Simultaneous X-ray and radio observations of the transitional millisecond pulsar candidate CXOU J110926.4-650224. The discovery of a variable radio counterpart
Campana, S.;
de Martino, D.;
Rea, N.;
Torres, D. F.;
Ferrigno, C.;
Papitto, A.;
Bozzo, E.;
Buckley, D. A. H.;
Migliari, S.;
Russell, T. D.;
Serylak, M.;
Coti Zelati, F.;
Li, J.;
Stappers, B. W.;
Monageng, I.;
Hugo, B.;
Van Rooyen, R.;
Titus, N.
Spain, Italy, South Africa, Switzerland, China, United Kingdom
Abstract
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 ≃33 μJy 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 15 μJy 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.
2021
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Astronomy and Astrophysics
XMM-Newton
Gaia
13
