X-ray images of a 8′ × 8′ field toward NGC 6540 (north to the top, east to the left). The images are obtained by summing the data of the three EPIC cameras in the 0.2–12 keV energy range. Left panel: whole observation with an exposure time of about 9 ks. Center panel: a 300 s time interval centered on the flare. Right panel: whole observation with the above time interval excluded. The source indicated by the arrow is clearly variable; the majority of its counts are detected during the short time interval containing the flare, but the source is also visible when the time interval containing the flare is excluded.