Table 3
Diffusion data: fractional mass in the convection zone, diffusion timescales τ for C and Si, and diffusion fluxes.
| Object | log (ΔMcvz/M) | log (ΔM(1) /M) | τ(C) [yrs] | τ(Si) [yrs] | fdiff(C) [g/s] | C/Si |
|
|
||||||
| WDJ1929+4447 | −12.661 | > −10.962 | 31.05 | 11.91 | < 4.67 × 105 | |
| WD1654+160 | −12.466 | > −10.721 | 36.23 | 15.14 | < 4.27 × 105 | |
| EC20058-5234 | −11.656 | −10.178 | 114.89 | 55.77 | 5.90 × 106 | 137.5 |
| EC04207-4748 | −11.592 | −10.045 | 179.67 | 85.29 | 6.81 × 106 | 512.0 |
| PG1115+158 | −11.373 | > −9.822 | 204.64 | 103.40 | 5.52 × 105 | 0.11 |
|
|
||||||
| WD0100-068 | −8.419 | > −6.062 | 1.82 × 104 | 1.40 × 104 | 1.26 × 106 | 0.52 |
| WD0435+410 | −6.676 | > −3.627 | 2.43 × 105 | 2.05 × 105 | < 9.36 × 104 | < 0.005 |
| WD0840+262 | −7.263 | > −4.437 | 8.49 × 104 | 6.81 × 104 | < 4.69 × 105 | < 1.72 |
| WD1557+192 | −8.184 | > −5.681 | 2.36 × 104 | 1.90 × 104 | < 5.63 × 105 | < 0.68 |
| WD1822+410 | −6.130 | > −3.644 | 7.42 × 105 | 6.64 × 105 | 7.16 × 106 | 0.61 |
| WD1940+374 | −6.393 | > −3.499 | 4.57 × 105 | 4.01 × 105 | < 3.35 × 105 | |
| WD2144-079 | −6.482 | > −3.686 | 3.28 × 105 | 2.81 × 105 | < 4.17 × 105 | <0.07 |
|
|
||||||
| Sun | 3.56 | |||||
| Bulk Earth | 0.0099−0.0228 | |||||
| CI | 0.325 | |||||
Notes. ΔM(1) /M is the fractional mass above the layer with [C/He] = 1. In the last column the mass ratio C/Si of the accreted matter is given (with the assumption that the metal pollution is caused by accretion). The last three rows in this column give the mass ratio C/Si for the Sun (Asplund et al. 2009), bulk Earth (Allègre et al. 2001), and CI chondrites (Lodders et al. 2009).
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