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symbiotic stars are interpreted as interacting binaries consisting of a cool visual primary and a compact secondary component accreting matter from the atmosphere of its companion . as a result of accretion
the compact object undergoes multiple outbursts accompanied with intensive mass ejection in the form of optically thick shells , stellar wind , single discreet ejections ( blobs ) as well as collimated bipolar jets .
the system z and is considered as a prototype of the classical symbiotic stars .
it consists of a normal cool giant of spectral type m  4.5 @xcite , a hot compact component with a temperature of 1.5@xmath6 k @xcite and an extended circumstellar nebula formed by the winds of the stellar components and partly photoionized by the compact object .
z and has underwent several active phases ( after 1915 , 1939 , 1960 , 1984 and 2000 ) characterized by repeated optical brightenings , partly realized as a result of a strong redistribution of the energy of the compact object .
the energy redistribution was caused by intensive loss of mass @xcite .
the last active phase of z and began in the end of august 2000 and continues up to that time .
the system underwent four consecutive optical brightenings , whose maxima were in december 2000 ( @xmath7 mag ) , november 2002 ( @xmath8 mag ) , september 2004 ( @xmath9 mag ) and july 2006 ( @xmath10 mag ) ( * ? ? ? * our @xmath11 data ) .
spectral indications for intensive loss of mass were obtained during three of them , whose maxima were in 2000 , 2002 and 2006 .
the uv line 1117 had a variable p  cyg profile containing one or two absorption components indicating velocities of 0300 kms@xmath1 in november and december 2000 . in all cases , however , the absorption reached its maximal depth in the velocity interval 050 kms@xmath1 @xcite . during the same time the profiles of the lines were of type p  cyg too and the absorption component indicated moderate velocities of the flow of 50100 kms@xmath1 @xcite . during the period september 
november 2002 the line 4686 , from its side , had two component emission profile consisting of a central narrow component and a broad component indicating stellar wind with a velocity of 11001200 kms@xmath1 @xcite .
@xcite concluded about intensive loss of mass by the compact object , realized at that time too , analyzing the wings of the line h@xmath0 .
our data show that the lines of and had p  cyg profile with absorption component indicating moderate velocity during the period july 
september 2006 . in some cases
the components were more than one . in july , however , these lines had additional absorption component with a high velocity of about 1400 kms@xmath1 as well . moreover , during the period july  september the h@xmath0 line had additional emission components , placed on the two sides of its central peak and having velocities of 12001500 kms@xmath1 .
the appearance of the h@xmath12 line was similar .
the additional emission line components of z  and were already reported by @xcite and @xcite , which consider them as indications of bipolar jets .
we suppose that all components indicating high velocities appear in bipolar outflow from the outbursting hot object .
the 2006 outburst of z  and is a first one , when optical bipolar outflow from this system was observed .
our note is devoted to this phenomenon , where preliminary results of one study of the h@xmath0 line are treated .
the region of the line h@xmath0 was observed on eight nights in july , august and september 2006 with the photometrics ccd camera mounted on the coude spectrograph of the 2 m rcc telescope of the national astronomical observatory rozhen . during the last of these nights besides the region of the line h@xmath0 , that of h@xmath12 was also observed .
the spectral resolution was 0.2 px@xmath1 on all occasions .
some of the exposures were comparatively long to obtain better ratio signal to noise of the continuum although the central emission component of the h@xmath0 line was saturated in some cases ( table 1 ) .
ever when we made more than one exposure per night , the spectra were added with the aim to improve the signal to noise ratio .
the iraf package was used for data reduction .
the additional emission components were fitted with a gaussian to measure their radial velocity and equivalent width .
it was made only for those spectra where they are intensive enough ( table 2 ) .
the inner uncertainty of the equivalent width in these cases is not more than 50 per cent .
the h@xmath0 flux was obtained using the equivalent width and the @xmath13 flux supposing that it is practically equal to the continuum flux at the position of this line . for this aim
we used the @xmath13 magnitudes of @xcite and @xcite taken very close to the time of our observations .
the uncertainty of the continuum flux is not more than 10 per cent and that of the line flux  not more than 50 per cent .
the fluxes were corrected for an interstellar extinction of @xmath14 according to the approach of @xcite .
it was used the ephemeris @xmath15 , where the orbital period is based on both photometric and spectral data @xcite .
.journal of observations .
[ cols="<,^,^ , < " , ]     this value is too great compared with the observed mass - loss rate of the hot compact component of the symbiotic systems during their active phases , which is most frequently about 10@xmath16 10@xmath17 m@xmath5yr@xmath1 @xcite .
the great value follows from our assumption for spherical symmetry of the outflowing material and the observed high velocity
. it can be in reasonable limits if the material does not flow in all directions , but only in some of them , related to areas with small angular sizes .
the material can flow mainly in the polar areas , if it is prevented in equatorial one for example by an accretion disk . in this case
the velocity in the polar areas increases to provide the mass ejection there .
this supposition can be related to the existence of two kinds of absorption components indicating very different expansion velocities .
we can assume that the dip feature of h@xmath0 is due to mass flow in the orbital plane with a moderate velocity .
the flowing material , however , is prevented by the accretion disk and the direction of its motion changes . in this way it is ejected in a direction , perpendicular to the plane of the disk , like the gas flowing in that direction .
all of the material gives rise to the high velocity components of the h@xmath0 line .
thus the blue shifted absorption indicates motion probably in the front part of the wind which is projected on the stellar disk .
then we can suppose that the weak emission feature with a velocity of 1500 kms@xmath1 appears in the nonocculted part of the back component of the wind .    as it is seen from the evolution of the spectrum in figs .
