Discovery of a Transient X-Ray Pulsar, AX J1841.0 $-$ 0536, in the Scutum Arm Region with ASCA

• Published in: Publications of the Astronomical Society of Japan Vol. 53; no. 6; pp. 1179 - 1183
• Main Authors: Bamba, Aya, Yokogawa, Jun, Ueno, Masaru, Koyama, Katsuji, Yamauchi, Shigeo
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford University Press 25.12.2001
• Subjects: stars: pulsars: individual (AX J1841.0-0536); X-rays: stars; X-rays: spectra; X-rays: transient; stars: neutron
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/53.6.1179

We report on the discovery of a transient X-ray pulsar, AX J1841.0 $-$ 0536, serendipitously found in the Scutum arm region with the ASCA in two separate observations. The X-ray flux is very faint at the beginning, but exhibits two flares in the second observation. The flare flux increases by a factor 10 within only $\sim 1 \,\mathrm{hr}$ . Coherent pulsations with a period of $4.7394 \pm 0.0008 \,\mathrm{s}$ were detected in the brightest flare phase. The X-ray spectra in the quiescent and flare phases were fitted with an absorbed power-law model with a photon index $\sim 1$ plus a narrow Gaussian line at the center energy of 6.4 keV. The interstellar column density of $\sim 3\times 10^{22} \,\mathrm{cm}^{-2}$ may indicate that AX J1841.0 $-$ 0536 is located at a tangential point of the Scutum arm at $\sim 10 \,\mathrm{kpc}$ distance. The coherent pulsations, large flux variability, and the spectral shape suggest that AX J1841.0 $-$ 0536 is a Be/X-ray binary pulsar.