The Astrophysical Journal, 814:32 (12pp), 2015 November 20 doi:10.1088/0004-637X/814/1/32 © 2015. The American Astronomical Society. All rights reserved. DIRECT IMAGING OF AN ASYMMETRIC DEBRIS DISK IN THE HD 106906 PLANETARY SYSTEM Paul G. Kalas1, Abhijith Rajan2, Jason J. Wang1, Maxwell A. Millar-Blanchaer3,30, Gaspard Duchene1,4,5, Christine Chen6, Michael P. Fitzgerald7, Ruobing Dong1, James R. Graham1, Jennifer Patience2, Bruce Macintosh8, Ruth Murray-Clay9, Brenda Matthews10, Julien Rameau11, Christian Marois10, Jeffrey Chilcote3,30, Robert J. De Rosa1, René Doyon11, Zachary H. Draper10, Samantha Lawler10, S. Mark Ammons12, Pauline Arriaga7, Joanna Bulger13, Tara Cotten14, Katherine B. Follette8, Stephen Goodsell15, Alexandra Greenbaum16, Pascale Hibon15, Sasha Hinkley17, Li-Wei Hung7, Patrick Ingraham18, Quinn Konapacky19, David Lafreniere11, James E. Larkin7, Douglas Long6, Jérôme Maire3, Franck Marchis20, Stan Metchev21,22,23, Katie M. Morzinski24, Eric L. Nielsen8,20, Rebecca Oppenheimer25, Marshall D. Perrin6, Laurent Pueyo6, Fredrik T. Rantakyrö15, Jean-Baptiste Ruffio8, Leslie Saddlemyer10, Dmitry Savransky26, Adam C. Schneider27, Anand Sivaramakrishnan6, Rémi Soummer6, Inseok Song14, Sandrine Thomas18, Gautam Vasisht28, Kimberly Ward-Duong2, Sloane J. Wiktorowicz29, and Schuyler G. Wolff6,16 1 Astronomy Department, University of California, Berkeley CA 94720-3411, USA 2 School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287, USA 3 Department of Astronomy & Astrophysics, University of Toronto, Toronto ON M5S 3H4, Canada 4 Université of Grenoble Alpes, IPAG, F-38000 Grenoble, France 5 CNRS, IPAG, F-38000 Grenoble, France 6 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 7 Department of Physics & Astronomy, UCLA, Los Angeles, CA 90095, USA 8 Kavli Institute for Particle Astrophysics & Cosmology, Stanford University, Stanford, CA 94305, USA 9 Department of Physics, University of California, Santa Barbara, CA 93106, USA 10 National Research Council of Canada Herzberg, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada 11 Institut de Recherche sur les Exoplanetes, Département de Physique, Université de Montréal, Montréal QC H3C 3J7, Canada 12 Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94040, USA 13 Subaru Telescope, National Astronomical Observatory of Japan, 650, North Aohoku Place, Hilo, HI 96720, USA 14 Department of Physics & Astronomy, The University of Georgia, Athens, GA 30602-2451, USA 15 Gemini Observatory, Casilla 603, La Serena, Chile 16 Physics & Astronomy Department, Johns Hopkins University, Baltimore, MD 21218, USA 17 School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK 18 AURA/LSST, 950 N. Cherry Avenue, Tucson, AZ 85719, USA 19 University of California, San Diego, La Jolla, CA 92093, USA 20 SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94043, USA 21 Physics & Astronomy Department, University of Western Ontario, London, ON N6A 3K7, Canada 22 Centre for Planetary & Space Exploration, University of Western Ontario, London, ON N6A 3K7, Canada 23 Physics & Astronomy Department, Stony Brook University, Stony Brook, NY 11794-3800, USA 24 Steward Observatory, Center for Astronomical Adaptive Optics, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA 25 American Museum of Natural History, New York, NY 10024, USA 26 Sibley School of Mechanical & Aerospace Engineering, Cornell University, Ithaca NY 14853, USA 27 University of Toledo, 2801 W. Bancroft Street, Toledo, OH 43606, USA 28 NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA 29 Department of Astronomy & Astrophysics, University of California, Santa Cruz, CA 95064, USA 30 Dunlap Institute for Astronomy & Astrophys., University of Toronto, Toronto ON M5S 3H4, Canada Received 2015 June 26; accepted 2015 October 8; published 2015 November 13 ABSTRACT We present the first scattered light detections of the HD 106906 debris disk using the Gemini/Gemini Planet Imager in the infrared and Hubble Space Telescope (HST)/Advanced Camera for Surveys in the optical. HD 106906 is a 13 Myr old F5V star in the Sco–Cen association, with a previously detected planet-mass candidate HD 106906b projected 650 AU from the host star. Our observations reveal a near edge-on debris disk that has a central cleared region with radius ∼50 AU, and an outer extent >500 AU. The HST data show that the outer regions are highly asymmetric, resembling the “needle” morphology seen for the HD 15115 debris disk. The planet candidate is oriented ∼21° away from the position angle of the primary’s debris disk, strongly suggesting non-coplanarity with the system. We hypothesize that HD 106906b could be dynamically involved in the perturbation of