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During two observational seasons of international campaign of YY Her we secured photometric data which covered the primary as well as the secondary minima and revealed unexpected outburst activity of this system.
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Revista Mexicana de Astronomía y Astrofísica
ISSN: 0185-1101
Instituto de Astronomía
Hric, L.; Dobrotka, A.; imon, V.; Petrík, K.; Niarchos, P.; Velič, Z.; Gazeas, K.; melser, L.; Hájek,
P.; Sobotka, P.; Koss, K.; Brát, L.; Lomoz, F.
New clues on the model of yy her after two seasons
Revista Mexicana de Astronomía y Astrofísica, vol. 20, julio, 2004, p. 222
Instituto de Astronomía
Distrito Federal, México
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Editors: G. Tovmassian & E. Sion
RevMexAA (Serie de Conferencias),20, 222–222 (2004)
L. Hric,1R. G´alis,2A. Dobrotka,3V. ˇ
Simon,4K. Petr´ık,5P. Niarchos,6Z. Veliˇc,7K. Gazeas,6L. ˇ
P. H´ajek,9P. Sobotka,10 K. Koss,9L. Br´at,10 and F. Lomoz10
During two observational seasons of interna-
tional campaign of YY Her we secured pho-
tometric data which covered the primary as
well as the secondary minima and revealed
unexpected outburst activity of this system.
YY Her belongs to the classical symbiotic bina-
ries with nova-like outbursts. Recently Mikolajew-
ska et al. (2002) explained the light variability of
YY Her by combining the ellipsoidal changes and
sinusoidal variations of the nebular continuum and
line emission. In 2001 (Hric et al. 2001) we discov-
ered in the binary system YY Her the presence of the
secondary minimum that was indicated, however, by
only three photometric observations from one obser-
vatory. This uncertainty stimulated us to activate
the international photometric campaign for detailed
covering of the light curve during the period of the
expected secondary minimum.
To this campaign were integrated the following
observatories: Star´a Lesn´a Observatory of the As-
tronomical Institute and Beluˇsa Observatory in Slo-
vakia, University of Athens and Kryonerion Obser-
vatory in Greece as well as Valaˇssk´e Meziˇıˇc´ı Obser-
vatory, Vyˇskov Observatory, N. Copernicus Observa-
tory Brno and Ondˇrejov Observatory of the Astro-
nomical Institute in Czech Republic. We obtained
in this campaign a total of 218, 465, 286 and 291 ob-
servational data in B, V, R and I filter respectively,
that cover the interval of JD 2 451 823 - 2 452 877.
There was a successful campaign conducted to
also cover the primary minimum and it produced
some interesting results. The periodic variations of
the brightness are explained by the eclipses of the
components in the symbiotic system. During the
primary minimum ab out JD 2 452 440 we observed
1Astronomical Institute of the Slovak Academy of Sciences,
059 60 Tatransk´a Lomnica, Slovakia (
2Faculty of Sciences, University of P. J. ˇ
Saf´arik, 041 54
Koˇsice, Slovakia (
3Faculty of Materials Science and Technology STU, 917 24
Trnava, Slovakia (
4Astronomical Institute, 251 65 Ondejov, Czech Republic.
5Faculty of Education, 918 43 Trnava University, Slovakia.
6Faculty of Physics, University of Athens, Greece.
7Observatory, 018 61 Beluˇsa, Slovakia.
8Observatory, 757 01 Valaˇssk´e Meziˇr´ıˇc´ı, Czech Republic.
9Observatory, 682 01 Vyˇskov, Czech Republic.
10MEDUZA Group, 616 01 Brno, Czech Republic.
51 900
52 400
52 900
15 .5
15 .0
14 .5
14 .0
13 .5
13 .0
12 .5
12 .0
11 .5
11 .0
10 .5
10 .0
Ma gn it u d e
Fig. 1. BVRI photometry of YY Her secured during
international campaign from 2001 to 2003.
the flares that were later followed by the energetic
outburst in about JD 2 452 700.
At the first glance at the light curve it is evident
that the amplitude of the outburst declines towards
longer wavelengths while for the particular colour
the following amplitudes in maximum were detected:
1.56 mag in B, 1.04 in V, 0.54 in R and 0.20 in I fil-
ter respectively. The monotonic decline of brightness
from maximum was interrupted by an apparent dip.
That coincides with the time of the secondary mini-
In this paper we outlined the idea that the pho-
tometric behaviour of YY Her is possible to describe
consistently by an eclipsing model. This explanation
requires the presence of an optically thick envelope
around the white dwarf with a temperature signifi-
cantly lower than the temperature of the hot compo-
nent. The existence of such an envelope is in agree-
ment with assumptions about steady state burning
of matter accreted on the white dwarf by a red gi-
ant wind. The occasionally observed outbursts are
caused by transfer of blob of matter through L1, by
collision in the ring (the first weaker outburst) and
by following impact on the white dwarf (the second
stronger outburst).
Hric, L., Petr´ık, K., Niarchos, P., Veliˇc, Z., G´alis, R. 2001,
IBVS No. 5046
Mikolajewska, J., Kolotilov, E.A., Shugarov, S. Yu,
Yudin, B.F. 2002, AA 392, 197
Full-text available
The indetermination of light curves behaviour of the symbiotic system YY Her stimulated us to call an international photometric campaign for a detailed coverage of its light curve. Our attention was oriented to cover the period of the expected secondary minimum that was discovered in 2001 tep{hr-hr2001}. The campaign was very successful; it covered the secondary as well as primary minimum affected by a flare in about JD 2,452,440 that was later followed by an energetic outburst (JD 2,452,700). One possibility to explain the periodic variations of the brightness of YY Her is the eclipsing model proposed by tet{hr-hr2003}. Some spectroscopic behaviour still remains inconsistent with this model. In the present work the energetic balances of the afore-mentioned events are calculated and a model with a deformed (non-homogeneous) envelope, surrounding the white dwarf is discussed.
Full-text available
The new photometric observational material of YY Her presented in this paper shows a very pronounced period of 587.54 days as well as its half value. Our results revealed the existence of secondary eclipses of the cool giant. The new ephemeris of primary minima is presented: JD(I,min) = (2450701.6 +/- 1) d + (587.54 +/- 0.5) d * E.
Full-text available
We present and analyze quiescent UBVRI light curves of the classical symbiotic binary YY Her. We show that the secondary minimum, which is clearly visible only in the quiescent VRI light curves, is due to ellipsoidal variability of the red giant component. Our simple light curve analysis, by fitting of the Fourier cosine series, resulted in a self-consistent phenomenological model of YY Her, in which the periodic changes can be described by a combination of the ellipsoidal changes and a sinusoidal changes of the nebular continuum and line emission. Comment: 5 pages, 2 figures, to appear in Astronomy & Astrophysics
  • J Mikolajewska
  • E A Kolotilov
  • S Shugarov
  • Yu
  • B F Yudin
Mikolajewska, J., Kolotilov, E.A., Shugarov, S. Yu, Yudin, B.F. 2002, AA 392, 197