SS 443: multicolour observations 1982-1990
aa r X i v : . [ a s t r o - ph . S R ] N ov Optical Multicolor Observations of the SS 433=V 1343 Aql Microquasar
Abstract
We report BVR photometry of the V1343 Aql= SS 433 microquasar at differentphases of the 13–day orbital cycle for the 1986–1990 observing seasons. The datainclude five complete cycles of the 163 d precession period of the system. We obtainmean light curves and color–color diagrams with the orbital period for all intervalsof precession phases. The optical component of the close binary system (CBS) fillsits critical Roche lobe and loses mass on the thermal relaxation time scale. Gaseousflow show up actively in the system and activity manifestations differ substantially atdifferent precession phases.The collimated relativistic jets perpendicular to the plane of the disk appearto be associated with supercritical accretion onto the compact relativistic object inthe massive CBS, which shows up in the shapes of the light curves at different orbitaland precession phases. An analysis of color indices confirmed the earlier discoveredpeculiarities of the system [1]:(1) A "disk corona"around the compact object.(2) Phase shifts between orbital light curves and different heights of light maximafor different passbands and at all phases of the 163 d precession period. Introduction
The unique astrophysical object SS 433 (V1343 Aql), α = 19 h m s . , δ + 04 ◦ ′ ′′ . (J2000), has been for many years attracting attention of observingastronomers as well as theoretical physicists all over the world. The evolutionary statusof the close binary system SS 433 is the X-ray stage of massive close binary systems(MCBS). The active state of these stars, which are at the X-ray stage of their evolution,is explained by a spectrum of changes in the process of accretion of material on the BS compact object. However, SS 433 is strongly distinguished among other X-raysources by that in the X-ray range radiate X-ray jets, not the accretion disk [2].The high rate of accretion on the compact object ( ∼ − M ⊙ /year) producesthese jets aligned with the accretion disk axis. The velocity of gas in the jets is ∼ , км/с = 0 . c . The orbital period of the system is . d , and the precessionperiod of the disk and jets is . d [3], [4].The main minimum of the orbital light curve corresponds to the eclipse of theaccretion disk by the normal star. In this CBS the optical star is at a later evolutionarystage. It overfills its critical Roche lobe and outflows onto the relativistic objecton the thermal relaxation timescale at a rate of ∼ − M ⊙ /year. This results insupercritical accretion onto the relativistic object [5], because the appearance ofcollimated relativistic outflows of material from the central parts of the thick accretiondisk is a novel and unexpected feature of the supercritical accretion mode.Simultaneous measurements of brightness in several spectral bands will yieldunbiased information for undistorted colors of the object SS 433 and for updatingexisting models of it. Observations
Systematic photoelectric
BVR observations ( W band observations are alsoavailable) were carried out by the author in 1986–1990. They are listed in Table 1,which can be found at(http://lnfm1.sai.msu.ru/ ∼ sazonov/V1343 Aql=SS 433).In these observations the mean errors in the BVR spectral bands were from 0 m .010to 0 m .035.In total we have obtained 1129 individual measurements in 295 nights duringfive years of observations. The observations were carried out with single–channel WBVR photometers on the following instruments: 600–mm reflector of the CrimeanLaboratory of the Sternberg Astronomical Institute (Ukraine, altitude above sea level550 m) with a ′′ diaphragm in the WBVR instrumental photometric system; Zeiss–600 reflector on Mt. Maidanak (Uzbekistan, altitude above sea level 2600 m); 480–mmreflector of the Trans-Ili Alatau Observatory (Kazakhstan, altitude above sea level
760 m).We have used as a radiation detector a FEU-79 photomultiplier tube (S-20 multi-alkali photocathode). The broadband
WBVR system has been used owing to its betterdeterminacy. The system was described by [6].
