HP Draconis
HP Draconis is a binary star system in the constellation of Draco. At an apparent magnitude of +7.974, it is not visible to the naked eye. Parallax measurements give a distance of.
Characteristics
This is an eclipsing binary system whose components are detached. Each 10.76 days, the apparent magnitude of the system drops to 0.26 in the primary eclipse and to 0.23 in the secondary eclipse. The variability of this system was discovered in 1997 by the Hipparcos satellite, and it was given its variable-star designation HP Draconis in 1999.The components of this binary system are separated by with an eccentricity of 0.036. Both are F-type main-sequence stars with identical stellar classifications of F9V. Star A has 1.135 times the mass, 1.247 times the radius, and 1.8 times the luminosity of the Sun, while star B has 1.098 times the mass, 1.15 times the radius, and 1.48 times the Sun's luminosity. The effective temperatures are 6,000 and, giving them the yellow-white hue typical of late-type F-type stars. The estimated age of the system is 3.5 billion years. There is evidence of a third component in the system from eclipse timing variations.
HP Draconis makes a wide triple system with a white dwarf that has a projected separation of 1,140 astronomical units, giving an estimated orbital period of 23,000 years. This companion has 0.45 times the Sun's mass, a temperature of and has been a white dwarf for an estimated 1.15 billion years.