GCN Circular 6298
E. Troja (U. Leicester/INAF-IASFPa), K. L. Page (U. Leicester), S. McBreen (MPE), D. N. Burrows (PSU) and N. Gehrels (NASA/GSFC) report on behalf of the Swift XRT team: Swift monitored the field of GRB 070406 (Cummings et al., GCN Circ. 6247) for nine days, starting 20.6 hr after the burst. From the analysis of the full data set, consisting of 115 ks of total exposure in XRT/Photon Counting mode, no X-ray afterglow is detected within the BAT refined error circle (Krimm et al., GCN Circ.6261). The two X-ray sources (S1 and S2 - Troja et al., GCN Circ. 6265) inside the BAT error region do not show a fading behavior, therefore none of them can be identified as the X-ray counterpart of GRB 070406. The non detection in the first follow-up observation (from T0+20.6 hr to T0+41.9 hr) implies an X-ray afterglow fainter than 7.5e-04 cts/s (3-sigma upper limit). Assuming a power-law spectral shape with photon index 2 and a Galactic absorption of 1.8e20 cm-2 (Dickey & Lockman, 1990), it corresponds to an observed (unabsorbed) limiting flux of 2.7e-14 (2.9e-14) erg cm-2 s-1 in the 0.3-10 keV band. No further Swift observations are planned. This circular is an official product of the Swift XRT Team.