Reduction to the standard system
In electrophotometric observations of great importance is proper matching ofinstrumental corrections to the standard Johnson photometric system. In jointobservations with T.R. Irsmambetova at the Mt.Maidanak Observatory in 1987–1989the author used the reduction coefficients of the instrumental system in the work on theZeiss-600 telescope (single-channel
WBVR electrophotometer with automatic controlsystem; as a radiation detector a FEU-79 photomultiplier tube was used).The relative spectral sensitivity of the system was rather stable. It was checkedtwice in the observational season (spring–summer and summer–autumn).The coefficients of reduction to the standard photometric system were obtainedfrom repeated measurements of standard stars in the areas SA 107, 108, 111–113 [7].We have the following quantities: B − V = 1 . b − v ) − m . ± . ± . V − R = 0 . v − r ) + 0 m . ± . ± . instrumental bvr stellar magnitudes; BVR stellar magnitudes in the Johnsonphotometric system.To calculate corrections to the determined stellar magnitudes from the knowninstrumental color indices we use the following expressions: B − b = 0 . b − v ) − m . − v = 0 . b − v ) − m . R − r = 0 . v − r ) − m . . In subsequent observations of 1991–1998 (including those at other observatories)we derived the coefficients of reduction to the standard Johnson photometric systemfrom measurements of standard stars in the areas of h and χ Per (NGC 869, the authormeasured 12 standard stars) and NGC 884 (13 standard stars).It should be noted that, owing to the extremely faint brightness of the objectSS 433, short integration time of the useful signal, s − s , and small aperture ofthe telescopes used (Zeiss–600), the W -band data were obtained only at the instantsof the maximum light of the system (T3) with a temporal resolution of 5–6 min on atime interval of 3–4 h (more seldom ∼ m . ,0 m . , 0 m . , 0 m . , 0 m . in the UBVRI bands, respectively.On small instruments (with an aperture of 480–600 mm) in the
BVR bands wehad rms errors estimated from pulse statistics with regard to the background in theperiods of maximum brightness 0 m . , 0 m . , 0 m . in the B, V, R bands. Themean errors of the estimated brightness can reach 0 m . in the W band, 0 m . in the B band, and do not exceed 0 m . in the V, R bands.
Ephemeris
In this work we have used photometric elements of the middle of eclipses (phases φ ) and maxima of the out-of-eclipse brightness (phases ψ ) taken from [8], [1],respectively: Min I Hel=2444332 d .98+13 d .086 . E (phasa φ ) (phase φ = 0 corresponds to the instant of the occultation of the accretion diskby the “normal” star) and Max=T3=2443666 d .29+163 d .34 . E (phasa ψ ) (where T3 is the instant of the maximum separation of the moving emission lines). t is accepted that at this instant ψ = 0 .All photometry was done with respect to the comparison star C1 = Kemp1 [12]and reference star B as in [1]:(C1=GSC 0471-01564 h m s .
66 + 5 ◦ ′ ′′ . J );(B=GSC 0471-00142 h m s .
04 + 4 ◦ ′ ′′ . J ),The star C1 was linked to standards from the list of [9]: U = m . ; W = m . ; B = m . ; V = m . ; R= m . .For the reference star B we took magnitudes: B = m . ; V = m . ; R = m . . Interpretation of the observations
All observational data reported in this paper as well as their interpretation werecompared with similar works of other authors for the last 30 years:[1], [4], [16], [17], [18], [19], [20], [21], [22], [23], [24], [26], [27].Optical light curves of the close binary system (CBS) V1343 Aql = SS 433 obtainedin B, V and R bands for the period 1986-1990 are qualitatively similar (Fig. 1a, 1band 1c).The average depths of the primary minimum (when the accretion disk around thetight companion is occulted by the "normal"star) for this period is 0 m . − m . ,0 m . − m . and 0 m . − m . mag in B , V and R –filters, respectively.The light curves evolve during the precession cycle of the system which maybe attributed to the gas streams activity in the CBS and their interaction with the"floating"accretion disk which spatial orientation drive the direction of the relativisticjets. Phase shifts of the orbital light curves and variation of the maxima heights confirmthe presence of asymmetry of the brightness distribution in the accretion disk. Theyalso support the fact that the backside of the disk (with respect to the orbital motion)is more luminous which was first noticed in [1].The variations of color indices with the orbital and precession periods are wellconfirmed for Min I and Min II by the above mentioned observation seasons (see, for xample, the 1988 data in Fig. 2a, 2b, 2c and Fig. 3a, 3b, 3c).Analyzing the photometric data, we should pay special attention to