- University of Nigeria Research Publications
NWEZE, Simon Samson Author PG/M.Sc./87/5481
Radio Emission from SS 433 Jets Title
Physical Sciences Faculty
Physics and Astronomy Department
June, 1989 Date
Signature
TITLE PAGE
RADIO EMISSION FROWSS 433 JETS
NIJEZE STMON SAMSON (PG/M.~C/87/5481)
DEPARTMENT OF PHYSICS AND ASTRONOMY UNIVERSITY OF NIGERIA NSUKKA, NIGERIA
M.SC PROJECT REPOR'i', 1989 CZRTISICATLON
I,Jo!ezs, Simon Samson, a Pos tqraduate student j.n the 13ep;llr4ritent of Physics and Astronomy and with the
Zegistrak5.on :<~rrnherPG/Ffm:Sc/87/548T has ~af:isfactorily. com~lntedthe requirements for course and research work for th? dcqrw of Waster of Science (II'~.SC. ! ?.n Phlrsics.
The :mrk ernbodid in this project r~!:lortts oriqinal
~ndhas not been suhrnitted in part or flu11 for any other di~Tornaur deqree of this nr any other
Un-iv~rsi ty,
O-..".j,*~*.....l....*.. Dr. $. IJ. ~k&ke Dr. P,N. Okeke, Head of Dcp7.r-tment Supervisor " DEDICATION
This project is dedicated to
my twin hildren
Eyiuche and Amauche-Chubu: TABLE OF CONTEN!t'
TITLE PAGE am o
APPROVAL PAGE .a.
DTDICATION maw TA3LE OF CONTENTS
ACSTRACT .ma ACKNO\dLEDGEMENT
CHAPTER I 1.00 GE?!ERAL INTRODUCTION 1010 Detection and Identification of the
Object At Different bv'avelcncjths OD. Otl-er Unique Objects Within the Galaxy Cyqnus X-3 ... Scnr~?-usX-1 ... SS 433 And Classes of Variable Ern?-ssion Sources ... DeTlni tion of Terms . .
CI-IAPTER I1 THE GENERAL PROPE2TIES OF SS 433 The Radio Structure of SS 433 and those of Zxtraqalactic Sources ., . .. TI13 !?adio Structure And Radio Flares of SS 433 .a* .. . SS 433 And the Associated Supernova !'.emnan t (Y50 ) ...... The Emission Variahj-lity of SS 433 .. . ';_'heRadio Emission (VdriabF 1; ky 1 ... Tlqc O~tlcal.Emission {Varia' ; lity) .. . '?'re X-Xay and Gamma-liay Oli.;crvatlons.. . 3, (30 Tile f;adio Jets of S5 433 ... 38 3.10 SS 433 Jets And Radio ?mission-
3.20 The Proton Beam CollisLon Model And A~plicationTo SS 433 -.. 58 3,30 Observed And Derived Paramaters or ss 433 ... 60 Eskimatirlq The Radio Fl.ux Density or SS 433 Jets At Different khvelenqths 60 3.50 Estlrnated And Observed Radio Flux Density of SS 133 Jets ... 64 CflA'3TER IV
4mOQ DISCUSSION OF RESULTS a a 66 4-03 Vzriable Magnetic Fields 4.02 S tell-ar Winds 4.03 Vzriation In Gravitatic,nal Potel
CHAPTER V 5.00 SUI?II.IARY AND CONCLUSION APPENDIX I ; The Ililliarc-St a-Id Structure of SS 433 ;it Differen. Observations APPEhlDIX Ie : X Typical Extende( Radio Structure of SS 433 Introduction to Appendix I1
istic Flux Density AIJ:JENDIX IIf : AnaLysea Lnalvlaut , Fl-xe Events from the Statistic; &.ta of Appendix IT -11 a P- i ABS TRACT
I ttempt is mkde to explain the origin of radio emission from
SS 433 bets using f$e inelastic proton beam collision model of I Anyakoha et a1 ( 19 88) . lhe estimated radio flux cknsity obtained compared favourably well with observed values. This result has considerably il luminated two irnportan t astrophysical iss-s . Firstly, the unique nature of variability of rdio emissicn from
SS 433 is suitably accounted for. Variability in the jet flux densi ty could be mainly attribu red to corre sponding vari ations in the thermal proton number density in the galactic medium along
the jet pa ths.
Finally, the general specula tion that astrophysical jets
(both galactic and extragalactic) may be governed by common dynamical processes is supported by this result.
viii . ACICN OWLE DGEME NT
I I I i I lljtroughout tfi4 period of this wo,rk, I got various assistance I in one form or the other from many people too numerous to receive
individual mmtim even if I could identify all of them.
Nontheless, I an indebted to Dr. P .N . &eke, my supervisor, for his invaluh le assis tmce adencouragement. My special
thanks go to Dr. W.M. hyakoha for his very useful coumtents and
suggestions. I am also grateful to Professor S .E. Ckoye,
Dr.(Mrs) L.I. Otluora, Dr. C.H. McGruder 111, and others in the
Department of Physics and Astronony , University of Nigeria,
Nsukka, whose cmtributions helped to make this work a reality.
Furthermore, I wish to thank the following, D.McCarthy,
U.S. Naval Research Laboratory, Washington D.C. ; R.T. S hilizzi,
Netherlands Foundation for Radio Astronomy, bingeloo; and I.
Fe jes , Institute of Geodesy, Cartography, and Remote Sensing,
Hungary; all of who made certain material8 available to me on 9.
Finally, I me a great deal to the Almighty God for His
guidance. ; I I. I a)servati.onalI :asults and Theoretical Predictions by several authors show that SS 433 resenbles, in many respect, sorue powerful extragalactic radio sources. The Bright core and its aligned s tructure , the highly collimated je t-features , and the flux Qnsities observed in both radio, optical and x-rays spectrum are all similar to those of some extragalactic radio sources (see for example Walker et al, 1981, Davidson and
McCray, 1980, Rees, 1982, Lamb et a1 1983, Wieler, 1983, Meurs, 1987, Vermeulen, 1988) . Thus, it is the view of many authors
that SS 433 may offer unpreaedented clues to the'nature of as tro- physical jets, in general.
The mast striking difference between SS 433 and most extra- galactic .radio sources is that the galactic source, (SS 433) , is associaed with time dependent and spatial variab ilities velocirty (v.) md,'k&line of sightinclination of the jets (8) I J I! 11 precisely wown -Rue to various limitations already I out by Lind and Blandford ( 198517- as it-"is- in the case of the galactic source - SS 433.
Several sugges tiom and mdels have been put forward to
explain the possible jet emission me&anism &d its intriguing
vari&ili ty . Some of them however were compounded with unresolved issues between theory and observations (see for exaqle Grindlay
et al, 1984, Davidson and McCray, 1980, Lipnunov and Shnkura,
1982, Begleman et al, 1980, Romney et al, 1987, Shapiro et a1 1982) .
In this project report, an attempt is made 'to check if the
inelas tic pro ton beam collision mode 1 of Any akoha e t a1 ( 19 88) vhich seems to explain the observed flux densi ties from some
jets of extragalactic radio sources will also explain the
observed flux densities from SS 433 radio je ts. Effort is also
made to dhcw' how the mob 1 explains the observed radio emission
variability from the jets of the object.
. CI " -tection and Identification of the Ob iect At Different -ve le ephensm and Sanduleak ( 19 77) reported a sumy of the
dh they aimed to dete&ne the 'sou position of the star was then given as:
RA(1950) = 19" 09~21.~28, dec(1950) = + 04~53154l1.04. It was believed that this coordinates differ significantly from those of some sources associated with a supernova remnant
1,150 (G 39.7, - Z~.O). Stephenson and Sanciuleak in their con- clusion noted that the source is variable on the basis of the fact that the star ought to have been detected in their previous surveys if the emission intensity had been constant.
David and T4urdin (19783 describing an tnusual emission line star, su? 1 associated with a variable point radio source. r r lt=y L C!XJL ILCU 11 ~ttXullard Radio As tronorny-Observatory
(n~rcnna1rnrnr7iini ratinn \ whi rh nave the nnci ti nn nf Ryle et a1.( 1978) investigated a point radio source and suggested that it is a new class of radio star associated with supernova rewants. I t was their belief that they had detected another point radio source of tfie same class as 1909 + 48,giving
their own posi tion as 19 10 + 052 but maintaining that they are all as socia ted with the same supernova reman t-WSO.
It was Sequis t et a1 (1978) who reported the detection of a variab le radio emission from the peculiar Hd emitting star -
SS 433. Ihe detection of radio emission from this object was the only successful radio survey of about benty objects from the list des cribed as 's trong' in Q emission. One year later,
Seaquis t et a1 ( 1979) repor ted again the discovery of an unusual emission line star associated with a variable unresolved radio source 1909 + 04, suggesting that all the sources may be associated with the same supernova remnant - WSO .
