GCN Circular 7638
K.L. Page (U. Leicester) and N. Gehrels (NASA/GSFC) report on behalf of the Swift-XRT team: Swift-XRT performed follow-up observations of the possible GRB 080315 (BAT trigger number 306323) about a month after the trigger, in order to determine whether or not the possible X-ray afterglow mentioned in GCN Circ. 7420 had faded. We find that this source is at a count rate consistent with that of our original observation, so conclude that it is not the afterglow. Thus, no afterglow was detected for this trigger. Excluding this constant X-ray source, the 3-sigma upper limit within the BAT error circle from the observation directly following the trigger (25 ks on 2008-03-15) was 5.9 x 10^-4 count s^-1; the late-time data (30 ks between 2008-04-16 and 2008-04-21) provide a limit of 5.2 x 10^-4 count s^-1. We cannot rule out that this was a real burst, but given the lack of XRT detection and marginal BAT detection it is not likely.