1. Low frequency pulsar science, 25 th June Wide profile drifting pulsars : Wide profile drifting pulsars : an elegant way to probe pulsar magnetosphere Low Frequency Observations with the GMRT Bhaswati Bhattacharyya Collaborators: Yashwant Gupta, Janusz Gil LoLo

2. Interpreted as Highly aligned “Rotation axis” & “Magnetic axis” ( α ranging from ~ 1-10 deg) Wide profile Pulsars : A special class Line of sight samples large region of the polar cap :  Observed emission from pulsar spanning wide longitude region (>90 deg) LOS cuts with corresponding pulse profiles

3. Possibility of emission from both inner and outer rings : Simultaneous multiple drift regions can be seen Can probe interrelation between emission processes in two rings Can put constraints on the theoretical models Wide profile pulsars probe detailed distribution of emission regions Wide profile pulsars probe detailed distribution of emission regions

4. Interpretation  Emission from two concentric rings Simulations with dipolar geometry reproduces: Pulse width evolution with frequency The overall pattern of drifting (Results from Bhattacharyya et al. 2007)  Three drift regions  Inner region: Multiple drift bands  Outer region: Single drift band  Drift regions : “Phase locked” Closely spaced  Measured P 3 (P 3 m )= 18.3 P 1 Example of an unique wide profile pulsar : PSR B0818-41 Single pulses at 325 MHz (regular drifting) Simulation of the single pulses

5. Phase relation between the leading outer and trailing outer regions Towards solution of aliasing problem Phase Locked relation between the inner and outer rings Probe of interrelation between emission from two rings Part-I Part-II

6. Drift regions Outer leading Inner saddle Outer trailing Peak emission from leading and trailing outer regions are out of phase to each other Correlated at ~ 9 P 1 Phase relation between outer leading and trailing regions This constant phase offset is referred as P 5 hereafter Cross correlation of pulse energy in outer trailing & outer leading components for different pulse lags. Solid (325 MHz), long-dash (610 MHz), short-dash (244 MHz) For different sequences of single pulses P 5 varies from 7 to 11 P 1

7. Angular separation between two consecutive sparks (measured around the magnetic axis) Determination of P 5 & Utilising P 5 for resolving aliasing Case-1 Stationary sparks : Integer part & : Fractional part Peak emission from leading and trailing peaks “Correlated” When = 0 Pulse width measured with respect to magnetic axis ≠ rotational phase P5P5 P 5 can be determined knowing geometry, N sp, D P5=0 P1

8.  Consider sparks drifting with drift rate = D deg/P 1  As the LOS traverses from leading to trailing peak, spark pattern rotates deg Henc e ~0.5 from observations of single pulses from B0818-41 Not possible for unaliased drifting Let us explore possibilities of aliased drifting.. Case-2 Drifting sparks P 5 =9 P 1

9. For alias order n, Apparent drift rate Where, k =INT((n+1)/2)‏ P 5 : time taken by the spark pattern to cover Amount by which a spark pattern with drift rate D will appear to move in one pulse period

10. N sp =20; 1 st order aliased (n=2, k=1); D=19 deg/P 1 ; P 5 =8.7 P 1 ; P 4 ~ 18 P 1 ~10 s N sp =18; 2 nd order aliased (n=4, k=2); D=41.053 deg/P 1 ; P 5 =10.8 P 1 ; P 4 ~ 9 P 1 ~5 s N sp =19; 2 st order aliased (n=4,k=2); D=38.9 deg/P 1 ; P 5 =7.4 P 1 ; P 4 ~9 P 1 ~5 s B0818-41 has the fastest carousel Possible nearby P 5 with aliased drifting Carousel periods (P 4 ) for other pulsars B0809+74 : 165 P 1 ~ 200 s (van Leeuwen et al. 2003) B0818-13 : 30 s (Janssen et al. 2004) B0826-34 : 14 P 1 ~ 25.9 s (Gupta et al. 2004) B0834+06 : 14.8 P 1 ~ 18.9 s (Asgekar & Deshpande, 2005) B0943+10 : 37 P 1 ~ 40 s (Deshpande & Rankin, 1999) P 5 ~9 P 1 Most probable choice

