Tracing High-Energy Radiation from T Tauri Stars Using Mid-Infrared Neon Emission from Disks

• Published in: arXiv.org 2012-11
• Main Authors: Espaillat, C, Ingleby, L, Furlan, E, McClure, M, Spatzier, A, Nieusma, J, Calvet, N, Bergin, E, Hartmann, L, Miller, J M, Muzerolle, J
• Format: Article
• Language: English
• Subjects: Accretion disks; Emission; Gas giant planets; Ionizing radiation; Neon; T Tauri stars
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1211.2335

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 IRS 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.