[ ha_log ] and [ abs - em ] the blue - shifted absorption component disappears and an emission rises .
thus two emission components on the two sides of the central peak form in july . the disappearance of the blue - shifted absorption and the rise of an emission is most probably due to decrease of the flow rate and/or increase of the number of the emitting atoms in that part of the wind which does not project on the stellar disk .
if the absorption is related to the inner part of the wind and the emission  to its outer one , not projecting on the stellar disk , the evolution of the spectrum shows that the velocity in the front wind component ( stream ) decreases with the distance to the star .
it is seen in fig .
[ ha_log ] that the emission on the long - wavelengths side of the central peak increases compared to the continuum .
it is seen also in the figure that the velocity of the line decreases from about 1500 kms@xmath1 to about 1200 kms@xmath1 .
taking into account the fact that the distance covered by the emitting gas increases with time it can be concluded that the velocity in the back stream decreases with the distance to the star too .
the h@xmath12 line had similar emission components , as it is seen on the unique frame taken in its region in september .    to know the energy emitted in the h@xmath0 high velocity components as well as the quantity of the emitting gas we calculated their line flux and emission measure .
the emission measure was obtained supposing that the gas medium is optically thin and has a constant density .
it is not possible to obtain the electron temperature and the electron density in the region where the outflow components are emitted from observation since we have no indication about the appearance in this region of certain lines giving information for these parameters .
we suppose that the electron temperature is 20000 k and the mean electron density is about 10@xmath18 @xmath3 in the nebular portion of the streams .
then we used recombination coefficient of 5.956@xmath19 @xmath20s@xmath1 for case b , corresponding to these temperature and density @xcite .
we adopted a helium abundance of 0.1 @xcite and a distance to the system of 1.5 kpc according to @xcite .
for the calculation of the emission measure we need to know the state of ionization of helium in the emitting region .
the line 4686 was very weak ( as it is seen from our data ) during the period of our observations which means that singly ionized helium is dominant in the circumbinary nebula at the times close to the epoch of the maximal light .
that is why we assume the state of ionization to be he@xmath21 in the region of the streams .
the line flux and the emission measure are listed in table 2 .
these data propose that the ejected matter increases till august 12 and after that decreases , which is probably due to decrease of the flow rate .
we calculated also the mass of the nebular portion of the streams on the basis of the greatest emission measure observed on august 12 .
it turned out to be about 8@xmath4 m@xmath5 for the front stream and 6@xmath4 m@xmath5 for the back one .
we present results of high resolution spectral observations carried out in the region of the line h@xmath0 of the spectrum of the symbiotic binary z and close to the light maximum of its 2006 optical brightening .
the line h@xmath0 had a blue - shifted absorption component with a velocity of about 1400 kms@xmath1 at the time of maximal light in july .
this line had also additional emission components placed at 12001500 kms@xmath1 on the two sides of its central peak in july , august and september .
the line h@xmath12 had similar components as far as it is seen on its unique frame .
it is supposed that both the absorption and the emission components are signature of bipolar wind outflow from the hot compact object in this system .
the different velocities observed at different spectra indicate probably the decrease of the flow velocity .
the energy flux of the outflow components of the h@xmath0 line and their emission measure were calculated on the basis of @xmath13 photometric data from the literature taken during the time of the spectral observations .
these quantities increased till august 12 and after that decreased , which is probably due to diminution of the flow rate .
the mass of the nebular part of the streams on august 12 was obtained , which amounts to 68@xmath4 m@xmath5 .
the authors thank their colleagues dr . h.
markov , dr . d. kjurkchieva , a. ivanova , b. spassov and d. dimitrov who contributed to obtaining the observational data .
they are also grateful to the referee prof .
j. mikolajewska whose remarks contributed to the improvement of the paper .
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high resolution data in the region of the line h@xmath0 have been obtained at the time of the light maximum and after it of the 2006 optical outburst of the symbiotic binary z and . 
 a blue - shifted absorption component indicating outflow velocity of about 1400 kms@xmath1 as well as additional emission components with similar velocities , situated on the two sides of the main peak of the line were observed during that time . 
 it is suggested that all of them are spectral signature of bipolar outflow , observed for the first time in the optical spectrum of this binary . the emission measure and the mass of the nebular part of the streams 
 were estimated approximately , which reached values of up to about 6@xmath2 @xmath3 and 8@xmath4 m@xmath5 .    
 [ firstpage ]    binaries : symbiotic - stars : mass - loss - stars : winds , outflows - stars : individual : z and .