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Showing results for tags 'radial velocities'.
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I finished observations of the Mizar A spectroscopic binary. Calibration for the Hα line made on water lines contained in the Earth's atmosphere. I used LowSpec spectrograph with 1800 grooves/mm reflective holographic grating, APM APO 107/700, QHY163M camera and HEQ5 mount with guiding. It turned out that the Earth's movement practically compensated for the radial velocity of the Mizar A system. Based on the analysis, I received the result: vr = -8.8 km/s in fact the system is approaching at a radial velocity of -6.3 km/s. I also determined the phase plot of radial velocities based on my measurements for the Na (together for both lines) and separately for Hα line: Error is based on half my spectral resolution (0.2 Å/pix corresponds to rv = 10 km/s). Each measurement corresponds to the stack a few images. The most important purpose of observing this binary system was to record the historical Ca II line (often called as CaK, 3933.66 Å). The distances in the violet part of the spectrum are almost 2x smaller than the corresponding shifts for the Hα line. This line initiated the discovery of spectroscopically binary systems, and Mizar A was the first discovered system of this type. These were the spectroscopic observations in the 19th century: Source: https://www.leosondra.cz/en/mizar/#b20 I've made several observations of this line in the last two weeks: Animation showing the changes in the CaK line based on my observations: Not only the Ca II is split, but the surrounding lines also, shown below in a wider environment: Balmer hydrogen lines are becoming more dense as Balmer's gap approaches (3646 Å). Observation result of the Hα line: And animation showing the changes in this line: The Na I doublet was much more difficult to observe, because stars with A spectral type contain very faint lines of this metal: Animation showing the changes in the sodium doublet: We received the sodium quartet
This system consists of two yellow giants having types G0III and G8III (some sources give K0III), similar masses and brightness. The orbital period of the components is 104 days. The fact that one of the stars has a later spectral type is very convenient . It has stronger spectral lines of metals, including sodium. This allows you to immediately recognize which star is approaching and which is currently moving away. I made 3 observations so far with using a DIY 3D printed LowSpec spectrograph in the version v2 designed by @Paul Gerlach and a 1800 l/mm holographic grating. Based on these observations, the spectral spread for both observations for the sodium line is 0.79 Å (0.079 nm) or 4 pixels, which gives a difference of radial velocities of 40 km/s. Assuming that component A belongs to G8III and component B to G0III: 2019-12-03 component A was moving at relative vr to the barycenter of the system of -20 km/s and component B was moving at a relative vr of +20 km/s. 2020-01-23 component A was moving at a relative vr of +20 km/s and component B was moving at a relative vr of -20 km/s. I called radial speeds relative, because the radial velocity of the Capella barycenter to the Solar System wasn't included. I took the radial velocity of the Capella barycenter into account and I received this phase plot: The background is the plot of radial velocities from paper: M. Weber, K. G. Strassmeier, 2011, The spectroscopic orbit of Capella revisited https://arxiv.org/pdf/1104.0342.pdf