Evidence for Evolution Among Primordial Disks in the 5 Myr Old Upper Scorpius OB Association

Abstract

Moderate-resolution, near-infrared spectra between 0.8 and 5.2 microns were obtained for 12 late-type (K0-M3) disk-bearing members of the ~5 Myr old Upper Scorpius OB association using SpeX on the NASA Infrared Telescope Facility. For most sources, continuum excess emission first becomes apparent between ~2.2 and 4.5 microns and is consistent with that produced by single-temperature blackbodies having characteristic temperatures ranging from ~500 to 1300 K. The near-infrared spectra for 5 of 12 Upper Scorpius sources exhibit Pa-gamma, Pa-beta and Br-gamma emission, indicators of disk accretion. Using a correlation between Pa-beta and Br-gamma emission line luminosity and accretion luminosity, mass accretion rates (Mdot) are derived for these sources that range from Mdot = 3.5 X 10^{-10} to 1.5 X 10^{-8} MSun per yr. Merging the SpeX observations with Spitzer Space Telescope mid-infrared (5.4-37.0 micron) spectroscopy and 24 and 70 micron broadband photometry, the observed spectral energy distributions are compared with those predicted by two-dimensional, radiative transfer accretion disk models. Of the 9 Upper Scorpius sources examined in this analysis, 3 exhibit spectral energy distributions that are most consistent with models having inner disk radii that substantially exceed their respective dust sublimation radii. The remaining Upper Scorpius members possess spectral energy distributions that either show significant dispersion among predicted inner disk radii or are best described by models having inner disk rims coincident with the dust sublimation radius.

35 pages, 5 figures, accepted for publication in the Astronomical Journal

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Cited by in corpus (7)

• ALMA Observations of Circumstellar Disks in the Upper Scorpius OB Association
• The Disk Population of the Upper Scorpius Association
• Rapid disappearance of a warm, dusty circumstellar disk
• A continuum of accretion burst behavior in young stars observed by K2
• The SEEDS High Contrast Imaging Survey of Exoplanets around Young Stellar Objects
• Dipper disks not inclined towards edge-on orbits
• A Correlation Between Circumstellar Disks and Rotation in the Upper Scorpius OB Association