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Symbiotic X-ray Binaries (SyXBs) are a recently discovered subclass of LowMass X-ray Binaries. Their growing number makes them an important evolutionarychannel of X-ray Binaries. Our goal is to perform spectral analysis andclassification of the proposed counterparts to IGR J16358-4726 and IGRJ16393-4643 and to establish their nature as X-ray systems. We used the ESO/UT1ISAAC spectrograph to observe the proposed counterparts to the two sources,obtaining K-band medium resolution spectra (R = 500) with a S/N > 140. Datareduction was performed with the standard procedure. We classified them bymeans of comparison with published atlases. We performed SED fitting in orderto refine the spectral classification. The two counterparts clearly exhibit thetypical features of late-type stars, notably strong CO absorption bands in thered part of the spectrum. With information from previous X-ray studies, weclassify the two systems as two new members of the SyXB class. For IGRJ16393-4643, we considered the most probable counterpart to the system,although three other objects cannot be completely discarded. For this system,we compared our findings with available orbital solutions, constraining theorbital parameters and the mass of the companion star. By including two moresystems, we increased to eight the number of known SyXBs, which emerges as anon-negligible category of galactic X-ray binaries.

K-band spectroscopy of IGR J16358-4726 and IGR J16393-4643: two new symbiotic X-ray binaries