Multiband Polarimetric Imaging of HR 4796A with the Gemini Planet Imager

Journal Article · Sat Aug 01 00:00:00 EDT 2020 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.3847/1538-3881/AB91B1· OSTI ID:23013311

Arriaga, Pauline; Fitzgerald, Michael P. ^[1]; Duchêne, Gaspard; Esposito, Thomas M. ^[2]; Kalas, Paul ^[3]; Millar-Blanchaer, Maxwell A.; Mazoyer, Johan; Bailey, Vanessa P. ^[4]; Perrin, Marshall D. ^[5]; Chen, Christine H. ^[6]; Ammons, Mark ^[7]; Barman, Trafis S. ^[8]; Bulger, Joanna ^[9]; Chilcote, Jeffrey K. ^[10]; Cotten, Tara ^[11]; De Rosa, Robert J. ^[12]; Doyon, Rene ^[13]; others, and

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1. Department of Physics and Astronomy, University of California, Los Angeles, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States)
2. Astronomy Department, University of California, Berkeley, Berkeley, CA 94720 (United States)
3. Astronomy Department, University of California, Berkeley, CA 94720 (United States)
4. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena (United States)
5. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
6. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218 (United States)
7. Lawrence Livermore National Laboratory, Livermore, CA (United States)
8. Lunar and Planetary Lab, University of Arizona, Tucson, AZ 85721 (United States)
9. Subaru Telescope, NAOJ, 650 North A’ohoku Place, Hilo, HI 96720 (United States)
10. Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN, 46556 (United States)
11. Department of Physics and Astronomy, University of Georgia, Athens, GA 30602 (United States)
12. European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile)
13. Institut de Recherche sur les Exoplanètes, Département de physique, Université de Montréal, Montréal, QC H3C 3J7 (Canada)

HR4796A hosts a well-studied debris disk with a long history due to its high fractional luminosity and favorable inclination, which facilitate both unresolved and resolved observations. We present new J- and K {sub 1}-band images of the resolved debris disk HR4796A taken in the polarimetric mode of the Gemini Planet Imager (GPI). The polarized intensity features a strongly forward-scattered brightness distribution and is undetected at the far side of the disk. The total intensity is detected at all scattering angles and also exhibits a strong forward-scattering peak. We use a forward-modeled geometric disk in order to extract geometric parameters, polarized fraction, and total intensity scattering phase functions for these data as well as H-band data previously taken by GPI. We find the polarized phase function becomes increasingly more forward-scattering as wavelength increases. We fit Mie and distribution of hollow spheres (DHS) grain models to the extracted functions. We find that it is possible to generate a satisfactory model for the total intensity using a DHS model, but not with a Mie model. We find that no single grain population of DHS or Mie grains of arbitrary composition can simultaneously reproduce the polarized fraction and total intensity scattering phase functions, indicating the need for more sophisticated grain models.

• OSTI ID: 23013311
• Journal Information: Astronomical Journal (New York, N.Y. Online), Vol. 160, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
DISTRIBUTION
INCLINATION
LUMINOSITY
PLANETS
WAVELENGTHS