comparitiveand qualitative analysis with early works of the author.The small amplitude of chanzing of color index B − V is clearly seen on thediagrams of color indexes.Evidently this is one of the consequences of relatively small difference in the B − V color of thermal continuum, radiated by the bright optical star and different parts ofaccretion disk in the system [1], because at temperature higher an 20000 K the color B − V of optical radiation practically does not depend on the temperature.We should note that the character of periodic brightness variations of SS 433 inthese observing seasons is in qualitative agreement vith the date from othei authorsfor the period 1978–1990.This allows us to conclude about some stability of regular brightness variationswith periods d (precession period, amplitude ∆ V = 0 m . ÷ m . ), d . (orbitalperiod, amplitude ∆ V = 0 m . ÷ m . ).In the observing period 1986–1990 a the series 5–7 flares were observed eachobserving season (the object was especially active in 1988) with amplitude frow ∼ m . to ∼ m . in the V band.The flares of optical radiation of SS 433 in these observing seasons are distributednearly evenly on all the phases of precession period.Undoubtedly, the amplitude and shape of the orbital light curve of the system isfunctionally dependent on the precessional phase of the appearance of the relativisticjets in space. This is well visible from the comparison of orbital light curves for differentobservational seasons (see, e.g., 1986 and 1988) at the same precessional phases.In these observations rms errors estimated from pulse statistics with regard to thebackground in periods of maximum brightness were 0 m .040, 0 m .020, 0 m .008 in the B,V, R bands, respectively. Mean errors of brightness estimates may reach m . .In the regular precessional variability the out-of-eclipse CBS brightness alsochanges with the precessional phase, and at instant T3, ψ = 0 . (maximum separationof the relativistic emission lines) the brightness is maximum ,whereas near ψ = 0 . the rightness is minimum. This is visible rather clearly in all graphs of this observationalinterval.These, relatively regular variations are superimposed by unpredictable bursts ofbrightness, which are caused by the active state of the object (these properties ofthe object persisted during all the years of the author’s observations). The brightnessincrease during these bursts is of the order of ∆ V max = 1 m . .The largest fluctuations of brightness take place at instant T3 ( ψ = 0 . ), whichcorresponds to the maximum opening of the disk toward the observer. Near the phase ψ = 0 . , when the disk turns its other pole to the observer, the scatter of the observedpoints becomes minimum; this is well visible from the lower envelope of the light curve.This is especially notable in the seasons of 1987 and 1989.In these seasons the accuracy of the photometric maxima (T3) was not very highbecause of substantial distortions of the orbital light curves due to the activity, whichmay last up to 90 days and longer. The upper level of the light curve is more rarefied,and it is formed by separate flares. The system’s flare activity
On the basis of long-term photometric observations and of their analysis, manyauthors have established that the object SS 433 spends in the active state more than of the time. In the optical range its flare activity manifests itself differently.Sometimes series of flares are observed, and sometimes isolated flares appear with a V band amplitude of ∼ m . and with varying duration.A series of flares can last up to 40% of the precessional period. It results in anappreciable chaos in the light curve geometry. Similar phenomena were observed, e.g.,in 1979, 1980, 1982, and 1986 (literary data) as well in the observations of 1988 (thiswork).In these observational seasons the optical flares of SS 433 are distributed almostuniformly over all phases of the precessional period, as it is visible from the entireobservational database reported here.Note prolonged flares recorded in these observational seasons: he system’s flare activity in 1986 was detected during: JD 2446619, JD 2446625, JD 2446652, JD 2446715.
The system’s flare activity in 1987 was detected during:
JD 2446995, JD 2447016, JD 2447062, JD 2447064, JD 2447082,JD 2447094, JD 2447096.
The system’s flare activity in 1988 was detected during:
JD 2447318, JD 2447423, JD 2447327, JD 2447345, JD 2447360.The flare at observing date JD 2447434 has the following parameters: 0 m . in B -band, 0 m . in V -band, 0 m . in R -band. The ϕ = 0 . , ψ = 0 . in this case. The system’s flare activity in 1989 was detected during:
JD 2447712, JD 2447721, JD 2447734, JD 2447747, JD 2447748,JD 2447798, JD 2447800.
