X-ray Analysis of 4U 1755−338's Re-emergence After 25 Years.

Using simultaneous NICER and NuSTAR data, we performed a comprehensive spectral analysis to determine the system's properties. Our findings indicate a low neutral hydrogen column density and a low-luminosity outburst characterized by a non-canonical hardness-intensity diagram (HID). The HID's correlated hardness and flux evolution suggests a thermal disk origin. Spectral analysis reveals a high-inclination system at a distance of 8.6 kpc, hosting a moderately spinning black hole with no detectable reflection features. The high spectral index, hardness ratio, lack of reflection, and weak variability in the power density spectra suggest the source remained in the high/soft state throughout the outburst.