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Table 1
Envelope parameters and assumptions for IK Tau in our fiducial model.
| 1. Shape | Spherical | |
| 2. Mass-loss rate | 4.5(–6) M⊙ yr-1 (De Beck et al. 2010) | |
| 3. Envelope expansion velocity | 24 km s-1 (Justtanont et al. 2012) | |
| 4. Stellar radius, R∗ | 2.1 × 1013 cm (Duari et al. 1999) | |
| 5. Inner radius of CSE | 1015 cm | |
| 6. External radiation field | Standard interstellar radiation field (Draine 1978), isotropic incidence | |
| 7. Grain surface reactions | Ignored | |
| 8. Gas density distribution | Falls as r-2, where r is the distance from the central star | |
| 9. Chemical evolution | Kinetic equations solved as a function of radius as material traverses the CSE | |
| 10. H2 | Fully self-shielded, no photodissociation | |
| 11. Parent species | See Table 2 | |
| 12. T, AV, and gas density | See Fig. 2 | |
| 13. Adopted cosmic-ray ionization rate of H2 | 1.2 × 10-17 s-1 |
Notes. a(b) = a × 10b.
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