OY Arae

Lore & Background

OY Arae was discovered by Williamina Fleming on a Harvard Observatory photographic plate taken on April 4, 1910, when it shone at magnitude 6.0. Examination of earlier plates revealed that before the outburst it was a magnitude 17.5 object, and by March 19, 1910, it had reached magnitude 12. The light curve shows a secondary maximum in June 1910. The first spectrum, obtained on July 5, 1910, resembled that of a gaseous nebula. An optical identification of the quiescent nova was made in 1994, and spectra taken at that time showed strong Balmer lines in emission atop a blue continuum. The system is an eclipsing binary with an orbital period of 3.73118 hours. The primary eclipse, in which the donor star eclipses the white dwarf and its accretion disk, is about 2 magnitudes deep and lasts less than 30 minutes. Most of the luminosity comes from the accretion disk, estimated to be 7 magnitudes brighter than the donor star, with the white dwarf being even fainter. The absolute magnitude of the system is given as +4.6, but this value is distorted by the nearly edge-on disk; a mean absolute magnitude adjusted for viewing angle is +3.6.

Reader's Guide

OY Arae is significant as a moderately fast nova that provides a well-documented example of the early photographic discovery era. Its discovery by Williamina Fleming highlights the contributions of women in early 20th-century astronomy at Harvard Observatory. The system's eclipsing nature, with a 3.73118-hour orbital period and primary eclipses about 2 magnitudes deep lasting less than 30 minutes, makes it a valuable target for studying binary interactions in cataclysmic variables. The light curve's secondary maximum in June 1910 offers insight into the post-outburst behavior of novae. The 1994 optical identification and subsequent spectra showing strong Balmer lines in emission atop a blue continuum have allowed for characterization of the quiescent state. The system's absolute magnitude, distorted by the nearly edge-on disk to +4.6, with an adjusted value of +3.6, underscores the importance of viewing angle corrections in such systems. The accretion disk dominates the system's luminosity, being 7 magnitudes brighter than the donor star, which is typical for novae in quiescence. OY Arae remains a reference object for studies of nova evolution, binary mass transfer, and eclipse timing variations.

Did You Know?

• Before its outburst, OY Arae was a magnitude 17.5 object.
• The orbital period of OY Arae is 3.73118 hours.