Top panel: light curve of 4U 1728–34 during the 12 yr of INTEGRAL data considered in this paper. Circles/triangles denote JEM-X1/JEM-X2 persistent emission levels in mCrab over the 3–25 keV in the science windows where X-ray bursts are detected. The color coding denotes the spectral grouping used in the paper (see Fig. 3). Note that the lack of X-ray bursts in autumn 2009 and spring 2014 was caused by less frequent Galactic center observations because INTEGRAL was observing a nearby supernova. Bottom panel: hardness ratio between fluxes in the 8–25 keV and 3–8 keV JEM-X spectral bands. A dashed vertical line is overlaid for January 1st of each year.