eROSITA X-ray analysis of the PeVatron candidate Westerlund 1

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Volume 695 (March 2025)

A&A, 695 (2025) A3

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Table 1.

Best-fit parameters of the 2apec model (second block) and the apec+pl model (third block), with corresponding parameters from Muno et al. (2006) and Kavanagh et al. (2011).

Parameter	This study	Muno et al. (2006)	Kavanagh et al. (2011)
`BACKSCAL` [arcmin⁻²]	23.11
`REGAREA` [arcmin⁻²]	28.57
N_H [10²² cm⁻²]	2.20

$N_{H}^{CGM}$ $N_{\mathrm{H}}^{\mathrm{CGM}}$ [10²² cm⁻²]	$0 . 4_{- 0.1}^{+ 0.1}$ $0.4_{-0.1}^{+0.1}$
$N_{H}^{cor}$ $N_{\mathrm{H}}^{\mathrm{cor}}$ [10²² cm⁻²]	$1 . 7_{- 0.5}^{2.2}$ $1.7_{-0.5}^{2.2}$

N_H^2apec [10²² cm⁻²]	$2 . 2_{- 0.22}^{2.2}$ $2.2_{-0.22}^{2.2}$	$2 . 2_{- 0.2}^{+ 0.2}$ $2.2_{-0.2}^{+0.2}$	$2 . 0_{- 0.2}^{+ 0.2}$ $2.0_{-0.2}^{+0.2}$
k_BT₁ [keV]	$0 . 46_{- 0.13}^{+ 0.11}$ $0.46_{-0.13}^{+0.11}$	$0 . 90_{- 0.14}^{+ 0.14}$ $0.90_{-0.14}^{+0.14}$	$0 . 68_{- 0.13}^{+ 0.12}$ $0.68_{-0.13}^{+0.12}$
η₁ [10⁻¹⁴ cm⁻⁵ arcmin⁻²]	$1 . 4_{- 0.6}^{+ 1.2} \cdot 10^{- 4}$ $1.4_{-0.6}^{+1.2}\cdot10^{-4}$	$5 . 4_{- 0.6}^{+ 1.5} \cdot 10^{- 5}$ $5.4_{-0.6}^{+1.5}\cdot10^{-5}$
k_BT₂ [keV]	$5 . 7_{- 2.5}^{+ 10}$ $5.7_{-2.5}^{+10}$	$9 . 1_{- 1.4}^{+ 2.8}$ $9.1_{-1.4}^{+2.8}$	$3 . 1_{- 0.4}^{+ 0.6}$ $3.1_{-0.4}^{+0.6}$
η₂ [10⁻¹⁴ cm⁻⁵ arcmin⁻²]	$1 . 1_{- 0.3}^{+ 0.4} \cdot 10^{- 4}$ $1.1_{-0.3}^{+0.4}\cdot10^{-4}$	$1 . 5_{- 0.1}^{+ 0.1} \cdot 10^{- 4}$ $1.5_{-0.1}^{+0.1}\cdot10^{-4}$
F_{2 − 8 keV} [erg cm⁻² s⁻¹ arcmin⁻²]	$10_{- 5}^{+ 5} \cdot 10^{- 14}$ $10_{-5}^{+5}\cdot10^{-14}$		14 ⋅ 10⁻¹⁴

$N_{H}^{CGM}$ $N_{\mathrm{H}}^{\mathrm{CGM}}$ [10²² cm⁻²]	$0 . 43_{- 0.09}^{+ 0.13}$ $0.43_{-0.09}^{+0.13}$
$N_{H}^{cor}$ $N_{\mathrm{H}}^{\mathrm{cor}}$ [10²² cm⁻²]	$1 . 4_{- 0.4}^{2.2}$ $1.4_{-0.4}^{2.2}$

N_H^apec+pl [10²² cm⁻²]	$2 . 2_{- 0.22}^{2.2}$ $2.2_{-0.22}^{2.2}$	$2 . 4_{- 0.2}^{+ 0.2}$ $2.4_{-0.2}^{+0.2}$	$2 . 1_{- 0.3}^{+ 0.3}$ $2.1_{-0.3}^{+0.3}$
k_BT_apec [keV]	$0 . 43_{- 0.12}^{+ 0.13}$ $0.43_{-0.12}^{+0.13}$	$0 . 96_{- 0.08}^{+ 0.14}$ $0.96_{-0.08}^{+0.14}$	$0 . 81_{- 0.09}^{+ 0.16}$ $0.81_{-0.09}^{+0.16}$
η_apec [10⁻¹⁴ cm⁻⁵ arcmin⁻²]	$1 . 2_{- 0.6}^{+ 1.4} \cdot 10^{- 4}$ $1.2_{-0.6}^{+1.4}\cdot10^{-4}$	$6 . 2_{- 1.2}^{+ 1.1} \cdot 10^{- 5}$ $6.2_{-1.2}^{+1.1}\cdot10^{-5}$
Γ	$2 . 1_{- 0.6}^{+ 0.5}$ $2.1_{-0.6}^{+0.5}$	$2 . 1_{- 0.1}^{+ 0.1}$ $2.1_{-0.1}^{+0.1}$	$2 . 4_{- 0.2}^{+ 0.2}$ $2.4_{-0.2}^{+0.2}$
η_PL [keV cm⁻⁵ arcmin⁻²]	$4 . 8_{- 2.0}^{+ 1.5} \cdot 10^{- 5}$ $4.8_{-2.0}^{+1.5}\cdot10^{-5}$	$6 . 5_{- 0.9}^{+ 1.0} \cdot 10^{- 4}$ $6.5_{-0.9}^{+1.0}\cdot10^{-4}$
F_{2 − 8keV} [erg cm⁻² s⁻¹ arcmin⁻²]	$9_{- 2.7}^{+ 5} \cdot 10^{- 14}$ $9_{-2.7}^{+5}\cdot10^{-14}$		12 ⋅ 10⁻¹⁴

Notes. The BACKSCAL and REGAREA parameters were taken from the header of the Wd 1 source spectrum fits file, while the N_H parameter was determined using nH. These three parameters are identical for both models. F_{2 − 8 keV} was determined using the cflux component from Xspec. All other parameters are Xspec best-fit parameters with 1σ confidence intervals determined via Xspec’s error command. All normalizations and fluxes were divided by the source areas in square arcminutes. Confidence intervals given without a plus or minus sign indicate that a parameter ran into a hard limit before it could sample its full 1σ region. The values from Muno et al. (2006) and Kavanagh et al. (2011) were determined as described in the main text.

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