A Deep Radio Limit on the 2016 Decay of Swift J1753.5-0127 from the Very Large Array

ATel #9765; R. M. Plotkin (ICRAR-Curtin), J. C. A. Miller-Jones (ICRAR-Curtin), P. G. Jonker (SRON), J. Homan (MIT), D. M. Russell (NYU Abu Dhabi), J. A. Tomsick (SSL/UCB)
on 17 Nov 2016; 09:20 UT
Credential Certification: James C.A. Miller-Jones (jmiller@science.uva.nl)

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We report on a radio non-detection of the black hole candidate X-ray binary (XRB) Swift J1753.5-0127 on 7 November 2016 with the Karl G. Jansky Very Large Array (VLA).

After spending >11 years in outburst, Swift J1753.5-0127 began its descent into quiescence in September 2016 (ATel #9708; also see ATels #9739, #9741, #9758). Observations of Swift J1753.5-0127 were taken by the Swift X-ray Telescope (XRT) on 6-7 November, and no X-rays were detected on either date (ATel #9735). We obtained VLA radio observations on 5 November UT 19:00-19:45 and 7 November UT 21:04-23:03 (VLA program 16A-060; PI Plotkin). The array was in its most extended A configuration, and observations were taken in two basebands centered at 9.0 and 10.65 GHz, with a total bandwidth of 3.7 GHz. Weather conditions on 5 November were sub-optimal and we could not obtain reasonable enough phase solutions to provide meaningful results. We therefore report only on the results of the 7 November epoch.

No radio emission was detected at the location of Swift J1753.5-0127 on 7 November, with a 3σ upper limit f_R < 7.5 μJy beam^-1. We can place Swift J1753.5-0127 on the radio/X-ray luminosity plane by combining our radio limit with the X-ray limit from Swift (F_X < 1.57E-13 erg s^-1 cm^-2; 90% confidence limit from 0.6-10 keV, assuming Γ=1.7, and N_H=2E21 cm^-2; ATel #9735). If we assume a distance <8 kpc (e.g., Rushton et al. 2016) and a flat radio spectrum, then L_R <5E27 erg s^-1 (8.4 GHz; 3σ limit, where L_R=4πd²νS_ν) and L_X <1E33 erg s^-1 (1-10 keV; 90% limit). For reference, our observation implies that the quiescent radio luminosity of Swift J1753.5-0127 is at least a factor of 2-3 lower than V404 Cygni in quiescence. Otherwise, the radio and X-ray limits are consistent with expectations from other quiescent systems (see, e.g., Figure 9 of Corbel et al. 2013), especially when considering that Swift J1753.5-0127 has one of the shortest known orbital periods for a black hole XRB (3.2 h; Zurita et al. 2008). We therefore expect its minimum quiescent X-ray luminosity to be relatively low, L_X≈a few times 1E30 - 1E31 erg s^-1 (e.g., Homan et al. 2013; Armas Padilla et al. 2014).

Swift J1753.5-0127 was a radio-underluminous XRB while in its outburst hard state (Soleri et al. 2010). Unfortunately, we cannot infer whether Swift J1753.5-0127 remained radio-underluminous during its entire decay into quiescence, or if it transitioned towards the ‘standard’ black hole XRB track, as has been observed for other systems like H1743-322 (Jonker et al. 2010; Coriat et al. 2011), XTE J1752-223 (Ratti et al. 2012), and MAXI J1659-152 (Jonker et al. 2012). The insufficient multiwavelength coverage of Swift J1753.5-0127 during its transition into quiescence highlights the importance of ongoing monitoring programs of XRBs. Such programs are crucial for providing timely notifications in order to arrange multiwavelength observations of outburst decays to track the evolution of the disk/jet connection.

We thank the VLA for scheduling these observations.