One of the most important achievements of 20th century astrophysics is the theory of stellar evolution that describes changes of stellar structure and observable parameters (mass, luminosity, surface temperature Te_x000B_ff , and chemical composition) throughout their lives. The changes are slow during some evolutionary stages (e.g., the main sequence stage). However, they can be fast and dramatic (e.g., at the asymptotic giant branch (AGB) stage), forcing stars to lose mass_x000D_ and form circumstellar (CS) envelopes. Such envelopes may include only gaseous material or they may provide favorable conditions for dust formation. Similarly, mass exchange between the stellar companions may result in a significant amount of CS matter in binary systems. Studying the CS matter and processes that lead to its formation provide an understanding of important issues, such as evolution of galaxies and planet formation, refine our knowledge of adjacent quiet_x000D_ evolutionary stages and explain the causes for evolutionary transitions._x000D_ In the 1960’s, the advent of multiwavelength detectors enabled studying the CS media and resulted in discovering new evolutionary phenomena. For example, the 1983 InfraRed Astronomical Satellite (IRAS) all-sky survey recognized Vega-type stars, which retain protostellar dust during most of their main-sequence lives, and Proto-Planetary Nebulae, post-AGB stars that drive earlier created CS dust into the interstellar medium. These discoveries gave a tremendous impetus to studies of the stellar evolution as well as to the theory of CS dust formation._x000D_ Nevertheless, not all CS phenomena are currently understood. This is particularly true for stars with initial masses ∼2–20 M⊙ that appear on the main-sequence as B- and early A-type stars (Teff_x000B_ ∼ 30000–9000 K). A noticeable fraction of them shows the Be and B[e] phenomena. The former is defined as the appearance of hydrogen emission lines in the spectra of nonsupergiant stars, while the latter refers to the simultaneous presence of forbidden lines and strong IR excess radiation due to CS dust and is not luminosity restricted. Both challenge the theory of stellar evolution, but also present unique opportunities for developing new techniques_x000D_ of astrophysical data analysis. The Be phenomenon receives much attention, while a more complex B[e] phenomenon has not yet been studied in detail. Our project seeks to study a newly defined group of ≥50 Galactic objects with the B[e] phenomenon and luminosities log L/L⊙ ∼2.5–4.5 (FSCMa objects). Their IR excesses indicate recent dust formation and emission-line spectra are extremely strong. These features in objects of the temperature and luminosity range in question remain unexplained. One third of the FSCMa objects are recognized binary systems, whose physical parameters are still poorly-known. Incompleteness of observational information makes it difficult to reveal their nature and evolutionary status and excludes them from theoretical consideration. Therefore, the project will address important questions concerning stellar evolution, mass loss in stellar systems, and CS dust formation. _x000D_

This proposal aims to define the properties of a class of objects with the B[e] phenomenon termed FSCMa objects, after the prototype object of the class. The class is characterized by a central B-type star that powers strong, low excitation forbidden lines and permitted lines, and large IR excesses due to CS dust. However, unlike the other types of B[e] stars, the FSCMa objects are not symbiotic binaries, Planetary Nebulae, pre-main-sequence stars, or supergiants. Instead they are probably binary systems not too far from the main sequence displaying large_x000D_ near-IR excesses. The FSCMa stars are important because 1) they manifest unusually high mass loss that is not currently accounted for in models of stellar evolution, 2) they can and probably do contribute significantly to the interstellar dust within the Galaxy, and 3) may have contributed significantly to dust formation in the very early universe. Only recently recognized, much of the uncertainty surrounding these objects results from the small amount of observational data currently existing. This proposal will address this deficit of data and the key scientific issues through a focused observational and interpretational program executed by a strong international collaboration of researchers.