A Radio Transient 0.1 Parsecs from Sagittarius A*

Abstract

We report the discovery of a transient radio source 27 (0.1 pc projected distance) south of the Galactic center massive black hole, Sgr A*. The source flared with a peak of at least 80 mJy in 2004 March. The source was resolved by the Very Large Array into two components with a separation of ~07 and characteristic sizes of ~02. The two components of the source faded with a power-law index of 1.1 ± 0.1. We detect an upper limit to the proper motion of the eastern component of ~3 × 103 km s-1 relative to Sgr A*. We detect a proper motion of ~104 km s-1 for the western component relative to Sgr A*. The transient was also detected at X-ray wavelengths with the Chandra X-Ray Observatory and XMM-Newton and given the designation CXOGC J174540.0-290031. The X-ray source falls in between the two radio components. The maximum luminosity of the X-ray source is ~1036 ergs s-1, significantly sub-Eddington. The radio jet flux density predicted by the X-ray/radio correlation for X-ray binaries is orders of magnitude less than the measured flux density. We conclude that the radio transient is the result of a bipolar jet originating in a single impulsive event from the X-ray source and interacting with the dense interstellar medium of the Galactic center.