High-contrast imaging of HD 163296 with the Keck/NIRC2 L′-band vortex coronograph

Creators: Guidi, G.; Ruane, G.; Williams, J. P.; Mawet, D.; Testi, L.; Zurlo, A.; Absil, O.; Bottom, M.; Choquet, É.; Christiaens, V.; Femenía-Castellá, B.; Huby, E.; Isella, A.; Kastner, J.; Meshkat, T.; Reggiani, M.; Riggs, A.; Serabyn, E.; Wallack, N.

Abstract

We present observations of the nearby (D∼100 pc) Herbig star HD 163296 taken with the vortex coronograph at Keck/NIRC2 in the L′ band (3.7 μm) to search for planetary mass companions in the ringed disc surrounding this pre-main-sequence star. The images reveal an arc-like region of scattered light from the disc surface layers that is likely associated with the first bright ring detected with ALMA in the λ = 1.3 mm dust continuum at ∼65 au. We also detect a point-like source at ∼0.5 arcsec projected separation in the north-east direction, close to the inner edge of the second gap in the millimetre images. Comparing the point source photometry with the atmospheric emission models of non-accreting giant planets, we obtain a mass of 6–7 M_J for a putative protoplanet, assuming a system age of 5 Myr. Based on the contrast at a 95 per cent level of completeness calculated on the emission-free regions of our images, we set upper limits for the masses of giant planets of 8–15 M_J, 4.5–6.5 M_J, and 2.5–4.0 M_J at the locations of the first, second, and third gap in the millimetre dust continuum, respectively. Further deep, high-resolution thermal IR imaging of the HD 163296 system are warranted to confirm the presence and nature of the point source and to better understand the structure of the dust disc.

Additional Information

© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices). Accepted 2018 June 15. Received 2018 June 14; in original form 2018 February 27. Published: 22 June 2018. GR is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1602444. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA). The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Part of this work was carried out at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under contract with NASA. JPW was supported by NASA grant NNX15AC92G. JHK acknowledges support from NASA Exoplanets programme grant NNX16AB43G to RIT. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (ERC Grant Agreement no. 337569), and from the French Community of Belgium through an ARC grant for Concerted Research Action. EC acknowledges support from NASA through Hubble Fellowship grant HF2-51355 awarded by STScI, which is operated by AURA, Inc. for NASA under contract NAS5-26555, for research carried out at the Jet Propulsion Laboratory, California Institute of Technology. This work used archival data from HST programme GO-10177 (PI: G. Schneider), which were obtained from the Mikulski Archive for Space Telescopes (MAST) at STScI, as well as data reprocessed as part of the ALICE program, which was supported by NASA through grants HST-AR-12652 (PI: R. Soummer), HST-GO-11136 (PI: D. Golimowski), HST-GO-13855 (PI: E. Choquet), HST-GO-13331 (PI: L. Pueyo), and STScI Director's Discretionary Research funds. AZ acknowledges support from the CONICYT + PAI/ Convocatoria nacional subvención a la instalación en la academia, convocatoria 2017 + Folio PAI77170087. This work was partly supported by the Italian Ministero dell'Istruzione, Università e Ricerca through the grant Progetti Premiali 2012 – iALMA (CUP C52I13000140001), by the Deutsche Forschungs-gemeinschaft (DFG, German Research Foundation) - Ref no. FOR 2634/1 TE 1024/1-1, and by the DFG cluster of excellence Origin and Structure of the Universe (www.universe-cluster.de).

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