Polarimetry and flux distribution in the debris disk around HD 32297

¹ Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden
e-mail: ruben.torres@astro.su.se; markus.janson@astro.su.se
² Astrobiology Center of NINS, 2-21-1, Osawa, Mitaka, 181-8588 Tokyo, Japan
³ Swiss Federal Institute of Technology (ETH Zurich), Institute for Astronomy, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
⁴ Subaru Telescope, National Astronomical Observatory of Japan, 650 North A’ohoku Place, Hilo, HI 96720, USA
⁵ Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguroku, 152-8551 Tokyo, Japan
⁶ Laboratoire Lagrange (UMR 7293), Universite de Nice-Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, 28 avenue Valrose, 06108 Nice Cedex 2, France
⁷ National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, 181-8588 Tokyo, Japan
⁸ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁹ Astrophysics Department, Institute for Advanced Study, Princeton, NJ 08540, USA
¹⁰ Department of Physics and Astronomy, College of Charleston, 68 George St., Charleston, SC 29424, USA
¹¹ Universitats-Sternwarte Munchen, Ludwig-Maximilians-Universitat, Scheinerstr. 1, 81679 Munchen, Germany
¹² Exoplanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771, USA
¹³ Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002, USA
¹⁴ Goddard Center for Astrobiology, Goddard Space Flight Center, Greenbelt, MD 20771, USA
¹⁵ Institute for Astronomy, University of Hawaii, 640 N. A’ohoku Place, Hilo, HI 96720, USA
¹⁶ Department of Astrophysical Science, Princeton University, Peyton Hall, Ivy Lane, Princeton, NJ 08544, USA
¹⁷ Department of Astronomy, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-0033 Tokyo, Japan
¹⁸ Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 Kyoto, Japan
¹⁹ The Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (SOKENDAI), Shonan International Village, Hayama-cho, Miura-gun, 240-0193 Kanagawa, Japan
²⁰ Hiroshima University, 1-3-2 Kagamiyama, Higashihiroshima, 739-8511 Hiroshima, Japan
²¹ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
²² Center for Astrophysical Sciences, Johns Hopkins University, Baltimore, MD 21218, USA
²³ Kavli Institute for Physics and Mathematics of the Universe, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, 277-8568 Chiba, Japan
²⁴ Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan
²⁵ Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, 10617 Taipei Taiwan
²⁶ Department of Cosmosciences, Hokkaido University, Kita-ku, Sapporo, 060-0810 Hokkaido, Japan
²⁷ H. L. Dodge Department of Physics & Astronomy, University of Oklahoma, 440 W Brooks St., Norman, OK 73019, USA
²⁸ Astronomical Institute, Tohoku University, Aoba-ku, Sendai, 980-8578 Miyagi, Japan

Received: 17 March 2016
Accepted: 3 May 2016

Abstract

We present high-contrast angular differential imaging (ADI) observations of the debris disk around HD 32297 in H-band, as well as the first polarimetric images for this system in polarized differential imaging (PDI) mode with Subaru/HICIAO. In ADI, we detect the nearly edge-on disk at ≥5σ levels from ~0.45″ to ~1.7″ (50–192 AU) from the star and recover the spine deviation from the midplane already found in previous works. We also find for the first time imaging and surface brightness (SB) indications for the presence of a gapped structure on both sides of the disk at distances of ~0.75″ (NE side) and ~0.65″ (SW side). Global forward-modelling work delivers a best-fit model disk and well-fitting parameter intervals that essentially match previous results, with high-forward scattering grains and a ring located at 110 AU. However, this single ring model cannot account for the gapped structure seen in our SB profiles. We create simple double ring models and achieve a satisfactory fit with two rings located at 60 and 95 AU, respectively, low-forward scattering grains and very sharp inner slopes. In polarized light we retrieve the disk extending from ~0.25–1.6″, although the central region is quite noisy and high S/N are only found in the range ~0.75–1.2″. The disk is polarized in the azimuthal direction, as expected, and the departure from the midplane is also clearly observed. Evidence for a gapped scenario is not found in the PDI data. We obtain a linear polarization degree of the grains that increases from ~10% at 0.55″ to ~25% at 1.6″. The maximum is found at scattering angles of ~90°, either from the main components of the disk or from dust grains blown out to larger radii.