DN Geminorum

DN Geminorum or Nova Geminorum 1912 was a classical nova which lit up in 1912 in the constellation Gemini. It was discovered by Norwegian variable star observer Sigurd Einbu[3] on March 12, 1912 before reaching peak brightness, which allowed early-stage spectra to be collected by Yerkes Observatory.[5] The nova reached a maximum brightness of around 3.5 mag before declining,[6] which means it was visible to the naked eye. Its brightness decreased over the following 36 days by 3 magnitudes as it gradually faded from sight. The light curve saw two maxima a few months after the outburst, along with strong oscillations.[6] Today its brightness is visual magnitude 15.5.[2]

DN Geminorum
Location of DN Geminorum (circled in red)
Observation data
Epoch J2000      Equinox J2000
Constellation Gemini
Right ascension 06h 54m 54.34929s[1]
Declination +32° 08′ 27.9247″[1]
Apparent magnitude (V) 15.5±0.5[2]
Astrometry
Proper motion (μ) RA: −0.794[1] mas/yr
Dec.: −4.323[1] mas/yr
Parallax (π)0.7288 ± 0.0807 mas[1]
Distanceapprox. 4,500 ly
(approx. 1,400 pc)
Absolute magnitude (MV)5.02±0.60[2]
Details
White dwarf
Mass0.93±0.15[2] M☉
Other designations
Nova Gem 1912, Nova Geminorum II[3], DN Gem, HD 50480[4]
Database references
SIMBADdata
The light curve of DN Geminorum, plotted from AAVSO data

This is a close binary star system consisting of a white dwarf with 93%[2] of the Sun's mass – the source for the nova explosion – and a lower mass red dwarf[6] companion from which the white dwarf is accreting matter.[2] The system is located approximately 4,500 light years from the Sun based on parallax, with its visual magnitude being diminished by an extinction of 0.53±0.12 due to interstellar dust.[2] Observations of this system showed a sinusoidal variation in luminosity with a period of 3.06840 ± 0.00012 h, which is likely the orbital period for the pair. This oscillation may be caused by irradiation of the companion star by the white dwarf.[6]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Selvelli, Pierluigi; Gilmozzi, Roberto (February 2019), "A UV and optical study of 18 old novae with Gaia DR2 distances: mass accretion rates, physical parameters, and MMRD", Astronomy & Astrophysics, 622: 16, arXiv:1903.05868, Bibcode:2019A&A...622A.186S, doi:10.1051/0004-6361/201834238, S2CID 119234563, A186.
  3. Pettersen, Bjørn Ragnvald (November 2012), "Sigurd Enebo and Variable Star Research: Nova Geminorum 1912 and the RV Tauri Stars", Journal of Astronomical History and Heritage, 15 (3): 246–254, Bibcode:2012JAHH...15..246P, doi:10.3724/SP.J.1440-2807.2012.03.08, S2CID 220705971.
  4. "DN Gem". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-08-15.
  5. Yerkes Observatory (June 14, 1912), "Note on Nova Geminorum 1912", Monthly Notices of the Royal Astronomical Society, 72 (8): 675–676, doi:10.1093/mnras/72.8.675.
  6. Retter, A.; et al. (September 1999), "An irradiation effect in Nova DN GEM 1912 and the significance of the period gap for classical novae", Monthly Notices of the Royal Astronomical Society, 308 (1): 140–146, arXiv:astro-ph/9905375, Bibcode:1999MNRAS.308..140R, doi:10.1046/j.1365-8711.1999.02704.x, S2CID 14377631.
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