Hydrodynamical simulations of the jet in the symbiotic star(5)

In papers I and II in this series, we presented hydrodynamical simulations of jet models with parameters representative of the symbiotic system MWC 560. These were simulations of a pulsed, initially underdense jet in a high density ambient medium. Since th

Fig.4.—Spectrumintheenergyrangebetween0.15–15keV;top:minosity,formodelity,solid)i’andondays155(close153(atominimumthemaximumoftheX-raytotalX-raylu-(dashed).dashed),wardsseethebytimeaThebottom:factorspectrumfordependenceof100plottedmodeliv’ondays105(solid)luminos-and107offortheclaritywithspectrum.

inaeachsolidplot.lineisOneshiftedcanclearlydown-relativelylowtemperatureplasma(107K)inthejetas

ζ=

f(0.2 0.7)keV

f(3)

9keV

Wechooseregionsinthespectrumwherenolinesarepresent,althoughphotonswiththesehighenergieshavenotbeenobservedfromthejetormightbeconfusedwithphotonsfromthecentralengineinobservedspectra.

4.2.Determiningthetemperaturefrommodelspectra

Inmodeli’,thehightemperatureproxy,log(ξ),varieswithtimespanningarangefrom1.5to3.Ithasitshigh-estvalue(i.e.thespectrumhasthesteepestslope,hencetheaveragetemperatureisatitslowest

value),whentheX-rayluminosityshowsaminimum(Fig.6).Compar-isonofthemodellog(ξ)valueswiththatofasingle-temperaturethermalplasma(Fig.5,bottom)givesustemperatureestimatesofthehotcomponentbetween8×106K(0.69keV)and1.7×107K(1.5keV).Thehighesttemperaturesareconsistentwiththatofpost-shockgaswithashockvelocityofabout1100kms 1.Theminimuminthelog(ξ)(i.e.maximuminaverage

5

Fig.5.—Temperatureproxiesasafunctionoftemperatureforahardnesssingle-temperaturetext.

ratioζ(top)thermaland uxplasmaratioξcalculated(bottom)aswithde nedATOMDB:intheFig.6.—X-rayluminosityofthejetasafunctionoftimeintheenergy(middle)range0.15–15keV(top), uxratioξasafunctionoftimemodelsi’.

andhardnessratioζasafunctionoftime(bottom)fortemperature)coincideswiththeemergenceofeachnewpulse;withinthenext2–3dayperiodthecompressedknotcoolsandtheemissivityincreases.ThereforethemaximumintheX-rayluminosityisreachedabout2–3dayslater.

Thelowtemperatureproxy,log(ζ),variesbetweenabout0.5and1.6,thecorrespondingtemperaturesliebetween1.6×106K(0.14keV)and3×106K(0.26keV).Thejetisthereforebetterdescribedasacombi-nationofawarmandahotcomponentratherthanasasingle-temperatureplasma.

Inmodeliv’,log(ξ)variesbetween2.16and2.8;thecorresponding7temperaturesare8×10K(0.69keV)and1.2×10K(1.03keV).Thelowtemperatureproxy,log(ζ),liesbetween0.1and0.6;thecorrespondingtem-peraturesare3×106K(0.26keV)and3.8×106K(0.33keV).Asinmodeli’,thejetisbettercharacterizedasacombinationofawarmandahotcomponent.

Therangeoftemperaturesinthehotcomponentoveronepulsecycleinmodeliv’issmallercomparedtothatinmodeli’;thisisbecausethehigherdensityinmodeliv’makesradiativecoolingmoree cient,suchthattheshockheatingisdampedmoree ciently.Thedi erentdensitycontrastsbetweenthejetpulsesandthesteadyjetinbothmodelsalsoleadtodi erentshockvelocitiesandthustodi erentshocktemperaturestowhichtheplasmaisheatedinitially.