V476 Cygni or Nova Cygni 1920 was a nova which occurred in the constellation Cygnus in 1920. It was discovered by William Frederick Denning, an English amateur astronomer, at 09:30 GMT on 20 August 1920, at which time it had a magnitude of 3.7.[4] It reached a peak brightness of magnitude 1.7 on 23 August 1920.[5][6][7] Its quiescent brightness is magnitude 17.09.
 RGB composite color image of the shell surrounding the nova V476 Cygni, 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 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 58m 24.46s[2] |
| Declination | +53° 37′ 07.5″[2] |
| Apparent magnitude (V) | 1.7Max. 17.09Min. |
| Astrometry | |
| Distance | 665+107 −53[3] pc |
| Characteristics | |
| Variable type | Nova |
| Other designations | |
| Database references | |
| SIMBAD | data |
V476 Cygni's light curve is quite unusual, showing a rapid decline from maximum brightness, followed by a slow nearly linear fading. It is classified as a very fast nova,[8] with a very long tail. The light curve shows a "dust dip", a fast decline to a local brightness minimum, then a small increase in brightness, and finally a long, slow decline. This dust dip is believed to is believed to coincide with the formation of dust in the material ejected from the nova as it moves away from the star and cools.[9]
All novae consist of a close binary star pair, with a white dwarf star and a "donor" star orbiting each other. The stars are so close together that the less dense donor star transfers matter to the white dwarf. In the case of V476 Cygni, modeling indicates that the white dwarf has a mass of 1.18M⊙, and it is receiving 6×10−10 M⊙ of material from the donor star, per year.[10] V476 Cygni has transitioned into a recurrent dwarf nova, although it has done so much earlier than expected.[11]
A small emission nebula (shell) is visible around the star, which resembles a planetary nebula. Santamaria et al. examined images of the nebula taken in 1944, 1993 and 2018 and found that the shell is clearly expanding. It is slightly elliptical, with major and minor axes of 14.6×13.4 arc seconds (as of 2018) expanding at a rate of 0.073×0.067 arc seconds per year, implying a physical expansion rate of 230×200 km/sec.[1] Surprisingly, a 1997 attempt to image the shell using the Hubble Space Telescope, was unsuccessful.[12]
Gallery
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The location of V476 Cygni (circled in red) -
The light curve of V476 Cygni, plotted from AAVSO data -
![Two images of the shell surrounding V476 Cygni taken 25 years apart, showing the nebula's expansion. Both were taken with Hα filters, left at the William Herschel Telescope, and right with the Nordic Optical Telescope.[1]](//upload.wikimedia.org/wikipedia/commons/thumb/9/90/V476CygNebulaExpanding.png/477px-V476CygNebulaExpanding.png)
Two images of the shell surrounding V476 Cygni taken 25 years apart, showing the nebula's expansion. Both were taken with Hα filters, left at the William Herschel Telescope, and right with the Nordic Optical Telescope.[1]
![Two images of the shell surrounding V476 Cygni taken 25 years apart, showing the nebula's expansion. Both were taken with Hα filters, left at the William Herschel Telescope, and right with the Nordic Optical Telescope.[1]](/wiki/File:V476CygNebulaExpanding.png)
References
edit- ^ a b c 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): 60. arXiv:2002.06749. Bibcode:2020ApJ...892...60S. doi:10.3847/1538-4357/ab76c5. S2CID 211132830.
- ^ a b "V476 Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 4 December 2020.
- ^ Schaefer, Bradley E. (20 September 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.
- ^ Denning, W.F. (September 1920). "Estimated magnitudes of Nova Cygni (1920)". Astronomische Nachrichten. 211 (22): 419. Bibcode:1920AN....211..419D. doi:10.1002/asna.19202112205. Retrieved 4 December 2020.
- ^ "Download Data". AAVSO. Retrieved 4 December 2020.
- ^ Warner, B. (February 2006). "Where have all the novae gone?". Astronomy & Geophysics. 47 (1): 29–32. Bibcode:2006A&G....47a..29W. doi:10.1111/j.1468-4004.2006.47129.x.
- ^ Beech, M. (1998). "The Makings of Meteor Astronomy: Part XVII. W.F. Denning and Comets, Nebulae, and Novae". WGN, Journal of the International Meteor Organization. 26 (6): 268–272. Bibcode:1998JIMO...26..268B. Retrieved 30 November 2020.
- ^ Slavin, A.J.; O'Brien, T.J.; Dunlop, J.S. (September 1995). "A deep optical imaging study of the nebular remnants of classical novae". Monthly Notices of the Royal Astronomical Society. 276 (2): 353–371. Bibcode:1995MNRAS.276..353S. doi:10.1093/mnras/276.2.353. Retrieved 4 December 2020.
- ^ Strope, Richard J.; Schaefer, Bradley E.; Henden, Arne A. (July 2010). "Catalog of 93 Nova Light Curves: Classification and Properties". The Astronomical Journal. 140 (1): 34–62. arXiv:1004.3698. Bibcode:2010AJ....140...34S. doi:10.1088/0004-6256/140/1/34. S2CID 118537823.
- ^ Shara, Michael M.; Prialnik, Dina; Hillman, Yael; Kovetz, Attay (June 2018). "The Masses and Accretion Rates of White Dwarfs in Classical and Recurrent Novae". The Astrophysical Journal. 860 (2): 110. arXiv:1804.06880. Bibcode:2018ApJ...860..110S. doi:10.3847/1538-4357/aabfbd. S2CID 55851634.
- ^ Kato, Taichi Kato (2022). "V476 Cyg (Nova Cyg 1920) is currently a dwarf nova — first such an object in the period gap?" (PDF). Variable Star Bulletin (95). Variable Star Observers League in Japan (VSOLJ).
- ^ Gill, C.D.; O'Brien, T.J. (May 2000). "Hubble Space Telescope imaging and ground-based spectroscopy of old nova shells - I. FH Ser, V533 Her, BT Mon, DK Lac and V476 Cyg". Monthly Notices of the Royal Astronomical Society. 314 (1): 175–182. arXiv:astro-ph/0001092. Bibcode:2000MNRAS.314..175G. doi:10.1046/j.1365-8711.2000.03342.x.