We conducted the first long-term ( 75 days ) X-ray monitoring of the black hole low mass X-ray binary V404 Cyg , with the goal of understanding and characterizing its variability during quiescence .
The X-ray light curve of V404 shows several flares on timescales of hours with a count rate change of a factor of about 5-8 .
The root mean square variability is F _ { var } = 57.0 \pm 3.2 \% .
The first order structure function is consistent with both a power spectrum of index -1 ( flicker noise ) , or with a power spectrum of index 0 ( white noise ) , implying that the light curve is variable on timescales from days to months .
The X-ray spectrum is well fitted by a power law with spectral index \Gamma = 2.10 - 2.35 , and we found that the spectral shape remains roughly constant as the flux changes .
A constant spectral shape with respect to a change in the X-ray flux may favour a scenario in which the X-ray emission is dominated by synchrotron radiation produced in a jet .