The radio/X-ray correlation in Swift J1753.5-0127
Abstract
Great effort has gone into trying to explain the two observed radio/X-ray correlation tracks seen in the low/hard state of black hole X-ray binaries in recent years. The original, ``standard'' correlation of the form L_R∝ Lb_X, where b=0.7±0.1, is paired with a separate, lower correlation track with a steeper slope of ∼ 1-1.4, at least at high luminosities. These outlier sources seem to show fainter radio emission than expected for a given X-ray luminosity, thus acquiring the term ``radio-quiet''. While most sources seem to maintain their intrinsic correlation slopes over decades in luminosity, a growing sample of sources have recently been reported to move from one correlation to the other. We present preliminary results from a coordinated radio/X-ray monitoring campaign of the radio-quiet black hole binary Swift J1753.5-0127, spanning nearly two years in time. Our observations add lower-luminosity coverage to an existing sample of observations, and we observe the radio-quiet track to proceed horizontally towards the standard correlation as the X-ray luminosity slowly starts to decrease. The source stays on the transition track for ∼ 60 days, during which its X-ray luminosity is observed to drop by more than an order of magnitude while its radio luminosity stays constant. Time-averaged X-ray energy spectra show very little change during this phase, leaving no obvious parameters to explain the observed transition behaviour.
- Publication:
-
Astronomische Nachrichten
- Pub Date:
- May 2016
- DOI:
- 10.1002/asna.201612334
- Bibcode:
- 2016AN....337..485K
- Keywords:
-
- accretion;
- accretion disks;
- black hole physics;
- radio continuum: stars;
- X-rays: binaries;
- X-rays: individuals (Swift J1753.5-0127)