the primary’s disk, and investigate whether or not there is evidence for a circumplanetary dust disk or cloud that is either primordial or captured from the primary. We show that both the existing optical properties and near-infrared colors of HD 106906b are weakly consistent with this possibility, motivating future work to test for the observational signatures of dust surrounding the planet. Key words: circumstellar matter – infrared: stars – stars: individual (HD 106906) – techniques: high angular resolution 1 The Astrophysical Journal, 814:32 (12pp), 2015 November 20 Kalas et al. 1. INTRODUCTION band spectral mode with 25°.3 of field rotation. An additional eight 90 s exposures were collected in imaging polarimetry The Gemini Planet Imager (GPI) Exoplanet Survey is mode at four different waveplate orientations (0°, 22°.5, 45°, targeting 600 young, nearby stars to directly detect and and 67°.5; two exposures per orientation) with 7°.1 of field characterize extrasolar planets and dusty debris disks. The rotation. general observing strategy is to obtain relatively deep (∼1 hr) The spectral and polarimetry mode data were reduced using observations of young stars with the spectroscopic mode of the GPI Data Reduction Pipeline (Perrin et al. 2014). The GPI, and shorter snapshots using GPI’s dual channel imaging spectral data were dark subtracted, flexure corrected, and polarimetry mode to detect polarized light scattered by wavelength calibrated with an H-band Ar discharge lamp taken circumstellar dust grains. The scientific motivations include immediately before the science sequence. Bad pixels were quantifying the frequency and masses of Jovians from 5 to repaired in the raw 2D data, the data were assembled into 50 AU, determining the properties of their atmospheres, and datacubes, and corrected for distortion. The polarimetry data understanding their dynamical co-evolution with the planete- were dark subtracted, flexure corrected using a cross-correla- simals that replenish reservoirs of dust grains seen as debris tion method, bad pixels repaired, corrected for the lenslet disks. In particular, well-resolved debris disks typically have response using the Gemini calibration flat field lamp, and features such as central holes, azimuthal clumps, and vertical assembled into a Stokes datacube using a Mueller matrix model warps that in a single snapshot reveal key properties of each of the instrument. The instrumental polarization was subtracted system’s recent dynamical history. as described in Millar-Blanchaer et al. (2015). The Stokes Fomalhaut, HR 8799, HD 95086, and β Pic are four datacube was then converted to the radial Stokes convention prominent examples of dusty debris disks dynamically ( IQUV,,, IQ , , UV , ;Schmid et al. 2006), which associated with directly imaged planets (Kalas et al. 2008; [ ][rr ] places the tangentially (ortho-radial) and radially polarized Marois et al. 2008, 2010; Lagrange et al. 2009; Rameau et al. intensity into the Q image. Under the convention used here, 2013), but a more recent candidate for planet-disk interactions r tangentially polarized intensity results in positive values in the is HD 106906 (HIP 59960; 92 ± 6 pc; F5V; 1.5 M ; 5.6 L ; 13 Q image. ± 2 Myr; Pecaut et al. 2012). The dusty debris disk was first r In polarimetry mode, the data outside of ∼0 3 is typically discovered with a Spitzer infrared survey of 25 stars comprising dominated by the photon noise of the point-spread function Lower Centaurus Crux (Chen et al. 2005). Excess infrared (PSF) halo and detector read noise (Perrin et al. 2014). To emission in both the Spitzer MIPS 24 and 70 μm bands improve the signal to noise, we apply a Gaussian filter with correspond to L L 1.4 103 and a blackbody radius of IR FWHM = 3 pixels (42 mas; the FWHM of Gemini’s diffraction ∼20 AU (Chen et al. 2011; see also Jang-Condell et al. 2015). limited PSF in the H-band). A comoving, substellar companion (11 ± 2 M ) was Jup The initial discovery of the disk in both the spectral and subsequently discovered at a projected separation of 7 11 polarimetry mode data prompted us to re-examine the archival (654 AU) and a position angle of PA = 307°.3 (Bailey HST data obtained with the Advanced Camera for Surveys et al. 2014) using the Magellan AO system (Close et al. 2013). High Resolution Channel (ACS/HRC) coronagraph. These At such a large projected distance, a key question is whether or optical data (F606W; 2 frames of 1250 s each) were obtained not HD 106906b originally formed like a planet in a UT 2004 December 01 as part of a follow-up imaging circumstellar disk surrounding the primary and was subse- campaign to stars with Spitzer-detected infrared