11. Support from Simulation Simulation with alpha= 11 deg, beta= -5.4 deg; N sp = 20, Drift rate D= 19 deg/P 1 ; Reproduces P 5 ~ 9 P 1 ; P 4 ~ 18 P 1

12.  Too slow to move the spark pattern so much that emission is correlated after 9P 1  Hence can not reproduce the observed phase relation Impossible to reproduce the phase relation between leading outer and trailing outer regions with unaliased drifting Possible to reproduce the phase relation with certain choice of alias orders Favoured one : 1 st order aliased P 4 ~10s Summary of Part-I

13. Single pulses from PSR B0818-41 at 325 MHz Outer ring Inner ring Phase locked emission from inner and outer rings Emission coming from two rings : B0818-41 Outer ring Inner ring Outer ring LOS cut through the polar cap

14.  Nulling is simultaneous  Changing drift rates are simultaneous Examples of irregular drifting and nulling of : PSR B0818-41 Single pulses at 325 MHz Emission from inner and outer rings,  Phase locked even after nulling and irregular drifting

15. Another pulsar with phase locked emission from inner and outer rings... PSR B0826-34

16. Emission coming from two rings : B0826-34 Single pulses from PSR B0826-34 at 610 MHz Phase locked emission from inner and outer rings MP IP Inner ring Outer ring

17. 13 drift bands Phase locked emission from inner and outer ring Similar results from Esamdin et al. 2005

18. Phase locked even after nulling and irregular difting Nulling is simultaneous Changing drift rates are simultaneous Emission from inner and outer rings, Significant correlation between main pulse & inter pulse Correlation of total energy of main pulse & inter pulse decrease similarly with increasing pulse number Similar to as observed for B0818-41 In addition…

19. Yet another pulsar with phase locked emission from inner and outer rings ? PSR B0815+09

20. Subpulse drift pattern in B0815+09 (Qiao et al. 2004, MNRAS, 274, 572) Vacuum gap + Inner core gap Phase locked emission from inner and outer rings ? Explained with

21. No Counter example observed  Signature of drifting from more than one ring for few pulsars  For all of those pulsars, emission from inner and outer rings are locked in phase Phase locked relation between the inner and outer rings : observed for all wide profile pulsars

22.  Common drift rate in the outer and inner rings  Emission in the two rings are not independent  Conditions responsible for drifting similar in both rings Interpretation The conditions are similar everywhere in the magnetosphere Implications to theoretical models …

23. Emission from two cones : Theoretical models Gil & Sendyk 2000 : At any given time polar cap is populated as densely as possible Characteristic dimension of a spark and typical distance between sparks ~h (polar cap height) Asseo et al. 2002 : Total magnetic field : superposition of global dipolar field and of star centered multi polar fields Closer to the gap the radial and azimuthally variations can not be separated the system of sub beams has to be treated as a whole three dimensional character of the perturbations will introduce drifting Wright et al. 2003 : Use observations to define and constrain the model Pulsar radio emission is global pan-magnetosphere phenomenon Two rings of emission reflect the intersection of the null surface with light cylinder and co rotating dead zones respectively

24. Summary PSR B0818-41 is an unique pulsar with simultaneous multiple drift regions Aliasing can be resolved using the phase relationship between leading outer and trailing outer regions; Predicts P 4 ~10s Phase locked emission from two emission rings : Pulsar radio emission is pan – magnetosphere phenomenon

25. Thank You

26. Examples of wide profile pulsars : PSR B0826-34 Average profile at multiple frequencies Single pulses at 325 MHz Results from: Bhattacharyya et al., 2008, MNRAS, 383, 1538B 157 MHz 325 MHz 1060 MHz 610 MHz

27. Examples of wide profile pulsars : PSR B0818-41 Average profile at multiple frequencies Single pulses at 325 MHz 157 MHz 244 MHz 325 MHz 610 MHz 1060 MHz Results from: Bhattacharyya et al., 2007, MNRAS, 377L, 10B Bhattacharyya et al., 2008, MNRAS, to be submitted