Suzaku View of the Neutron Star in the Dipping Source 4U 1822 37

The dipping X-ray source 4U 1822−37 was observed by Suzaku on 2006 Octrober 20 for a net exposure of 37 ks. The source was detected with the XIS at a 1-10 keV flux of 5.5×10 −10 erg cm −2 s −1 , and with the HXD (HXD-PIN) at a 10-50 keV flux of 8.9×10 −10 erg cm −2 s −1 . With HXD-PIN, the pulsation was detected at a barycentric period of 0.592437 s, and its change rate was reconfirmed as −2.43×10 −12 s s −1 . The 1-50 keV spectra of 4U 1822-37 were found to be very similar to those of Her X1 in the slopes, cutoff and iron lines. Three iron lines (Fe K�, Fe XXV, and Fe XXVI) were detected, on top of a 1-50 keV continuum that is described by an NPEX model plus a soft blackbody. In addition, a cyclotron resonance scattering feature was detected significantly (>99% confidence), at an energy of 33±2 keV with a depth of 0.4 +0.6 −0.3. Therefore, the neutron star in this source is concluded to have a strong magnetic field of 2.8×10 12 G. Further assuming that the source has a relatively high intrinsic luminosity of several times 10 37 erg s −1 , its spectral and timing properties