V4142 Sgr: Double periodic variable with an accretor surrounded by the accretion disk’s atmosphere

Context. A detailed study of the close interacting binary V4142 Sgr, based on photometric and spectroscopic analyses, indicates that this system belongs to enigmatic class Algol-like variables exhibiting a long cycle an unknown nature. Aims. By performing data-mining observations covering orbital cycle, we obtained parameters stellar properties system, along with physical accretion disk located around hot star. In addition, gained insights into evolutive path system. Methods. We modeled light curve through inverse method, using theoretical considers contribution both stars star obtain fundamental parameters. To constrain main parameters, mass ratio was fixed in addition donor temperature, values from our analysis, which includes deblending methods isolate spectral lines components. The were compared grid models order gain evolutionary history Results. period re-calculated, following result: 30 d ​​.633 ± 0 ​​.002 1201 14 days. analysis reveals H α double emission persistent V ≤ R asymmetry, is considered evidence possible wind emerging hotspot region. cold evolved M = 1.11 0.2 ⊙ , T 4500 125 K 19.4 as well rejuvenated B-dwarf companion g 3.86 0.3 380 700 K, 6.35 found. gainer surrounded by concave geometrically thick disk, creating its own atmosphere component radial extension, ℛ 22.8 contributing ∼1.4 percent total luminosity at -band phase 0.25. characterized hot-spot roughly placed where stream hits additional bright-spot separated 102.​​° 5 0.​​° 04 degrees edge rim direction motion. seen under inclination 81.​​° 3 distance Gaia 1140 35 pc. Doppler maps reveal sites enhanced line second third velocity quadrants. former would correspond latter bright spot detected analysis. find comes initially shorter inverted due exchange. plausible model scenario that, present, K-type giant should have been depleted hydrogen core, while about 2 process lasting Myr.