet REsearch). Applied to extended objects such as circumstellar disks, the method is still successful but produces significant biases in terms of photometry and morphology. We developed a new model-matching procedure to correct for these biases and hence provide constraints on the morphology of debris disks. Results. From our program, we present new images of the disk around the star HD 32297 obtained in the H (1.6 μm) and Ks (2.2 μm) bands with an unprecedented angular resolution (∼65 mas). The images show an inclined thin disk detected at separations larger than 0.5−0.6 . The modeling stage confirms a very high inclination (i = 88 • ) and the presence of an inner cavity inside r 0 ≈ 110 AU. We also find that the spine (line of maximum intensity along the midplane) of the disk is curved, which we attribute to a large anisotropic scattering-factor (g ≈ 0.5, which is valid for an non-edge-on disk). Conclusions. Our modeling procedure is relevant to interpreting images of circumstellar disks observed with angular differential imaging. It allows us to both reduce the biases and estimate the disk parameters.

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Section: Data Reduction and Resultsmentioning

confidence: 99%

“…Model disks were inserted at 90 • from the observed disk so there was no possible overlap in-between. A similar strategy was adopted by Thalmann et al (2011). We used the same approach as described above for measuring the PA.…”

Section: Reliability Of the Spine Deviation From Midplanementioning

confidence: 99%

Morphology of the very inclined debris disk around HD 32297

Boccaletti

Augereau

Lagrange

et al. 2012

A&A

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“…The observed rotation speed of HR 4796A is v sin i = 152 km s −1 (Royer et al 2002), the radius is 1.6 R (Rhee et al 2007), and the disk inclination is 76 • (Schneider et al 2009;Thalmann et al 2011). If the stellar and disk inclinations are the same, the stellar equatorial velocity is 157 km s −1 and the rotation period is about 0.5 days.…”

Section: Confronting Theory and Observationsmentioning

confidence: 98%

“…Its disk was later imaged at high spatial resolution by the Hubble Space Telescope (Schneider et al 1999(Schneider et al , 2009) and by groundbased adaptive optics (Thalmann et al 2011). Imaging revealed signs of asymmetry and clearing that could be signatures of planetary mass perturbers (Wyatt et al 1999;Schneider et al 2009;Thalmann et al 2011) but ruled out close stellar mass companions.…”

Section: Hr 4796amentioning

confidence: 99%

Burn Out or Fade Away? On the X-Ray and Magnetic Death of Intermediate Mass Stars

Drake

Braithwaite²,

Kashyap

et al. 2014

ApJ

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The nature of the mechanisms apparently driving X-rays from intermediate mass stars lacking strong convection zones or massive winds remains poorly understood, and the possible role of hidden, lower mass close companions is still unclear. A 20 ks Chandra HRC-I observation of HR 4796A, an 8 Myr old main sequence A0 star devoid of close stellar companions, has been used to search for a signature or remnant of magnetic activity from the Herbig Ae phase. X-rays were not detected and the X-ray luminosity upper limit was L X 1.3 × 10 27 erg s −1 . The result is discussed in the context of various scenarios for generating magnetic activity, including rotational shear and subsurface convection. A dynamo driven by natal differential rotation is unlikely to produce observable X rays, chiefly because of the difficulty in getting the dissipated energy up to the surface of the star. A subsurface convection layer produced by the ionization of helium could host a dynamo that should be effective throughout the main sequence but can only produce X-ray luminosities of the order 10 25 erg s −1 . This luminosity lies only moderately below the current detection limit for Vega. Our study supports the idea that X-ray production in Herbig Ae/Be stars is linked largely to the accretion process rather than the properties of the underlying star, and that early A stars generally decline in X-ray luminosity at least 100,000 fold in only a few million years.

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“…However, the model based on the Hedman & Stark fit shows the degree to which the total brightness of the disc in scattered light may be underestimated. Accordingly, non-Mie fits to observed discs find weaker anisotropy, with g < 0.5 (e. g., Kalas et al 2005;Schneider et al 2006;Debes et al 2008;Thalmann et al 2011;Schneider et al 2014). …”

Section: Spectral Energy Distributions and Imagesmentioning

confidence: 99%

Collisions and drag in debris discs with eccentric parent belts

Löhne

Krivov

Kirchschlager

et al. 2017

A&A

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Context. High-resolution images of circumstellar debris discs reveal off-centred rings that indicate past or ongoing perturbation, possibly caused by secular gravitational interaction with unseen stellar or substellar companions. The purely dynamical aspects of this departure from radial symmetry are well understood. However, the observed dust is subject to additional forces and effects, most notably collisions and drag. Aims. To complement the studies of dynamics, we therefore aim to understand how new asymmetries are created by the addition of collisional evolution and drag forces, and existing ones strengthened or overridden. Methods. We augmented our existing numerical code "Analysis of Collisional Evolution" (ACE) by an azimuthal dimension, the longitude of periapse. A set of fiducial discs with global eccentricities ranging from 0 to 0.4 is evolved over giga-year timescales. Size distribution and spatial variation of dust are analysed and interpreted. The basic impact of belt eccentricity on spectral energy distributions (SEDs) and images is discussed. Results. We find features imposed on characteristic timescales. First, radiation pressure defines size cutoffs that differ between periapse and apoapse, resulting in an asymmetric halo. The differences in size distribution make the observable asymmetry of the halo depend on wavelength. Second, collisional equilibrium prefers smaller grains on the apastron side of the parent belt, reducing the effect of pericentre glow and the overall asymmetry. Third, Poynting-Robertson drag fills the region interior to an eccentric belt such that the apastron side is more tenuous. Interpretation and prediction of the appearance in scattered light is problematic when spatial and size distribution are coupled.

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Images of the Extended Outer Regions of the Debris Ring Around Hr 4796 A

Cited by 72 publications

References 46 publications

Morphology of the very inclined debris disk around HD 32297

Morphology of the very inclined debris disk around HD 32297

Burn Out or Fade Away? On the X-Ray and Magnetic Death of Intermediate Mass Stars

Collisions and drag in debris discs with eccentric parent belts

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