On the Diversity of the Taurus Transitional Disks: UX Tau A & Lk Ca 15

Abstract

The recently recognized class of "transitional disk" systems consists of young starswith optically-thick outer disks but inner disks which are mostly devoid of small dust. Here we introduce a further class of "pre-transitional disks" with significant near-infrared excesses which indicate the presence of an optically thick inner disk separated from an optically thick outer disk; thus, the spectral energy distributions of pre-transitional disks suggest the incipient development of disk gaps rather than inner holes. In UX Tau A, our analysis of the Spitzer IRS spectrum finds that the near-infrared excess is produced by an inner optically thick disk and a gap of ~56 AU is present. The Spitzer IRS spectrum of LkCa 15 is suggestive of a gap of ~46 AU, confirming previous millimeter imaging. In addition, UX Tau A contains crystalline silicates in its disk at radii >~ 56 AU which poses a challenge to our understanding of the production of this crystalline material. In contrast, LkCa 15's silicates are amorphous and pristine. UX Tau A and LkCa 15 increase our knowledge of the diversity of dust clearing in low-mass star formation.

4 pages, accepted ApJL

References in corpus (5)

• Dust dynamics during protoplanetary disc clearing
• Demographics of Transition Objects
• An Inner Hole in the Disk around TW Hydrae Resolved in 7 Millimeter Dust Emission
• Probing the Dust and Gas in the Transitional Disk of CS Cha with Spitzer
• Dust Processing in Disks around T Tauri Stars

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• New Low-Mass Stars and Brown Dwarfs with Disks in the Chamaeleon I Star-Forming Region
• Spitzer Spectroscopy of Circumstellar Disks in the 5 Myr Old Upper Scorpius OB Association
• The TEXES Survey For H2 Emission From Protoplanetary Disks
• A slowly accreting ~10 Myr old transitional disk in Orion OB1a
• Discovery of a Circumbinary Disk around Herbig Ae/Be system v892 Tau
• CO Fundamental Emission from V836 Tau
• The Structure of the DoAr 25 Circumstellar Disk
• 10 $\mu$m interferometry of disks around young stars