(ORDO NEWS) — Indian astronomers at the Aryabhata Research Institute for Observational Sciences reported the discovery of two new polars – cataclysmic variables in binary star systems with a strong magnetic field.
Cataclysmic Variables (CV) are binary star systems consisting of a white dwarf and a main sequence star that increase their brightness unevenly by several times and then re-enter a state of rest.
Polars are a subclass of CVs, where white dwarfs have a very strong magnetic field that interferes with the formation of the usual accretion disk for other cataclysmic variables. Instead, matter from the companion star falls onto the white dwarf along the field lines.
In a new work, Indian scientists studied two CVs – J1743 and YY Sex.
They analyzed data from ground-based instruments such as the DFOT telescope in India and the Maidanak Alpine Observatory telescopes in Uzbekistan, as well as the XMM-Newton spacecraft.
It turned out that both variables are polars, while their spectra turned out to be very similar to the spectra of other known polars.
Both objects show a characteristic sign of mass accretion of matter the emission lines of He I and He II, as well as the lines of the Balmer series.
In the case of J1743, the accretion rate varies on a scale of several days. The polar is characterized by a mass accretion rate of about 5 times 10 to the minus 12th power of solar masses per year and a bolometric luminosity (total luminosity over the entire spectrum) of about 40 times 10 to the 30-1 power erg per second.
The white dwarf has a mass of approximately 0.75 solar masses, and the mass of the companion star is estimated at 0.15 solar masses.
The presence of several emission lines and lines of the Balmer series in the variable YY Sex confirmed the magnetic nature of the accretion flow, and the mass of the companion is estimated at 0.09 solar masses.
Lines of the Balmer series are called spectral lines that appear in the spectrum due to radiation generated by electron transitions between the second and higher levels in hydrogen atoms.
Due to the abundance of hydrogen in the Universe, Balmer lines are observed in the spectrum of most space objects, which allows them to be used to determine radial velocities, for example, during the accretion of matter.
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