Evolution of the radio outflow in LS 5039 and PSR B

Transcription

1 Evolution of the radio outflow in LS 539 and PSR B Javier Moldón ASTRON Netherlands Institute for Radio Astronomy/Universitat de Barcelona M. Ribó, Josep M. Paredes Universitat de Barcelona Variable Galactic Gamma-Ray Sources (II) Barcelona, Apr 16, 213

2 LS 539 The periodic milliarcsecond radio morphology of LS 539 [Ribó, M., Paredes, J. M., Moldón, J., Martí, J., & Massi, M. 28, A&A, 481, 17] [Moldón, J., Ribó, M., & Paredes, J. M., 212, A&A, 548, A13] LS / 25

3 Context and motivation [Adapted from Paredes et al. 2, Science, 288, 234] Very compact orbit. Periodic and stable light curves in X-rays and gamma-rays. Extended bipolar radio emission on mas scales. LS 539 Context and motivation 2 / 25

4 VLBI observations of LS 539 [Ribó et al. 28, A&A, 481, 17] Two VLBA runs separated by 5 days. Changing morphology. LS 539 Morphology of LS / 25

5 VLBI observations of LS 539 Five VLBA observations separated one day. Covering a whole orbital cycle. LS 539 Morphology of LS / 25

6 Results Changing morphology in 24 hours. Strong hints of orbital periodicity. LS 539 Morphology of LS / 25

7 All VLBI observations Project Array Epoch Orbital Freq. Y-M-D phase [GHz] BP51 VLBA ER11 EVN GR21A VLBA GR21B VLBA BD87G VLBA BD15A VLBA BD15G VLBA EF18A EVN EF18B EVN EF18C EVN BR127A VLBA BR127B VLBA BR127C VLBA BR127D VLBA BR127E VLBA EM74 EVN LS 539 Morphology of LS / 25

8 Results Dec. offset [mas] E N BD15A φ orb =.2 BR127A φ orb =.3 BR127E φ orb =.6 φ orb..1 φ orb.15.4 φ orb.5.6 φ orb.75.9 LS 539 Morphology of LS / 25

9 Results Dec. offset [mas] E N BP51 φ orb =.16 BR127B φ orb =.29 EF18B φ orb =.4 φ orb..1 φ orb.15.4 φ orb.5.6 φ orb.75.9 LS 539 Morphology of LS / 25

10 Results Dec. offset [mas] E N GR21A φ orb =.49 BD15G φ orb =.51 BR127C φ orb =.55 BD87G φ orb =.58 φ orb..1 φ orb.15.4 φ orb.5.6 φ orb.75.9 LS 539 Morphology of LS / 25

11 Results Dec. offset [mas] E N GR21B φ orb =.77 BR127D φ orb =.8 EF18A φ orb =.89 EF18C φ orb =.91 φ orb..1 φ orb.15.4 φ orb.5.6 φ orb.75.9 LS 539 Morphology of LS / 25

12 Summary The gamma-ray binary LS 539 shows periodic orbital morphological variability Morphological changes every 24h. Images at similar orbital phases show similar morphology. This behaviour is stable on time scales of years. LS 539 Morphology of LS / 25

13 Model of the flow of relativistic particles Aim: reproduce global changes in the extended emission. We assume the presence of a young non-accreting pulsar. We consider an outflow originated at distances beyond 5 1a [Bosch-Ramon et al. 212, A&A, 544, A59]. We compute the flow evolution at different orbital phases. Produce synthetic radio maps and compare them with the VLBI observations. LS 539 Morphology of LS / 25

