088521

We propose a single TOO XMM follow-up observation of the faint hard X-ray transient that will revealed by the ART-XC telescope in the frame of the ongoing all-sky survey. The corresponding program is aimed at studies of the Very Faint X-ray Transients (VFXTs) detected both in X-rays with ART-XC and optics either during public surveys (ZTF GAIA etc.) or in dedicated observations. We will support this follow-up effort with ground-based optical telescopes of CMO SAI MSU RTT-150 and AZT-33IK telescopes as well as telescopes of the SAAO observatory in order to perform spectroscopic and photometric observations. The main purpose of this proposal and the joint X-ray-optical follow-up program is to constrain physical properties of the binary system and unveil the nature of the compact object. [truncated! Please see actual data for full text]