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The nature of ultra-luminous X-ray sources in NGC4565

H. Wu·S. J. Xue·X. Y. Xia·Z. G. Deng·S. Mao
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Abstract

We report the optical identifications of two X-ray luminous point sources in the spiral galaxy NGC4565 based on archive data of Chandra and the Hubble Space Telescope. The central X-ray point source, RXJ1236.3+2559, is found to be the nucleus of NGC4565 with an X-ray luminosity of Lx= 4.3 10^{39} erg. We show that its multi-waveband properties are consistent with it being a low-luminosity active galactic nucleus. A faint optical counterpart with B=25.1 and I=24.0 was identified for the off-nucleus X-ray point source, RXJ1236.2+2558. Its extinction corrected B magnitude is estimated to be 24.5. The X-ray to optical flux ratio (fx/fB) is about 540. From the optical and X-ray properties we argue that RXJ1236.2+2558 is an ultra-luminous X-ray compact source with Lx=6.5 10^{39} erg. The source is probably located in a faint globular cluster at the outer edge of NGC4565's bulge.

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H. Wu, S. J. Xue, X. Y. Xia, Z. G. Deng, S. Mao. 2002-05-15. The nature of ultra-luminous X-ray sources in NGC4565. https://doi.org/10.1086/341862

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