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A Layered Debris Disk around M Star TWA 7 in Scattered Light

Abstract : We have obtained Hubble Space Telescope (HST) coronagraphic observations of the circumstellar disk around M star TWA 7 using the Space Telescope Imaging Spectrograph (STIS) instrument in visible light. Together with archival observations, including HST/NICMOS using the F160W filter and Very Large Telescope/SPHERE at the H-band in polarized light, we investigate the system in scattered light. By studying this nearly face-on system using geometric disk models and Henyey-Greenstein phase functions, we report a new discovery of a tertiary ring and a clump. We identify a layered architecture: three rings, a spiral, and an ≈150 au 2 elliptical clump. The most extended ring peaks at 28 au, and the other components are on its outskirts. Our point-source detection-limit calculations demonstrate the necessity of disk modeling in imaging fainter planets. Morphologically, we witness a clockwise spiral motion, and the motion pattern is consistent with both solid body motion and local Keplerian motion; we also observe underdensity regions for the secondary ring that might result from mean-motion resonance or moving shadows: both call for re-observations to determine their nature. Comparing multi-instrument observations, we obtain blue STIS-NICMOS color, a STIS-SPHERE radial distribution peak difference for the tertiary ring, and a high SPHERE-NICMOS polarization fraction; these aspects indicate that TWA 7 could retain small dust particles. By viewing the debris disk around M star TWA 7 at a nearly face-on vantage point, our study allows for the understanding of such disks in scattered light in both system architecture and dust property.
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Contributor : Elodie Choquet Connect in order to contact the contributor
Submitted on : Wednesday, July 28, 2021 - 6:27:24 PM
Last modification on : Tuesday, October 19, 2021 - 10:59:27 PM


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Bin Ren, Élodie Choquet, Marshall Perrin, Dimitri Mawet, Christine Chen, et al.. A Layered Debris Disk around M Star TWA 7 in Scattered Light. The Astrophysical Journal, American Astronomical Society, 2021, 914 (2), pp.95. ⟨10.3847/1538-4357/ac03b9⟩. ⟨hal-03304881⟩



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