We present spectral energy distribution ( SED ) models for the edge-on classical T Tauri star HH30 IRS that indicate dust grains have grown to larger than 50 \mu { m } within its circumstellar disk .
The disk geometry and inclination are known from previous modeling of multiwavelength Hubble Space Telescope images and we use the SED ( 0.5 \mu { m } \leq \lambda \leq 3 mm ) to constrain the dust size distribution .
Model spectra are shown for different circumstellar dust models : a standard ISM mixture and larger grain models .
As compared to ISM grains , the larger dust grain models have a shallower wavelength dependent opacity : smaller at short wavelengths and larger at long wavelengths .
Models with the larger dust grains provide a good match to the observed SED of HH30 IRS .
Although the currently available SED is poorly sampled , we estimate L _ { \star } \approx 0.2 L _ { \odot } , M _ { disk } \approx 1.5 \times 10 ^ { -3 } M _ { \odot } , and a power-law with exponential cutoff dust grain size distribution .
This model provides a good fit to the currently available data , but mid and far-IR observations are required to more tightly constrain the size distribution .
The accretion luminosity in our models is L _ { acc } \lesssim 0.2 L _ { \star } corresponding to an accretion rate \dot { M } \lesssim 4 \times 10 ^ { -9 } M _ { \odot } { yr } ^ { -1 } .
Dust size distributions that are simple power-law extensions ( i.e. , no exponential cutoff ) yield acceptable fits to the optical/near-IR but too much emission at mm wavelengths and require larger disk masses up to M _ { disk } \sim 0.5 M _ { \odot } .
Such a simple size distribution would not be expected in an environment such as the disk of HH30 IRS , ( i.e. , where coagulation and accretion processes are occurring in addition to grain shattering ) , particularly over such a large range in grain sizes .
However , its ability to adequately characterize the grain populations may be determined from more complete observational sampling of the SED in the mid to far-IR .