Observing Vela With XDM The First Year Sarah Buchner KAT Bursary conference Dec 2009 Observing Vela with XDM2 Summary Pulsar timing Timing Vela pulsar Looking for glitches sudden spin-ups For last year I have observed Vela pulsar with XDM for 15 hours per day. Observing Vela with XDM3 Outline Introduction What is a pulsar glitch? Motivation for XDM observations Pulsar Timing 101 Early results Challenges! Conclusion Observing Vela with XDM4 Observing Pulsars Observing Vela with XDM5 Pulsars as clocks Massive flywheel -> very good clock Can unambiguously number pulses Model rotation and compare observed arrival of pulse with predicted arrival Observing Vela with XDM6 Pulsar Glitches Very good clock but Sudden increase in frequency or spin-up Frequency increases by few parts per million In energy terms earthquake of 17 on Richter scale surface of the earth moves by 15 m. Observing Vela with XDM7 HartRAO Glitch observations Observing Vela with XDM8 Questions How fast does the crust spin-up? What is the recovery? Interior of neutron star Observing Vela with XDM9 XDM Glitch observations Hart 26m bearing failure Observe Vela while above the horizon (15 hours / day) Why? First prize: Catch a glitch in the act Second Prize: Parameterize the recovery Free gift: Pulsar timing provides exacting test of polarization and timing of XDM. Soak test continous observing Observing Vela with XDM10 XDM: First light Observing Vela with XDM11 Effect of ISM Observe over wide-bandwidth to increase sensitivity BUT Observing Vela with XDM12 Dispersive Smearing Observing Vela with XDM13 Dedispersion Observing Vela with XDM14 Dedispersion and folding DBE DedisperseFoldFind TOA Barycentre Find residuals clock DMP Std Profile Pls position Timestamp Obs x,y,z Observing Vela with XDM15 Arrival Times (TOA) Observing Vela with XDM16 1 st order - frequency early late Observed - Predicted Observing Vela with XDM17 2 nd order Observing Vela with XDM18 2 nd order Observing Vela with XDM19 Residuals us Observing Vela with XDM20 12 Parkes us Hobbs et al, Observing Vela with XDM21 Residuals us Observing Vela with XDM22 Aside What does a glitch look like? Observing Vela with XDM days of Vela Observing Vela with XDM24 Challenges Observing Vela with XDM days of Vela Observing Vela with XDM26 Offset relative to 26m transit Observing Vela with XDM27 Residuals us Observing Vela with XDM28 Slopes Observing Vela with XDM29 Observing Vela with XDM30 Diurnal Slopes 100 us / day Observing Vela with XDM31 No slopes in 26m data!! We do not see similar slopes in the HartRAO 26m data What causes the slopes? What causes the offset? What is the difference between the two systems? Does the problem lies in the signal or our system? Or in the wetware? Observing Vela with XDM32 HartRAO vs XDM DBE Dedisperse Fold Find TOA correlate Barycentre Find residuals GPS rudidiumDM Pobs Std Profile Timestamp Pls RA/Dec XDM Alt/Az Linear pol WOPT Find TOA Gaussian Barycentre Find residuals Hart 26m Equatorial Circular polarizatio n H maser XDM x,y,z Hart x,y,z model Observing Vela with XDM33 Clocks DBE GPS disciplined rubidium HartRAO Timer Hart hydrogen maser Feed 5MHz and 1 pps from H-maser into DBE Both systems now run off of the same clock Observing Vela with XDM34 Position offset Part of the formation of residuals involves transformation from observatory reference frame to solar system barycentre Need to know position of observatory Is this correct? 