Tuesday, March 24, 2015

Latest Imagery of epsilon Eridani's Debris Disk Strongly Supports Exoplanet Presence

MAMBO image of the debris disk around epsilon Eridani : robustness of the azimuthal structure


Lestrade et al


The debris disk closest to Earth is the one around the star epsilon Eridani at a distance of 3.2 pc. It is the prime target for detailed studies of a belt of planetesimals left from the early phase of planet formation other than the Kuiper Belt. The non-uniform ring-like structure around epsilon Eridani, originally discovered at lambda=850 microns with the bolometer camera SCUBA, could be the signpost of unseen long-period planets interior to the disk that gravitationally interact with it through mean-motion resonances. However, the reliability of the structure at 850 microns, which has been debated, has not been verified with independent observations until now. We present a high signal-to-noise ratio image of this structure at lambda=1.2 mm made with the bolometer camera MAMBO and compare this with the SCUBA image. We have found that three of the four emission clumps (NE, NW, SW) and the two deep hollows to the east and west are at the same positions in the MAMBO and SCUBA images within astrometric uncertainty. The SE clump is at odds, significantly brighter and more extended in the SCUBA than in the MAMBO images, but it is possible that this mismatch is an artifact. We conclude that this degree of positional coincidence provides tentative evidence that the observed structure is robust. In addition, we present the radial brightness profile of our MAMBO image and show that the width of the planetesimal belt around epsilon Eridani is narrower than 22 AU, a more stringent upper limit than determined from previous observations. The corresponding relative width is 0.1 less than ΔR/R less than 0.4, which is lower than for the Kuiper Belt.

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