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Table 7
Shock wave, and Na and Hα layer movements in stellar rest frame during a typical pulsation cycle of RR Lyrae, as described in Sect. 4.
| φ interval | Na movements | Hα movements | Shock wave |
|---|---|---|---|
| 0.874–0.90 | Up to about φ = 0.90, the Na layer is receding. When it is traversed by the shock, it reverses its motion and starts an ascending motion in the atmosphere. | Highest layer receding at an average velocity near + 46 km s−1 | s1 and s2 shock waves are initiated below photosphere, but are not observed individually. When above the photosphere, the main shock (s1+s2) is crossing the Na layer. |
| 0.90–0.943 | Ascending acceleration from 0 to − 24 km s−1 | Highest layer receding at + 46 km s−1 throughout this phase interval and deepest layer ascending (producing emission in shock wake) | Deceleration of the main shock from 133 to about 100 km s−1. First apparition of Hα emission (0.892 ≲ φ ≲ 0.911). |
| 0.943–1.074 | The Na layer reaches its maximum ascending velocity (− 31.3 km s−1) at φ = 0.991 | Ascending deceleration from − 58 to − 63 km s−1. Short line doubling (0.953 < φ < 1.027) | Deceleration of the main shock followed by disappearance (radiative dissipation). The main shock leaves the Hα layer around φ = 1.05. |
| 1.074–1.302 | Ascending deceleration from − 24 to 0 km s−1. The Na layer reaches its maximum radius. | Ascending deceleration from − 52 to − 21 km s−1 | The main shock has leftthe Hα formation layer. |
| 1.302–1.320 | Maximum expansion of Na layer | The highest part of the Hα layer is still ascending. | The main shock has left the atmosphere. Apparition of the third Hα emission (0.20 ≲ φ ≲ 0.40) induced by the compression of the high atmosphere. |
| 1.320–1.455 | Receding acceleration from 0 to + 10 km s−1. Two-step infalling motion. Strong compression of deep photospheric layers at φ ~ 0.36 | Ascending deceleration from − 19 to 0 km s−1. Maximum expansion of Hα layer. | The main shock has left the atmosphere. |
| 1.455–1.600 | Receding acceleration from + 10 to + 24 km s−1. | Receding acceleration from 0 to + 23 km s−1 | The main shock has left the atmosphere. |
| 1.600–1.874 | Receding acceleration from + 24 to + 37 km s−1 near φ ~ 0.82. Then slight slowdown until + 32 km s−1 at φ = 0.874 just before the arrival of a new main shock. | Receding acceleration from + 23 to + 42 km s−1. | A new shock emerges from the photosphere near φ = 0.874. Apparition of second Hα emission (φ ~ 0.7) due to atmospheric compression. |
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