Tracking the Enigmatic Globular Cluster Ultracompact X-Ray Binary X1850–087: Extreme Radio Variability in the Hard State

Abstract The conditions under which accreting neutron stars launch radio-emitting jets and/or outflows are still poorly understood. ultracompact X-ray binary X1850–087, located in the globular cluster NGC 6712, is a persistent atoll-type source that has previously shown unusual radio-continuum variability. Here we present results of pilot radio-monitoring program X1850–087 undertaken with Karl G. Jansky Very Large Array, simultaneous or quasi-simultaneous Swift/XRT data obtained at each epoch. clearly detected radio two six new epochs. When combined previous data, these suggest shows emission slightly elevated hard-state luminosity L X ≳ 2 × 10 36 erg s −1 , but no its baseline hard state ∼ . No clear spectral changes associated this factor ≳10 At all epochs, flat to inverted index, more consistent partially absorbed optically thick synchrotron compact jet rather than evolving thin transient expanding synchrotron-emitting ejecta. If indeed due jet, then it plausibly being launched and quenched on timescales as short few days. Future monitoring could help elucidate produced around stars.