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Astron. Astrophys. 318, 908-924 (1997)

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5. Basic equations

5.1. Case of axial symmetry

Radial velocities of the expanding equatorial ring and polar blobs determined spectroscopically and tangential velocities determined from the HST or radio images can be used simultaneously for calculation of the true expansion velocities v of the ring and blobs, as indicated in Fig. 12, using the equations:

[EQUATION]

[EQUATION]

The most important parameter - the inclination angle i - can be calculated, using the equation:

[EQUATION]

The ratio of radial velocities can be found directly from spectroscopic observations. The ratio of tangential velocities is identical to the ratio of expansion rates for the blobs and ring determined in Fig. 7. If the inclination angle i is known, the true velocities of the ring and blobs can be calculated using the Eq. (4).

[FIGURE] Fig. 12. Radial, tangential and true velocities of the components (blob and ring) of the nova envelope

5.2. Non-axially symmetric case

In this case the inclination angle of the ring i' differs from the inclination angle i of the blobs. The basic equations are modified as follows

[EQUATION]

[EQUATION]

The two inclination angles i and i' are related by the equation:

[EQUATION]

5.3. Spherical envelope with outflow in polar region

The basic equations are modified as follows:

[EQUATION]

[EQUATION]

The inclination angle can be calculated using the equation

[EQUATION]

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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