Table 2: Neutral oxygen wavelengths (1s-2p transition). 1) Mc Laughlin & Kirby (1998); 2) Krause (1994); 3) Stolte et al. (1997); 4) Paerels et al. (2001); 5) Nicastro et al. (2002); 6) de Vries et al. (2003); 7) Cagnoni et al. (2004).
$\lambda$ (Å) Method Ref.

23.467 Theoretical 1

$23.489\pm0.004$ Experimental 2

$23.536\pm0.002$ Experimental 3

$23.52\pm0.03$ Chandra, X0614+091 4

$\rm 23.509^{+0.008}_{-0.018}$ Chandra, PKS 2155-304 5

$23.50 \pm 0.01$ XMM 6

$23.510\pm0.015$ XMM, PKS 2155-304 7

$23.510\pm0.007$ XMM, Mkn 421 ToO obs.

$23.507\pm0.013$ XMM, Mkn 421 Arch. data

$23.510\pm0.013$ XMM, Mkn 421 Total

**Table 2:** Neutral oxygen wavelengths (1s-2p transition). 1) Mc Laughlin & Kirby (1998); 2) Krause (1994); 3) Stolte et al. (1997); 4) Paerels et al. (2001); 5) Nicastro et al. (2002); 6) de Vries et al. (2003); 7) Cagnoni et al. (2004).
$\lambda$ (Å)	Method	Ref.
23.467	Theoretical	1
$23.489\pm0.004$	Experimental	2
$23.536\pm0.002$	Experimental	3
$23.52\pm0.03$	Chandra, X0614+091	4
$\rm 23.509^{+0.008}_{-0.018}$	Chandra, PKS 2155-304	5
$23.50 \pm 0.01$	XMM	6
$23.510\pm0.015$	XMM, PKS 2155-304	7
$23.510\pm0.007$	XMM, Mkn 421	ToO obs.
$23.507\pm0.013$	XMM, Mkn 421	Arch. data
$23.510\pm0.013$	XMM, Mkn 421	Total

Source LaTeX | All tables | In the text

	1 Introduction
	2 The XMM-Newton observations and data reduction
	3 Looking for lines in various segments of the spectra
	4 Discussion
	5 Conclusions
	References
	Online Material
	Appendix A: RGS spectral analysis and comparison with EPIC-PN