SIMBAD references

The X-ray transient pulsar EXO 2030+375 was observed by ROSAT in November 1990 during the All-Sky survey. The observation took place very close to periastron passage and the source was clearly visible over an interval of two days. The average flux level suggests an active companion star although the ROSAT flux is lower than the observed flux in most of the EXOSAT observations. The spectrum is heavily absorbed below 1 keV and the hardness ratio indicates a column density of 2-3 x 10²² cm^–2, consistent with previous measurements. The amount of pulsed flux in the soft X-ray band and the absence of a soft excess in EXOSAT archival data suggest that the soft X-rays originate from the immediate vicinity of the neutron star. Joint spectral fits of soft and hard X-ray EXOSAT data further show that the neutral column density, intrinsic to the source, is of the order of 10²² cm^–2.