High-contrast imaging of ϵ Eridani with ground-based instruments

¹ Astronomical Institute, Tohoku University, Aoba-ku, Sendai, 980-8578 Miyagi, Japan
e-mail: mizuki@astr.tohoku.ac.jp
² Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Sagamihara, Kanagawa Japan
³ Department of Physics and Astronomy, College of Charleston, 58 Coming St., Charleston, SC 29424, USA
⁴ Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, 152-8551 Tokyo, Japan
⁵ Astrobiology Center of NINS, 2-21-1, Osawa, Mitaka, 181-8588 Tokyo, Japan
⁶ National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, 181-8588 Tokyo, Japan
⁷ Department of Physics, University of Cincinnati, Cincinnati, OH 45221-0011, USA
⁸ Subaru Telescope, National Astronomical Observatory of Japan, 650 North A’ohoku Place, Hilo, HI96720, USA
⁹ Laboratoire Lagrange (UMR 7293), Université de Nice-Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, 28 avenue Valrose, 06108 Nice Cedex 2, France
¹⁰ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹¹ Astrophysics Department, Institute for Advanced Study, Princeton, NJ 08540, USA
¹² Universitäts-Sternwarte München, Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 München, Germany
¹³ Exoplanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771, USA
¹⁴ Eureka Scientific, 2452 Delmer, Suite 100, Oakland CA96002, USA
¹⁵ Goddard Center for Astrobiology, USA
¹⁶ Institute for Astronomy, University of Hawaii, 640 N. A’ohoku Place, Hilo, HI 96720, USA
¹⁷ Department of Astrophysical Science, Princeton University, Peyton Hall, Ivy Lane, Princeton, NJ08544, USA
¹⁸ Department of Astronomy, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, 113-0033 Tokyo, Japan
¹⁹ Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyamacho, Toyonaka, 560-0043 Osaka, Japan
²⁰ Hiroshima University, 1-3-2, Kagamiyama, Higashihiroshima, 739-8511 Hiroshima, Japan
²¹ Department of Astrophysics, CAB-CSIC/INTA, 28850 Torrej’on de Ardoz, Madrid, Spain
²² Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 171-113, USA
²³ Department of Astronomical Science, The Graduate University for Advanced Studies, 2-21-1, Osawa, Mitaka, 181-8588 Tokyo, Japan
²⁴ Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, 10617 Taipei, Taiwan
²⁵ Swiss Federal Institute of Technology (ETH Zurich), Institute for Astronomy, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
²⁶ Kavli Institute for Physics and Mathematics of the Universe, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, 277-8568 Chiba, Japan
²⁷ Department of Cosmosciences, Hokkaido University, Kita-ku, Sapporo, 060-0810 Hokkaido, Japan
²⁸ H. L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 WBrooks St Norman, OK 73019, USA

Received: 18 March 2016
Accepted: 23 August 2016

Abstract

ϵ Eridani is one of the nearest solar-type stars. Its proximity and relatively young age allow high-contrast imaging observations to achieve sensitivities to planets at narrow separations down to an inner radius of ~5 AU. Previous observational studies of the system report a dust disk with asymmetric morphology as well as a giant planet with large orbital eccentricity, which may require another massive companion to induce the peculiar morphology and to enhance the large orbital eccentricity. In this paper, we report results from deep high-contrastimaging observations to detect the previously reported planet and search for other unseen less massive companions with Subaru/HiCIAO, Gemini-South/NICI, and VLT/NACO. No positive detection was made, but high-contrast measurements with the CH₄S narrow-band filter of HiCIAO achieved sensitivities at 14.7 mag differential magnitude level, at an angular separation of 1.0″. In terms of planetary mass, as determined by cooling evolutionary models, the highest sensitivities were achieved by the Lp broad-band filter of NACO, resulting in sensitivities corresponding to 1.8, 2.8, and 4.5 M_jup at the projected separation of 3 AU, if 200, 400, and 800 Myr is assumed for the age of the system, respectively. We also discuss origins of the dust disk from the detection sensitivity in the planetary mass and find that a less massive eccentric planet is preferred for disk stirring, which is consistent with the orbital parameters of ϵ Eri b claimed from the previous long-term radial velocity monitoring.