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In 2004, SGR 1806-20 underwent a period of intense and long-lasting burstactivity that included the giant flare of 27 December 2004 -- the most intenseextra-solar transient event ever detected at Earth. During this active episode,we routinely monitored the source with Rossi X-ray Timing Explorer andoccasionally with Chandra. During the course of these observations, weidentified two relatively bright bursts observed with Konus-Wind in hard X-raysthat were followed by extended X-ray tails or afterglows lasting hundreds tothousands of seconds. Here, we present detailed spectral and temporal analysisof these events observed about 6 and 1.5 months prior to the 27 December 2004Giant Flare. We find that both X-ray tails are consistent with a coolingblackbody of constant radius. These spectral results are qualitatively similarto those of the burst afterglows recorded from SGR 1900+14 and recently fromSGR 1550-5418. However, the latter two sources exhibit significant increase intheir pulsed X-ray intensity following the burst, while we did not detect anysignificant changes in the RMS pulsed amplitude during the SGR 1806-20 events.Moreover, we find that the fraction of energy partitioned to the burst (promptenergy release) and the tail (afterglow) differs by an order of magnitudebetween SGR 1900+14 and SGR 1806-20. We suggest that such differences can beattributed to differences in the crustal heating mechanism of these neutronstars combined with the geometry of the emitting areas.

Extended Tails from SGR 1806-20 Bursts