2016A&A...592A..58D

Symbiotic stars are a heterogeneous class of interacting binaries. Among them, RT Cru has been classified as prototype of a subclass that is characterised by hard X-ray spectra that extend past ∼20keV. We analyse ∼8.6Ms of archival INTEGRAL data collected during the period 2003-2014, ∼140ks of Swift/XRT data, and a Suzaku observation of 39ks, to study the spectral X-ray emission and investigate the nature of the compact object. Based on the 2MASS photometry, we estimate the distance to the source of 1.2-2.4kpc. The X-ray spectrum obtained with Swift/XRT, JEM-X, IBIS/ISGRI, and Suzaku data is well fitted by a cooling flow model modified by an absorber that fully covers the source and two partially covering absorbers. Assuming that the hard X-ray emission of RT Cru originates from an optically thin boundary layer around a non-magnetic white dwarf, we estimated a mass of the white dwarf of M_WD~=1.2M_☉. The mass accretion rate obtained for this source might be too high for the optically thin boundary layer scenario. Therefore we investigate other plausible scenarios to model its hard X-ray emission. We show that, alternatively, the observed X-ray spectrum can be explained with the X-ray emission from the post-shock region above the polar caps of a magnetised white dwarf with mass M_WD~=0.9-1.1M_☉.