A new redback pulsar candidate 4FGL J2054.2+6904

Abstract The Fermi catalogue contains about 2000 unassociated γ-ray sources. Some of them were recently identified as pulsars, including so called redbacks and black widows, which are millisecond pulsars in tight binary systems with non- partially-degenerate low-mass stellar companions irradiated by the pulsar wind. We study a likely optical X-ray counterpart source 4FGL J2054.2+6904 proposed earlier candidate. use archival data well Swift/XRT SRG/eROSITA to clarify its nature. Using Zwicky Transient Facility g r bands spanning over 4.7 years, we find period ≈7.5 h. folded light curve has smooth sinusoidal shape peak-to-peak amplitude ≈0.4 mag. spectral fit energy distribution candidate gives star radius 0.5±0.1 R⊙ temperature 5500±300 K implying G2–G9-type star. Its spectrum is fitted an absorbed power law photon index 1.0±0.3 unabsorbed flux ≈2 × 10−13 erg s−1 cm−2. All properties presumed suggest that it member redback family.