The system’s flare activity in 1990 was detected during:
JD 2448105, JD 2448190–JD 2448191.
The star’s nutation light curve
We also analyze the nutational light curve of the object based on opticalobservations made in 1980–1990 (see paper [1]): we first subtracted the precessionaland orbital variations and phased the residual with the 6.28-day nutational period (Fig.4a, 4b, 4c). The nutational light curve qualitatively resembles a similar light curve from[22]. We adopted the ephemeris for the maxima of the nutational variations from [30].The nutation phenomenon manifests itself as wobble of the relativistic jets in thesystem.Nutation is the third reliably established period in the optical light variations ofSS 433. It is accepted that, irrespective of the CBS precessional orientation in space,total eclipses of the accretion disk by the optical star are never observed in SS 433.All these regularities testify that in the CBS SS 433 there are partial eclipses ofthe precessing accretion disk by the “normal” star.From the analysis of the five–year photometric database we obtain thatthe nutational period remains stable within the errors of the observations and athematical processing.In the interpretation of the observational data of the seasons of 1986–1990(together with unpublished author’s data of 1991–1994 and 1996–1998) attention isdrawn to some data obtained near precessional phases ψ = 0 . ± . (T3, the instantof the maximum separation of the relativistic emission lines), which have found nosatisfactory explanation in the framework of generally accepted other authors’ scenariosof the behaviour of the CBS SS 433 = V1343 Aql. In this paper the author attemptedto explain the above-mentioned observational features of the system.At precessional phases ψ = 0 . − . (and different orbital phases φ ) there areobserved points at which the brightness has an increased amplitude (but they are notflares, because the points relax rather quickly to the mean brightness) as compared toneighboring points within a relatively short time interval and in brightness.As a rule, we chose good photometric nights. We selected statistical photometricdata in three (more seldom in four) spectral bands to refine the already existingcorrelations. Special points on the light curves
Some researchers attribute these features to the nonstationary nature of theactivity of SS 433 and to the strong variability of the mass-loss rate in relativisticjets. However, inflection points are by no means the only singularities to be foundon radial-velocity curves. Other possible singular points include, e.g., points of self-intersection of gas jets in the system [25].Sazonov and Shakura [25] already pointed out the above feature of particletrajectories in the gas flow in a close binary system - i.e., their tendency tointersect (even in the celestial-mechanics approximation). The intersection of ballistictrajectories of flow particles may prove to be one of the factors of the formation ofirregularities in the gaseous jet. The formation of irregularities may may, in turn,result in the scintillation of the "hotspot"that develops where the jet meets the disklikeenvelope of the relativistic object of the close binary system or where it intersects withthe neighboring trajectories of the jet flow. Possible cases include the the collimated et trajectory portions located near time T3 (or, rather, at phases ϕ =0.03-0.15).The authors of papers [32] and [33] and review [34] point out various instabilitiesof the gas flow in the vicinity of the compact object in the CBS and indicate that thegas-flow instability shows up, among other things, as quasi-periodic oscillations of themass accretion rate M and the rate of change J of the angular momentum of thematter located near the secondary component of the CBS. The above authors used thecomputed density, velocity, and temperature fields to calculate the emission profiles ofthe H??? line, and found the wings of these lines to form near the accretor and theirbroadening to be determined by the high velocities of the gas flow in the accretingmatter and disk. The gas velocities near the accretor were found to exceed the averagegas velocity in the system by a factor of more than 10 [33]. This result agrees wellwith the interpretation of our optical observations.Furthermore, we also established in our earlier papers that gas in the jet isconcentrated in individual clouds [35], [36], [37], in line with the above scenario thatexplains the observed data points with a somewhat excessive amplitude at precessionphases ψ =0.02-0.16 (and various orbital phases ϕ ) of SS 433. Rapid variations of the object
