Relating jet structure to photometric variability: the Herbig Ae star HD 163296^⋆,⋆⋆

¹ Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
e-mail: lucas.ellerbroek@gmail.com
² Institut de Planétologie et d’Astrophysique de Grenoble, 414 rue de la Piscine, 38400 St.-Martin d’ Hères, France
³ INAF − Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Florence, Italy
⁴ CNRS/Universidad de Chile, Laboratoire Franco-Chilien d’Astronomie (LFCA), UMI 3386 Santiago, Chile
⁵ LERMA, Observatoire de Paris, UMR 8112 du CNRS, 61 Av. de l’Observatoire, 75014 Paris, France
⁶ Department of Physics, University of Cincinnati, Cincinnati OH 45221, USA
⁷ Space Science Institute, 4750 Walnut Street, Boulder, CO 80303, USA
⁸ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁹ Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
¹⁰ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹¹ Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, USA
¹² Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978, USA
¹³ Eureka Scientific, Inc., Oakland, CA 94602, USA
¹⁴ Exoplanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771, USA
¹⁵ Crimean Astrophysical Observatory, Scientific Research institute, 98409 Crimea, Nauchny, Ukraine
¹⁶ The Aerospace Corporation, Los Angeles, CA 90009, USA
¹⁷ Thule Scientific, Topanga, CA 90290, USA
¹⁸ Associated Universities for Research in Astronomy, Inc., 1212 New York Ave. NW, Washington, DC 20005, USA
¹⁹ Department of Astronomy, University of Washington, Seattle, WA 98105, USA
²⁰ Department of Physics, Miami University, Oxford, OH 45056, USA
²¹ Department of Management Science and Engineering, Stanford University, Stanford, CA 94305, USA
²² American Association of Variable Star Observers, 49 Bay State Road, Cambridge, MA 02138, USA
²³ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

Received: 20 November 2013
Accepted: 15 January 2014

Abstract

Herbig Ae/Be stars are intermediate-mass pre-main sequence stars surrounded by circumstellar dust disks. Some are observed to produce jets, whose appearance as a sequence of shock fronts (knots) suggests a past episodic outflow variability. This “jet fossil record” can be used to reconstruct the outflow history. We present the first optical to near-infrared (NIR) spectra of the jet from the Herbig Ae star HD 163296, obtained with VLT/X-shooter. We determine the physical conditions in the knots and also their kinematic “launch epochs”. Knots are formed simultaneously on either side of the disk, with a regular interval of ~16 yr. The velocity dispersion versus jet velocity and the energy input are comparable between both lobes. However, the mass-loss rate, velocity,and shock conditions are asymmetric. We find Ṁ_jet/Ṁ_acc ~ 0.01−0.1, which is consistent with magneto-centrifugal jet launching models. No evidence of any dust is found in the high-velocity jet, suggesting a launch region within the sublimation radius (<0.5 au). The jet inclination measured from proper motions and radial velocities confirms that it is perpendicular to the disk. A tentative relation is found between the structure of the jet and the photometric variability of the central source. Episodes of NIR brightening were previously detected and attributed to a dusty disk wind. We report for the first time significant optical fadings lasting from a few days up to a year, coinciding with the NIR brightenings. These are very likely caused by dust lifted high above the disk plane, and this supports the disk wind scenario. The disk wind is launched at a larger radius than the high-velocity atomic jet, although their outflow variability may have a common origin. No significant relation between outflow and accretion variability could be established. Our findings confirm that this source undergoes periodic ejection events, which may be coupled with dust ejections above the disk plane.