Precision analysis of 12C/13C ratios in Orion IRc2 acetylene isotopologs via χ2 fitting

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Table 7

Comparison of ¹²C/¹³C isotopic ratios derived using the traditional RD method and the χ² fitting method for the blue and red clumps in the Orion IRc2.

Source \ Clump	Blue Clump	Method	Red Clump	Method
Nickerson et al. (2023) (¹²C/¹³C)	21.3 ± 2.2	RD	19.8 ± 3.4	RD
This Work (¹²C/¹³C)	${18.73}_{- 1.47}^{+ 1.54}$ $18.73^{+1.54}_{-1.47}$	χ²	${15.07}_{- 1.60}^{+ 1.61}$ $15.07^{+1.61}_{-1.60}$	χ² (¹²C) +RD (¹³C)
Difference	$- {2.57}_{- 0.73}^{- 0.66}$ $-2.57^{-0.66}_{-0.73}$	–	$- {4.73}_{- 1.80}^{- 1.79}$ $-4.73^{-1.79}_{-1.80}$	–
Percent Difference (%)	$- {12.1}_{- 33.2}^{- 30.0}$ $-12.1^{-30.0}_{-33.2}$	–	$- {23.9}_{- 52.9}^{- 52.6}$ $-23.9^{-52.6}_{-52.9}$	–

Notes. For the red clump, the χ² (¹²C) + RD (¹³ C) approach was used, where the χ² fitting method determined the ¹²C column density, and the RD method was applied to the ¹³C isotopolog due to limited observational data. The differences and percentage differences between the methods are also presented. References: Nickerson et al. (2023).

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