A VIEW OF PKS 2155-304 WITH XMM-NEWTON REFLECTION GRATING SPECTROMETERS

摘要

We present the high-resolution X-ray spectrum of the BL Lac object PKS 2155-304 taken with the RGS units on board XMM-Newton in 2000 November. We detect an O Ⅶ Kα resonant absorption line from warm/hot local gas at 21.59 A (～4.5 σ detection). The line profile is possibly double peaked. We do not confirm the strong 20.02 A absorption line seen with Chandra and interpreted as z ～ 0.05 O Ⅷ Kα. We set a 3 σ upper limit of 14 mA on the equivalent width. We also detect the ～23.5 A interstellar O Ⅰ 1s→2p line and derive a factor of ≤ 1.5 subsolar O/H ratio in the interstellar medium along the PKS 2155- 304 line of sight.