At virtually the same time, Ryle et a1 (1978) reported the result of observations of a number of compact radio sources poss ib ly associated with supernova remnants . One of the sources was 1909 + 048 whi& they specifically proposed to be associated with SS 433 and which is considered to be a supernova remnant W50
(G 39O.7, -2 0 .0). and V1383 Aql. CKholopov et a1 13Gll. Naving been i(1cntified as nnaVLLb rnmmnnbVIIIIIIVI. Lp=Jifi ULL-V YVHAkbCnvvFpn J1l;n 4979,-L it is now known that the radio, o~tlcaland X-ray names refe.r'
---- -l.r--L-- ' - -2 ---.- -- . CCJVLUL~I~L~SIS Trven ~ts:
0 1 = 39O.7, b = -2 ,2 (de Vegt i
shall hencefort refer to as SS
2-3 Other Unique Objects NithL.. ,.. - ,,,,.., ,
There are t]lree galactic objeck- - 1-2 -c&-nUl. LC1I I1C:aC.Lel~nnr: JUCUknA 43=.-. ..-4UI ILqUI--.to - due to certain properties and/or bethaviours characterised by chaotic variab.ility in all the spec:Ira1 wavelengths, These objects are SS 433, Sco x-1 and Cyg X-3, They are usually referred to as x-ray binaries in the x-ray wavelengths. SS 433 is considered to be the only source that shows rich iet features
Ln aII b~3velengLhsfrom radio to gawrna rays o x-4 end Cyg x-3 helncj evident only in the radio region, Models to cxylain the em.ir,sions from them (x-ray binaries) Invoke a close binsry system ii~c!.udincj a compact object; the eni thc system beincj rxplained as accretion onto a cc rotation,
1 Cyqnus X-?,
At A1gonquS.n Radio Observatory .Ln C.I ~Cario,an x-ray ,..)urce,
Cyr~X-3 discovered in 1366, was recorc!cd as having sudL.~enlybecome one of the briohtest source in radi3 sky (Gregory et a1 1972).
i'I15.s was consic!ered as an astonishiqg discovery for the fact
that the ftrst detection of radio eqission from Cyg X-3 was ann-
ounced onIy tw3 months earlier. It was clear from observations
Cy5 X-3 can be cxtrcmely variable cn a time scale of hours.
Uan discovery, communications between obser-
high-pitch. Cyg X-3 is today described as a
unique oh jcc t thougl-I at a longer distance (- 10 kpc Dickey 1983)
than SS 433 (oskimat:ed ta he at a distance of - 5-5 kpc), During qiant retdio outbursts, it can attain a peak radio n -1 luminosity of 10' '5 erqs (Gregory et a1 ?.972). A recent radic
outburst sho1:~cd eviciencc for jet-like emission expandin2 at
5.t: a1 l3E3 1, O:~ticalflux from Cyg X-3
-. -. . -- , . , . cannot, howevcr, he observed Because lntersteller extlnctlon
(visual zabsor!3tion) S.s believed to he too high for visual light
The radio flux density of the source varies sporadically
and In some c3ses dramatically in a short ti.rne span (e,g,Hjel l-i~~inc
2nd Hermann 11?72), A long term observfi[.ions of Cyg ;:-3 .. . x-ray hznd (3-12 ':ev) suggest a 4.8 hr pcriod considered I-o be the 1.32 Sconi-us X-2.
This source is usually described as a compact eclipsing x- ray source because of the characteristic lrarinhi 1 i +\r- and also as the kightest x-ray source in the sky . It is at an estimated distance of 250-500 IJ~L.Y~C;Sinectcec than
SS 433) and ms discovered in 1962. Sco X-l has optical and radLo counterparts all of which are spatially coincident with the x-ray sc~urcebut no correlatf-on has been found among the
21zres observed at different wav(=lengths.
It is one of the only known galactic radio source having the same morphology as the lurninlms extragalactic lfdoublelt rcLdLo sourcf2s (see :or example Geldzahler et a1 1981). The eztended structure of Sco X-l is remarkably similar to that of the hot spots 5.n luminous extracalactic radio sources such
2s 3C 234 :?iley and Pooley 2975 1, 3C 244.1 and 3C 265 en' _ns. r,.-, 4- al '13771, and Cyq A (Hargravc and I?... 1 e 1976). ScalS I J laws both the unique galactic objects and those of extragalactic sources. I t is, hwever, no tewor thy that the spectral emission of these three galactic objects are peculiarly variable, each of them having unique cherac teristics in both emission varia- bility and morphology.
SS 433 And Classes of Variable Emission Sources.
SS 433 was identified and knm to be a variable source in all its emitting spectrum although its nature of variability has defied specific classification. It has not been possible to determine precisely whether the variability of this source is intrinsic or gene tic. Intrinsic variab le sources are sources that vary in brightness or in other respects for reasons that are internal t.o the source rather than external. Variable emi tting sources are believed to be giving important informa tion about &e structure, evolution and properties of the sources.
For instance, the timescale of the variation may be correlated with the luminosity of the source. The brightness variations in some sources especially stars can even be seen by the unaided eye.
Classes of variable , Variability may be environmental or genetic in origin. If a source has a conpanion $n orbit around :lL, then its brightness may vary due ir-1 cclip~eor tidal dis-
An eclipse occurs only if the cjl~cerveris si-uatecl near the plane cf the mutual orbit of t
-;;:!a ohjects/~;ources. flence an eclipse f s not an
the observer.
The simplect classification scheme for variables 4s based un whether the ?lc_rht;curve fs period:-c or nonperiodic. Periodic variah!-cs are subclassified accordincr to eclinisina. ~ulsatina.
COII;~IJ~LUU~UL L LI; III LL IIIJAL VUL ACIUIC~. IUIY ~WULLC 3~~11ua s tcir that rotat2s find has permanent or semi-permallmi: surf ace
:ca-tvlres will a!?l;car to vary in hriqhtti, -,.; unless the rotation
'::is points to the observer or unle~sthe surface features are r 12trical abcut the axis. Pulsati ng .111c~1:ruptive vari : - 2 e;:arn:~l.cs of genetic variability. A .:tar for instanc~ is ' Gr17 with cc.rtrin ~ropcrties,?srtic:ul qrly tl~emass, Lflat 1 Lg-srrnines the Future evolution of .-t 1url:f nosity and surface temperature. %is evolution results from the finite nature of the star' s energy supply. During its lifetime, a star may become unstable. several time s and efiibi t dif feren t types of variabili ty. But evolution is known to be so s low that evo lu tion ary changes that take p 1ace are rarely seen. Pulsating variablrsl Pulsating varizb les in s tar emission ocmr when it brightens and fades beciuse of what is thought to be qclic expansion and contraction of the whole star. As a result, the outer layers of the star alternately approach the observer and then recede from him. These motions produce a periodic Doppler shift in the lines in t21e spectrum of the star. The largest rnos t luminous stars are knam to have the longest periods. Luminom vari Ales are massive young stars but less luminous variab 1-es are those with ages and mass es similar to those of the S un . EFINITIONS of wm. Some terms would occur rather f ~qlently in this work and s o i t be comes ne cess ary to define them he re \ Dopp ler shift. displacement of spectral lines in the radiaticn reeived from a source due to its relative motion in the line of si&t. Blw shift (-), shift of spectral lines towards shorterwave- lengths in spectrum which occurs when the souroe is approaching the observer. kdshif t (+) . shift of spectral lines twards longer wavelengths in spec trun which occurs when the source is recedinglmoving away from the observer. Ephemeris, a list of computed positions occupied by a ce les ti a1 body over successive in tervals of time. Galactic Coordinate. a sys rem of coordinates based on the mean plane of the Gataxy. Galactic latitude (b) is measured from the galactic equator north(+) or south (-1 ; galactic longitude (1) is masured eastwards along the galactic plane from the gal actic cen tre . Elastic collisionl a collision bemeen two particles which conserves the total kine tic energy and mmen turn of the system. : 9r;t o'? the star' r;. substance is blovn off leaving behind an extremely dense core at least in some cases (as in the case of Qab Nebula) which may be a neutron star. Supernova reman t(SNR) i a gaseous nebula; the expanding she11 ejected by a supernova. T Tauri Stars. Eruptive variable subgiant stars associatedwith intestellar mcQ rter and believed to be still in the process of gravitational contraction on their way to the main sequence. Found in nebulae or very young clusters, they have lm temperature spectra, strong emission lines and broad hsorp tion lines . -ect -(H-H object) an object with many of the characteristics of T Tauri stars believed to be a star in the very early stages of evolution. Black Hole, a gravitationally collapsed mass inside the s chwarzs child radius from which no light, matter, or signal of any kind can es cape. S &warm child Radius.- the critical radius , according co the general theory of relativity at which a massive body becomes a black hole i.e. at which light is unable to escape to infinity . Inters tellar E'edium. the space be tween the individual stars in galaxy. Intergalactic Medium. the space be Ween the Galaxies. Number Density. The Nuder of particles per unit volume. Proper Hotion. apparent angular rate of motion of a star across the line of sight on the celestial sphere. Flux Density, the strength of an electromagnetic wave defined as the armunt oE power incident per unit area. Jansky (Jy) . Unit of flux density adopted by the IAU in 1973. JJY= IO-~~W~-%Z-'. Flares. electromagnetic radiation from some souroes which unpredictably brighten by up to four orders of magnitude in few seconds , then fade in few minutes . _&side. the major axis of an ellip tical orbit. bsidal Motion* rota tion of the line of apsides in rhe plane of the orbit; (in a binary) precession of the line of apsides due to mutual tidal motion. Binary Stars. two stars close together and revolving around their common centre of gravity. There are three distinct classes. Visual binaries i- when the two stars can be separated with a telescope. Spe ctros mpic binaries, - when the stars are so clos e toge ther that the telescope cannot separate them but the spectroscope shows the per!.odic oscillation of tt'eir spectri1:;li Eclj-psLng bbnarLes:- when the orbit of revolution a nearly edqevrlse to the earth that the two stars ecl other. Lrrrninosi tv: to t2.1 radiant energy o~ Lpu t per second usually -1 ex~ressedin ergs or in magnitudes, or the amount of radiant energy emitted by a source irrespective of its distance from ~&lvfn-~~lmho?