Then we used the packages of C-Munipack program to do the photometry and extract the magnitude variability for each system by means of differential photometry. Differential photometry is performed for measuring the small variations in brightness of the target variable star in comparison with other two non-variable stars known as comparison C and check stars Ck. This technique is widely used in variable stars, especially for short period variables and eclipsing binary systems.
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In differential photometry a comparison and a check stars together with the variable are exposed in the same CCD frame. Fig 4 displays the field chart of the system.
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The differential photometry was performed with respect to BCB and BCB as comparison and check stars respectively, Table 3 lists their coordinates. Table 3 List of the comparison and the check of DQ Her. The most obvious spectral lines features are seen in the spectra of the system: These spectral lines are produced in the accretion curtain region as suggested by Bloemen et al.
The fluxes of spectral lines vary with orbital phases between high, intermediate and low values on short time scale of some hours and long time scale of some years. The emission lines of the intermediate polars DQ Her originated in the accretion curtain region.
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The high energy photons in the emitting region produce the ultraviolet emission lines seen in this system. In this view, we can refer the luminosity of DQ Her to be correlated to the rate of its mass transfer and the origin of the ultraviolet spectral lines to the accretion curtain region. So as the rate of mass transfer increases, the gravitational potential energy increases, and this will lead to an increase in the temperature and consequently in the strength of ultraviolet spectral lines.
In this model the emission lines seem to be originated in the region where the strength of the magnetic field prohibit the formation of the disk. As shown from the fig our photometric observations almost covered the whole period of variations of DQ Her. We see that light reprocessed through the accretion disk because we see the disk edge-on, and the white dwarf itself is obscured. Different characteristic features of DQ Her variations, i. In both figures, the KAO photometry is in red.
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Where M a , R a are the mass and radius of the accreting star, L acc is the accretion luminosity, and G is the gravitational constant. We report the results of the photometric and spectroscopic behavior of DQ Her. The main results for the system can be summarized as:. Photometry of DQ Her revealed that the system is an eclipsing binary with high inclination deg. The light variation reveal very deep primary minimum where, main sequence component lie in front of the white dwarf The intermediate Polar system DQ Herculis, in which the white dwarf is gravitationally stripped the matter from the main-sequence companion star and forms an accretion disk around the white dwarf and the inner disk region is truncated by the magnetic field of the white dwarf.
Disk material passes through the curtains and then accretes onto the white dwarf near one of its magnetic poles. One periodicity is related to the orbital period of the binary star system. A second periodic signal originates from the rotation of the white dwarf spinning on its axis and it is shorter than the orbital period.
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