THE HERSCHEL DIGIT SURVEY OF WEAK-LINE T TAURI STARS: IMPLICATIONS FOR DISK EVOLUTION AND DISSIPATION
- Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)
- Max Planck Institute fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)
- Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205 (United States)
- National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 86719 (United States)
- Herschel Science Centre, European Space Astronomy Centre, ESA, P.O. Box 78, E-28691 Villanueva de la Canada, Madrid (Spain)
- Department of Astronomy, University of Vienna, Tuerkenschanzstr. 17, A-1180 Vienna (Austria)
- UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d'Astrophysique (IPAG) UMR 5274, BP 53, F-38041 Grenoble cedex 9 (France)
As part of the 'Dust, Ice, and Gas In Time (DIGIT)' Herschel Open Time Key Program, we present Herschel photometry (at 70, 160, 250, 350, and 500 {mu}m) of 31 weak-line T Tauri star (WTTS) candidates in order to investigate the evolutionary status of their circumstellar disks. Of the stars in our sample, 13 had circumstellar disks previously known from infrared observations at shorter wavelengths, while 18 of them had no previous evidence for a disk. We detect a total of 15 disks as all previously known disks are detected at one or more Herschel wavelengths and two additional disks are identified for the first time. The spectral energy distributions (SEDs) of our targets seem to trace the dissipation of the primordial disk and the transition to the debris disk regime. Of the 15 disks, 7 appear to be optically thick primordial disks, including 2 objects with SEDs indistinguishable from those of typical Classical T Tauri stars, 4 objects that have significant deficit of excess emission at all IR wavelengths, and 1 'pre-transitional' object with a known gap in the disk. Despite their previous WTTS classification, we find that the seven targets in our sample with optically thick disks show evidence for accretion. The remaining eight disks have weaker IR excesses similar to those of optically thin debris disks. Six of them are warm and show significant 24 {mu}m Spitzer excesses, while the last two are newly identified cold debris-like disks with photospheric 24 {mu}m fluxes, but significant excess emission at longer wavelengths. The Herschel photometry also places strong constraints on the non-detections, where systems with F {sub 70}/F {sub 70,*} {approx}> 5-15 and L {sub disk}/L {sub *} {approx}> 10{sup -3} to 10{sup -4} can be ruled out. We present preliminary models for both the optically thick and optically thin disks and discuss our results in the context of the evolution and dissipation of circumstellar disks.
- OSTI ID:
- 22167272
- Journal Information:
- Astrophysical Journal, Vol. 762, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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