SIMBAD references

2009MNRAS.397..124G - Mon. Not. R. Astron. Soc., 397, 124-134 (2009/July-3)

The ultraluminous X-ray source population of NGC 4485/4490.


Abstract (from CDS):

We report the results of spectral and temporal variability studies of the ultraluminous X-ray sources (ULXs) contained within the interacting pair of galaxies NGC 4485/4490, combining Chandra and XMM-Newton observations. Each of the four separate observations provide at least modest quality spectra and light curves for each of the six previously identified ULXs in this system; we also note the presence of a new transient ULX in the most recent observation. No short-term variability was observed for any ULX within our sample, but three out of five sources show correlated flux/spectral changes over longer time-scales, with two others remaining stable in spectrum and luminosity over a period of at least 5yr. We model the spectra with simple power-law and multicolour disc blackbody models. Although the data are insufficient to statistically distinguish models in each epoch, those better modelled (in terms of their χ2 fit) by a multicolour disc blackbody appear to show a disc-like correlation between luminosity and temperature, whereas those modelled by a power-law veer sharply away from such a relationship. The ULXs with possible correlated flux/spectral changes appear to change spectral form at ∼2x1039erg/s, suggestive of a possible change in spectral state at high luminosities. If this transition is occurring between the very high state and a super-Eddington ultraluminous state, it indicates that the mass of the black holes in these ULXs is around 10-15M.

Abstract Copyright: © 2009 The Authors. Journal compilation © 2009 RAS

Journal keyword(s): black hole physics - galaxies: individual: NGC 4485 - galaxies: individual: NGC 4490 - X-rays: binaries - X-rays: galaxies

Simbad objects: 22

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