2011A&A...525A..48F

The burst-only source SwiftJ1749.4-2807 was discovered in a high X-ray-active state, during an INTEGRAL observations of the Galactic bulge on 2010 April 10. Pulsations at 518Hz were discovered in the RXTE data, confirming previous suggestions of possible associations between burst-only sources and accreting millisecond X-ray pulsars. The subsequent discovery of X-ray eclipses made SwiftJ1749.4-2807 the first eclipsing accreting millisecond X-ray pulsar. We obtain additional information on SwiftJ1749.4-2807 and other burst-only sources. We report on the results of a monitoring campaign on the source, carried out for about two weeks with the Swift, INTEGRAL, and RXTE satellites. The observations showed that the X-ray spectrum (energy range 0.5-40keV) of SwiftJ1749.4-2807 during the entire event was accurately modeled by an absorbed power-law model (N_H≃3x10²²cm^–2, Γ≃1.7). X-ray eclipses were also detected in the Swift data and provides a clear evidence of a dust-scattering halo located along the line of sight to the source. Only one type-I X-ray burst was observed throughout the two-weeks long monitoring. The X-ray flux of SwiftJ1749.4-2807 decayed below the detection threshold of Swift/XRT about 11 days after the discovery, in a exponential fashion (e-folding time of τ=12⁺⁷_–3days). We compare the properties of the outburst observed from SwiftJ1749.4-2807 with those of the previously known millisecond X-ray pulsars and other transient low mass X-ray binaries.