A Population of Compact Radio Variables and Transients in the Radio-bright Zone at the Galactic Center Observed with the Jansky Very Large Array

Abstract

Abstract Using Jansky Very Large Array data obtained from high-resolution observations at 5.5 GHz at multiple epochs in 2014 and 2019, we have detected a population of radio variables and transients in the radio-bright zone at the Galactic center. With observations covering a sky area of 180 arcmin2 at an angular resolution of 0.″4, we report new detections of 110 Galactic center compact radio (GCCR) sources with a size of <1″. The flux densities of GCCR sources exceed 70 μJy, with at least 10σ significance. Among these sources, 82 are variable or transient and 28 are nonvariable. About 10% of them are expected to be extragalactic background sources. We discuss the possible astrophysical nature of the detected sources. As compared to the Galactic disk (GD) population of normal pulsars (NPs) and millisecond pulsars (MSPs), a majority (80%) of the GCCR sources appear to fall within the high flux density tail of the pulsar distribution, as extrapolated from a sample of NPs in the GD. However, MSPs extrapolated from the GD population are too weak to have contributed significantly to the GCCR population that has been detected. We also cross-correlated the GCCR sources with X-ray sources in Chandra X-ray catalogs and found that 42 GCCR sources have candidate X-ray counterparts. Most of the GCCR sources having X-ray counterparts are likely to be associated with unresolved or slightly resolved radio jets launched from X-ray binaries with a compact object, either a black hole or a neutron star.