BT Monocerotis
Encyclopedia
BT Monocerotis was a nova
, which lit up in the constellation Monoceros
in 1939. It was discovered on a spectral plate by Fred L. Whipple on December 23, 1939. BT Monocerotis reached a brightness of 4.5 mag
. Its brightness decreased after the outbreak in 36 days by 3 mag. The light curve
for the eruption had a long plateau period.
Photographic plates taken for 30 years prior to the eruption show that BT Monocerotis remained visible during that period. Prior to 1933, BT Monocerotis had an average magnitude of 15.52 with a variation of 1.2 magnitudes. It retained the same magnitude up until the eruption, showing a variation of 0.9 magnitudes. Thus it did not show a pre-eruption rise in brightness.
This is an interacting binary star
system consisting of a white dwarf
primary star and a main sequence
star with a stellar classification
of G8V. The orbit has a period of 0.33381379 days and an inclination
of 88.2° to the line of sight to the Earth, resulting in an eclipsing binary. The nova eruption is believed to have been driven by mass transferred from the secondary star to the white dwarf. It remains uncertain whether the white dwarf has an accretion disk formed by this material. Matter outflowing from the system has a line of sight velocity of 450 km s−1, but may be moving at up to 3,200 km s−1 if the flow is strictly bipolar.
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
, which lit up in the constellation Monoceros
Monoceros
Monoceros is a faint constellation on the celestial equator. Its name is Greek for unicorn. Its definition is attributed to the 17th-century Dutch cartographer Petrus Plancius. It is bordered by Orion to the west, Gemini to the north, Canis Major to the south and Hydra to the east...
in 1939. It was discovered on a spectral plate by Fred L. Whipple on December 23, 1939. BT Monocerotis reached a brightness of 4.5 mag
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
. Its brightness decreased after the outbreak in 36 days by 3 mag. The light curve
Light curve
In astronomy, a light curve is a graph of light intensity of a celestial object or region, as a function of time. The light is usually in a particular frequency interval or band...
for the eruption had a long plateau period.
Photographic plates taken for 30 years prior to the eruption show that BT Monocerotis remained visible during that period. Prior to 1933, BT Monocerotis had an average magnitude of 15.52 with a variation of 1.2 magnitudes. It retained the same magnitude up until the eruption, showing a variation of 0.9 magnitudes. Thus it did not show a pre-eruption rise in brightness.
This is an interacting binary star
Binary star
A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
system consisting of a white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
primary star and a main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
star with a stellar classification
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
of G8V. The orbit has a period of 0.33381379 days and an inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
of 88.2° to the line of sight to the Earth, resulting in an eclipsing binary. The nova eruption is believed to have been driven by mass transferred from the secondary star to the white dwarf. It remains uncertain whether the white dwarf has an accretion disk formed by this material. Matter outflowing from the system has a line of sight velocity of 450 km s−1, but may be moving at up to 3,200 km s−1 if the flow is strictly bipolar.