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Title: UNDERSTANDING THE ORIGIN OF THE [O I] LOW-VELOCITY COMPONENT FROM T TAURI STARS

The formation time, masses, and location of planets are strongly impacted by the physical mechanisms that disperse protoplanetary disks and the timescale over which protoplanetary material is cleared out. Accretion of matter onto the central star, protostellar winds/jets, magnetic disk winds, and photoevaporative winds operate concurrently. Hence, disentangling their relative contribution to disk dispersal requires identifying diagnostics that trace different star-disk environments. Here, we analyze the low-velocity component (LVC) of the oxygen optical forbidden lines, which is found to be blueshifted by a few km s{sup -1} with respect to the stellar velocity. We find that the [O I] LVC profiles are different from those of [Ne II] at 12.81 {mu}m and CO at 4.7 {mu}m lines pointing to different origins for these gas lines. We report a correlation between the luminosity of the [O I] LVC and the accretion luminosity L{sub acc}. We do not find any correlation with the X-ray luminosity, while we find that the higher is the stellar far-UV (FUV) luminosity, the higher is the luminosity of the [O I] LVC. In addition, we show that the [O I] {lambda}6300/{lambda}5577 ratio is low (ranging between 1 and 8). These findings favor an origin of the [Omore » I] LVC in a region where OH is photodissociated by stellar FUV photons and argue against thermal emission from an X-ray-heated layer. Detailed modeling of two spectra with the highest S/N and resolution shows that there are two components within the LVC: a broad, centrally peaked component that can be attributed to gas arising in a warm disk surface in Keplerian rotation (with FWHM between {approx}40 and {approx}60 km s{sup -1}), and a narrow component (with FWHM {approx} 10 km s{sup -1} and small blueshifts of {approx}2 km s{sup -1}) that may arise in a cool ({approx}<1000 K) molecular wind.« less
Authors:
;  [1] ; ;  [2] ;  [3]
  1. Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States)
  2. SETI Institute, Mountain View, CA (United States)
  3. Astronomy Department, Smith College, Northampton, MA 01063 (United States)
Publication Date:
OSTI Identifier:
22121863
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 772; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; CARBON MONOXIDE; COMPUTERIZED SIMULATION; EMISSION; FAR ULTRAVIOLET RADIATION; JETS; LUMINOSITY; MAGNETIC DISKS; MASS; OXYGEN; PHOTONS; PROTOPLANETS; PROTOSTARS; SPECTRA; STELLAR WINDS; T TAURI STARS; X RADIATION