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AG Dra - a symbiotic mystery
The 14th North American Workshop on Cataclysmic Variables and Related Objects 15-19 March 2009, University of Arizona, Tucson, Arizona
L. Hric1, R. Gális2 and E. Kundra1
1 Astronomical Institute of the Slovak Academy of Sciences, 059 60 Tatranská Lomnica, Slovak Republic2 Faculty of Sciences, University of P. J. Šafárik, Moyzesova 16, 041 54 Košice, Slovak Republic
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, 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…
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.
10000 12000 14000 16000 18000 20000 22000 24000 26000 28000 30000 32000 34000 36000 38000 40000
JD - 2 400 000 [days]
11.5
11.0
10.5
10.0
9.5
9.0
ma
g
1890 1895 1900 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965
AG Dra
Q1 A Q2 B Q3 C
Long-term photometric behaviour
Long-term photometric behaviour
42000 43000 44000 45000 46000 47000 48000 49000 50000 51000 52000 53000 54000 55000JD - 2 400 000 [days]
10.0
9.5
9.0
8 .5
V [m
ag
]
11.0
10.5
10.0
9.5
9.0
B [
ma
g]
12.0
11.5
11.0
10.5
10.0
9.5
9.0
8 .5
8 .0
U [m
ag
]
1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008
FQ5 EDQ4
AG Dra
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.
45000 45500 46000 46500 47000 47500 48000 48500 49000 49500 50000 50500 51000 51500 52000Julian Date (2 400 000 +)
-160
-158
-156
-154
-152
-150
-148
-146
-144
-142
-140
-138
-136
Ra
dia
l ve
loc
ity
[k
m.s
-1
]
AG Dra
M ikola jew ska et a l. (1995)Sm ith et a l. (1996)Tom ov & Tom ova (1997)
O rbita l ResponsePulsation ResponseO rbita l + Pulsation Response
Fekel e t a l. (2000)
Radial velocity analysis
AG Dra
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0Phase
- 6
- 5
- 4
- 3
- 2
- 1
0
1
2
3
4
5
6
Ra
dia
l ve
loc
ity
[km
.s -
1 ]
pulsation synthetic curvepulsation rad ia l ve locity
Radial velocity analysisAG Dra
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0Phase
-156
-154
-152
-150
-148
-146
-144
-142
-140
Ra
dia
l ve
loc
ity
[km
.s -
1 ]
e llip tica l syn thetic curvec ircu la r syn the tic curveorb ita l rad ia l ve locityorb ita l rad ia l ve loc ity by Feke l e t a l. (2000)
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
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.
50500 51000 51500 52000 52500 53000 53500
JD - 2 400 000 [days]
-170.0
-160.0
-150.0
-140.0
-130.0
-120.0
-110.0
-100.0
RV
[km
/s]
1998 1999 2000 2001 2002 2003 2004 2005 2006
10.0
20.0
30.0
40.0
50.0
60.0
70.0
EW
[10
-1 n
m]
AG Dra
H
50500 51000 51500 52000 52500 53000 53500
JD - 2 400 000 [days]
-220.0
-200.0
-180.0
-160.0
-140.0
-120.0
-100.0
-80.0
-60.0
-40.0
RV
[km
/s]
1998 1999 2000 2001 2002 2003 2004 2005 2006
40.0
50.0
60.0
70.0
80.0
90.0
100.0
110.0
120.0
130.0
EW
[10
-1 n
m]
AG Dra
H
Period analysis of emission lines
50500 51000 51500 52000 52500 53000 53500
JD - 2 400 000 [days]
-170.0
-160.0
-150.0
-140.0
-130.0
-120.0
RV
[km
/s]
1998 1999 2000 2001 2002 2003 2004 2005 2006
0.0
10.0
20.0
30.0
40.0
50.0
60.0
EW
[10
-1 n
m]
AG DraHe II (4686 Å)
50500 51000 51500 52000 52500 53000 53500
JD - 2 400 000 [days]
-190.0
-180.0
-170.0
-160.0
-150.0
-140.0
-130.0
-120.0
-110.0
-100.0
RV
[km
/s]
1998 1999 2000 2001 2002 2003 2004 2005 2006
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
EW
[10
-1 n
m]
AG DraHe I (6678 Å)
Period analysis of emission lines
ResonanceWe 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
42000 43000 44000 45000 46000 47000 48000 49000 50000 51000 52000 53000JD - 2400000 [days]
-160
-150
-140
Ra
dia
l ve
loc
ity
[k
m.s
-1
]
12.0
11.0
10.0
9.0
B [
ma
g]
AG Dra Radial velocity
V
U
B
orb ita l responsepulsation response
orb ita l + pu lsa tion response
12.0
11.0
10.0
9.0
8.0
U [m
ag
]
10.0
9.0
8.0 V [m
ag
]
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.
Recent cycle of outburst activity
49000 49500 50000 50500 51000 51500 52000 52500 53000 53500 54000 54500 55000JD - 2 400 000 [days]
10.0
9.5
9.0
8 .5
V [m
ag
]
11.0
10.5
10.0
9.5
9.0
B [
ma
g]
11.5
11.0
10.5
10.0
9.5
9.0
8 .5
8 .0
U [m
ag
]
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
AG Dra
E1
E2
E3
E4
E5E6
E7
E8 E9 E10
F1
F2
(Q6)
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 undeterminedNevertheless, many mysteries of AG Dra remain still undetermined.
„Wild Stars in the Old West“, or
We are „Old Stars in the Wild West“