-tz- Yodes: a kind of hydrodynamic instability for stz.tic fluids F? v~hfchthe energy is transmitted in form of waves, i I:a ?lot of rnaqnitude or intensity versus time for a varizhle stsr; a graph shob~ingthe course of variations in hriqhtness of a varFab1.e star. Irnrlulatincr: wavy form; risinq and falling like a wave, JuTian Date: the number of ephemeris days that have elapsed since lzh ephernnrls time on January 1, 4713 BC. JD for 1970 January 1, is 2440588; the number of any given day in a system of reconing hy successive days, Independently of varlous calenders. CHAPTER I1 3.00 THE GEF!EFAI, PROPERTIES OF SS 433. SS 433 is a g~~.lacticsource (Davidson and McCray 1980) !.!hose spectrosconic observations have revealed remarkable c~~ii-ssionfeatures that 'wanders 'icros:; the spectrum1 (Fabian xd Rees, 1979). The general ~ropertlfof this source (SS 433) ?-s often described as unusual or bizarre. Much of the research !.nto SS 433 are 7rompted by the hope ]:hat it would prove to h 2 nearby, and th~reforerelatively eazy to observe, version o the extragalactic jet sources; having more in common with ~xtragalacticSOL rces than with any galactic source (Verrnenlen 7-988). The !.!ell collimated jet: featurbes, the beam open!-ng angle 06 a fe7.v degrees, the relativistic hu1.k speed of about 0.26C are I:vdcal-. of extracalactic large systems, It is also established that llkn the cl~sslcaldouble radio sources, the beams of SS 433 can he traced over to at least eight orders of rnagn%tude in size vith evidence for a radio brightening zone (and/or gap) at long 1e central system. this complex and possibly unique stellar a set of significant and diverse astro- !lhy~icalprohl.ems, For although many thw~reticalpostulati 11s 11~1vebeen put forward to explain the in+cr.rction of a ~y~stern q!i~ich can procIuc~3 the charactt2risti.c f 2atures (jets) of SS 433, i.t is as yet consid~red{rngossible t.i determine exfjctly what the jets are tor-sidered to be confined to the same position angles (100~-+ 20'). Features occuring in the radio jet s tructure when extrapolated back to a hypothetical time of e je ction based on the proper motion show that the posi tion angle of the rat50 jets are not only consis tent with those of the optical jets but also corresponds reasonably well with b ulges of what i.s considered to be a large scale radio source (W50) surrounding the ob je ct (H jellming and Johns ton, I98 1) . Spencer (1 979) in his observation of the close similarities between SS 433 and so= powerful extragal-actic radio sources pointed out specifically that the galactic object is like what is seen in the central regions of 3C 236 and LGC 6251, where he believed, are the sites of radio emission from beam of relativistic matter flowing out from the entral sys tern. The sam beams, he suggested, may be present in SS 433 though at a much lower power level and smaller scale. 3C 236 is a giant radio galaxy of a double radio source and like the galactic ob je ct , has a compact radio component believed to have an impor tan t role in producing and wintaining the extended radio features - (the lobes and jets). ,.- A A . - , . ..U. ,, -- - ." . ' , had shown th2.t series of simf lar emission patches are observable within the conkcur of both the main These, accordlnq to him, are partly chance superposFt?on of unrelated CGCIL~~~. In an analysls of "Rddio jets in strong core classical 90ubles~~Jacj (7984) showed that most of the jets in this category 2re clum~v.verv much resembling a st:rlng of knots than the con- lower luminosity jets; pointing out that observable in a source like 3C 200 is unusurll. :.:.I..L:c,L~~~uIIe~ QL (1984) drawing ronclusion from FP~I*~~(-11 :;i.riilar observa sfons believed th~t hi qhl y luminous-radio .aurces usually have jets which are often xenr \ably tangled ;Iirti distorted, and even suggested that the most likely cause of the distortion is a strong interection between the radio emitting plasma and its environment. 2.20 The Radio Structure and Radio Flares of SS 433. VLBI observat.ion8 of SS 433 and the radio structure deriv- able from them show numerous discrete emission features which appear to be ejected from the centre of the sys tern in association with flares in the flux density (Ronmey et a1 1987). These features are believed to be ejected symnetrically most often but evidence of an apparent one-sided activity have also been observed. Some of the images reveal structures at position angles found to be beyond the cone permitted by the kinematic mdel- while others are believed to be in excellent agreement with predictions of this same model which posits ballistic motions at midly relativistic velocity along a mne of direction swept out in about 164 day cycle. In the milliarceecond scale, the radio structure of SS 433 is variable. The variability is thought to be well correlated with flares in flux density. Structures obtained at different observations are shown in appendix I - a 5. In figure Ia, the structure derived consists of an unresolved core aomponent and an extremely elongated feature reportedly containing 0. I6 Jy and 0 .O5 Jy respective 2y. mere was no signi- mated to be 62' and well beyond the kinematic model's cone. The state of the source was also uncertain due to the calibration source lapses. Appendix Ie is a typical radio structure of SS 433 in whioh the jet features are shown with a reported decrease in intensity (within amdist:ance from the peak/core) to the 2-42 level. The evidence of this jet features are available but the positions becoms uncertain. Below it are. the evidence of continued presence of jet features at the 2-4% level (of flux density). It is shown in the small amp li tude periodic behaviour of ~ffe-lsberg-~estc visibility amplitude. 2.30 SS 433 and the Associated Supernova Remnant (W50) . The possible in£luence of some objects associated wii SS 433 has not been precisely determined (Mazeh e t a1 198: SS 433 is almost exactly at the centre of W50 and this cor buted to the recognition of the unusual nature of the objr (SS 433) by Clark and Nurdin (1978). Location inside a SI nova rewant was even thought to be a distinguishing char; istic of the SS 433 class of objects proposed by Ryle et (1978) but which is presently known to be nonexis tent. The diffuse nebula has been known for a long tim and classified as a supernova remnant on account of its shell-like structure and nonthermal spectral index (Holden and Caswell, 1969). Detailed radio maps of this nebula at different frequencies are generally considered to be in agreement with previous assertion that W50 is brighter than its linear size (linear size to surface brightness ratio) would indicate if it is a conventional supernova remnant (Ge ldzahler e t a1 J 980) . According to Ge ldzahler e t a1 (1980)~W50 has a roughly elliptical shape with its major axis runningfrom east to west at right angles to the galactic plane; and delineated by a shell-like ridge both in the eas t and west. Thee is also radio ernissioc. outside the ellipse and from the regions often called "wings or ears". This largescale radio-structure is believed to have the Sam! Position angles as the jets seen on an arcsecond scale in SS 433 with the opening angle of the ears about equal to that of the precession cone of the jets. Murdin and Clark, (1980) Kirshnev and Chevalier (1980) have shown that the interstellar extinctions for W50 and SS 433 are compatible. Weiler (1983) had pointed out that even the radio flux inside the shell is not as low as is usual inside supernova-remnants. There are several small ridges of enhanced emission inside the nebula association y!?t!~, and effect, on WTO. The alignment rl: the long sre actually believed to occur in a region \ shell abruptly ends. Elston and Saum (1987) found support fc j-n which a rou~ily spherical blask-wave she: n suFernova has subsequently been modified by tne ram-pressure Fr~sentsmuch enouc-jh difficulty with a supernova oriqin for the shel.1 (Elstnn 2nd Saun 1987), If W50 is an old supernova remr-. nt !.il:e the Cynnrlf; Loo?, ovticat ernissi~nF$.orn some of the F' ~1 The evidence that the jets of S'.' ??3 modified the object - !*!50 to product? ",he ears incl.urle : (i) the unique morphology of the ears and the sudden termination of the shell-like structure at the base of the radio ears. (ii) the minimum energy pressure in the ear filaments are 2.8 and 3.5 times that in the shell for eastern and wes tern fila- men ts respective ly (E lston and Baum, 1987) . (iii) these appear to be an association between the x-ray lobes, optical filaments and the radio filaments. The fact that these features only occur in an object with the high-ve locity out- flows of SS 433 is a generally acoepted circumsGntia1 evidence that the jets are responsible for the creation of the ears. Added to the fact that the ears are aligned with the arcsecond radio jets and x-ray lobes; the case for a mnnection between the jets of SS 433 and the ears becoues s trong, indicating s trongly that the momen turn flux from the jets must stay we 11 colliminated until, perhaps, the jets strike the shell (Elston and Barn, I 987) The great similarity between SS 433 and extragalactic radio sources sugges ts that the interaction of SS 433 wi th W50 may shed light on how extragalactic radio jets intereact with their environment. The relative proximity of SS 433 allows the study of this interaction at high resolution. 