of sources [@Dotani90; @diStefano02; @Maccarone07] and luminosity functions [@Sivakoff07]. For example, an apparent contradiction in the qualities of the LMXB in M15 was resolved by the identification of two persistent X-ray sources in the cluster [@White01]. Identification with  of multiple quiescent LMXBs in several globular clusters [@Grindlay01a; @Pooley02b; @Heinke03d] has suggested that transient LMXB outbursts from a cluster might arise from different sources, although some LMXBs possess distinctive characteristics [e.g. the Rapid Burster, @Homer01]. Here we report the discovery and outburst monitoring of the 14th luminous LMXB in a Galactic globular cluster, NGC 6440, the first cluster to show two luminous transient LMXBs (both of which show millisecond pulsations). In a companion paper, @Altamirano09 identify this LMXB as a new ultracompact accreting millisecond X-ray pulsar (AMXP), after discovering coherent 206 Hz pulsations [@Altamirano09b] and fitting the frequency drift to a 57.3 minute orbital period.

NGC 6440 is a globular cluster near the Galactic Center, at a distance of 8.5 kpc [@Ortolani94], with $N_H=5.9\times10^{21}$ cm$^{-2}$ [@Harris96]. A luminous X-ray source (MX 1746-20) was identified in this cluster in 1971 [@Markert75], and the cluster was detected at a much lower flux level in 1980 [@Hertz83], identified with quiescent emission from the luminous 