GK Persei (also Nova Persei 1901) was a bright nova first observed on Earth in 1901. It was discovered by Thomas David Anderson, an Edinburgh clergyman, at 02:40 UT on 22 February 1901 when it was at magnitude 2.7. It reached a maximum magnitude of 0.2, the brightest nova of modern times until Nova Aquilae 1918. After fading into obscurity at about magnitude 12 to 13 during the early 20th century, GK Persei began displaying infrequent outbursts of 2 to 3 magnitudes (about 7 to 15 times quiescent brightness). Since about 1980, these outbursts have become quite regular, typically lasting about two months and occurring about every three years. Thus, GK Persei seems to have changed from a classical nova like Nova Aquilae 1918 to something resembling a typical dwarf nova-type cataclysmic variable star.
GK Persei and the surrounding Firework nebula.
Epoch J2000.0 Equinox J2000.0
|Right ascension||03h 31m 11.82s|
|Declination||+43° 54′ 16.8″|
|Apparent magnitude (V)||0.02 - 14.0|
|Radial velocity (Rv)||5.5 km/s|
|Proper motion (μ)|| RA: −6.878 mas/yr |
Dec.: −17.348 mas/yr
|Parallax (π)||2.3063 ± 0.0415 mas|
|Absolute magnitude (MV)||−9.1 - +3.7|
|Period (P)||1.996872 ± 0.000009 d|
|Inclination (i)||67 ± 5°|
|126.4 ± 0.9 km/s|
|Radius||2.26 ± 0.11 R☉|
GK Persei has precise parallaxes reported from Gaia DR2 and Gaia EDR3, but these are thought to be badly affected by the binary nature of the system. The Hubble Space Telescope has used a different method to derive the distance to GK Persei using nebular expansion velocity and compares that with its own astrometric parallax calculation. This gave a somewhat smaller parallax (larger distance) than the Gaia measurements.
Novae consist of a main-sequence to giant star that accretes mass onto a white dwarf. The two stars of GK Persei orbit each other with a period of nearly 2 days. The white dwarf, with a mass of 1.03 M☉, has one of the highest masses measured in a cataclysmic variable. The donor star, having donated much of its mass to the white dwarf, is only 0.39 M☉ despite being a subgiant star.
The location of GK Persei (circled in red)
GK Persei by the 32-inch Schulman Telescope at the Mt. Lemmon Observatory.
Expanding Nebula around GK Persei. Images range from 1953 to 2012.