2.40 ,The Emission Variability of SS 433, SS 433 is associated with unusual emission variability in all its emitting spectrum. The radio emissions, the x-ray and gamma radiations emitted from this source were relatively easy to be associated ui th one and this same object partly because of h peculiar edssion variabilities , dowever, eventhouefr the general emision is characterized by similar variation at different wave lengths of electromagnetic spectrum, there is an almost complete lack of well correlated variability at different wave lengths , 2.41 The RadioEmission. The radio emissionwas found to be assaciateA with the peculiar galactic object - SS 433, simultenou~~ I wifh the discovery of being time radio variable, sometimes changing by 50% in few hours see for example (Fiedler et a1 1987, Seaquist et a1 1979, Johnston et a1 1981). I Ryle et a1 (1978) and Seaquist et al. (1979) made radio observations at various frequencies between 2.7 and 15.4 QIz and showed that the radio emission of SS 433 is nontharmal and extremely variable. At frequencie:; of 2695 and 8085 Mlz, Johns ton et a1 (1981) postulated that the r~~dioradiation is one with a quies oen t and active flaring phases in which the flux densi ty -. -- . . - -* ---- . . . _. B ons ignori- faconde e t a1 ( 1986b) described the general pattern of variations (during flares) as a sequenoe of outbursts superinposed to a relatively st&le flux level. They shwed that the radio flux density varies from 1.46 Jy to 4.33 Jy (+3%)- while the s table flux level ranges be tween I .4-2.3 Jy. (see also appendix I1 for variation of flux density). In an analysis of short timescale variations at a frequency of 408 MHz, Bonsignori-Facondi and Bracaesi ( 1985) found similar probalities for both negative adlor positive man flux devise ions gith an estimated root man square deviation of 0.53 Jy. This led them to point out that those views whi& hold that variability of emission in SS 433 is intrinsic to the emitter require to provide an ad hoc model to jus tify sum a behaviour. It is also known that pulsed *radiation from SS 433 has been looked for at 1.4 QIz particularly and other spectral regions but no de te ction h as been reported (See also appendix 11) . At 2695 and 8085 MHz, observations spanning the period of seven years (July 1979 to Lkcenber 1985) was reported by Fiedler e t a1 (1987). They also shaded that the flux density variations are Somwhat characterised by flare events separated by periods of quies cent-emission. A harmonic analysis , they emphacised, ei ther reveals no significant periodicities in :- . the entire seven year data set or in subse ts corresponding to active and quies cent tirne frames. They found that mos t flares occur wi thin 25 days of ea& other, and from a radio light cum analysis, described it as clustering of flares. It was their view that the reservoir of maerial ejected from the binary sys tern (SS 433) is quasi- periodically loaded and duuped, The loading and dumping time+- Sles, they believed, mrrespond to the quiescent period between eah flare events. Radio observations, apart from their mn interest, are relevant for a proper tmckrsmding of simultaneom &senrations in other regions of electromagneticspectrum. A clear and efficient detection of the quiescent and active flaring periock of the sou-re (SS 433) whi& correlate with rrq and optical features are yet to be established. 2.42. Op ti cal Emission (Variabi li ty ) . Among the prin dpal features which make SS 433 s o mw ual is the presence of intense optical emission lines which shcw redshif t and blue-shif t simultaneous ly . The magnitude of the -c.tif t varies , reahing a corresponding maxima of 50,000 km/s (pd) and -30,000 km/s (blue) . Of ten, the red- and b 1m- shifted lines behave like mirror images although the reds hif ted lines occasionally have a more complex profile than their blueshifted counterparts and the reverse does not. occur !!he "moving lines" have been sham (see for example Verrneulen 1988) tx~be Doppler shifted hydrogen and helium lines. ?he Boppler shifted lines exhibit variations on a large range of tims cales, from se~raldays dmto half an hour. Vermnlen (19~8)~ointedout episobs of a rather smooth Qmge in wave- kng~s well as ins tanes of a ell-knwn "bulle t-like" behaviour when a line at one parti cular waie length diminishes in s trength while a new, separate one rises to prominane at different wavelength. In the case of multiple lines, the brightest is often the newest one although the behaviour can vary enormously; for there are lwo to three day observing periods known when no Doppler shifted emission lines could be detected at all (Vermenlen 1988). Milgrom (1981) had believed that the spread in the absolute value of the w locities in the mavincline emitting regions may arise from the acceleration or ck eleration of the gas in the moving-line emi tting region or from systematic variations of the thermal wlocity of the accelerated gas along different direct- ions within the beam. Although several periodicities thought to be due to pre @- ss ion and orbital cycle of the jet and system respectively have been ~ostulated, these pos tulations are not without pitfalls. Besides, there is neither a specific period believed to be ?resent in the optical bandwhich has any correlation in other s?ectral region; nor is there sny evidence for a correlation between the wmZutirl?n seen in the radio observation and the I~chaviourof the optLcal Doppler-shifted lines. Vermenlen (2988) in a qeneral review noted that there is no s~ecificevent in sly of the emittLnn spectra which has so far been linked to the occurence OF the radio flares and that it has not been possible zlso to identify any s~eci-ficfeature in the VLSI mans in which a certa;~Dop?ler-shbf ted lines originate. A uhomo~eneousrecordtt 05 optic21 photoelectric photometric measurement of this "special object" (SS 433) coverin? 800 obser- vations (rar?nlnq bdween 1979-198S in the V-band m.s reported hy ICcmp et 31- !?-956). They equally pointed out that, SS 433 is a faint star (of visual magnitude V = 141 and that the erratic lrpht Fl-uctuatlons in the object is indeed complex, There ?re also l'stationaryl spectral features observable -in SS 433. '."he spectral featurrc. which do not display periodic do!-)nler-shifting are said to he 5 tationary, though some are il - fact Lnov.-!n to undergo small spor-bdi cal velocity variatior. The rrost ylrorninrtnk emission lines are those of hydrogen, ' ~nceits -i nclucion in SS catal-ogue. The lrne profile are dl.ycrihr+d as 35. broxl, variable, and complex (see for instance Murdin et al, l?Gr.I ). Of ten the profile are described as having a narrow &ip and a broad uneulating base. sometimes the structure is even doi~l-,leor multiple (see Gatti et a1 1983). Anderson et aI(19113a) Flnd that per!-odic variations with timescales of 6.5, 13, 81, and 162 days are present, Many strong intersteller absorption lines me reportedly present in the spectrum of SS 43?0 Clarlc and r.:ilone (1981) note that there is more variability noing to shortcr lwavelengths, but !~~ynn-Willltarnsand Becklin (1973) have found the o~positeresult, Margon et a1 (1979a) state optical ws9nltudcs of V = 14.2, (B-v) = 2.1 and (u-B) = 0,6 but variations of un to t mag. are known to be present. There is variability in a1.l continurn bands on many timescales. Photo- mekric variatlons on a timescale of 264 days are also reported (see Flenson et 21 1983). .4n extensive liqht curves in the U, 9 2nd V bandc is given by Leiho~~I.tzet al ('1984). It is dernon- strated th?t these curves can be ffuite complex, In general, cventhough vw5.ability in the optical ernissjon of SS 433 on 41.FTerent timescales, ranging from hours to months, have hem ohs~rved,there is no acceptably dett.r11i;.ie13period at nrr rite 2.43 q'17~ %-Vnv ,?nd Gamma F!av Obs~rvstions. The x-ray emission associated 1,; L!) SS 433 5.5 Gn unusual in its x-ray ?roperties as its 0ptfc31 and radio counterparts are in their properties (Grindlay et a!. 1984). It is believed to be the only galactic x-ray source which displays a double lobe and/or jet morphology as well as a bright central source (Seward et a1 2980; Watson et a1 1983). The pattern of x-ray emission variability has also been extensively studied. In particular, x-ray flares (as observable in radio emissions), with periodicities that would indicate binary system or precession, have been looked for (Grindlay 1984). It was then established from this and other observations that the central object in SS 433 is also variable In x-ray intensity and spectrum on a wide range of timescales. There was neither evidence for vari-ability on timescales less than 5 minutes, which led them to suggest that the compact object itself is not directly vFsible, nor has there been any evidence for pulsation. It is widely considered that the x-ray bursts azsociated with this source is likely due to positive enhancements in the ~~7urceflux ?-n the form of flares rather than (partial?) eclipses of an otherwise constant source. The presence of a large srl3le x-r~~yjets has be~nconfirrr- .I from this source is strongly believed to be nontherrn?.? )II~has 35 an nhserved luminosity valk~evarying between (2.17-Q.30) x 10 Gamma Xay, The detection of gamma-ray spectral lines near I .20 to 1.50 MeV from the general direction of SS 433 was reported by Lamb et a1 (1983). From the peculiar variation in energies of the lines spectrum with time and in a manner em- s istent with the ephemeris for the "moving" lines (op tical emission line variation), it was easily established that the gamna ray lines originated from the object. The pwer in the gamnaray lines is intermdiate beween that seen in x-rays -1 ( 10~~-10~)erg a (Marshall et a1 1979) and that in the 39 optical region ( 10 ) Ald~ough the mode of gamma-ray 3 7 production in SS 433 jets of such considerable pwer ( 10 erg S-') is not yet established, the implication of the obser vation of the gamna-ray for the properties of the jets is significant, The gamma-ray production from this object involv- ing collisions of the jets with the interstellar medium is indeed plausible. CHAPTER I11 3.0 TNE RADIO JETS OF SS 433. The radio emission from SS 433 jets is associated with time- dependent andspatial variabilities. The combinedeffect of both variabilities lead to difficulties in interpreting the radio s tructure of the source (Vermenlen e t al, 1988) . The jets are synanetrically located (east and west) on either side of the mre. Emission from both jets have been found to be, sorme times, identical and some other tias at variance with each other (see for exanple Vermenlen et al, 1987, Fejes et al, 1988, Fe jes, 1986). &cause of the pe culiat emission variabilities , the length of the radio emitting jets are not precisely known; although i t is generally estimated to be about 2 parsecs. At about this dis tan= the radio emission intensity re dues dras tically to about 2% of its original value (see for example Hjellming and Johnston, 1981, Johnston et al, 1984, Fejes et al, 1988). The posi rion of the jets at the 2% leve 1 is cansidered to be unreliable due to various factors, but the presene of these jets at longer &s tanms have been evihntely detected (Fe jess 1986). There are radio gaps or radio bri&tening zone estimated to be at a distance of about 4x10'~ cm from the core (Ve-nlen et al, 1987). Well collimated b lob-like s tructures or knots are mually observed