Discovery of a New X-Ray Transient Source in the Scutum Region with Suzaku

Abstract

During an observation of the Galactic plane in the Scutum region with the Suzaku satellite, we discovered a new X-ray transient source, designated Suzaku J1844-0404. Compared with previous Chandra observations of the same field, four Chandra X-ray sources exist within the current positional uncertainty of Suzaku J1844-0404. A firm identification is not possible. From the beginning of the observation, the X-ray intensity was significant at ∼ 5 × 10^-14 erg s^-1 cm^-2 (2-10keV), which may be a possible precursor. Later, the source exhibited a flare with a peak flux of ∼ 10^-12 erg s^-1 cm^-2 (2-10keV). A strong and narrow emission line at ∼ 6.66 keV was observed during the flare, most likely the He-like Fe line. The spectrum in 1-10keV is consistent with a heavily absorbed (N_H ∼ 3 × 10²² H cm^-2) thin thermal emission with kT as high as ∼ 7 keV. A single short flare, as observed, is rather unlikely for a cataclysmic variable. The source is probably an active binary star or a young stellar object.