Astrophys. J., 762, 62 (2013/January-1)
Tracing high-energy radiation from T Tauri stars using mid-infrared neon emission from disks.
ESPAILLAT C., INGLEBY L., FURLAN E., McCLURE M., SPATZIER A., NIEUSMA J., CALVET N., BERGIN E., HARTMANN L., MILLER J.M. and MUZEROLLE J.
Abstract (from CDS):
High-energy radiation from T Tauri stars (TTS) influences the amount and longevity of gas in disks, thereby playing a crucial role in the creation of gas giant planets. Here we probe the high-energy ionizing radiation from TTS using high-resolution mid-infrared (MIR) Spitzer Infrared Spectrograph neon forbidden line detections in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We report three new detections of [Ne III] from CS Cha, SZ Cha, and T 54, doubling the known number of [Ne III] detections from TTS. Using [Ne III]-to-[Ne II] ratios in conjunction with X-ray emission measurements, we probe high-energy radiation from TTS. The majority of previously inferred [Ne III]/[Ne II] ratios based on [Ne III] line upper limits are significantly less than 1, pointing to the dominance of either X-ray radiation or soft extreme-ultraviolet (EUV) radiation in producing these lines. Here we report the first observational evidence for hard EUV-dominated Ne forbidden line production in a T Tauri disk: [Ne III]/[Ne II] ∼ 1 in SZ Cha. Our results provide a unique insight into the EUV emission from TTS, by suggesting that EUV radiation may dominate the creation of Ne forbidden lines, albeit in a minority of cases.
accretion, accretion disks - circumstellar matter - protoplanetary disks
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