Evolution of the radio outflow in LS 539 and PSR B1259 63 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
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 539 1 / 25
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
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 539 3 / 25
VLBI observations of LS 539 Five VLBA observations separated one day. Covering a whole orbital cycle. LS 539 Morphology of LS 539 4 / 25
Results Changing morphology in 24 hours. Strong hints of orbital periodicity. LS 539 Morphology of LS 539 5 / 25
All VLBI observations Project Array Epoch Orbital Freq. Y-M-D phase [GHz] BP51 VLBA 1999-5-8.16 5. ER11 EVN 2-3-1.39 5. GR21A VLBA 2-6-3.49 5. GR21B VLBA 2-6-8.77 5. BD87G VLBA 24-6-11.58 8.5 BD15A VLBA 25-6-11.2 8.4 BD15G VLBA 26-1-29.51 8.4 EF18A EVN 27-3-1.89 5. EF18B EVN 27-3-3.4 5. EF18C EVN 27-3-5.91 5. BR127A VLBA 27-7-5.3 5. BR127B VLBA 27-7-6.29 5. BR127C VLBA 27-7-7.55 5. BR127D VLBA 27-7-8.8 5. BR127E VLBA 27-7-9.6 5. EM74 EVN 29-3-7.46 1.7 LS 539 Morphology of LS 539 6 / 25
Results Dec. offset [mas] 1 5 5 1 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 539 7 / 25
Results Dec. offset [mas] 1 5 5 1 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 539 7 / 25
Results Dec. offset [mas] 1 5 5 1 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 539 7 / 25
Results Dec. offset [mas] 1 5 5 1 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 539 7 / 25
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 539 8 / 25
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 539 9 / 25
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 539 1 / 25
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 539 11 / 25
Results of the model Dec. offset [mas] 1 5 5 1 E N BP51 φ orb =.16 BR127B φ orb =.29 EF18B φ orb =.4 Observations Dec. offset [mas] 1 5 5 1 E N Synthetic model LS 539 Morphology of LS 539 11 / 25
Results of the model Dec. offset [mas] 1 5 5 1 E N GR21A φ orb =.49 BD15G φ orb =.51 BR127C φ orb =.55 BD87G φ orb =.58 Dec. offset [mas] 1 5 5 1 E N LS 539 Morphology of LS 539 11 / 25
Results of the model Dec. offset [mas] 1 5 5 1 E N GR21B φ orb =.77 BR127D φ orb =.8 EF18A φ orb =.89 EF18C φ orb =.91 Dec. offset [mas] 1 5 5 1 E N LS 539 Morphology of LS 539 11 / 25
Results of the model Dec. offset [mas] 1 5 5 1 E N BD15A φ orb =.2 BR127A φ orb =.3 BR127E φ orb =.6 Dec. offset [mas] 1 5 5 1 E N LS 539 Morphology of LS 539 12 / 25
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 1.3 2.7 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 539 13 / 25
PSR B1259 63 Discovery of extended emission from PSR B1259 63 [Moldón, J., Johnston, S., Ribó, M., Paredes, J. M., & Deller, A. T. 211, ApJL, 732, L1] [Moldón, et al. 213, in preparation] PSR B1259 63 13 / 25
Context and motivation PSR B1259 63 is the only gamma-ray binary in which the presence of a pulsar has been confirmed. PSR B1259 63 The orbit of PSR B1259 63 14 / 25
VLBI observations of PSR B1259 63 Run Y-M-D Epoch A 27-7-28 τ + 1 B 27-8-17 τ + 21 C 28-6-6 τ + 315 PSR B1259 63 The orbit of PSR B1259 63 15 / 25
Results 8 6 Run A τ+1 27 July 28 Run B 6 τ+21 8 27 August 17 Run C 6 τ+315 8 28 June 6 4 4 4 MilliARC SEC 2-2 2a 2= 14.4 AU MilliARC SEC 2-2 MilliARC SEC 2-2 -4-4 -4-6 -6-6 -8-8 -8 8 6 4 2-2 -4-6 -8 MilliARC SEC 8 6 4 2-2 -4-6 -8 MilliARC SEC 8 6 4 2-2 -4-6 -8 MilliARC SEC [Moldón, J., et al. 211, ApJL, 732, L1] PSR B1259 63 Results 16 / 25
New VLBI campaign 21-211 Five LBA observations 21-211. τ-21, +, +29, +55, and +17 days. Correlated using pulsar gating. PSR B1259 63 Results 17 / 25
Results τ 21 d τ + d τ + 29 d τ + 55 d τ + 17 d 1 Dec. offset [mas] 5 5 5 5 1 5 5 1 5 5 1 5 5 1 5 5 1 PRELIMINARY. Nebula already formed at τ 21 days. P.A. changes. Three main directions. PSR B1259 63 Results 18 / 25
Pulsar astrometry.15.1 Relativeamplitude.5...1.2.3.4.5.6.7.8.9 1. Pulsephase Three correlation passes. We can measure the pulsar position within the nebula. PSR B1259 63 Results 19 / 25
Conclusions VLBI coverage of the 21-211 periastron passage of PSR B1259 63. 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 B1259 63 Conclusions 2 / 25