HR Lyrae or Nova Lyrae 1919 was a

nova A nova ( novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", Latin for "new") that slowly fades over weeks or months. All observed novae involve white ...

which occurred in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Lyra , from ; pronounced: ) is a small constellation. It is one of the 48 listed by the 2nd century astronomer Ptolemy, and is one of the modern 88 constellations recognized by the International Astronomical Union. Lyra was often represented on star ...

in 1919. Its discovery was announced by Johanna C. Mackie on 6 December 1919. She discovered it while examining

photographic plate Photographic plates preceded film as the primary medium for capturing images in photography. These plates, made of metal or glass and coated with a light-sensitive emulsion, were integral to early photographic processes such as heliography, d ...

s taken at the

Harvard College Observatory The Harvard College Observatory (HCO) is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, United St ...

. The bulletin announcing the discovery (H.C.O. bulletin 705) states "''Between December 4 and 6 it rose rapidly from the sixteenth

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

or fainter, to a maximum of about 6.5''". It was the first nova ever reported in Lyra, and Mackie was awarded the AAVSO gold medal for her discovery. Its peak magnitude of 6.5 implies that it might have been visible to the naked eye, under ideal conditions. HR Lyrae's outburst occurred in December 1919, when Lyra was only visible in the early evening for most northern observers. Visibility was even more limited in the first months of 1920, so its

light curve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

near maximum brightness is poorly sampled. But it is very likely that it declined from peak brightness by 3 magnitudes in less than 100 days, making it a "fast" nova. By November 1921 the star had dimmed to 14th magnitude, which is close to its quiescent brightness. It continues to show brightness fluctuations of 1 magnitude or less above its quiescent magnitude with no clear periodicity, as well as dimming (down to 17th magnitude) episodes. Although only one nova event has been seen, there are suggestions based primarily on the light curve that HR Lyrae might be a recurrent nova. All novae are binary stars, with a "donor" star orbiting a

white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...

. The two stars are so close to each other that matter is transferred from the donor to the white dwarf. In the case of HR Lyrae the binary's orbital period is uncertain, but a value of 2.4 hours has been reported. The white dwarf's mass has been estimated to be 0.78±0.15

References

External links

*http://www.britastro.org/vss/obj-18.html *http://astro.corlan.net/stars/LYR/HR-LYR.html *https://web.archive.org/web/20050909054008/http://www.tsm.toyama.toyama.jp/curators/aroom/var/nova/1910.htm {{var-star-stub Novae Lyra 1919 in science Lyrae, HR 175268