100 us per day is 30 km light travel Can rule out Incorrect observatory position Distortion of antenna Cable expansion Observing Vela with XDM35 HartRAO vs XDM DBE Dedisperse Fold Find TOA correlate Barycentre Find residuals DM Pobs Std Profile Timestamp Pls RA/Dec XDM Alt/Az Linear pol WOPT Find TOA Gaussian Barycentre Find residuals Hart 26m Equatorial Circular polarizatio n H maser XDM x,y,z Hart x,y,z model Observing Vela with XDM36 DBE or signal? Mix RF from XDM down to IF of 160 MHz and feed a 8 MHz band into Mark I timer. Now the same signal is being fed into both timers Mark 1 timer narrow bandwidth & only one channel Observing Vela with XDM37 DBE or signal Same slope Problem lies in signal Polarisation issue!! Observing Vela with XDM38 Polarization XDM is alt-az mount with linear feeds Hart 26m is equatorial with circular feeds Observing Vela with XDM39 Effect of mount sunsetsunrise Polarization axes seem to shift in sky relative to feed Observing Vela with XDM40 Parallactic angle XDM compensates by rotating the feed in order to keep the polarization axis constant Is this being done correctly? How would this effect the residuals? Observing Vela with XDM41 Parallactic angle Feed rotation and parallactic angle Observing Vela with XDM42 Pulse shape changes Observing Vela with XDM43 WARNING!! Sensitive KAT engineers should close their eyes Observing Vela with XDM44 Experimental RA Observing Vela with XDM45 Circular polarization Convert from linear to circular using a hybrid Observing Vela with XDM46 Results Mark I timer DBE Observing Vela with XDM47 Conclusion There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know. Donald Rumsfeld Observing Vela with XDM48 Conclusion There are two effects Polarization effect corrected with circular polarization Timing problem in the DBE We now obtained slope free residuals from XDM Using circular polarization, narrow BW, Mark I timer Observing Vela with XDM49 Concluding remarks Pulsars are amazing! Pulsar timing provides stringent testing Timing polarization Highly recommend that pulsar timing forms part of single dish commisioning for KAT-7. meerKAT will be great pulsar instrument galactic centre Pulsar observing is more than plugging a timer into data spigot Capacity building of pulsar timing community First South African observations using multi channel pulsar timer with dedispersion Steep learning curve International community Observing Vela with XDM50 Thanks meerKAT team especially Adriaan Pens-Hough George Nicolson Observing Vela with XDM51 meerKAT science case Please see Roy if you would like to be involved Meeting planned in January Observing Vela with XDM52 Questions? Answers? Observing Vela with XDM53 Observing Vela with XDM54 Pointing Problems Observing Vela with XDM55 XDM prototype at HartRAO Kitty Observing Vela with XDM56 KAT-7 Observing Vela with XDM57 KAT -> meerKAT Observing Vela with XDM58 meerKAT Observing Vela with XDM59 Observing Vela with XDM60 Neutron Stars and Pulsars Observing Vela with XDM61 Observing Vela with XDM 62 Sudden increase in frequency or spin-up Frequency increases by few parts per million In energy terms equivalent to earthquake of 17 on Richter scale in which the surface of the earth moves by 15 m. Pulsar Glitches Observing Vela with XDM63 Waiting for Vela to glitch Observing Vela with XDM64 Storm clouds over HartRAO Observing Vela with XDM65 Sudden increase in frequency or spin-up Frequency increases by few parts per million In energy terms equivalent to earthquake of 17 on Richter scale in which the surface of the earth moves by 15 m. Pulsar Glitches Observing Vela with XDM66 Timing Vela with XDM Observing Vela with XDM67 Observing Vela with XDM68 Observing Vela with XDM69 KAT Glitch detection strategies Regular observations needed Find glitching pulsars Pre-cursors? Observing Vela with XDM70 Vela Pulsar Glitches Observing Vela with XDM71 Predicting glitches Observing Vela with XDM72 Observing Vela with XDM73 Observing Vela with XDM74 Parallactic angle Parallactic angle is the angle between the objects hour circle and its vertical circle Observing Vela with XDM75 Observing Vela with XDM76 Observing Vela with XDM77 sunset sunrise Observing Vela with XDM78 Observing Vela with XDM79 Observing Vela with XDM80 Observing Vela with XDM81 Pulsars and Neutron Stars Very dense Rapidly spinning High magnetic field Cosmic lighthouse