tokens: Chandraobserved 4C +74.26for 70 ks in total using the HETGS in combination with the ACIS detector. The total exposure time was split into two observations that were taken two days apart. For both Obs-ID 4000 and 5195 we retrieved the Medium (MEG) and High Energy Grating (HEG) spectra and their respective response matrices from the tgcat 1 archive. We further treated these spectral products with the CIAO tools (version 4.6). For each observation and for both HEG and MEG, we combined the first positive and negative spectral order using the CIAO script add_spectral_orders. Hence, we fitted jointly HEG and MEG (allowing a free intercalibration factor) with a simple phenomenological power law to check for variability between the two observations. The fitted slopes (, ) and normalizations (Norm, Norm) were very consistent with each other (see below for a physically motivated fit). Therefore, we were able to sum the spectra of individual observations into a single spectrum to improve the signal-to-noise ratio. We did this using the CIAO script add_grating_spectra. We reduced the raw XMM-NewtonObservation Data Files (ODF), available at the ESA archive 2 , using the Science Analysis Software (SAS, version 13) and the HEASARC FTOOLS. We created calibrated EPIC-pn event files selecting only the unflagged single events. To check the time stability of the background we used the light curve in the hard 10–12 keV band, which is background dominated. A high level of background light due to soft proton contamination is evident towards the end of the observation. Thus, we cleaned the event file using a time filter, following the same procedure explained in Di Gesu et al. (2013) . For RGS-1 and RGS-2 we created calibrated event files and background light curves taking the background from CCD 9. The RGS background light curve was quiescent. Next, for all the instruments, we extracted the source and background spectra and we created the spectral response matrices. Finally, we extracted the source count rate in all the available OM filters, namely ( Å), ( Å) and ( Å). Using the interactive SAS tool omsource, we computed the source count in a circular region centered on the source coordinates and with a radius of 6 pixels. For the background we used another circular region of 12 pixels, free from other sources and instrumental contamination. We converted the count rates to fluxes using the standard conversion factors provided in the SAS watchout web page 3 . Hence, assuming , we corrected all the fluxes for the Galactic reddening ( =0.39, Schlafly Finkbeiner 2011 ). For the correction, we used the IDL routine ccm_unred, which dereddens a user-defined vector of fluxes using the Galactic extinction curve of Cardelli et al. (1989) . Fig. 1 Spectral energy distributions for 4C +74.26. Filled circles: OM fluxes corrected for the Galactic extinction. Open squares: X-ray intrinsic continuum obtained from a phenomenological fit of the EPIC-pn spectrum. Fig. 2
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