We also performed observations on time scales corresponding to rapid variability,ranging from 90 to 180 s per single exposure. We studied the object over time intervalsranging from 1 to 2.5 hours. The authors of [39] concluded, based on the results ofx-ray, optical, and radio observations made with a temporal resolution of 16 s, thatindividual clouds show up at all wavelengths.The existence of fast variability in the brightness of the object SS 433 on timescalesfrom several minutes to 20–30 min was established and confirmed in [13], [14], [15]. Atthe present stage of the study of this object we need high - precision photometric datafor updating the existing model of the fast variability and for revealing still unknownmechanisms of its origin.The observed brightness difference in all spectral bands within the sameobservational night can be explained physically by fast variability with a timescale f 10–30 min and amplitude from m . to m . [22], [14], [10].Parallel photometric and spectral observations of the research team of the SpecialAstrophysical Observatory [13] have shown that the fast photometric and spectralvariability on timescales ∼ B bandis deeper than in the other bands, especially at precessional phases ψ = BVR or WBVR bands) have confirmed thatthe dependences of ( B − V ) on B and ( V − R ) on V are fulfilled unambiguously:the ( B − V ) and ( V − R ) color indices decrease with increasing B and V brightness,respectfully.The authors of [13] have drawn a conclusion about the causes of fast variabilityas a result of the passage of the relativistic jets through the circumbinary envelope. Atshort timescales the fast variability is explained by the discrete character of the jet,which consists of separate ionized gas clouds.Rapid variability was observed in all photometric bands (variations were found inthe BVR data obtained by the author of this paper and in the U BV RI data obtainedin [1]). The authors of [1] found that orbital light variations exhibit phase shifts andthe heights of the maxima (amplitudes) differ for different passbands and differentphases of the 163 - day period.The amplitude of physical intranight variability of SS 433 may amount to about m . mag or more (see plots for the 1988 season).The object shows persistent light fluctuations in the R and I bands ( [1] and thispaper) on time scales of 60 - 90 s. Recent coordinated optical and x - ray observationsfound such fluctuations in the optical R band on time scales of about 10 s as a resultof relatively [40].The outbursts that occur rather frequently in the system studied produceconsiderable distortions in the orbital light curves observed during every season. The
988 season is especially remarkable in this regard.According to published data, both relativistic hydrogen lines and stationary linesexhibit rapid variations. Relativistic hydrogen lines have a complex multicomponentstructure, which varies from night to night. The objects shows variations in the R band (see [1] for similar observations in the R and I bands). The variations involvedbrightness increases amounting to . m and . m in the R and I bands, respectively,over a 10 - minute long observation (during the same night).Such variations were recorded several times in U BV RI - (1980 - 1986) and
W BV R - band (1986 - 1990) observations: JD 2445249, JD 2446302, JD 2446995,JD 2447082, JD 2447096, JD 2448053. According to the classification proposed in[22], the "blue" component of emission was present in this case with a color index ofV - R=1.9, whereas the "red" emission component was absent.
Conclusions
Our interpretation of the data set obtained during the entire 1986 - 1990 observingperiod leads us to the following important conclusions:1. One of the new results of this work is that we obtained simultaneous andhomogeneous multicolor observations of the object in the
