We present the results of simultaneous observations of the transitional millisecond pulsar (tMSP) candidate CXOU J110926.4-650224 with the XMM-Newton satellite and the MeerKAT telescope. The source was found at an average X-ray luminosity of LX≃7×1033 erg s−1 over the 0.3-10 keV band (assuming a distance of 4 kpc) and displayed a peculiar variability pattern in the X-ray emission, switching between high, low and flaring modes on timescales of tens of seconds. A radio counterpart was detected at a significance of 7.9σ with an average flux density of ≃33μJy at 1.28 GHz. It showed variability over the course of hours and emitted a ≃10-min long flare just a few minutes after a brief sequence of multiple X-ray flares. No clear evidence for a significant correlated or anticorrelated variability pattern was found between the X-ray and radio emissions over timescales of tens of minutes and longer. CXOU J110926.4-650224 was undetected at higher radio frequencies in subsequent observations performed with the Australia Telescope Compact Array, when the source was still in the same X-ray sub-luminous state observed before, down to a flux density upper limit of 15μJy at 7.25 GHz (at 3σ). We compare the radio emission properties of CXOU J110926.4-650224 with those observed in known and candidate tMSPs and discuss physical scenarios that may account for its persistent and flaring radio emissions.
Simultaneous X-ray and radio observations of the transitional millisecond pulsar candidate CXOU J110926.4-650224. The discovery of a variable radio counterpart, F. Coti Zelati, B. Hugo, D. F. Torres, D. de Martino, A. Papitto, D. A. H. Buckley, T. D. Russell, S. Campana, R. Van Rooyen, E. Bozzo, C. Ferrigno, J. Li, S. Migliari, I. Monageng, N. Rea, M. Serylak, B. W. Stappers, N. Titus, Accepted for publication in A&A, arXiv:2109.13281