The New AM Herculis–Type Object AX J2315−592 Discovered with [ITAL]ASCA[/ITAL

Abstract

The new AM Her-type object AX J2315-592 was discovered with ASCA during the observation of IRAS 23128-5919. The light curve shows a clear periodic modulation at 1.489 ± 0.013 hr. Follow-up phase-resolved optical spectroscopy confirmed coincidence of the rotational period of the white dwarf and the orbital period and identified AX J2315-592 as a new AM Her-type object. The shape of the X-ray light curve is quasi-sinusoidal, the amplitude of which decreases with increasing X-ray energy, which is the property of intermediate polars. The X-ray emission at the maximum of the folded light curve has an optically thin thermal plasma emission spectrum with a temperature of 17 ± 4 keV with negligible absorption. The spectrum at the minimum, on the other hand, suffers from complex absorption. The X-ray light curve and the spectral characteristics indicate that a single accreting pole is always within the visible hemisphere of the white dwarf, and the rotational minimum occurs when the pole points toward the observer.