W BV R photometric bands.We obtained the orbital light curves of SS 433 at the precession phases of ψ =0.0 - 0.1, ψ =0.1 - 0.2, ψ =0.2 - 0.3, ψ =0.3 - 0.4, and ψ =0.4 - 0.5, thereby extending substantiallyour cycle of works that we began earlier [1], [25].2. The manifestations of the activity of the system differ rather significantly atdifferent phases of the 163 - day precession period.3. During all the observing years the light curve exhibited persistent Min I and MinII, which have the standard depths typical for the precession phase considered in all four- to - five photometric bands observed: the minima do not go below m . , m . ,and m . in the B , R , and R passbands, respectively (in my other papers I reportobservations made in the U and W bands using intermediate telescopes [1], [25], [38]).4. At these times the primary eclipses Min I and Min II appear as rather sharpand deep dips seen against somewhat excessive brightness. The light curve is somewhat symmetric - by about 0.006 periods - with respect to the theoretical Min I at timeT3. In the quiescent state the orbital light curve covers a single wave per period atthis phase.5. The average magnitude of the system is somewhat brighter than its usual level,by . m − . m .6. The observed phase shift of the BV R light curves (and also in the U and I - band light curves obtained in 1996) whose magnitudes and signs differ at differentprecession phases: the eclipse in long - wavelength bands occurs later than in short -wavelength bands ( ψ =0.10 - 0.12), i.e., first the cooler (dark) regions of the accretiondisk are eclipsed, and only then hotter and brighter regions; however, the situation isreversed at the ψ =0.40 - 0.45 phase:6.1. We thus have well - defined phase shifts in the light curves in allthe photometric bands observed ( U BV RI ), which are unambiguously related towavelength.6.2. Moreover, the maxima (Min I, Min II) are clearly asymmetric at precessionphases ψ =0.10 and ψ =0.60, and this asymmetry is especially apparent in the B and V bands. It also follows from the asymmetry of the light maxima that at the precessionphase of ψ =0.10 (and, less conspicuosly, but clearly enough, at the phase of ψ =0.60)the brightness of the leading part (with respect to orbital motion) of the accretion diskis lower than that of the trailing part.6.3. Both these features (6.1-6.2) conclusively indicate that the accretion disk ofthe primary component of the CBS is irregular and asymmetric, and, more generally,that so is the structure of the accretion formation of the entire SS 433=V1343 Aqlsystem.7. The (W-B), (B-V), (V-R), and (R-I) color indices are functionally dependenton W, B, V , and R -band magnitudes. These linear relations strictly obey the pattern:color index decreases with increasing brightness.8. The source of rapid variations in SS 433=V1343 Aql does not disappear in thesystem’s activity stage and is not eclipsed.9. The brightness amplitude increases towards shorter wavelengths for all Kinds f variations of the binary (orbital, precession, nutation variations, rapid variationswithin a night of observations). Список литературы [1] N.M. Shakhovskoi , A.N. Sazonov // 1996, Pis’ma Astron. Zh/” , , №8, p.580-586.[2] G.C. Ctewart , H.C. Pan , N. Kawaii // // , 824 .[4] A.M. Cherepashchuk // ,183.[5] N.I. Shakura , R.A. Sunayev // , p.337-355.[6] V.L. Straizys // // , p.627.[8] A. Wittone, L. Rusconi, G. Sedmak et al. // , p.109.[9] Th. Neckel ,R. Chini // , p.411.[10] A.N. Sazonov, Three- colour Photometry of SS 433 = V1343 Aql in 1986-87 // // , 761 .[12] J.C. Kemp , G.D. Henson , D.I. Krauss et al. // , p.805.[13] I.M. Kopylov, R.N. Kumaigorodskaya, N.N. Somov et al. // , p.690.
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29] T. Korhonen, V. Piirola, A. Reiz // // ,№ 2, P. 240.[31] I.M. Kopylov, R.N. Kumaigorodskaya, N.N. Somov, T.A. Somova, S.N. Fabrika // , vyp.4, P.786.[32] D.V. Bisikalo, A.A. Boyarchuk, O.A. Kuznetsov, Yu.P. Popov, V.M. Chechetkin // , P.560.[33] D.V. Bisikalo, A.A. Boyarchuk, O.A. Kuznetsov, V.M. Chechetkin // , P.717.[34] S.H. Lubow // // , p.135.[36] I.S. Shklovskii // , P. 554.[37] S.A. Grandi, R.P.S. Stone // , p.80.[38] A.N. Sazonov // // // orb. phase B SS 433 (1986−1990)
Рис. 1: The 1986-1990 B-band light curve folded with the period P = 13 d , orb. phase V SS 433 (1986−1990)
Рис. 2: The 1986-1990 V-band light curve folded with the period P = 13 d , orb. phase R SS 433 (1986−1990)
Рис. 3: The 1986-1990 R-band light curve folded with the period P = 13 d , B−V B SS 433 (1988)
Рис. 4: The 1986-1990 B–V color of SS 433 as a function of B-mag18 .8 2 2.2 2.4 2.6 2.8 313.613.81414.214.414.614.81515.2
V−R V SS 433 (1988)
Рис. 5: The 1986-1990 V–R color of SS 433 as a function of V-mag orb. phase V − R SS 433 (1988)
Рис. 6: SS 433 (1988): V-R as a function of the orbital phase19 ksi (163) B SS 433 (1986−1990)
Рис. 7: The 1986-1990 B-band light curve folded with the precession phase20 ksi (163) V SS 433 (1986−1990)