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Excited Si^+ and Fe^+ species are routinely observed in the host environmentof gamma-ray burst (GRB) afterglows, but are not commonly seen in otherextragalactic locations. Their presence signals unusual properties in thegaseous environment of these GRB hosts that arise either as a result of theintense ionizing radiation of the afterglow or through collision excitation ina dense cloud. In particular, the photon pumping scenario has explicitexpectations for temporal variation in the strength of the excited lines, owingto the decline in the ionizing flux of the GRB afterglow. We analyze afterglowspectra of GRB 020813 obtained in two epochs of ~16 hours apart, and examinetransitions from the first excited state of Fe^+ at J=7/2 in these two sets ofdata. We report a significant decline by at least a factor of five in theequivalent width of the FeII 2396 transition, the strongest from the J=7/2state. We perform a Monte-Carlo analysis and determine that this temporalvariation is present at more than 3sigma level of significance. Thisobservation represents the first detection in the temporal variation of theexcited Fe+ states in the GRB host ISM, a direct influence of the burst itselfon its environment. We further estimate that the Fe^+ gas resides in 50-100 pcfrom the afterglow, based on the afterglow lightcurve and the presence andabsence of the excited FeII 2396 in the two-epoch observations.Comment: 10 pages, 3 figures. Submitted to ApJ

Temporal Variation in the Abundance of Excited Fe[FORMULA][F][SUP]+[/SUP][/F][/FORMULA] Near a Gamma-Ray Burst Afterglow