AG Dra - a symbiotic mystery The 14th North American Workshop on Cataclysmic Variables and Related Objects March 2009, University of Arizona, Tucson, Arizona L. Hric 1, R. Gális 2 and E. Kundra 1 1 Astronomical Institute of the Slovak Academy of Sciences, Tatranská Lomnica, Slovak Republic 2 Faculty of Sciences, University of P. J. Šafárik, Moyzesova 16, Košice, Slovak Republic

Abstract AG Dra is well known bright symbiotic binary with the white dwarf and pulsating red giant. Long-term photometry monitoring and new behavior of the system are discussed. In the system of AG Dra were detected two periods of variability. The longer day is connected with orbital motion and the shorter one was interpreted in our older paper as the pulsation of the red giant. Moreover we found resonance between both periods. We understand that this resonance can produce an activity of the system. Nevertheless, many questions are still open and it is also worth noting them: where is the recent stage of quiescence?, why the maximum of brightness during the year 2008 was occurred 60 days earlier?, how many types of outbursts are present in the system?

Outline AG Dra – overview of the system Long-term photometric behaviour (historical LC, quiescence and activity, UBV photometry, period analysis, discovery of 350 days period, R photometry) Radial velocity analysis (detection of 550 days period, confirmation of 350 days period, symmetric curve – radial pulsation) Period analysis of emission lines (RV and EW, EW variations with orbital (orientation of the system) and pulsation periods (transfer of angular momentum and density changes to the wind)) Resonance as a general cause of activity (14/9 resonance between 550 days and 350 days periods) Recent cycle of outburst activity (2 kinds of active phase, missing quiescence phase, shift of maximum brightness, missing last outburst) Conclusions

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

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, T eff = 4300 K and the mass M G = 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…

Long-term photometric behaviour Robinson 1969 collected photographic observations of AG Dra from 1890 to 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 (Q 1, Q 2...) Our period analysis confirmed 550 days orbital period and discovered new 350 days period, interpreted by pulsations of red giant.

Long-term photometric behaviour

Radial velocity analysis Radial velocities from: Smith et al. 1996, Mikolajewska et al. 1995, Tomov and Tomova 1997, Fekel et al 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.

Radial velocity analysis

JD max = ( ± 2.8) days P orbital = (549.8 ± 0.8) days γ = ( ± 0.1) km/s K = (4.9 ± 0.2) km/s e = 0.06 ω = 359.8º A 1 sin i = R  f(M) = M  JD max = ( ± 5.8) days P pulsation = (352.8 ± 1.1) days γ = ( ± 0.1) km/s K = (1.8 ± 0.2) km/s

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 ± 5.1, ± 10.5 ║ ± 11.0, ± 14.8 Hβ ± 5.1, ± 13.0 ║ ± 6.6, ± 17.8 He I (6678 Å) ± 7.0, ± 12.7 ║ ± 5.4, ± 3.3 He II (4686 Å) ± 4.4, ± 16.8 ║ ± 9.3, ± 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.

Period analysis of emission lines

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

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 ) 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.

Recent cycle of outburst activity

Conclusions The reccurency of activities in the system every more or less 14 years. Two periods in AG Dra were confirmed by independent data. 350 day period was confirmed as the pulsations of the giant. Orbital as well as the pulsation period were detected by variations of emission line EWs. We have deciphered 2 kinds of activity cycles, double-peaked and sharp. The new cycle of activity started 500 days earlier as we expected. Is it possible to explain such behaviour by larger amount of transferred material? Nevertheless, many mysteries of AG Dra remain still undetermined Nevertheless, many mysteries of AG Dra remain still undetermined.

„Wild Stars in the Old West“, or We are „Old Stars in the Wild West“