MA, CHEN-HSUN (NCKU); Kwan-Lok Li (NCKU)
We present the X-ray properties of the bright X-ray point sources, in particular the so-called ultra-luminousX-ray sources (ULXs; X-ray luminosity higher than 10^39 erg/s), in the spiral galaxy NGC 1559. The dataset of NGC 1559 was observed by the Chandra X-Ray Observatory in 2016. To analyze the X-ray spectrum, we focused on the energy band of 0.3-7 keV and used the software, XSPEC, to fit the data with an absorbed power-law model. The spectral parameters were then used to infer the luminosities of the X-ray sources, with which we determined which of them are ULXs. Within the half-light radius of the galaxy, we found 33 X-ray sources and 9 of them are ULXs. Compared with many galaxies that host only a few ULXs, the ULX population is significantly larger in NGC 1559, indicating that the galaxy can be a good target for Chandra as well as other X-ray observatories for further ULX studies in the future.