Table 6: Summary of absorption features observed in the RGS spectrum of Mkn 421. ^a Archival data analyzed by us. ^b Detected in one of the two observations. C01: Cagnoni (2001); N01: Nicastro et al. (2001); P01: Paerels et al. (2001); N02: Nicastro et al. (2002); N03: Nicastro et al. (2003); dV03: de Vries (2003); F03: Fang et al. (2003); C04: Cagnoni et al. (2004).
Feature RGS-1 RGS-2 Crab Literature Other

number $\lambda$ (Å) sources

2 $18.680\pm0.004$ 18.697 (ToO) $\rm 18.674^{+0.002}_{-0.003}$ YES (C01-XMM) PKS 2155-304 (N02-Cha)

18.718 (4/11/02) NO (N01-Cha) PKS 2155-304 (C04-XMM)

instrumental YES (N03-Cha)

3 $18.953\pm0.003$ NO instrumental YES (C01-XMM) PKS 2155-304 (N02-Cha)

NO (N01-Cha) 3C 273 (F03-Cha)

YES (N03-Cha) NO PKS 2155-304 (C04-XMM)

5 $19.676\pm0.003$ NO NO NO NO

6 $19.904\pm0.004$ instrumental instrumental NO PKS 2155-304 (C04-XMM)

NO PKS 2155-304 (N02-Cha)

7 $21.603\pm0.008$ no data NO YES (C01-XMM) PKS 2155-304 (N02-Cha)

NO (N01-Cha) PKS 2155-304 (C04-XMM)

YES (N03-Cha) 3C 273 (F03-Cha)

8 $21.823\pm0.001$ no data instrumental YES (C01-XMM) PKS 2155-304^a (XMM)

YES^b (N01-Cha) NO PKS 2155-304 (C04-XMM)

YES (N03-Cha)

9 $22.778\pm0.001$ no data NO YES (dV03-XMM) PKS 2155-304 (dV03-XMM)

near PKS 2155-304 (dV03-Cha)

instrumental PKS 2155-304 (C04-XMM)

feature NO ScoX1(dV03-XMM)

NO 4U 0614+91 (dV03-XMM)

10 $23.510\pm0.007$ no data YES (dV03-XMM) PKS 2155-304 (P01-Cha)

PKS 2155-304 (N02-Cha)

PKS 2155-304 (C04-XMM)

**Table 6:** Summary of absorption features observed in the RGS spectrum of Mkn 421. ^a Archival data analyzed by us. ^b Detected in one of the two observations. C01: Cagnoni (2001); N01: Nicastro et al. (2001); P01: Paerels et al. (2001); N02: Nicastro et al. (2002); N03: Nicastro et al. (2003); dV03: de Vries (2003); F03: Fang et al. (2003); C04: Cagnoni et al. (2004).
Feature	RGS-1	RGS-2	Crab	Literature	Other
number	$\lambda$ (Å)				sources
2	$18.680\pm0.004$	18.697 (ToO)	$\rm 18.674^{+0.002}_{-0.003}$	YES (C01-XMM)	PKS 2155-304 (N02-Cha)
		18.718 (4/11/02)		NO (N01-Cha)	PKS 2155-304 (C04-XMM)
		instrumental		YES (N03-Cha)
3	$18.953\pm0.003$	NO	instrumental	YES (C01-XMM)	PKS 2155-304 (N02-Cha)
				NO (N01-Cha)	3C 273 (F03-Cha)
				YES (N03-Cha)	NO PKS 2155-304 (C04-XMM)
5	$19.676\pm0.003$	NO	NO	NO	NO
6	$19.904\pm0.004$	instrumental	instrumental	NO	PKS 2155-304 (C04-XMM)
					NO PKS 2155-304 (N02-Cha)
7	$21.603\pm0.008$	no data	NO	YES (C01-XMM)	PKS 2155-304 (N02-Cha)
				NO (N01-Cha)	PKS 2155-304 (C04-XMM)
				YES (N03-Cha)	3C 273 (F03-Cha)
8	$21.823\pm0.001$	no data	instrumental	YES (C01-XMM)	PKS 2155-304^a (XMM)
				YES^b (N01-Cha)	NO PKS 2155-304 (C04-XMM)
				YES (N03-Cha)
9	$22.778\pm0.001$	no data	NO	YES (dV03-XMM)	PKS 2155-304 (dV03-XMM)
			near		PKS 2155-304 (dV03-Cha)
			instrumental		PKS 2155-304 (C04-XMM)
			feature		NO ScoX1(dV03-XMM)
					NO 4U 0614+91 (dV03-XMM)
10	$23.510\pm0.007$	no data		YES (dV03-XMM)	PKS 2155-304 (P01-Cha)
					PKS 2155-304 (N02-Cha)
					PKS 2155-304 (C04-XMM)

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