Transitional millisecond pulsars are millisecond pulsars that switch between a rotation-powered millisecond pulsar state and an accretion-powered X-ray binary state, and are thought to be an evolutionary stage between neutron star low-mass X-ray binaries and millisecond pulsars. So far, only three confirmed systems have been identified in addition to a handful of candidates. We present the results of a multiwavelength study of the low-mass X-ray binary NGC 6652B in the globular cluster NGC 6652, including simultaneous radio and X-ray observations taken by the Karl G. Jansky Very Large Array and the Chandra X-ray Observatory, and optical spectroscopy and photometry. This source is the second brightest X-ray source in NGC 6652 ($L_{\textrm {X}}\sim 1.8 \times 10^{34}{\, \mathrm{erg\, s}^{-1}}$) and is known to be variable. We observe several X-ray flares over the duration of our X-ray observations, in addition to persistent radio emission and occasional radio flares. Simultaneous radio and X-ray data show no clear evidence of anticorrelated variability. Optical spectra of NGC 6652B indicate variable, broad H α emission that transitions from double-peaked emission to absorption over a time-scale of hours. We consider a variety of possible explanations for the source behaviour, and conclude that based on the radio and X-ray luminosities, short time-scale variability and X-ray flaring, and optical spectra, NGC 6652B is best explained as a transitional millisecond pulsar candidate that displays prolonged X-ray flaring behaviour. However, this could only be confirmed with observations of a change to the rotation-powered millisecond pulsar state.

中文翻译：

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MAVERIC 巡天：同时 Chandra 和 VLA 观测过渡毫秒脉冲星候选 NGC 6652B

过渡毫秒脉冲星是在旋转驱动的毫秒脉冲星状态和吸积驱动的 X 射线双星状态之间切换的毫秒脉冲星，被认为是中子星低质量 X 射线双星和毫秒脉冲星之间的演化阶段。到目前为止，除了少数候选系统外，仅确定了三个已确认的系统。我们展示了对球状星团 NGC 6652 中的低质量 X 射线二元 NGC 6652B 的多波长研究结果，包括由 Karl G. Jansky 甚大阵列和钱德拉 X 射线同时进行的无线电和 X 射线观测天文台，以及光谱学和光度学。这个源是 NGC 6652 中第二亮的 X 射线源 ($L_{\textrm {X}}\sim 1.8 \times 10^{34}{\, \mathrm{erg\, s}^{-1}} $) 并且已知是可变的。除了持续的射电辐射和偶尔的射电耀斑外，我们在 X 射线观测期间还观察到了几次 X 射线耀斑。同时的无线电和 X 射线数据显示没有明显的反相关变异性证据。NGC 6652B 的光谱表明可变的宽 H α 发射在数小时的时间尺度内从双峰发射转变为吸收。我们考虑了对源行为的多种可能解释，并得出结论，基于射电和 X 射线光度、短时间尺度变化和 X 射线耀斑以及光谱，NGC 6652B 最好被解释为过渡毫秒脉冲星表现出长时间 X 射线闪光行为的候选人。然而，这只能通过观察旋转动力毫秒脉冲星状态的变化来证实。