Variation mechanisms in symbiotic nova V1329 Cygni

Abstract

U, B, V light curves of symbiotic nova V1329 Cygni (=HBV 475) are modelled in terms of combined wind and chromospheric fluorescence, with eclipses and shadowing of fluorescent regions, eccentric orbit effects, and conversion of far‐ultraviolet energy into the optical bands. Observational evidence regarding fluorescent brightness variation mechanisms is provided by waveforms and amplitudes and their changes from bandpass to bandpass. The combined set of U, B, V variations cannot be satisfied with a wind‐only or chromosphere‐only model. Contrary to arguments in the literature, chromospheric fluorescence can be comparable to wind fluorescence in brightness and can be far stronger than photospheric emission from a red giant. We show why there is no conflict between the existence of strong chromospheric fluorescence and symbiotic binary energetics, at least in this example. Ultraviolet and optical radial velocities are also discussed and fitted. Some parts of the fluorescent binary model omitted from the original paper by Wilson for lack of space are given here. Fitting was done both subjectively and by differential corrections (least‐squares criterion), thus providing insight into the interplay of wind and chromospheric effects. The large bandpass‐dependent waveform and amplitude changes are accounted for by differing relative amounts of wind and chromosphere fluorescence, with the chromosphere relatively bright in U and the wind relatively bright in B and V. A strong test of the model is provided by the way the amplitude and waveform change together – larger amplitude must go with wider minima, as observed. The differential corrections solutions fit the light curves rather well. Because they were done in JD rather than in phase, the solutions were also able to find ephemeris parameters. Potentially interesting is an enormous period change of dP/dt≈−0.0020±0.0004 s.d. which, if confirmed, means that the ≈955 d period is dropping by 2 d each cycle. Parameter results are tabulated, but our emphasis is on identification of variation mechanisms rather than specific numbers. Observational selection favours discovery of periodic fluorescent variation for arguments of periastron near ω=π/2 because wind and chromospheric fluorescence then combine to give maximum amplitude. The possibility of pre‐outburst drops in brightness being eclipses is examined. We urge spectroscopic observers to gather infrared radial velocities of the red giant and to search for subtle evidence of eclipses of the hot object. Infrared light curves also would be helpful if reasonably large numbers of data points could be accumulated.

Rotational velocities of the giants in symbiotic stars - II. Are S-type symbiotics synchronized?★

“…V1329 Cyg: It has P orb = 963.1 ± 9.8 d (Chochol & Wilson 2001) and inclination i = 86°± 2° (Schild & Schmid 1997). We calculate P rot ≈ 734−1571 d.…”

The remarkable properties of the symbiotic star AE Circinus

“…It is, in principle, possible that the 342 d period is the orbital period of a binary star. In this case, the ephemeris for the main minimum is We note that the symbiotic nova V1329 Cyg shows a similar oscillatory behaviour, with a period of about 955 d (Chochol & Wilson 2001). In that system, polarimetry and radial velocity measurements prove this period to be the orbital period of the binary system.…”

“…We note that the symbiotic nova V1329 Cyg shows a similar oscillatory behavior, with a period of about 955 days (Chochol & Wilson 2001). In that system, polarimetry and radial velocity measurements prove this period to be the orbital period of the binary system.…”

Eb Light Curve Models – What’s Next?

“…In addition to the public version, numerous special purpose versions have been developed to handle, for example, photospheric and circumstellar polarization (Wilson and Liou, 1993), X-ray pulse arrival times (Wilson and Terrell, 1998), and wind/chromosphere fluorescence (Wilson, 1998;Chochol and Wilson, 2001;. Criteria for inclusion of phenomena in the distributed version concern whether there is sufficient user interest and whether enough observations exist to justify the very time consuming tests required for a public program.…”