The Gemini NICI Planet-Finding Campaign: The Offset Ring of HR 4796 A

Abstract

We present J, H, CH_4 short (1.578 micron), CH_4 long (1.652 micron) and K_s-band images of the dust ring around the 10 Myr old star HR 4796 A obtained using the Near Infrared Coronagraphic Imager (NICI) on the Gemini-South 8.1 meter Telescope. Our images clearly show for the first time the position of the star relative to its circumstellar ring thanks to NICI's translucent focal plane occulting mask. We employ a Bayesian Markov Chain Monte Carlo method to constrain the offset vector between the two. The resulting probability distribution shows that the ring center is offset from the star by 16.7+/-1.3 milliarcseconds along a position angle of 26+/-3 degrees, along the PA of the ring, 26.47+/-0.04 degrees. We find that the size of this offset is not large enough to explain the brightness asymmetry of the ring. The ring is measured to have mostly red reflectivity across the JHK_s filters, which seems to indicate micron-sized grains. Just like Neptune's 3:2 and 2:1 mean-motion resonances delineate the inner and outer edges of the classical Kuiper Belt, we find that the radial extent of the HR 4796 A and Fomalhaut rings could correspond to the 3:2 and 2:1 mean-motion resonances of hypothetical planets at 54.7 AU and 97.7 AU in the two systems, respectively. A planet orbiting HR 4796 A at 54.7 AU would have to be less massive than 1.6 Mjup so as not to widen the ring too much by stirring.

Accepted to A&A for publication on April 23, 2014 (15 pages, 9 figures, 4 tables)

References in corpus (11)

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• Structure and evolution of pre-main sequence circumstellar disks
• Debris from giant impacts between planetary embryos at large orbital radii
• STIS Imaging of the HR 4796A Circumstellar Debris Ring
• Herschel images of Fomalhaut. An extrasolar Kuiper Belt at the height of its dynamical activity
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• Performance of the Near-infrared coronagraphic imager on Gemini-South
• High-Resolution Imaging of the Dust Disk around 49 Ceti
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Cited by in corpus (16)

• Polarimetry with the Gemini Planet Imager: Methods, Performance at First Light, and the Circumstellar Ring around HR 4796A
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• Five steps in the evolution from protoplanetary to debris disk
• ALMA observations of the narrow HR 4796A debris ring
• Optical polarized phase function of the HR\,4796A dust ring
• On the Morphology and Chemical Composition of the HR 4796A Debris Disk
• The SHARDDS survey: first resolved image of the HD114082 debris disk in Lower Centaurus Crux with SPHERE
• Multiband GPI Imaging of the HR 4796A Debris Disk
• New constraints on the dust surrounding HR 4796A
• The First Scattered Light Image of the Debris Disk around the Sco-Cen target HD 129590
• Capture and evolution of dust in planetary mean-motion resonances: a fast, semi-analytic method for generating resonantly trapped disk images
• Infrared Spectroscopy of HR 4796A's Bright Outer Cometary Ring + Tenuous Inner Hot Dust Cloud
• Discovery of an Edge-on Circumstellar Debris Disk Around BD+45${}^{\circ }$598: a Newly Identifed Member of the $\beta$ Pictoris Moving Group
• Adaptive optics in high-contrast imaging
• The first scattered light images of HD 112810, a faint debris disk in the Sco-Cen association
• A Multiband Study of the HR 4796A Disk in the Optical Using MagAO-X