Historical light curves in observer frame. a) Gamma-ray light curve. The small filled circles (black) represent the Fermi-LAT (0.1–300 GeV) weekly-binned light curve; the 90% confidence upper limits are also reported; crosses and big upper limits (blue) represent the CGRO-EGRET (>100 MeV) fluxes from 3rd EGRET catalog (Hartman et al. 1999); squares (red) are the CGRO-EGRET fluxes from the revised EGRET catalog (Casandjian & Grenier 2008); diamonds (green) are AGILE-GRID (>100 MeV) detections (Pucella et al. 2008; D’Ammando et al. 2009; Striani et al. 2010). b) X-ray Rossi XTE light curve (2–15 keV) and 3σ upper limits.The average (median) separation between consecutive observations, once upper limits are removed, is 4.2 ± 6.5 days (3.4 days). The reported uncertainty is the rms dispersion. c) X-ray Rossi XTE hardness ratio(7.5–15 keV vs. 2–7.5 keV channels). d) Optical V-band historical light curve, corrected for Galactic dust absorption (E_B−V = 0.09, Schlafly & Finkbeiner 2011), using the extinction curve from Cardelli et al. (1989). The REM observations (red crosses) are from (Sandrinelli et al. 2014a); the black circles represent photometry obtained at the Steward Observatory (Smith et al. 2009); the blue squares are our NOT data (Table 3). e) Radio VLBA I-band (15 GHz) light curve from the MOJAVE database (Lister et al. 2009).