Daily variation of the detected flux density around V404 Cygni during the two months from 2015 May 18 (MJD 57160) to July 18 UT (MJD 57221), including the period of the V404 Cygni outburst. Except for the 10 d from June 21 (MJD 57194) to June 30 UT (MJD 57203), the detected signal was below the detection limit (filled red triangle). These detection limits can sometimes be high, mainly due to bad weather at the observation site. The date of the X-ray outburst is also shown here. (Color online)