tracing the predicted locus of the radio jets - (see for example Verrnenlen et al, 1988). Variable series of dis- crete emission patches outside the expected jet locus are cons tanqobserved and often interpreted as arising from lm e je ction ve loci ty and/ or deviant ejection angle. TIE integrated flux density at the frequency of 5 CXz varies between zero to 0.029 Jy (Vermenlen et a1 1987); 0.11 to 0.24 Jy at 4885 LYHZ (H je llming and Johns ton, I98 1) , and zero to I .I Jy at the frequenq of 408 NHz (Spencer 1979). During the quiescent radio state, the source generally has a relatively flat spectrum. From a daily measurement and the integrated flux density estimate at the frequency range bemeen 408 MHz and about 8 GHz, Vermnlen et a1 (1 987) found the spectral index to be -0.65 -+ 1 when the obsenration was interupted by small flares. But from a comparative analysis of data from variors observat- ions within the same frequency range, Fiedler et a1 (1987) shmed that the spectral index is cons tan t wi th an es timated value of -0.6 exaept for times shortly a£ter flaring (see also Hjellming and Johnston, 1981) , 3.10 SS 433 Jets and Radio Emission Mechanisms. Various observations of SS 433 at different spectral wave- lengths confirm the existence of what is often described as blob Zike features, flared as well as corscrew-shaped trails. Sonre of these features and in particular the "blobs or lqy beams" are usually thought to be emanating from the core (see for example Vermenlen e t a1 1987). Similarly, regularly spaced knots have been de te cted in many other as trophysi cal je ts s ud~ as, the radio jets of NGC 6253 (Perley e t a1 1984) , QSO 0800 -+ 608, M87 (Nei to and klievre 19821, and even in the optical jets like 3C 2 73 (Lelievre e t a1 1984) . In partiahr, the mdels proposed so far to explain the formation of knots in jets generally are of two types . Rees ( 1978), and Blandford and Konigl (1 980) have discussed how irregularities in the f lw rate and inhomogenei ties (clouds) in the plasma density, respectively, can give rise to internal shocks where, they believed, particle aceleration and heating produce the o bserved brightness enhancemnt. It is, haweves, notioe d that in this framework, la10 ts are trans cien t s tructures which are convected along the flow. The explanation for the lpgularity of knot spacing was hmever not provided in this model. Ferrari et a1 (1984, 1983) have instead proposed that the &we lopment of long wave length Kelvin-IIelnholt. (K-H) modes create localized, regularly spaced compression regions which are convected along the jet direction but at velocities belw hat of the jet materials itself. The wavelength (K-H) is thought to vary, depending on the physical parameters, of the jets namely density, intensity of the magnetic field and the presence of a smooth transition of velocity between the inner jet and the external medium (Ferrari et a1 1983). Ferrari e t a1 (1986) proposed a wind-type f lw model in which it was sham that a jet propagating through an inter s tellar or intergalactic medium is very likely to undergo K-H ins tabili ty whe ther mnf inemen t is by external gas pressure or magne tic field; and that only for ultra-re la tivis tic ve loci ties and/or very strong magnetic fields do these modes tend to be s tabilized. On application of this model to the haracteris tic large-s tale mrphology of jets (such as that in M87), they believed that the features in the jet of this source can be described in terms of simple hydrodynamic effects within the flow. Tne cohined effects of the galactic matter distribution and of the channel crosssection perturbations due to fluid ins tabili ties, they sugges red, determine the shape of the nozzle within whi& the jet flows, ,and further determine the f la topologies (Ferrari e t a1 1986) . An essential point is then indicated as being that the efficiency of particle acceleration depends only slightly on the shock strength whid-i is found to be relative ly weak in the wind-type f lw model. Ik! the other hand, the K-H ins tabili ties require that the je t boundaries be thermally or magne tically confined while the question of jet confinement is s till unresolved. A free jet is that which is not ~lhermallyor magnetically confined. It is often ass wed that this type of jet will be a nearly perfect cone (~Yiley 1980) ; bur this is true only if as a condition, the jet source/emissian does not vary in ti~lle (Roberts 1986). Both jets and jet sources are generally thought to show considerable evidence of nonuniformi ty . Extragalactic jets as observed in high-resolution radio maps (e.g. NGC 6251) frequently exhibit nonuniformity on increasing finer scales as resolution improves (see for example Bridle and Perky 1984). VLBI maps of radio source cores show what seems to be lllmpytt emission from the core region some times with observable proper motion. According to Psberts (1986), it would be suprising if a jet did not have at least fractionof variability in density that we see in 6 comparable region in our galaxy (a factor of 10 even ignoring s tars). Nor should we expect, as he puts it, that fluid or MID nozzle some tines believed to be producing the jet, whatever its detail nature is, would maintain a directed, even flow, especially given the likelihood of uneven fueling of the central engine. After the jet has left its initial collimatim region and then considered to be only little influenced by the external mdium, the implication is that external pressure confinement is inadequate for some jets (see Lified and Perley 1984 for strong argunren t in a specif i c case) . Magne tic self-con£ inemn t according to Benf ord ( 19 78) remains a possibility but its characteris tic Faraday rotation signature across a jet, he pointed out, has yet to be observed. The existence of wiggles and flaring in som jets is taken to be an arguement against jet freedom. Xoberts (1986) postulated that lumpy noisy ballis tic jets exhibit knots, wiggles and flaring as kine tic effect, not requiring the in£ luence of external shaping for~salong the jet length. It was pointed out that even the most seemingly periodic knots in M87 (Nieto and Lelievre 1982) vary considerably in intensi ty . In his analysis of observable jet features, Benford ( 1986) opined that jets my be expected to be of many different types depending both on their internal properties and external environments. He was of the view that no model of any particular jet ot class of jets can currently claim to be consis tent with all known facts, except in a very vague way. In conclusion, he suggsted that here are two classes of jet those which are pressure confined and o them that are free or magnetically confined. The problem of jet confinement is, however, outside the s cope of this proje ct report. We mere ly conside re d, the propagation of jets through the intersteIlar/intgrgalactic mdium to shm haw the model may account for the qpical observed emissions when the dynami cal interactions of the jet flows with, a variable galactic matter dis tribution are taken into accom t. Although various mck 1s aimd at exp laining the emission mehanisrn and the associated variabilities of SS 433 have been proposed, the possible aceleration me chanism is obs cure (Vermenlen 1987). This object is usually placed in the "extra- galactic s cene" because it strongly promises to be nearby scale mde 1 of active galactic objects. Even Extragalactic radio jets are known to display an intriguing form of varieties (S todte 1984, Siah and Wiita 1984, Wikinson et: a1 1984, Meurs 1987). Wieler (1983) postulated that a continous range of ejection products edst (to explain variation in jets) depending on the type of object causing it. He proposed that the extended features of SS 433 is a supernova rermant similar to Crab Nebula; both of which he suggested contain a surviving neutron star or blackholes. Upscaling such compact objecm, he believed, would lead to the wpe of extragalactic objects called double radio sources. By the app licatian of the theory of hydrodynamic winds to the interpretation of mllimated flows (jets) from galactic and extragalactic objects, Konigle e t a1 (1986) showed that different classes of astrophysical jets are governed by common dynamical proclesses. Rees (1982) proposed scaling laws to show that the observed similarities between the galactic object and extragalactic sources are rooted in common dynamical processess . An optically derived kinematic model of Abel and Margan (1979) whi& is otherwise called precessing beam mdel is con- sidered almost always in relation to sow un-usual observations in SS 433. This model presupposes that a midfy relativistic matter (0.26C) from the central region is being ejected along two oppositely directed and highly collimated beams. E lements of the barns follm undeoelerated ballistic trajectories, and that the ejection axis precesses with about 162 day period. The rotation of the jet axis imposes a spiral s tructulle on the outer regions of the beam. The Doppler-shif ts are interpreted as resulting from the radial projections of motion in the inner beam regions. Radio observations confirm the exis tence of mrks crew shaped trails (Vermenlen et a1 1987). Although the kinematic model is regarded to be an excellent approxima tion, there are various deviations from observations whicfi are thought to be of three types (Katz et a1 1982, hderson et a1 1983, Katz and Piram 1982). These are (i) Periodic ( 6 day) variations of 5-10X in amplitude which som authors consider as due to uneven sampling of data. (ii) Variations on a times cale of months which may or may not be periodic. hderson et a1 (1983) pointed out that these variations give the impression that the Doppler shifts are systematically early or late, (iii) Jitter variations an a timescale of one to several days without any dependence on the predicted 162 day period nor on the 6 day period. The jitter is found to be symtri c in the blue and red components (Katz and Piram 1982). A study of flux density variations by Fiedler et a1 (1987) whicfi covered a period of seven years at 2695 and 8085 MHz showed no evidence for any phase stable periodicities . In their analysis, it was pointed out that eventhough s tatis tically significant periods appear to be present in various subsets of the data, unique periods were neither found over