Toward Understanding the B[e] Phenomenon. VIII. Nature and Variability of IRAS 07080+0605

Abstract

We report the results of spectroscopic and photometric observations of the emission-line object IRAS 07080+0605 carried out in 2004–2021. We found that the object is significantly underluminous for its spectroscopic properties (T eff = 8500 ± 500 K, g = 2.0 ± 0.5), if a strong visual attenuation by a factor of ∼43 found through the spectral energy distribution modeling is not taken into account. Visual brightness variations with a stable period of 190 days but a variable amplitude of ∼0.2 mag were found in the ASAS SN data and attributed to variable circumstellar extinction in the dusty disk. We also found that the observed behavior of IRAS 07080+0605 is similar to that of the protoplanetary nebula Red Rectangle. The dusty disk of IRAS 07080+0605 shows the presence of carbonaceous particles (∼10%–20% of the total dust content) and polycyclic aromatic hydrocarbon emission bands. However, IRAS 07080+0605 shows no obvious signs of the refractory element depletion, which is common in post–asymptotic giant branch (AGB) dusty binaries, or of a visual nebula. Absorption-line positions vary with an amplitude of ∼25 km s−1, suggesting the presence of a secondary component. Spectroscopic monitoring on a timescale from days to months is needed to search for regular variations. We conclude that IRAS 07080+0605 is most likely a binary system with an A-type component on its way toward the post-AGB evolutionary stage, as binarity is capable of explaining most of the observed features.