A Radio Transient 0.1 pc from Sagittarius A*

Abstract

We report the discovery of a transient radio source 2.7 arcsec (0.1 pc projected distance) South of the Galactic Center massive black hole, Sagittarius A*. The source flared with a peak of at least 80 mJy in March 2004. The source was resolved by the Very Large Array into two components with a separation of ~0.7 arcsec and characteristic sizes of ~0.2 arcsec. 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 x 10^3 km s^-1 relative to Sgr A*. We detect a proper motion of ~10^4 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 the XMM-Newton telescope 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 ~10^36 erg 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.