1999/10/27 by K. P. Singh, Kulinder Pal Singh, Singh, Kulinder Pal +3
Physics and Astronomy · #Advanced X-ray Imaging Techniques #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #FOS: Physical sciences #X-ray Spectroscopy and Fluorescence Analysis #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9910486
8 pages, 7 figures, Accepted for publication in MNRAS
arxiv created 1999/10/27 · openalex publication_date 1999/10/27 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Two optical candidates - a galaxy and a star, are found within the error circle of the X-ray source position of an ultra-soft X-ray source discovered with ROSAT. Optical spectroscopy of the two candidates reveals that a) the galaxy is a narrow-line Seyfert type 1 galaxy, and b) the star is a late A-type or an early F-type. The Fx/Fopt ratio is too high for the star to be the counterpart of the X-ray source, but consistent with that for an active galaxy. Although higher resolution X-ray imaging of the region is needed to definitely settle the question of the counterpart of the X-ray source, the narrow-line Seyfert 1 galaxy is the best candidate. The spectral properties of the newly discovered narrow-line Seyfert 1 galaxy are also presented, including its extreme X-ray power law spectral (photon) index > 4.