The MAVERIC Survey: A Transitional Millisecond Pulsar Candidate in Terzan 5
Strader, Jay; Bahramian, Arash; Maccarone, Thomas J.; Chomiuk, Laura; Heinke, Craig O.; Wijnands, Rudy; Degenaar, Nathalie; Shishkovsky, Laura; Miller-Jones, James C. A.; Tremou, Evangelia; Sivakoff, Gregory R.; Tetarenko, Alexandra J.; Tudor, Vlad; Ransom, Scott
United States, Australia, Canada, Netherlands, France
Abstract
Transitional millisecond pulsars are accreting millisecond pulsars that switch between accreting X-ray binary and millisecond radio pulsar states. Only a handful of these objects have been identified so far. Terzan 5 CX1 is a variable hard-X-ray source in the globular cluster Terzan 5. In this paper, we identify a radio counterpart to CX1 in deep Very Large Array radio continuum data. Chandra observations over the last 14 years indicate that CX1 shows two brightness states: in 2003 and 2016 the source was the brightest X-ray source in the cluster (at L X ∼ 1033 erg s-1), while in many intermediate observations, its luminosity was almost an order of magnitude lower. We analyze all available X-ray data of CX1, showing that the two states are consistent with the spectral and variability properties observed for the X-ray active and radio pulsar states of known transitional millisecond pulsars. Finally, we discuss the prospects for the detection of CX1 as a radio pulsar in existing timing data.