Discovery of Galactic O iv and O v X-ray absorption due to transition temperature gas in the PKS 2155-304 spectrum

J. Nevalainen; B. Wakker; J. Kaastra; M. Bonamente; S. Snowden; F. Paerels; C. de Vries

doi:10.1051/0004-6361/201630336

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Volume 605 (September 2017)

A&A, 605 (2017) A47

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Table 1

Galactic absorption line measurements.

Ion	Transition		RGS1 1st		RGS2 1st		LETG/HRC-S		LETG/ACIS-S
	name	λ₀^a (Å)	EW (mÅ)^b	N _σ ^c	EW (mÅ)^b	N _σ ^c	EW (mÅ)^b	N _σ ^c	EW (mÅ)^b	N _σ ^c

Ne ix	1s–2p	13.447	n/c	–	5.1 ± 1.5	3.4	8.0 ± 2.1	3.9	≤2.0	n/d
O vii	1s–3b	18.628	4.7 ± 1.5	3.2	3.0 ± 1.5 ^d	2.0^d	2.6 ± 1.9	1.3	4.6 ± 1.5	3.0
O viii	1s–2p	18.967	9.0 ± 1.7	5.2	5.5 ± 1.6	5.7	7.8 ± 2.4	3.3	5.3 ± 1.7	3.2
O viii	1s–2p	18.972	9.0 ± 1.7	5.2	5.5 ± 1.6	5.7	7.8 ± 2.4	3.3	5.3 ± 1.7	3.2
O vii	1s–2p	21.602	15.4 ± 1.5	10.1	n/c	–	11.3 ± 2.6	4.3	10.0 ± 1.7	6.0
O v	1s–2p	22.370	3.0 ± 1.5	2.0	n/c	–	3.7 ± 2.3	1.6	≤1.1	n/d
O iv	1s–2p ²S	22.571	7.0 ± 2.8	2.5	n/c	–	8.2 ± 3.1	2.6	≤4.2	n/d
	1s–2p ²P	22.741
	1s–2p ²D	22.777
O i	1s–2p	23.510	–	–	–	–	17.3 ± 3.3	5.2	9.0 ± 2.0	4.5
O i	1s–2p	23.511					17.3 ± 3.3	5.2	9.0 ± 2.0	4.5
N vi	1s–2p	28.788	4.5 ± 2.0^d	2.3^d	3.1 ± 1.6	1.9	5.0 ± 2.4	2.1	≤3.2	n/d
N i	1s–2p	31.286	–	–	–	–	10.6 ± 2.9	3.6	≤6.1	n/d
C vi	1s–2p	33.734	7.7 ± 2.6^d	2.9^d	8.8 ± 2.0	4.3	3.6 ± 2.6	1.4	≤6.1	n/d
C vi	1s–2p	33.740	7.7 ± 2.6^d	2.9^d	8.8 ± 2.0	4.3	3.6 ± 2.6	1.4	≤6.1	n/d

Notes.

^(a)

A priori values from Verner et al. (1996), Kaastra et al. (1996), and Gu et al. (2005).

^(b)

Equivalent width and total 1σ uncertainties (i.e. statistical uncertainties and systematic 1 mÅ) for detected lines. For the non-detections (n/d), the upper 1σ limit is given; n/c means that the line is not covered by the instrument.

^(c)

Significance of the line detection in terms of 1σ uncertainty.

^(d)

The problematic single channel has been omitted when deriving the values.

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