14 Model of the flow of relativistic particles The model: Electrons are accelerated at 1a Outflow forming a cone with openning angle of 2 Evolution of the flow following conservation of the number of particles N(r, γ)dγ = N(r, γ )dγ Energetics: Synchrotron radiation, γ syn = 4 σ T γ 2 B 2 3 8πmc 2 Inverse Compton in the Thomson regime, γ IC,Th = 4 3 σ T L star γ 2 4π mc 2 r 2 Adiabatic cooling, which dominates along the flow, γ ad = 2 3 v γ r Considering a magnetic field B = B r r : γ syn γ2 r 2 γ IC,Th γ2 r 2 γ ad γ r γ = γ syn + γ IC,Th + γ ad dγ dγ N(r, γ) LS 539 Morphology of LS / 25

15 Model of the flow of relativistic particles The free parameters of the model: Constant injection of electrons with energies 1 < γ e < 1 4, Q inj.2l sd Magnetic field B =.1 G, compatible with equipartition Flow velocity, approximated to v =.4c Geometrical free parameters: Inclination of the orbit, i Longitude of the ascending node, Ω. Orientation on the sky LS 539 Morphology of LS / 25

16 Results of the model Dec. offset [mas] E N BP51 φ orb =.16 BR127B φ orb =.29 EF18B φ orb =.4 Observations Dec. offset [mas] E N Synthetic model LS 539 Morphology of LS / 25

17 Results of the model Dec. offset [mas] E N GR21A φ orb =.49 BD15G φ orb =.51 BR127C φ orb =.55 BD87G φ orb =.58 Dec. offset [mas] E N LS 539 Morphology of LS / 25

18 Results of the model Dec. offset [mas] E N GR21B φ orb =.77 BR127D φ orb =.8 EF18A φ orb =.89 EF18C φ orb =.91 Dec. offset [mas] E N LS 539 Morphology of LS / 25

19 Results of the model Dec. offset [mas] E N BD15A φ orb =.2 BR127A φ orb =.3 BR127E φ orb =.6 Dec. offset [mas] E N LS 539 Morphology of LS / 25

20 Summary of the outflow modelisation The model accounts for the main morphological features of LS 539 It reproduces the orientation and size of the extended emission, including the bipolar structures The changes are explained for i 7 and Ω 13 Using the system inclination we determine the mass of the compact object The mass of the compact object is M. This mass is compatible with the presence of a pulsar. Limitations of the model The model does not provide information about the core component Fails to explain the main component short after periastron LS 539 Morphology of LS / 25

21 PSR B Discovery of extended emission from PSR B [Moldón, J., Johnston, S., Ribó, M., Paredes, J. M., & Deller, A. T. 211, ApJL, 732, L1] [Moldón, et al. 213, in preparation] PSR B / 25

22 Context and motivation PSR B is the only gamma-ray binary in which the presence of a pulsar has been confirmed. PSR B The orbit of PSR B / 25

23 VLBI observations of PSR B Run Y-M-D Epoch A τ + 1 B τ + 21 C τ PSR B The orbit of PSR B / 25

24 Results 8 6 Run A τ+1 27 July 28 Run B 6 τ August 17 Run C 6 τ June MilliARC SEC 2-2 2a 2= 14.4 AU MilliARC SEC 2-2 MilliARC SEC MilliARC SEC MilliARC SEC MilliARC SEC [Moldón, J., et al. 211, ApJL, 732, L1] PSR B Results 16 / 25

25 New VLBI campaign Five LBA observations τ-21, +, +29, +55, and +17 days. Correlated using pulsar gating. PSR B Results 17 / 25

26 Results τ 21 d τ + d τ + 29 d τ + 55 d τ + 17 d 1 Dec. offset [mas] PRELIMINARY. Nebula already formed at τ 21 days. P.A. changes. Three main directions. PSR B Results 18 / 25

27 Pulsar astrometry.15.1 Relativeamplitude Pulsephase Three correlation passes. We can measure the pulsar position within the nebula. PSR B Results 19 / 25

28 Conclusions VLBI coverage of the periastron passage of PSR B Similar morphology to the one seen in previous periastron passage. Although important P.A. changes can be seen. Outflow seen in three main directions. PSR B Conclusions 2 / 25