Absorption line features were detected at 4.1 keV from X 1636-536 with the Tenma satellite in the spectra of X-ray bursts (Waki et al., 1984). Similar features were also detected from X 1608-52 and EXO 1747-214 during bursts (Nakamura et al., 1988; Magnier et al., 1989). These features at 4.1 keV may be interpreted as the redshifted Kα absorption line of helium-like iron atoms. However, such interpretation requires extremely soft equation of state for the nuclear matter, and confirmation with high resolution detectors is urged (Lewin et al., 1993). To investigate the line features, we observed X 1636-536 with ASCA for ~ 240 ksec.
Detection of Absorption‐Line Features in the X‐Ray Spectra of the Galactic Superluminal Source GRO J1655−40