NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-26 T13:07:01 PDT
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For refcode 2017MNRAS.467.2690E:
Retrieve 4 NED objects in this reference.
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NED Abstract

Copyright by Royal Astronomical Society. 2017MNRAS.467.2690E Soft extragalactic X-ray binaries at the Eddington Threshold Earnshaw, Hannah M.; Roberts, Timothy P. Abstract. The luminosity range at and just below the 10^39^ erg s^-1^ cut-off for defining ultraluminous X-ray sources (ULXs) is a little-explored regime. It none the less hosts a large number of X-ray sources, and has great potential for improving our understanding of sources with ~Eddington accretion rates. We select a sample of four sources in this Eddington Threshold regime with good data for further study; these objects possess a variety of soft spectral shapes. We perform X-ray spectral and timing analysis on the XMM-Newton and Chandra data for these objects to gain insight into their accretion mechanisms, and also examine their optical counterparts using Hubble Space Telescope images. NGC 300 X-1 is a highly luminous and well-known example of the canonical steep power-law accretion state. M51 ULS exhibits a cool blackbody-like spectrum and is consistent with being an ultraluminous supersoft source (ULS), possibly a super-Eddington accreting object viewed at a high inclination through an optically thick outflowing wind. NGC 4395 ULX-1 and NGC 6946 ULX-1 have unusually steep power-law tails, for which we discuss a variety of possible physical mechanisms and links to similar features in Galactic microquasars, and we conclude that these sources are likely intermediate objects between the soft ultraluminous regime of ULXs and classic ULSs. Key words: accretion, accretion discs, black hole physics, X-rays: binaries
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