European astronomers have noticed the unusual activity of the double star system, known as the Dragon AG. New observations show that recent changes in the brightness of this star are slightly different from the changes observed in previous eruptions.
Located in the spherical halo surrounding the Milky Way galaxy, the Dragon Star AG is a classical symbiotic variable of the double type S. This system consists of a cold red giant (effective temperature of 4300 Kelvin) and a hot white dwarf (effective temperature of 100,000 Kelvin). The size of the red giant is about 30 times larger than the size of the Sun, and its mass is only 1.5 solar masses. The mass of the white dwarf is about 40-60 percent of the mass of the Sun. The period of revolution of the stars with respect to each other is 550 days.
The Dragon AG shows activity characteristic of symbiotic stars: its apparent magnitude, about 9.8, can increase to 1.4 during flares in the active phase. The time intervals between two adjacent active phases are from 9 to 15 years.
Previous observations showed that the active phase of the star AG Dragon begins with a powerful flash, followed by an interval of about one year followed by less powerful flares. However, in a new study, astronomers led by Jaroslav Merc from the University of Paul Josef Shafarik, Slovakia, discovered by analyzing observational data from the Astronomical Ring for Access to Spectroscopy (ARAS) database that in 2015 the active phase of the star AG Dragon began with two small flashes instead of the usual first strong flash for the star and the second, a small flare following it.
According to the authors, these unusual flares can be attributed to a new type of flare or to be a transitional type between powerful and weak flares.