the entire observing period, nor in subsets corresponding to active and q uies aent time frames . In most models conceived for SS 433, there is a prima~y conponent of the object which allms for matter to be accreted, liberating energy to drive the jets. Johnston et a1 (1984) pointed out that the radio emissions from SS 433 are consistent with the decay of synchrotron radiarim - originating from compact binary object in a stellar wind ballis tically travelling along the precessing beam axis. They proposed that some materials are always leaving the accre ting disk of the entral binary system, supplying materials to be accreted into the beams ad in this way, emission can be observed in the different regions of its emitting spectrum. They suggested that variability arises from the variation in accretion flow; the rates of accmula tion and release of materials in the aentral system corresponding to the quies ent and flaring periods respe ctive ly . In a binary star model of De Young and Geoffery (1979), it was proposed that SS 433 is a nrember 05 astrophysical sys ems whose elds tence has been confirmed by observations ; believing that it is a binary star comprising of a massive early-type s tar and magnetic white &arf. They opined that the observed characteris ti= of the sys tern can arise if the rotating whi te dwarf possesses gas embedded in a dipole field either aligned with or at large obliquity to its spin axis and with the plane of the orbit lying nearly in the plane of the sky, It was established at SS 433 has an optical continuum spectrum and surf at^ gravity which led to the suggs tion that it is an early 0-type star suffering interstellar absorption of kv 9 mg (Murdin e t a1 1980) . The rest emission lines appear to be fiw d to a primary object (type 05 f) in a binary s tar and a broad sys tern presumably representing mass loss. The moving features is thought to arise from discrete "bulle tsf' syme tri- cally shot out in two opposite jets. The bullets arise from a common source whi& is the compact object in the system. Martin and Rees (1979) in an attempt to explain the variable emission features in SS 433 proposed a model in which the high jet velocity (w 0.26C) is believed to be an indication that aceleration and collimation takes p lace in a relativis ti- cally deep potential well from which the jets escape along the direction of least resistance being aligned with the rotation axis of the gas cloud or disk close to the cwpact object. The gas escape or jet formation fr0.m a deep potential well is plaus ibk but mnsidered to be incompatible with current obser- va tions of monodire ctional je ts , wiggles and b lobs of-ten obserm d in larges cale jets. Grindlay et a1 (1984) opined that the entire nature of variability in spectral emission of SS 433 are pointers to the fact that macerials incorporated into the jets vary whether by an increase in mass transfer or by different distribution of accreted matter between disk and jets. Johnston et a1 (1981) enphadsed that a model consistent vith observatians in SS 433 is a continuous collimated ejection of energetic particles along the jets. These jets precess, and as they do so, they interact with the medium immediately surround- ing the binary object. The jets are more than likely associated with a mnstant injection of relativistic particles beaming from the accretion disk of collapsed object. There is, they believed, likely to be considerable mass loss from the canpanion star probably of order of low5 Mo y;J. This rmss loss is being 10s t to the collapsed object but is also being ejected from the binary system such that the system is surrounded by a &me inhomo- genousmedium. This is the medium into which the beam travels. When the beams encounters considerable mass-loss globules, it causes particles in these globules to become relativistic and to radiate producing flaring events. They therefore associated times of flaring activity with considerable mass loss activiw in the stellar sys tern. The model is preferred over a vari ab le beam type because of the short-time acale of flare activity. In radiative acmleration md-ianism of Davidson et a1 (1980), it was proposed that SS 433 has cool gas within its jets which is being acczlerated by radiative pressure and also being partially collimated by nozzles which are formed where a dense accretion disk encomters heating at high pressures. 'ke inter- action with the ambient mdium, perhaps a stellar wind, they s ugges ted, could even be responsible for the qtical line emiss- ion usually observed from the source. The gas moving along each jet is then thought to be inhomogenous; and turbulenae as may be the case in extragalactic radio source can be partly respon- sible for the particle acceleration. But the available or es timated pmer and that of &e flow rate in this model are found to be out of proportion to ea& other. Mnlgrom ( 19 79) also be lieve d that radiative acceleration is possible through line-lo king ue &anism in whi& momn turn transfer occurs mostly through the optical line absorption such that as the velociry of the particles increase, continuum photon of progressively high frequenq are Doppler-shifted. ~~~ericalcalculation by Shapiro (1982), based on this mode 1, indicate that the line locking rnehanism can only be partly reasonable at very high degree of clumping. Spener (1979) attempted explaning the jet emission variab- i li ty in terms of change in ejection angles of the beam in relation to the line of sight as may be the case in more powerful radio soures. spatial variability, he argued, arises from adiabatic expansion of small emitting regions in the jets. There is, however, no periodic variation that has so far been wrtainly observed in any of the radio or other spectral wave lengths . SS 433 is almost generally believed to be a binary sys tern in which a companion star loose mass to a thick accretion disk (Vermnlen 1987). Many authors do infact. indicate that mass transfer can occur in binary systems; but neutron stars often invoked by many to exp lain the characteris tic emission varia- bility has been proved to be neither ejecting sufficient matter in their evolutionary phase, nor does the phase last long enough to explain the nature of emission from the object (Lipunov and 52. Shakura, 111982, van den Htauvel et al, 9.1980). On the other hand, no very rapid or well pa+-ternedvariation has so far been ,=islzabli?I,. I t ,r-m r,?~u>.~:~, 'e inhncbon r:+ 71 1Qp4)l -1~~1?n there is no definite probability uf the currll)~tl~i.onstar (in SS 433 system) being a pulsx, Vermenl-en (1958) is of the opinjon that the radio beams (accelerated relativistic particles producing the radio emission in the jets) .ire rlr:,i, curlt I .I~IUCI.'; ',I ! , i - , , i ., c,f ct series of discre.te bLohs emanatLng from Lllc core. He I-1t.l i.eved that the ruotlon of the radio blahs is the sii:lnle as that of the thermal matter vhich mlts Doppler-shifted lines. But the emission being radiated are not limi bed 417 l.?ne -1~cl:r-:~n~nnly hrir: rather covers a hroad range of radio and other ~[~ectralregion. Besides, the presence of larqescale x-ray jets have been confirmed (Watson et al 1983) all of which are believed to be resulting from the 2ctivities in the central system, Beglern3n et a1 (1980) in an - !ld!.ysis of the energetics GY?: the models for SS 433 proposed that the emission lines (both shifted and unshifted) arise from the b~-dmswhich power the x- SLY source and the radio source, by dissipaf ncj a small frzct: CL of . their kine.ti.c en ern^ as they snee? th! i\(jh sn mh.'_ent (.tseous mdiwn. They noted that the ohject exhibit redshift and blue-, shift emission lines sys terns whim oscillate across the spectrum with aw li tudes corresponding to Dopp ler-shif ts of more than 45000 km/s. They showed that views attributing the variable Doppler shifts to orbital mtion fall prey to a number of serious shortcomings, In situ acelera tion is then believed to be ne cessary to exp lain the emissions at long dis tan QS in jets where even the radiation life-times of emitting electrons should expectedly be exhausted; just as it is believed to be equally important in extragalactic sour Qs In 1978, SS 433 was proposed to belong to what was thought to bel'a new class of radio stars". The suggestion of this class was based on the facts that these objects were nonpuLsating s te llar remnants of s upernovae and also on the basis of other radio properties like time-variability , flat spectrum or inverted spe ctra among others. It was euphacised that many exrra- galacric objects share these sam characteris tics (van Gorkom e t a1 1982), and that the radio morphology and the diffuse x-ray emission extending from SS 433 provided evidence of association with SNR(W50) . flthough the ~werfulextended radio sources we= among the first es tragalactic radio soures to be extensively studied, a detailed understanding of their nature is s till considered to be illusive (Blake 1972). Blake interpreted jets as a sys tern involving multiple ejections of ram pressure-confined plasmns in whi& instabilities lead to the formation of turbulent hot spots. Christiansen e t a1 (1977) argued that the "ram pressure deceleration in jets" whirh lead to instabilities;. far from destroying the plasmns, lead to in si tu reacce leration of the relativisticparticles present in it, The acceleration, they believed, provides a mans of transforming a fraction of the tremndous kinetic energy into relativistic particles and mgne tic energy. Linearized calculations of ins tabi li ties, hcweve r, indicate that ram-pressure confined plasmons (jets) are Ray leigh-Taylor and Kelvin-Helmholtz unstable. The instabilities grw rapidly enough to disrupt the plasmns (Blake 1972). Eilet (1979) in an application of magnetohydrodynamic wave for particle reacaeleration shcwed also that the passage of plasmon cloud through an interstellar =dim can generate turbu- lenoe capable of acelerating particles that can aonpensate for various energy losses; but the process is considered to be in- efficient as most of the kine tic energy may go into heating of the background gas rather than the assumd transformation into turbulence. In an analysis of quasi-steady ,component of radiations of variable radio sources, kuril' chik (19 78) opined that variable radio emissions very likely results from an isotropic