Spiral Structure in the Circumstellar Disk around AB Aurigae

We present a near-infrared image of the Herbig Ae star AB Aur obtained with the Coronagraphic Imager with Adaptive Optics mounted on the Subaru Telescope. The image shows a circumstellar emission extending out to a radius of r = 580 AU, with a double spiral structure detected at r = 200-450 AU. The surface brightness decreases as r-3.0±0.1, steeper than the radial profile of the optical emission possibly affected by the scattered light from the envelope surrounding AB Aur. This result, together with the size of the infrared emission similar to that of the 13CO (J = 1-0) disk, suggests that the spiral structure is indeed associated with the circumstellar disk but is not part of the extended envelope. We identified four major spiral arms, which are trailing if the brighter southeastern part of the disk is the near side. The weak gravitational instability, maintained for millions of years by continuous mass supply from the envelope, might explain the presence of the spiral structure at the relatively late phase of the pre-main-sequence period.

[1]  C. Dominik,et al.  Understanding the spectra of isolated Herbig stars in the frame of a passive disk model , 2002, astro-ph/0212032.

[2]  Dynamics of Circumstellar Disks , 1998, astro-ph/9802191.

[3]  Timothy G. Hawarden,et al.  JHK standard stars for large telescopes: the UKIRT Fundamental and Extended lists , 2001, astro-ph/0102287.

[4]  E. Guinan,et al.  Intrinsic Properties of the Young Stellar Object SU Aurigae , 2003 .

[5]  Yosuke Minowa,et al.  Performance of Subaru Cassegrain Adaptive Optics System , 2004 .

[6]  M. Tamura,et al.  Near-Infrared Coronagraphy of the GG Tauri A Binary System ∗ , 2002 .

[7]  M. Franx,et al.  Hubble Space Telescope ACS Coronagraphic Imaging of the Circumstellar Disk around HD 141569A , 2003 .

[8]  Rafael Millan-Gabet,et al.  Spatially Resolved Circumstellar Structure of Herbig Ae/Be Stars in the Near-Infrared , 2000 .

[9]  J. Pollack,et al.  Composition and radiative properties of grains in molecular clouds and accretion disks , 1994 .

[10]  T. Henning,et al.  The Disk and Environment of the Herbig Be Star HD 100546 , 2001 .

[11]  T. Guillot,et al.  A Nongray Theory of Extrasolar Giant Planets and Brown Dwarfs , 1997, astro-ph/9705201.

[12]  Accretion Disks around Young Objects. I. The Detailed Vertical Structure , 1998, astro-ph/9806060.

[13]  Hst/nicmos2 coronagraphic observations of the circumstellar environment of three old pms stars: hd 100546, sao 206462 and mwc 480 , 2000, astro-ph/0009496.

[14]  Saeko S. Hayashi,et al.  Coronagraph imager with adaptive optics (CIAO): description and first results , 2000, Astronomical Telescopes and Instrumentation.

[15]  Mark Clampin,et al.  Hubble Space Telescope Space Telescope Imaging Spectrograph Coronagraphic Imaging of the Herbig Ae Star AB Aurigae , 1999 .

[16]  K. Wood,et al.  NICMOS Coronagraphic Observations of the GM Aurigae Circumstellar Disk , 2003 .

[17]  D. Lin,et al.  Gap Formation in Protoplanetary Disks , 1996 .

[18]  L. Hillenbrand,et al.  Accepted for publication in the Astrophysical Journal Near-Infrared Interferometric Measurements of Herbig Ae/Be Stars , 2003 .

[19]  M. Tamura,et al.  Investigation of the Physical Properties of Protoplanetary Disks around T Tauri Stars by a 1 Arcsecond Imaging Survey: Evolution and Diversity of the Disks in Their Accretion Stage , 2002 .

[20]  L. Hartmann,et al.  Model scattering envelopes of young stellar objects. I - Method and application to circumstellar disks , 1992 .

[21]  S. Lubow,et al.  Three-dimensional calculations of high- and low-mass planets embedded in protoplanetary discs , 2003, astro-ph/0301154.

[22]  Frederick J. Vrba,et al.  Herbig Ae/Be Stars: Intermediate-Mass Stars Surrounded by Massive Circumstellar Accretion Disks , 1992 .

[23]  V. Mannings,et al.  A High-Resolution Study of Gas and Dust around Young Intermediate-Mass Stars: Evidence for Circumstellar Disks in Herbig Ae Systems , 1997 .

[24]  T. Nakajima,et al.  Coronagraphic imaging of pre-main-sequence stars: Remnant evvelopes of star formation seen in reflection , 1995 .

[25]  David R. Alexander,et al.  THE LIMITING EFFECTS OF DUST IN BROWN DWARF MODEL ATMOSPHERES , 2001 .

[26]  Berkeley,et al.  Infrared Views of the TW Hydra Disk , 2001, astro-ph/0110342.