Photometry And Spectroscopy Of The New Symbiotic Star 2sxps J173508.4-292958

We present and discuss the results of our photometric and spec-troscopic monitoring of 2SXPS J173508.4-292958 carried out from April to August 2020. This X-ray source, in the foreground with respect to the Galac-tic center, brightened in X-rays during 2020, prompting our follow-up optical observations. We found the star to contain a K4III giant with a modest but highly variable H alpha emission, composed by a similar to 470 km s(-1) wide component with superimposed a narrow absorption, offset by a positive velocity with re-spect to the giant. No orbital motion is detected for the K4III, showing an heliocentric radial velocity stable at -12 +/- 1 km s(-1). No flickering in excess of 0.005 mag in B band was observed at three separate visits of 2SXPS J173508.4-292958. While photometrically stable in 2016 through 2018, in 2019 the star developed a limited photometric variability, that in 2020 took the form of a sinusoidal modulation with a period of 38 days and an amplitude of 0.12 mag in V band. We argue this variability cannot be ascribed to Roche-lobe filling by the K4III star. No correlation is observed between the photometric variabil-ity and the amount of emission in H alpha, the latter probably originating directly from the accretion disk around the accreting companion. While no emission from dust is detected at mid-IR wavelengths, an excess in U-band is probably present and caused by direct emission from the accretion disk. We conclude that 2SXPS J173508.4-292958 is a new symbiotic star of the accreting-only variety (AO-SySt).