motion of irregularities in the flux density of relativistic electrons outward from the nucleus where they are permanently being generated into a tube of steadj magnetic field that expands gradually with distance. He proposed that the process probhly occurs at the magne tic poles of a nucleus having a bipolar magnetic field. This, he believed, could provide a natural explanation of non triva 1 p roper ties including the variable radio- structures as well as the apparent velocities of relative motion faster than light detected in soavl objects such as 3C 120 (radio galaxy) . In the same vein, Meurs (1987) shmed that observed jet forms and their ansequent brightness dis tribution (implying emission variabilities) could be due to any or some of the factors like jet precession, gravitational encounters with other ob je cts , binary orbi ts of the cen tral sys tern and movemen t in the potential yell of groups or elus ters . Wi th particular reference to SS 433, he suggested that the effects of these f actor(s) could be oorplicated by rawpressure of ambient gas or an intergalactic wind. In their s tu* of distortions of classical double structure of radio sources, hristiansen et a1 (1984) emphacised that observational results of nearby radio galaxies provi & new insights into the nature of local environment of radio soures. They pointed out tSat preession of radio ejection axis; &nsi ty gradients; motion of the source in an external wdium and/or the elds ten= of larges cale density or pressure gradients external to the soure can result to great ds tortions in jets. For the obvious role of magnetic fie lds in jets , Siah and Xiitta (1984) poin&d out that jets shw evidene of ordered largescale magnetic fields without whih "gas pressu~mnfine- mnt of the jets" become insufficient to provide focusing of radio jets, In a simple model of magnetohydrodynamic calculat- ion, they shmed that not only can magnetic fields aid collimat- ion and jet development, but ?hat too mu& energy in the form of magnetic field around the jet is very likely to disrupt the beam. Magnetic variabilities can, therefore, give rise to different types of dis tortion or mmon radio emission variability ckpend- ing, perhaps, on tbe direction of the field causing the distortion. ~~~~rdingto Turland (1975), jets mrry readily be explained by variow mode 1s whi& pos tulates a. continuous s upply of energy from the to the outer mmponents, but most of these mackls becom helpless or do not appear mmpartible with mrtain features currently observed in jets, IIe was of the opinim that in m&ls of radio souroes , it is neessary to cunsider that the beam interaction with a plasma leads to radio emission. S&- sequent s tudies of radio emission at low frequencies, he pointed out, suggest strongly that there is sorrle non-relativis tic plasma assodatedwith the radio jets. This, itwas emphacised, led to a preliminary analysis which indicated that accelerated and collimated beams from the nutlets will involw entrainment. For extended radio soures and jets, it is widely considered th at the mos t ten& le mock 1s are those in which energy are con- tinuous Ijr s upp lie d by be an; >hi ch mq coon is t of a s tron g e le ctrc- magne ti c waves or re la tivis tic par ti cks from a continuing soure of enerm wi thin the mntral sys tem/nucleus (H argrave and Mallin 1975). Theae are commonly referred to as continuous flow mdels. Fer vis tually all the models proposed for SS 433, there are direct iaplications which suggest correlations between the radio behaviour and other & tectable emissions from the source amng ottlers, but whicfi is yet to be observed. 3,30 The Proton Beam Collision Model and Application to SS 433, Some galactic objects like T Tauri s tars and Herbig-IIaro objects have earlier been associated with well collimated flms (the degree of collimation varying from object to object), ad in som cases knot-like structures and extended features ( -10 l7 cm) from tfie parent object have been seen (De Young 1986). & Young (198Qhas pointed out that: the same beam inter- action with the surrounding medurn (i.e. entrainmnt process) nus t also be o ccuring as in the case of extragalactic sources. It is shown by Anyakoha et a1 (1988) that if significant amun t of mate rial are en trained in the jet of extragalactic radio sources as reoently suggested by Jk Young (1986), the proton-proton collision prooess may becotre a viable me&anism for genera tion of radio emitting electrons in the jets . The resultant flux density, S(V), fron this process being where Sw) = the radio luminosity at t5e frequency . the DL = the luminosity distance of source. Z = the redshift. The magni tude of the radio luminosity is then & taine d from the relations . where also (,?E/?lp ) Ne =electron nuder density = v V =volume of the jet = I .r21 -26 2 bp = pro ton cross-se ction = 3 x 10 an 1 C = the velocity of light = 3 x lo1' cm S- -7 ~k 2 = 8 x 10 ergs 5 A = 8.11 x10 . g = the magne tic field whi& varies from source to s our= . = the fmquency of observation. = the spe ctral index 2 -1 Au-lgd-l P w) = 9.57 ~p ne v 6~ ~(70)';~ (& c ) v -"... (iii) 3.30 Obserwd and DerivedParaueters of SS 433, (a) Distance = 5.0 -+ 0.5 Kpc (Venrenlen, 1987; Fejes, 1986: Rowey et a1 1987). (b) hngth of radio emitting jet -2pc (1.2 x l0I7 an) (ti jellming and Jchnston, 1981; Johnston et a1 1984, Romney et a1 1987). (c) Radius of jet 1.7pc (0.17 Bwhere R- loz0 an) -3 (d) &an electron cknsity = (lom2 - 4) em . (d je llming and Johns ton, 1981, Begleman e t a1 1980) . -3 ,f2 C (e) Magnetic field in jets = 13 - (Johns ton e L al, 1984; Hje llnring and Jahns ton I9 81) . (f) Average spectral index - 0.6. (Spencer, 1979; H jellming and Johnston, 1981; Johns ton e t al, 1981; Fiedler et a1 1987). (g) Redshift .* 0 - 1.32. 3.40 Estimating the Radio Flux Density of SS 433 Jets at Different Wave lengths . S ubs ti tu ting the above values in equation (iv) , we ge t 3.83926 x loZo 1 P(J) = erg s - 5.6288544 16 Also 1 pc = 3 x 1018 m = 3 x 10 2 1 -1 = 2.72826 x 10 erg s -2 - At 8085 Mlz andne = 10 cm 3; we obtain by substitution 3 2 1 -I P (v) = 2.04484 x 10 erg s 19 2.04484 x 10'' x 10 and SO) = ( ) JY -2 3 ~t a fmquenq of 4885 MHz andne = 10 cm ; andby making similar substitutions, we have . 3.89324 x 10'' - 1 1 '()'I a (5.6288544 erg s 18 -1 = 6.91658 x 10 erg s and ~(9)gives 1.32 r 10-I Jjr. LC - -.0 - 4 t33Z.&: ,-- ,-- 3 For ne = 4 cm- at the same frequency, 1.55729 x - 1 PW) =( 1 erg s 5.62 885 44 -3 At 408 Miz and ne = cm , we also obtain by substituting the necessary values a 4 1 = 3.06771 n 10'' erg s - 19 3.06771 x 10" x 10 and S()I) becornes = ( 1 JY 40 2 2.25 x 10 m -3 For ne = 4 cm at the same frequency = 1.22708 x lo2' erg s - 1 = 5.450.l~~ Es timated and Obse me d Radio Flux Densi tv of SS 433 Je t-s . For a particular frequency, it is thought that the flux dens it^ varies be cause of the possible variations /f luctuations in the electron number density (ne) . An average value of 10-3 G for the magee tic fields in the jet is adopted (Johnston et al, 1984, H jellming and Johns ton, 1981). Because of the pe culiar variabi li ty of emiss ion from the object, (SS 433) , the observed flux density also is not constant for any particular frequencg. ?he estimated and masured flux &nsiq are aham in table below. ESTIMATED &ID MEASUFED FLUX DENSL'JTES : I I FREQUENCY EIECTR~NUMBER ESTIMATED nux OBSERVED FLUX ENSI~ -DENSITY D~NSI n n (cm-3 (JY) (JY) -2 5 QIz 10 0.030 0 - 0.029 (a) 5 mz 4 1.210 4885 >Hz 1o-~ 0.136 0.1 1 - 0.240(b) 4 8GPC-I z 4 1 ,239 - - 408 HHz I 0-2 1.360 0 - 1.100 (c) 4 5.459 (a) Vermnlen et a1 (1987) (b) H jellming and Johns ton (1981) (c) Spencer (1 979). 00 DISUJSSION OF RESULTS Prom the table, observational results show that the flux density variation at the observed frequency range is between 0 to 1.1 Jy. The estimated flux densities from the lower Iirnit of 2 -3 electron nuder density (n = 1U cm ) compares reasonably e , well with the corresponding observed values. Exoep t for the upper limit of electron number density, -3 (ne = 4 cm ), at the frequency of 408 MIz, the overall estimated result approximates the range of flux variability within the obserwd frequency range. The very high value of flux densi ty, (5.45 Jy) obtained at this frequency, (408 lMz) likely arises from the &rived value of electron number Lnsity (n = 4 e in literature which we had assumed. None the less , by consi de ring the minimum and maximum values -2 -3 -3 of electronnumber density (ne = 10 cm andn =4 cm ) , e from literature in our estimates, we comfortably favour differen- tial environmental effect as possible cause of emission variab- ility rather than intrinsic factors associated with ejection promss in the central sys tern. Since the existence of large scale x-ray jets, far beyond the radio jets, have been confirmed, (see for exarnp le Gilmore and Seaquis t, 1981, Watson et al, l983), we further argue that all the jets (x-ray, radio, and optical) are attributable to the initial beams being e je cted at cons tant rate from the core. An intrinsic cause of variability is more likely to limit emission from the sours (SS 433) to a narrow spectral-region rather than its characteristic meandering across wide region of spectrum. On the other hand, variation at different spectral regions as observable in all the emissions from SS 433 can hardly be correlated in the case of extrinsic factor. In particular, we believe that the %parent cluinpy beams or blobs usually observed along the jets are typically indicating regions of inhomgenous target matter along the jet paths, Sparse dis tribution of target4 atter in a continuous f low-ra te of beam implies very little emission as may be the observed case at some distances along the jets of SS 433, A1though the length of the radio emitting jet is not precisely known, as the emission reduces drastically at sow distances, (see for example Verlnenlen et al, 1987, Xjellming and Johnston, 1981, Fejes et al, 1988), it should be emphacised that the Pro ton beam collision model could account for the range of flux density values within the observed frequency range. Factors which may lead to electron density fluctuation and consequent variability in emissions from SS 433 could be any or some of the following ,. (i) Variable magnet fields (ii) S te ller wind (iii) Variation in gravitational potentials . 