ar X iv : a st ro - p h / 05 07 22 1 v 1 8 J ul 2 00 5 A Radio Transient 0 . 1 pc from Sagittarius A *

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× 10 km s relative to Sgr A*. We detect a proper motion of ∼ 10 km s 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 erg s, 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. Subject headings: Galaxy: center — ISM: jets and outflows — radio continuum: general — X-rays: binaries Astronomy Department & Radio Astronomy Laboratory, University of California, Berkeley, CA 94720; gbower,dbacker,[email protected] Adler Planetarium and Astronomy Museum, 1300 South Lake Shore Drive, Chicago, IL 60605 Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208; dougroberts,[email protected] National Radio Astronomy Observatory, Charlottesville, VA 22903; [email protected] National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801; [email protected] Department of Physics and Astronomy, University of Iowa, 203 Van Allen Hall, Iowa City, IA 52245; [email protected]