A very metal-poor star, it is surrounded by a thick unique circumbinary disk enriched in several molecules.

[9][10] It also shows a strong infrared excess, corresponding closely to a 1,200 K blackbody produced by a disk of material surrounding the star.

[11] The star is also undergoing intense mass-loss[12] HR 4049 has an unseen companion, detected from variations in the doppler shift of its spectral lines.

The properties of the companion can only be estimated by making certain assumptions about the inclination of the orbit and the mass function.

[5] Although HR 4049 apparently has the spectrum of a blue supergiant, it is an old low-mass star which has exhausted nuclear fusion and is losing its outer layers as it transitions towards a white dwarf and possibly a planetary nebula.