4.01 Variable Magnetic Fields; Observations have f imly established that the Galaxy has a magnetic field, and even the approximate value for the magnetic field strength has been s tudied extensively. The amplitude of its irregular fluctuating part has also been studied from Faraday rotation measure (Rm) of radio sources by virtue of the direct physical relation between the rota tion n-easure and the magnetic field (Rusmaikin e t a1 1978). Faraday rotation rneasur#(Rm) spe cifies the angle (0) by which the polarization plane of linearly polarized radio wave turns in a magnetic field and is directly related to the field strength (B), Neasurernent of Faraday effect on distant object provides information on the magnetic fields as well as the electron-densities in clouds of interstellar space. Rusmaikin et a1 (1978) found the variability or amplitude of the 2 galactic rotation measure to be - 18.9 -+ 14.1 rad/m within 0 0 galactic mmdinates of lo = 35O -+5j'O, bo = -6 -+ 45 . Ma g ne tic field variations have dire ct consequences on the electron number density, and therefore has the sane effect on radio emission from jets as postulated by the proton beam collision model, Dolginov, and Urpin (1978) have also shown that in the neighbourhood of many stars having magnetic fields; conditions for constant and variable magnetic fields elds t. Since SS 433 is a galactic object, the galactic-magne tic field os d llations and possibly magnetic field variations of the neighbouring Stars could affect the inters te ller space around i t res ulting in electron dens ity f lucruation with variable emission 4.02 S tellar Wind* Young galaxies, quasars as we 11 as nuclei of active sources have long been viewed as likely sources of bating and ioniization for the in~rgalacticmedium (Ozernoi and Chernamordik, 1978). Among the agents that mi&t generate these effects are; radiation {ultraviolet and so£ t x-rays) , subasmi c rays, plasma waves and shoe waves, Carlberg (1980) had sham that thare are three types of instabilities associated ~ithstellar winds, hng these is whnt is termed "a new gradient instability," all of which, he pointed out, leads to densiw and velocity perturbation, Bugno lo (1978) in the analysis of variations in the galactic electron density influence on the characteris tics of a Pulsar as observed on the earth, showed that variations from the mean e le ctron density may arise from such factors as , regions along the path and the generally turbulent maracter of the galactic plasma or interstellar wind. Thus, he gave the magnitude of electron fluctuations resulting from the later as 6 where ,b Ne is the electron density whose mean value is denoted by <~e) Stellar winds in massive s tars are known to be inhomogenous (Lmg and White 1980) and display short period variability (Wagner and Snm 1978) . The density of the stellar wind for s om large stars with approximately 1.3 s te llar radii ( 10 l2 a) 11 -3 is estimared to be 10 an (Jdnnston et a1 1981) and shows an inverse pdratic dependenoe (ra2) on distanae. A mob1 of a massive secondary star in SS 433 system appears quite attrac- tive eventhough this project report is particularly concerned with radio emiss ion from the je ts . 4.03 Variation In Gravitational Potential. For pulses of electromagnetic radiation, the effect of qravitational potential/waves would be manifested as a change in the period between pulses (Sazhin 1978). It was shown thdt the time required for a pulse of electromagnetic radiation moving in a gravltational wave to cover the path from the transmitter to receiver will depend on the, amplitude and phase of the gravitational waves. Harris (1974) also emphacised that, not only are more complicated configurations of radio jet features result from gravitational potential variations, but the presence of other objects will introduce fluctuations in gravi tati-onal potential leading to yet another complex radio source structure. The effects of these factor(s) discussed can, therefore, not only be responsible for the emission variability from SS 433 hut may also be accountable for the variable jet structure of the source, CHAPTER V SUMMARY AND CON CLUSI (N Many models of the energy sources in extra- galactic radio sources are very likely the scaled-up versions of Galactic phenomena (Rees 1971). These models are supporte d by observations which disclose the presence of compact radio core in the nuclei of normal galaxies, radio galaxies, and quasars as we 11 as Galactic objects . Although the energy output of Galactic and extragalactic phenomena differ by many orders of magnitude, they are similar in other respects 1 morphology, spectrum, variability and magnetic field strength among others. Extragalactic sources are generally associated with kilo- parsec-sized extended emission with a linear morphology (double structure and/or jets) in addition to a radio core. Extended radio emission associated with Galactic sources are usually identified with supernova remnants (SNR) and have either a shell- like morphology (Cas A) or a filled ellipsoidal morphology (Tan A). However, few unique Galactic sources and in particular SS 433 have sxtended emission features (je ts and perhaps lobes) s imilar to that in extraglactic objects. There are oppositely directed 73. jets of x-ray, optical-, and radio emitting materials moving at velocity of 0,26C with only the linear size and energy output differing from extragalactic sources. Scaling laws relating the stellar size sources (e.g. SS 433, and Sco X-?) to the extragalactic sources have been proposed. The possibility of the same phenomena operating in both classes has spurred intense study of these galactic objects in hope of gaining insight into the physics of extra- galactic sources. In the same light, and on the strength of the positive attempt of the Proton Beam Collision model in explaining the acceleration mechanism in some extr,galac tic radio sources (hnyakoha et a1 1988); coupled with the precept of slmilar entrainment possibility in ~rnallgrscale jets as polnted out by De Young (29861, we have shown in this project re?ort that the Proton Beam Collision model can, infact, account for the observed radio flux densities observable in SS 433 jets at different wavelengths. The flux density variation, depending on the nbserved wavelength being in crl .,e a greernent with the estimated values. We have also attempted to use this model in explaining the variability of emission from the jets of SS 433 as being due to differential environmental factors rather than intrinsic causes usually associated with ejection processes in the central system. By possible variation of the presupposed target matter along the jet reqions, we have demonstrated, that flux-density variat- ion can arise from a corresponding thermal matter density- f l_uctuations along the jet path. We have als~suggested three possible factors namely : (i)variable magnetic field (ii) stellar wind and (iii ) variation in gravitational notentials as the likely cause(s1 of the thermal matter density fluctuations. In particular, blackground Rotation Measures (RMs) of many Galactic sources indicate clearly that there is a magnetic irregularity scale of order 10 pc within our own Galaxy (see for example Kim et a1 1988). This may vary considerably depending on the source galactic co-ordinates, The vital relationship between Rotation Measure, magnetic fields and electron number density in the interstellar or interrja! - 1-tic medium cannr- ' 'je overemphasized. In conclusion, it :v~sfound that the variability of radio emissions in SE 43hcould be explained in terms of density fluctuations of i-arget matter along the beam paths within the jet volume. The Proton-Beam collision mcdel is then viable in explaining the typical radio emissions of this qaLzc tic object, Proton-proton collision process may therefarc be a likely common phenomena in both galactic and exkagal~cticradio jei emissions. - -T----T---- (ti) DECEMBER 1980 FIG. I.--Images of SS 433 a1 cigl I cpo~hs.l'11e hor~~on~alarid vert~caldxcl arc nyhi itxcnslon ;lnJ declination, respcctivcly, relative ro an arbitrary origin. Contour lmls arc 5%. 10%. 20%. JU ,,,, WK,, m - (c) FEBRUARY 1981 200 0 -200 - MlLLlARC SEC I I(, I4 I I I 1 I-I 150 103 50 0 -M -1r.x) - 150 MlLLlARC SEC 1 I<. Id I I h 1527 2, 1987 I -- , 1 I i I -1 100- ( (e) MAY 1981- - 50 - Y 0 0 tI A - R 0 -- C '3 - -50 - -100 I I 1 15 I 100 50 0 - 50 -100 -150 MlLLlAFiC SEC I.lt.. 1,. MlLLlARC SEC 1-11 11 (g) AUGUST 1981 m . . MltLlARC SEC 1200 , 800 bO0 0 -400 -800. -1200 'RELATIVE RIGHT ASCENSION(MAS) (.. - -+I- ; Hybrid map or SS433 at 21 nn, JD: 2h5865. The convolving clean beam was 162 x 32 mas w th PA 20". The map warn obt~d'm ERclsberg - Westerbork - Jodrell Bank Mark 11 and ElTcclsbrrg - Wcs~erhork Mark I11 VLBI data. Su rrimpwcd is the model trajaaory, bud on the parameters of Anderson et al. (1983), fhc PA of premsion axis was 98" and fhc assumed distance 5.0 kpc. The model poiatn arc pk#W ia 5 days intervals. The contour levels are dashed. -5. -2; solid: 2, 3, 5. 7, 10, IS, 20, 30, 40, 50. 70, gnu,,o the peak intensity SSL33 EFF WSRT JOO 180 INTRODUCTION TO APPENDIX I1 PgpeIldix lIa-IIe is a typical radio flux densi ty masurements of SS 433 at 408 MHz covering a period of four years (April 1980 to March 1985)- Quiescent and active flaring periods are dis tin- guishe d on s tatis tical grow d. The emission was dominated by what was terued quies~ntlevel, but at leas t 72 individual flares, as well as six periods of intense flaring activity we= observed during whi & the source more than doubled its flux density (Bansignori-Facondi e t a1 1986) . From the data analysis, flares are present at an average rate of one every 10 days, both in the quiescent and in the active phase. The two phases differ mainly in the awerage flux density level whi& in the quiescent period remains well below the values attained during the active phase. Appendix IIf depicts the individual flare events as analysed from the statis tical data of appendix IIa-IIe. There is s om evidence for two different kinds of active f laring periods which, apart from a common fast rise-time of a few days, significantly differ in their average lifetime, decay properties and number of constituent individual flare events. : : -.Obseped Flux densities of SS433 measured at 408 MHz. 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