Modeling apparent variations in extinction vectors of young stars

Young stars are surrounded by circumstellar dust. Light is extinguished as it passes through dust; it gets redder and fainter. The properties of the dust determine how the light is extinguished. Typically, models for visual extinction are based on a standard star and do not consider the effects of circumstellar dust. Studying star formation requires correcting observational data for the effects of circumstellar dust. Models may need to be adjusted to accurately describe the extinction of light from young stars. We can calculate the effects of extinction by applying an extinction law to a synthetic stellar spectrum and examining the effects on brightness at various wavelengths. Two properties are examined: the brightness, or magnitude, of light at visual wavelengths in the so-called V band, and the magnitude of light at infrared wavelengths in the K band. Without a disk, we expect models to show a linear relationship between V magnitude and the V-K magnitude difference as extinction increases. By adding a 1200K blackbody to the stellar spectrum to simulate emission from dust in a circumstellar disk, we can determine how the extinction of the spectrum behaves differently than a model without a disk. After simulating over 10 magnitudes of visual extinction, we see that the relationship between V and V-K is not completely linear for stars with disks. The slope between V and V-K changes as extinction increases. Brighter circumstellar disks cause a more drastic slope change with increasing extinction. For a 5700K star and a 1200K disk emitting equal amounts of energy, the slope decreases from 1.011 to 1.006 over 10 magnitudes of extinction and decreases to nearly 0 over 25 magnitudes of extinction