T Aurigae

T Aurigae (or Nova Aurigae 1891) was a nova, which lit up in the constellation Auriga in 1891. Thomas David Anderson, an amateur astronomer in Edinburgh, reported that he was "almost certain" he saw the nova at 02:00 UT on 24 January 1892, when it was slightly brighter than χ Aurigae (apparent magnitude 4.74). He mistook the star for 26 Aurigae, although he noted to himself that it seemed brighter than he remembered it being. He saw it twice more during the following week. On 31 January 1892 he realized his mistake, and wrote a note to Ralph Copeland (the Astronomer Royal of Scotland) reporting his discovery.[4] Professor Copeland immediately reported the discovery via telegram to William Huggins, who made the first spectroscopic observations of T Aurigae on 2 February 1892, when the star was a magnitude 4.5 object.[5] T Aurigae was the first nova to be observed spectroscopically.[6]

The light curve of T Aurigae, plotted from photographic magnitude data tabulated by Shapley.[7] Data values listed with identical times were averaged before being plotted.
T Aurigae

RGB composite color image of the shell surrounding the nova T Aurigae, made from three narrow band images: Blue = 4800Å, green = Hα at 6563 Å and red = [NII] at 6583 Å. From Santamaria et al. 2020[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Auriga
Right ascension 05h 31m 59.118s[2]
Declination +30° 26′ 45.03″[2]
Apparent magnitude (V) 4.5Max.
15Min.
Astrometry
Distance880+46
−35[3] pc
Characteristics
Variable type Classical Nova, Eclipsing Binary
Other designations
Nova Aur 1891, GCRV 56251, Lan 652, SBC9 326, BD+30° 923a, HD 36294, CDS 507, HR 1841, AAVSO 0525+30, Gaia DR2 3446266197646225536
Database references
SIMBADdata
Location of T Aurigae (circled in red)

Strope and Schaefer report that the peak brightness of T Aurigae was magnitude 4.5,[8]. Pre-discovery images on photographic plates allowed the a light curve beginning in late 1891 to be constructed.[7] AAVSO data shows that T Aurigae's quiescent magnitude is 15.3.

In 1958 observations of the stars forming T Aurigae with the Crossley telescope showed that it is an eclipsing binary, with a period of 4.9 hours, and an eclipse depth of 0.18 magnitudes.[9] T Aurigae was the third nova that was discovered to be a short period eclipsing binary, and that discovery lead to increased speculation that the nova phenomenon was connected to close binary star pairs. [10] Today it is believed that all novae are binary stars, with a "donor" star orbiting a white dwarf. The stars are so close to each other that matter is transferred from the donor star to the white dwarf.

Two images of the shell surrounding T Aurigae taken 38 years apart, showing the nebula's expansion. Both were taken with Hα filters, left at the Kitt Peak National Observatory, and right with the Nordic Optical Telescope.[1]

T Aurigae is surrounded by an emission nebula (shell) which is roughly elliptical (25 arc seconds by 19 arc seconds in size) and resembles a planetary nebula. Santamaria et al. obtained images of this shell from 2016 through 2019 and by comparing those images to archival images dating back to 1956, they were able to determine that the shell is expanding at about 0.01 arc seconds per year, corresponding to an expansion velocity of about 350 km/sec.[1]

References
  1. Santamaria, E.; Guerrero, M.A.; Ramos-Larios, G.; Toala, J.A.; Sabin, L.; Rubio, G.; Quino-Mendoza, J.A. (March 2020). "Angular Expansion of Nova Shells". The Astrophysical Journal. 892 (1). arXiv:2002.06749. doi:10.3847/1538-4357/ab76c5. Retrieved 11 December 2020.
  2. 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.
  3. Schaefer, Bradley E. (2018). "The distances to Novae as seen by Gaia". Monthly Notices of the Royal Astronomical Society. 481 (3): 3033–3051. arXiv:1809.00180. Bibcode:2018MNRAS.481.3033S. doi:10.1093/mnras/sty2388. S2CID 118925493.
  4. Copeland, Ralph; Becker, L. (August 1892). "On the new star in the constellation Auriga". Astronomy and Astro-Physics. 11: 593–602. Retrieved 11 December 2020.
  5. Huggins, William; Huggins, Margaret Lindsay (August 1892). "On Nova Aurigae". Astronomy and Astro-Physics. 11: 571–581. Retrieved 11 December 2020.
  6. Mclaughlin, Dean B. (October 1950). "Problems in the Spectra of Novae". Publications of the Astronomical Society of the Pacific. 62 (367): 185. doi:10.1086/126273. Retrieved 9 January 2021.
  7. Shapley, Harlow (January 1933). "The photographic light curves of 11 novae". Annals of the Astronomical Observatory of Harvard College. 84 (5): 121–155. Retrieved 23 January 2021.
  8. Strope, Richard J. (July 2010). "Catalog of 93 Nova Light Curves: Classification and Properties". The Astronomical Journal. 140: 34–62. doi:10.1088/0004-6256/140/1/34. Retrieved 11 December 2020.
  9. Walker, Merle F. (January 1962). "Nova T Aurigae 1891: a New Short-Period Eclipsing Binary". Information Bulletin on Variable Stars. 2: 1. Retrieved 11 December 2020.
  10. Walker, Merle F. (August 1963). "Nova T Aurigae 1891: a New Short-Period Eclipsing Binary". Astrophysical Journal. 138: 313. doi:10.1086/147646. Retrieved 11 December 2020.
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