The ASCA observation of GRO J1744-28 Original Research Article

The ASCA results of the bursting X-ray pulsar GRO J1744-28 are reported. The observations were made twice, in February 1996 and March 1997. We detected 12 and 17 Type II bursts during the two observations, with mean bursting intervals of about 27 min and 37 min. Each burst is followed by an intensity dip with the depleted flux depending on the burst fluence. The energy spectra are approximated by an absorbed power law with additional structure around 6–7 keV, which is most probably due to iron and maybe reproduced by the disk line model with additional broadening mechanism. The absorption column is constant ((5 − 6) × 1022 cm−2), independent of the observation dates and emission phase (persistent, burst and dip). This means the source may be actually located near the galactic center (8.5kpc).