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156 Chapter 6. EVN and MERLIN observations Table 6.5: Model fitted positions of the components in the 1RXS J001442.2+580201 radio jets and obtained jet parameters. Comp. Distance P.A. βmin θmax [mas] [ ◦ ] [ ◦ ] N1 8.6 ± 0.3 2 0.23 ± 0.02 77 ± 1 N2 3.6 ± 0.2 −10 0.16 ± 0.02 81 ± 1 S2 5.0 ± 0.1 177 0.16 ± 0.02 81 ± 1 S1 13.7 ± 0.3 177 0.23 ± 0.02 77 ± 1 nents are present southwards, one (S2) of 1.1 mJy at 5.0 mas (P.A. 177 ◦ , FWHM of 0.8 mas) and the other one (S1) of 0.4 mJy at 13.7 mas (P.A. 177 ◦ , FWHM below 0.3 mas). If we assume that components S1 and N1 correspond to a pair of plasma clouds ejected at the same epoch near the compact object and perpendicularly to the accretion disk, we can estimate some parameters of the jets by using the following equation: β cos θ = µa − µr µa + µr = da − dr da + dr , (6.1) β being the velocity of the clouds in units of the speed of light, θ the angle between the direction of motion of the ejecta and the line of sight and µa and µr the proper motions of the approaching and receding components, respectively (see Sect. 1.2.1). Although we do not know the epoch of ejection of the clouds, we can cancel the time variable by using the relative distances to the core da and dr, as expressed in Eq. 6.1. Since both variables, β and cos θ, take values between 0 and 1, it is clear that knowing β cos θ allows us to compute a lower limit for the velocity (βmin) and an upper limit for the angle (θmax). The same applies for the S2 and N2 components. In Table 6.5 we list the positions of the components obtained from model fitting, together with the derived values from βmin and θmax for each one of the pairs. The slightly different results obtained using pair 1 or 2, could be due to the fact that the position for the S1 component obtained with model fitting happens to be at the lower part of this elongated component, hence increasing β cos θ, or to intrinsic different velocities for each one of the pairs. Hereafter we will use β > 0.20 ± 0.02 and θ < 78 ± 1 ◦ . A similar approach to obtain the jet parameters of the source can be performed
6.3. Results and discussion 157 thanks to the brightness asymmetry of the components using the following equation (see Sect. 1.2.1): β cos θ = (Sa/Sr) 1/(k−α) − 1 (Sa/Sr) 1/(k−α) + 1 , (6.2) where Sa and Sr are the flux densities of the approaching and receding components, respectively, k equals 2 for a continuous jet and 3 for discrete condensations, and α is the spectral index of the emission (Sν ∝ ν +α ). However, the equation above is only valid when the components are at the same distance from the core. If this is not the case (i.e., dr < da), the ratio Sa/Sr will be lower than the one that should be used in Eq. 6.2 (because the flux density decreases with increasing distance from the core). In consequence, Eq. 6.2 only allows us to obtain a lower limit for β cos θ. In order to use this approach we will consider k = 3, because the components seem to be discrete condensations, and α = −0.20 ± 0.05, according to the overall spectral index reported in Table 5.1, since we do not have spectral index information of the components. The use of the flux densities obtained after model fitting gives β cos θ > 0.09 ± 0.04 for the S2–N2 pair and β cos θ > −0.07 ± 0.08 for the S1–N1 pair. This last value is certainly surprising, although it can be explained by the fact that the S1 flux density obtained after model fitting does not account for the total flux of this plasma cloud. In fact, better estimates of the flux densities can be obtained summing together the flux densities of the clean components obtained within each one of the four plasma clouds. This yields to β cos θ > 0.13 ± 0.05 for the S2–N2 pair and β cos θ > 0.17±0.02 for the S1–N1 pair, in good agreement with the values computed using the distances from the components to the core, shown in Table 6.5. If we compare the VLA position reported in Table 5.1 with the MERLIN position in Table 6.2 we can see that they are different. In fact, taking into account the errors, the MERLIN−VLA position offsets can be expressed as: ∆α cos δ = 16 ± 10 mas and ∆δ = 27 ± 10 mas. Assuming that the difference in position is due to intrinsic proper motions and considering the time span between both observations, 224 days, we obtain: µα cos δ = 26 ± 16 mas yr −1 and µδ = 44 ± 16 mas yr −1 . Although a proper motion of the source would clearly indicate its microquasar nature, because no proper motion would be detected in an extragalactic source, we must be cautious with this result. First of all, the phase-reference sources where different in the VLA and MERLIN observations, as well as the observing frequencies from which positions were estimated. On the other hand, none of these results exceeds the 3σ
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UNIVERSITAT DE BARCELONA Departamen
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Per a la meva neboda Blanca, que va
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feina no presentada en aquesta tesi
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desfogar-nos conjuntament, per la s
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From the scientifical point of view
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Gràcies a la meva germana Nàdia,
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ii CONTENTS I Discovery and study o
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iv CONTENTS II A search for new mic
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vi CONTENTS
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viii Resum de la tesi d’Eddington
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x Resum de la tesi imprescindible p
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xii Resum de la tesi dels sistemes
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xiv Resum de la tesi un comportamen
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xvi Resum de la tesi MilliARC SEC 4
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xviii Resum de la tesi per poder de
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xx Resum de la tesi valors força s
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xxii Resum de la tesi 2. D’entre
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xxiv Resum de la tesi pano Alemán
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xxvi Resum de la tesi 3.3 Observaci
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xxviii Resum de la tesi habitual en
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xxx Resum de la tesi Per tant, si l
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xxxii BIBLIOGRAFIA
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28 BIBLIOGRAPHY Lewin, W. H. G., va
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30 BIBLIOGRAPHY
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Chapter 2 Multiwavelength approach
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2.3. An interesting target in the s
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2.4. The radio counterpart: NVSS J1
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2.5. The optical/IR star: LS 5039 5
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2.6. The X-ray counterpart: RX J182
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2.7. The γ-ray counterpart: 3EG J1
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2.7. The γ-ray counterpart: 3EG J1
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2.8. A proposed scenario to explain
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Figure 2.23: Scenario where the mul
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2.9. Conclusions 87 8. We have carr
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Bibliography Blandford, R. D., & K
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BIBLIOGRAPHY 91 Merck, M., Bertsch,
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Chapter 3 LS 5039 as a runaway micr
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3.1. Positions and proper motions 9
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3.1. Positions and proper motions 9
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3.3. The past trajectory of LS 5039
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3.4. SNR G016.8−01.1 101 DECLINAT
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3.4. SNR G016.8−01.1 103 Normaliz
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