DK Lacertae (Nova Lacertae 1950) was a nova, which lit up in the constellation

Lacerta Lacerta is one of the 88 modern constellations defined by the International Astronomical Union. Its name is Latin for lizard. A small, faint constellation, it was defined in 1687 by the astronomer Johannes Hevelius. Its brightest stars form a "W" ...

in 1950. The nova was discovered by Charles Bertaud of the Paris Observatory on a photographic plate taken on 23 January 1950. At the time of its discovery, it had an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

of 6.1. DK Lacertae reached peak magnitude 5.0, making it easily visible to the naked eye. DK Lacertae's post-eruption

light curve In astronomy, a light curve is a graph of light intensity of a celestial object or region as a function of time, typically with the magnitude of light received on the y axis and with time on the x axis. The light is usually in a particular frequ ...

was remarkable for the large number of outbursts of a magnitude or more which occurred in the months after the main nova event. Strope ''et al.'' (2010) reported that there were 14 of these "jitters" in the light curve, and they used this star as the prototype object for their type J light curve class. It took about 60 days for the nova to drop from peak brightness by 3 magnitudes, which makes DK Lacertae a "fast" nova. X-ray emission has been detected from this system. All novae are binary stars, with a "donor" star orbiting a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes ...

. The donor star is so close to the white dwarf that matter is transferred from the donor to an accretion disk surrounding the white dwarf. In the case of DK Lacertae, Shara ''et al.'' (2018) estimate that the white dwarf has a mass of 1.03 and the donor star is transferring to the accretion disk. The orbital periods of nova are typically a few hours, but no photometric periodicity on that timescale has been found for DK Lac, suggesting that we are viewing the accretion disk nearly face-on. A faint shell was detected around the source in 1995, with a radius of about , but later observations with the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

failed to detect the shell.

References

External links

* https://web.archive.org/web/20070928040256/http://www.tsm.toyama.toyama.jp/curators/aroom/var/nova/1950.htm {{DEFAULTSORT:DK Lacertae Novae Lacerta 1950 in science Lacertae, DK