Molecular abundances in the inner layers of IRC +10216

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Table 9

IRC +10216’s model parameters.

Parameter	Value

Distance (D)	130 pc
Stellar radius (R_∗)	4 × 10¹³ cm
Stellar effective temperature (T_∗)	2330 K
Stellar luminosity (L_∗)	8750 L_⊙
Stellar mass (M_∗)	0.8 M_⊙
End of static atmosphere (R₀)	1.2 R_∗
Dust condensation radius (R_c)	5 R_∗
End of dust acceleration region (R_w)	20 R_∗
Gas expansion velocity (v_exp)^a	14.5 km s^-1
Microturbulence velocity (Δv_turb)^b	1 km s^-1
Mass loss rate (Ṁ)	2 × 10^-5M_⊙ yr^-1
Gas kinetic temperature (T_k)^c	T_∗ × (r/R_∗)^-0.55
Gas-to-dust mass ratio ()	300
Dust temperature (T_d)	800 K × (r/R_c)^-0.375

Notes.

^(a)

v_exp = 5 km s^-1 for regions inner to R_c, 11 km s^-1 for the dust acceleration region between R_c and R_w, and 14.5 km s^-1 beyond R_w.

^(b)

Δv_turb = 5 km s^-1 × (R_∗/r) for regions inner to R_c and 1 km s^-1 in the rest of the envelope.

^(c)

T_k ∝ r^-0.55 for regions inner to 75 R_∗, T_k ∝ r^-0.85 between 75 and 200 R_∗, and T_k ∝ r^-1.40 beyond 200 R_∗.

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