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AG Dra - a symbiotic mystery

AG Dra - a symbiotic mystery. L. Hric 1 , R. Gális 2 and E. Kundra 1. 1 Astronomical Institute of the Slovak Academy of Sciences, 059 60 Tatransk á Lomnica , Slovak Republic 2 Faculty of Sciences, University of P. J. Š af á rik , Moyzesova 16, 041 54 Ko ši ce , S lovak Republic.

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AG Dra - a symbiotic mystery

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  1. AG Dra - a symbiotic mystery L. Hric1, R. Gális2 and E. Kundra1 1Astronomical Institute of the Slovak Academy of Sciences, 059 60TatranskáLomnica, Slovak Republic 2Faculty of Sciences, University of P. J. Šafárik, Moyzesova 16, 041 54Košice, Slovak Republic The 14th North American Workshop on Cataclysmic Variables and Related Objects 15-19 March 2009, University of Arizona, Tucson, Arizona

  2. Outline • AG Dra – overview of the system • Long-term photometric behaviour • Radial velocity analysis • Period analysis of emission lines • Resonance as a general cause of activity • Recent cycle of outburst activity • Conclusions

  3. AG Dra – overview of the system • AG Dra is a symbiotic binary type Z And. • The cool component is a red giant with the spectral classification of K3 III, log (g) = 1.6, Teff = 4300 K and the mass MG = 1.5 M • The giant radius is estimated on 20 Rand the diameter of the Roche lobe is to 170 R • The distance of AG Dra is not determined definitely: Hipparcos – 1 kpc, Mikolajewska et al. (1995) determined the distance 2.5 kpc from classification of giant and Skopal et al. (2004) determined from relation distance-bolometric flux of the giant the value 1.1 ± 0.4 kpc. • As well as the light curves also radial velocities show the presence of two periods 549 days and 355 days. For 355 days period we have suggested the explanation of pulsation period of red giant (Gális et al. 1999). • We discovered the resonance 14/9 between orbital and pulsation periods which can be responsible for the activity in the system. • There are still some mysteries in the system…

  4. Long-term photometric behaviour • Robinson 1969 collected photographic observations of AG Dra from 1890 to 1965. • We used the new photoelectric and CCD observational material obtained at observatories Skalnaté Pleso and Stará Lesná (Slovakia), Valašské Meziříčí (Czech Republic). Moreover we used the same data as in our previous paper (Gális et al. 1999) as well as published photometry by Skopal et al. (2002, 2004) and Leedjärv et al. (2004). • In AG Dra alternate two distinct periods differing by activities of the system. We call them periods of activities (A, B, C ...) and periods of quiescence (Q1 , Q2...) • Our period analysis confirmed 550 days orbital period and discovered new 350 days period, interpreted by pulsations of red giant.

  5. Long-term photometric behaviour

  6. Long-term photometric behaviour

  7. Radial velocity analysis • Radial velocities from: Smith et al. 1996, Mikolajewska et al. 1995, Tomov and Tomova 1997, Fekel et al. 2000. • We have used the method of Fourier harmonic analysis, principal components analysis (PCA), the method of residua and few iteration steps to improve the parameters of orbital motion and pulsation. The final solution of orbital elements was obtained by the code based on the simplex method (Kratka 1990). • The orbital as well as the pulsation radial velocities are very symmetric. We can conclude, that the orbit is very close to circular and pulsations are more or less radial.

  8. Radial velocity analysis

  9. Radial velocity analysis JDmax = (2 448 996.4 ± 2.8) days P orbital = (549.8 ± 0.8) days γ = (- 147.6 ± 0.1) km/s K = (4.9 ± 0.2) km/s e = 0.06 ω = 359.8º A1 sin i = 50.69 R f(M) = 0.00579 M JDmax = (2 448 181.0 ± 5.8) days P pulsation = (352.8 ± 1.1) days γ = (- 147.4 ± 0.1) km/s K = (1.8 ± 0.2) km/s

  10. Period analysis of emission lines • The variability of EW of some spectral lines of AG Dra is well known already for many years. Many authors made a great effort to assign this variability to find running physical mechanisms in the system. Up to now this variability is still one of the great mystery of AG Dra. • For the period analysis of the EW we have used 131 medium dispersion spectra taken at the Tartu Observatory (Estonia). We selected emission lines Hα, Hβ, He I (6678 Å) and He II (4686 Å). In the table are results of period analysis for EW as well as for radial velocities. Periods from EW [days] Periods from RV [days] • Hα 382.8 ± 5.1, 543.7 ± 10.5 ║ 381.5 ± 11.0, 586.5 ± 14.8 Hβ 380.7 ± 5.1, 535.1 ± 13.0 ║ 361.9 ± 6.6, 575.8 ± 17.8 He I (6678 Å) 327.3 ± 7.0, 569.5 ± 12.7 ║ 350.7 ± 5.4, 279.6 ± 3.3 He II (4686 Å) 374.8 ± 4.4, 575.1 ± 16.8 ║ 362.9 ± 9.3, 549.2 ± 11.9 • The circumbinary envelope is modulated by orbital motion, but red giant’s wind can be modulated in addition by giant pulsations. The number of emitted/absorbed particles changes what is possible to detect in EW variability.

  11. Period analysis of emission lines

  12. Period analysis of emission lines

  13. Resonance • We discovered the resonance 14/9 between orbital and pulsation periods. • P orbital = (549.8 ± 0.8) days x 9 = 4948.2 ± 7.2 P pulsation = (352.8 ± 1.1) days x 14 = 4939.2 ± 15.4

  14. Recent cycle of outburst activity • From the LC of the recent activity cycle is visible that the presence of quiescence is questionable (?). • The new cycle of activity has already started during the year 2006 (JD 2 454 000) by double–peaked outburst followed by very deep minimum (energy crisis?). • From the morphology of the historical LC is apparent the alternation of two kinds of activity cycles with duration around 9 orbital periods. The first one is typical by double-peaked and the second by sharp outbursts. • Nevertheless, we believe that the resonance is responsible for the activity in this system and maybe there are many other similar systems with fixed orbital and pulsation periods.

  15. Recent cycle of outburst activity

  16. Conclusions • Thereccurencyofactivities in thesystemevery more or less 14 years. • Twoperiods in AG Drawereconfirmed by independentdata. • 350 dayperiodwasconfirmedasthepulsationsofthegiant. • Orbitalaswellasthepulsationperiodweredetected by variationsofemissionlineEWs. • We have deciphered 2 kinds of activity cycles, double-peaked and sharp. • The new cycleofactivitystarted 500 daysearlierasweexpected. Is it possible to explain such behaviour by larger amount of transferred material? • Nevertheless, many mysteries of AG Dra remain still undetermined.

  17. Thank you very much for your attention „Wild Stars in the Old West“, or We are „Old Stars in the Wild West“

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