OY Arae

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OY Arae

A light curve for OY Arae. The main plot (from data published by Walker and Shapley)[1] shows the 1910 eruption, and the inset plot (adapted from Zhao and McClintock)[2] shows the eclipse light curve measured in 1995.
Observation data
Epoch J2000      Equinox J2000
Constellation Ara
Right ascension 16h 40m 50.456s[3]
Declination −52° 25′ 47.98″[3]
Apparent magnitude (V) 18.7[4]
Characteristics
Apparent magnitude (B) 6.0 – 18.6[5]
B−V color index −0.15[6]
Variable type
eclipsing[5]
Distance
approx. 12,000 ly
(approx. 3,700 pc)
Absolute magnitude (MV)−6.7 (at peak) 4.6 (quiescent)[7]
Inclination (i)
74.3±1.2[2]°
Details
white dwarf
Mass0.82±0.12[2] M☉
donor
Mass0.34±0.01[2] M☉
Other designations
Nova Arae 1910, HD 149990, 2MASS J16405045-5225479
Database references
SIMBADdata

OY Arae, also known as Nova Arae 1910, is a nova in the constellation Ara. It was discovered by Williamina Fleming on a Harvard Observatory photographic plate taken on April 4, 1910. At that time it had a magnitude of 6.0, making it faintly visible to the naked eye under ideal observing conditions. Examination of earlier plates showed that before the outburst it was a magnitude 17.5 object, and by March 19, 1910, it had reached magnitude 12.[9][2]

OY Arae is considered to be a moderately fast nova, because it faded by 3 magnitudes during the 83 days after discovery.[10][9] The light curve shows a secondary maximum in June 1910. The first spectrum of the nova was obtained on July 5, 1910, and resembled that of a gaseous nebula.[11] 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.[2]

All novae are binary stars, with a "donor" star orbiting a

eclipsing binaries, and OY Arae does show eclipses. The primary eclipse, in which the donor star eclipses the white dwarf and its accretion disk, are about 2 magnitudes deep and last less than 30 minutes. The orbital period is 3.73118 hours. The mass of the white dwarf is 0.82±0.12 M☉, and the mass of the donor star is 0.34±0.01 M☉. The two stars are separated by 1.28±0.04 R☉.[2]

Most of the

luminosity of the system is produced by the disk of material being stripped from the donor star. This is estimated to be 7 magnitudes brighter than the donor star itself, 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 shape of the disk, seen nearly edge-on. A mean absolute magnitude adjusted for viewing angle is +3.6.[2]

References

  1. Bibcode:1933AnHar..84..189W
    .
  2. ^
    S2CID 119710755
    .
  3. ^
    S2CID 244398875
    . Gaia DR3 record for this source at VizieR.
  4. S2CID 54503839
    .
  5. ^ a b "OY Ara". The International Variable Star Index. AAVSO. Retrieved 6 October 2022.
  6. doi:10.1007/BF00668127
    .
  7. doi:10.1093/mnras/227.1.23
    .
  8. S2CID 232380319
    .
  9. ^
    S2CID 115854775
    .
  10. S2CID 121397724
    .
  11. Bibcode:1916AnHar..76...19C
    .
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