Harry Nussbaumer

High resolution spectroscopy of symbiotic stars - VI. Orbital and stellar parameters for AR Pavonis

We present new dynamical parameters of the AR Pav binary system. Our observations consist of a series of high resolution optical/NIR spectra from which we derive the radial velocity curve of the red giant as well as its rotation velocity. Assuming co-rotation, we determine the stellar radius (130

Lemaître’s Hubble relationship

R_{\odot}

Historical notes on the expanding universe

) of the red giant. Based on this we derive the red giants luminosity and mass (2.0

Symbiotic stars with Wolf-Rayet spectra as protoplanetary nebulae?

M_{\odot}

Discovering the Expanding Universe

) as well as the distance of the system (4.9 kpc). The binary mass function finally yields the companions mass (0.75

Einstein’s conversion from his static to an expanding universe

M_{\odot}

Temperature and luminosity of hot components in symbiotic stars

) and the binary separation (1.95 AU). We find that the red giant does not fill its Roche lobe. We review the radial velocity data of Thackeray & Hutchings ([CITE]), and compare it with our red giants orbit. We find that their RV curves of the blue absorption system and the permitted emission lines are in anti-phase with the red giant, and that the forbidden emission lines are shifted by a quarter of a period. The blue absorptions and the permitted emission lines are associated with the hot companion but not in a straightforward way. The blue absorption system only tracks the hot components orbital motion whilst it is in front of the red giant, whereas at other phases line blanketing by interbinary material leads to perturbations. We finally present UV light curves based on IUE archive spectra. We clearly detect eclipses in the continuum at all wavelengths. The eclipse light curves are unusual in that they show a slow and gradual decline prior to eclipse which is followed by a sharp increase after eclipse.

PU Vulpeculae: the outburst of a symbiotic nova

Edwin Hubble is often credited with discovering the expanding Universe based on spectra taken by him. This statement is incorrect and we feel that it is the responsibility of those who are aware of the historical facts to set the record straight.

Temperatures and luminosities of symbiotic novae

The article Measuring the Hubble constant by Mario Livio and Adam Riess (Physics Today, October 2013, page 41) reviewed studies of the expanding universe from the 1920s to the present. Although the history of the subject underwent considerable compression to fit the length of a magazine article, we think it may leave a misleading impression of some of the key steps to our current understanding. We therefore offer the following clarifications. Most significantly, papers by Arthur Eddington and by Willem de Sitter in 1930, who successfully promoted Georges Lematres 1927 article for the Scientific Society of Brussels, effected a paradigm shift in interpretation of extragalactic redshifts in 1930. Before then, the astronomical community was generally unaware of the existence of nonstatic cosmological solutions and did not broadly appreciate that redshifts could be thought of locally as Doppler shifts in an expanding matter distribution. Certainly, in 1929 Edwin Hubble referred only to the de Sitter solution of 1917. At the time, the relation between distance and redshift predicted in that model was generally seen purely as a manifestation of static spacetime curvature.

The ultraviolet variability of the symbiotic star HBV 475. IIIL The periodicity of HBV 475

Symbiotic systems, in particular symbiotic novae, have been suggested to be very early stages of planetary nebulae. Some of them have been described as going through a Wolf-Rayet phase. We argue that there may be a direct relation between symbiotic objects and planetary nebulae, and that the Wolf-Rayet phase is connected to an active spell of the hot companion. Symbiotic stars could lead to planetary nebulae with two central stars with different radiation temperatures and luminosities, where each has the power to ionize a planetary nebula on its own.