K. Kinugasa, K. Torii, Y. Hashimoto, H. Tsunemi, K. Hayashida, S. Kitamoto, Y. Kamata, T. Dotani, F. Nagase, M. Sugizaki, Y. Ueda, N. Kawai, K. Makishima, S. Yamauchi

Journal: Astrophysical Journal v.495, p.435

Abstract

A new X-ray pulsar, AX J1820.5-1434, has been discovered during the ASCA Galactic plane survey project on April 9, at R.A. = 18h20m29.s5, decl. = -14 deg34'24" (equinox 2000.0; error radius 0.'5). A coherent pulsation was detected from the source with an apparent barycentric pulse period of 152.26 +/- 0.04 s. The mean flux, not corrected for the interstellar absorption, was 2.3 x 10-11 ergs s-1 cm-2 in the 2-10 keV energy band. The energy spectra obtained by the GIS and SIS can be fitted by a power-law model (photon index = 0.9 +/- 0.2) with a large column density of 9.8 +/- 1.7 x 1022 H atoms cm-2. These parameters indicate that the new pulsar is a highly obscured accretion-driven binary X-ray pulsar. This discovery of a faint pulsar suggests existence of many hidden pulsars in our Galaxy.