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dc.contributor.authorGallo, E.
dc.contributor.authorMiller-Jones, James
dc.contributor.authorRussell, D.
dc.contributor.authorJonker, P.
dc.contributor.authorHoman, J.
dc.contributor.authorPlotkin, R.
dc.contributor.authorMarkoff, S.
dc.contributor.authorMiller, B.
dc.contributor.authorCorbel, S.
dc.contributor.authorFender, R.
dc.identifier.citationGallo, E. and Miller-Jones, J. and Russell, D. and Jonker, P. and Homan, J. and Plotkin, R. and Markoff, S. et al. 2014. The radio/X-ray domain of black hole X-ray binaries at the lowest radio luminosities. Monthly Notices of the Royal Astronomical Society. 445: pp. 290-300.

We report on deep, coordinated radio and X-ray observations of the black hole X-ray binary XTE J1118+480 in quiescence. The source was observed with the Karl G. Jansky Very Large Array for a total of 17.5 h at 5.3 GHz, yielding a 4.8 ± 1.4 μJy radio source at a position consistent with the binary system. At a distance of 1.7 kpc, this corresponds to an integrated radio luminosity between 4 and 8 × 1025 erg s−1, depending on the spectral index. This is the lowest radio luminosity measured for any accreting black hole to date. Simultaneous observations with the Chandra X-ray Telescope detected XTE J1118+480 at 1.2 × 10−14 erg s−1 cm−2 (1–10 keV), corresponding to an Eddington ratio of ~4 × 10−9 for a 7.5 M☉ black hole. Combining these new measurements with data from the 2005 and 2000 outbursts available in the literature, we find evidence for a relationship of the form lr = α+βlX (where l denotes logarithmic luminosities), with β = 0.72 ± 0.09. XTE J1118+480 is thus the third system – together with GX339-4 and V404 Cyg – for which a tight, non-linear radio/X-ray correlation has been reported over more than 5 dex in lX. Confirming previous results, we find no evidence for a dependence of the correlation normalization of an individual system on orbital parameters, relativistic boosting, reported black hole spin and/or black hole mass. We then perform a clustering and linear regression analysis on what is arguably the most up-to-date collection of coordinated radio and X-ray luminosity measurements from quiescent and hard-state black hole X-ray binaries, including 24 systems. At variance with previous results, a two-cluster description is statistically preferred only for random errors <~0.3 dex in both lr and lX, a level which we argue can be easily reached when the known spectral shape/distance uncertainties and intrinsic variability are accounted for. A linear regression analysis performed on the whole data set returns a best-fitting slope β = 0.61 ± 0.03 and intrinsic scatter σ0 = 0.31 ± 0.03 dex.

dc.publisherOxford University Press
dc.subjectradio continuum: general
dc.subjectblack hole physics
dc.subjectaccretion discs
dc.subjectX-rays: binaries
dc.subjectISM: jets and outflows
dc.subjectmethods: statistical
dc.titleThe radio/X-ray domain of black hole X-ray binaries at the lowest radio luminosities
dc.typeJournal Article
dcterms.source.titleMonthly Notices of the Royal Astronomical Society

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

curtin.departmentCurtin Institute of Radio Astronomy (Physics)
curtin.accessStatusOpen access

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