Quantifying jet–interstellar medium interactions in Cyg X-1: Insights from dual-frequency bow shock detection with MeerKAT

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Volume 696 (April 2025)

A&A, 696 (2025) A223

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Table 1.

Known, measured, and estimated parameters of the Cyg X-1 bow shock.

Known parameters of Cyg X-1 from literature

Parameter	Value	Reference
Distance	2.22 $_{- 0.17}^{+ 0.18}$ $^{+0.18}_{-0.17}$ kpc	[1]
Jet inclination angle	27.18 ± 0.18°	[1]
De-reddened H_α flux of the bow shock (S_Hα)	1.3 × 10⁻¹⁶ ergs cm⁻² arcsec⁻²	[2, 3]
Jet opening angle (^a)	0.2°–2°	[4]
Width of the H_α ring (Δ)	1.6 × 10¹⁸ cm	[2]

Bow shock parameters using L-band map

	Measured values	Physical values
Separation between Cyg X-1 and apex of bow shock (L_l)	10.8 arcmin	6.8 pc
Separation between closest edges of bow shock (R_l)	7.3 arcmin	4.6 pc
Bow shock width (ΔR_l)	1.5 ± 0.2 arcmin	0.9 pc
Projected area of the bow shock	97 771 arcsec²	11 pc²
Volume of the bow shock	–	10 pc³
Mean bow shock brightness	110 ± 24 μJy bm⁻¹	–

Bow shock parameters using S-band map

	Measured values	Physical values

Separation between Cyg X-1 and apex of bow shock (L_s)	10.5 arcmin	6.7 pc
Separation between closest edges of bow shock (R_s)	7.0 arcmin	4.4 pc
Bow shock width (ΔR_s)	1.4 ± 0.2 arcmin	0.9 pc
Projected area of the bow shock	95 689 arcsec²	11 pc²
Volume of the bow shock	–	9 pc³
Mean bow shock brightness	38 ± 13 μJy bm⁻¹	–

Properties of the bow shock and the ISM

Electron density (L band) (n_eL(T))	$24_{- 8}^{+ 12}$ $24^{+12}_{-8}$ cm⁻³
Electron density (S band) (n_eS(T))	$28_{- 9}^{+ 14}$ $28^{+14}_{-9}$ cm⁻³
Electron density (H_α maps) (n_eh)	11 ± 2 cm⁻³
Velocity of leading edge of bow shock ( $\dot{L}$ $\dot{L}$ )	21 km s $^{- 1} < \dot{L} < 364$ $^{-1} < \dot{L} < \,364$ km s⁻¹
Age of the jet	0.04–0.3 Myr
Jet power ( $Q_{jet}^{b}$ $Q_{\mathrm{jet}}^{\mathrm{b}}$ ; Jet opening angle 0°–30°)	2 × 10³⁴ ergs s $^{- 1} < Q_{jet}^{b} < 1 \times 10^{37}$ ${^{-1}} < Q_{\mathrm{jet}}^{\mathrm{b}} < 1\times10^{37}$ ergs s⁻¹
Jet power ( $Q_{jet}^{a}$ $Q_{\mathrm{jet}}^{\mathrm{a}}$ )	2 × 10³¹ ergs s $^{- 1} < Q_{jet}^{a} < 1 \times 10^{35}$ $^{-1} < Q_{\mathrm{jet}}^{\mathrm{a}} < 1\times10^{35}$ ergs s⁻¹
Pressure inside the bow shock	3 × 10⁻¹³–2 × 10⁻¹¹ ergs cm⁻³

Notes. The superscript a and b represent the estimates using two different opening angle ranges. [1] Miller-Jones et al. (2021), [2] Russell et al. (2007), [3] Sell et al. (2015) and [4] Stirling et al. (2001).

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