A COMBINED SPITZER AND HERSCHEL INFRARED STUDY OF GAS AND DUST IN THE CIRCUMBINARY DISK ORBITING V4046 Sgr

We present results from a spectroscopic Spitzer and Herschel mid-to-far-infrared study of the circumbinary disk orbiting the evolved (age similar to 12-23 Myr) close binary T Tauri system V4046 Sgr. Spitzer InfraRed Spectrograph spectra show emission lines of [Ne H-2 S(1), CO2, and HCN, while Herschel Photodetector Array Camera and Spectrometer and Spectral and Photometric Imaging Receiver spectra reveal emission from [0 OH, and tentative detections of H2O and high-J transitions of CO. We measure [Ne III]/ less than or similar to 0.13, which is comparable to other X-ray/EUV luminous T Tauri stars that lack jets. We use the H-2 S(1) line luminosity to estimate the gas mass in the relatively warm surface layers of the inner disk. The presence of [O-1] emission suggests that CO, H2O, and/or OH is being photodissociated, and the lack of [CI] emission suggests any excess C may be locked up in HCN, CN, and other organic molecules. Modeling of silicate dust grain emission features in the mid-infrared indicates that the inner disk is composed mainly of large (r similar to 5 pm) amorphous pyroxene and olivine grains (-86% by mass) with a relatively large proportion of crystalline silicates. These results are consistent with other lines of evidence indicating that planet building is ongoing in regions of the disk within similar to 30 AU of the central, close binary.NASA by JPL/Caltech; National Science Foundation [AST-1108950]SCI(E)ARTICLEvar5998@rit.edu181