1. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 1 Discovery frontier for + CR + GWs –Less so at high energies BATSE, RXTE/ASM, Beppo/Sax, SWIFT, GLAST, etc. –More so for optical, radio GLAST: full-sky survey every three hours for 1+ years Optical PanSTARRS = Panoramic Survey Telescope and Rapid Response System LSST (LST) = Large Synoptic Survey Telescope (rename to OSST!) Science goals: includes transients on minute  10 yr time scales Radio Phase space: –Knowns: already a very rich set –Hypotheticals Radio Synoptic Survey Telescopes Survey metric for transients The mid-frequency SKA as the RSST Axes of Discovery: the Time Variable Universe Jim Cordes, Cornell University Heraclitus “You don’t observe the same universe twice”

2. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 2 Why Radio Transients? No comprehensive survey of large phase space Need large A  T (area, solid angle and time coverage) ns to years complex structures in the frequency-time plane  HPC processing Nature can produce cheap radio photons via coherent radiation processes (N 2 vs N) so detectable to great distances Fast transients are linked to extreme matter states (  t < 1s) … or ETI Counterparts to known source classes Prompt radio bursts from GRBs Gamma-ray quiet, radio-loud GRBs Expect new source classes (ETI, evaporating BHs, particle events) Beacons for probing the cosmic web and fundamental constants Intervening plasmas (IPM, ISM, IGM)  dispersion, scattering, scintillation Photon mass, charge from measured dispersion law (de Broglie 1940)

3. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 3 GCRT J1745-3009 Hyman et al. 2005 Bower et al. 2005 Spk ~ 80 mJy SD 2 ~ 5.1 Jy kpc 2 W ~ 100 d Galactic Center Transients

4. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 4  Roughly 1/3 of all psrs detected with FFT also detected in SP search  Some objects detected only in SP search  Wide range of single-pulse properties apparent  Galactic pulsar population may be much larger than previously thought PMB Single Pulse Search McLaughlin et al. (2006) J1840–0815 P = 1.1 s DM = 225 pc cm -3 J1840–0809 P = 0.96 s DM = 353 pc cm -3  RRATs: rotating radio transients (Andrew Lyne’s talk)

5. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 5 Pulsar Survey with Arecibo Multibeam System (ALFA) (Arecibo ~ 10% SKA) Detection of a strong pulsar amid RFI Detection of a weak millisecond pulsar in beam 1

6. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 6

7. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 7 Asteroid disk from SN fallback material Only ~ 10 -4 Earth masses needed to provide enough material to perturb coherent radiation from a pulsar over its 10 Myr lifetime Asteroids evaporate at ~10 9 cm from the NS and trigger or quench pair production from gaps in the magnetosphere Expect induced torque fluctuations astro-ph/0605145

8. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 8 Artist's impression of a brown dwarf with "super-aurorae" at its magnetic poles, causing the pulsed radio emission. (Credit: Copyright National University of Ireland, Armagh Observatory, National Radio Astronomy Observatory, United States Naval Observatory & Vatican Observatory, Arizona) Time series of the radio emission detected with the VLA from the M9 dwarf TVLM 513-46546. Every 1.958 hours a periodic pulse is detected when extremely bright, beams of radiation originating at the poles sweep Earth when the dwarf rotates. Brown dwarf pulsations Hallinan et al. 2007

9. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 9 Bursting radio emission from magnetars Correlated torque and radio variations Camilo et al. 2007 1E 1547-5408 Flat spectrum (not pulsar like)

10. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 10 Crab giant pulses: the highest brightness temperatures known “nano shots”

11. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 11 Frequency-time structure in a Crab Giant Pulse Eilek & Hankins 2006, Hankins & Eilek 2007 Arecibo data

12. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 12 Phase Space for Transients: S pk D 2 vs. W W = pulse width or characteristic time scale

13. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 13 Filling phase space with hypothetical new discoveries: Prompt Gamma-ray emission Evaporating black holes Maximal giant pulse emission from pulsars ETI’s asteriod radar What else?

14. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 14 Detection limits for the SKA: S pk D 2 >threshold  Prompt GRBs and GRB afterglows easily seen to cosmological distances Giant pulses detectable to Virgo cluster Radio magnetars detectable to Virgo ET radar across Galaxy

15. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 15 Lazio et al. 2003 Bastian, Dulk & Leblanc (2000) Cyclotron maser emission Radiometric Bodes Law Desch & Kaiser 1984 Planetary Radio Emission

16. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 16 W ~ 4.6 ms ( / 1.4 GHz) -4.8  0.4 DM ~ 375 pc cm -3 Steep spectrum (  =-4) Science Express 27 Sep 2007

17. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 17 Detection limits for the SKA: S pk D 2 >threshold  Prompt GRBs and GRB afterglows easily seen to cosmological distances Giant pulses detectable to Virgo cluster Radio magnetars detectable to Virgo ET radar across Galaxy Parkes SP (if D>500 Mpc)

18. Jim Cordes Modern Radio Universe Manchester 2 Oct 2007 18 Maximal Amplitudes of Giant Pulses High-field millisecond pulsars Reactivation of magnetospheres in merging NS-NS binaries (short GRBs, chirped GW sources) W S pk

19. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 19 Prompt Radio Bursts from  -ray Bursts Scale from  -ray fluence: Implied flux density: Reasonable? Compare with maximal pulsar energy losses Can radiation get out? (Macquart 2007) Induced Compton and Raman scattering Long bursts: hypernovae  dense plasma from pre-SN stellar wind, immersed in SF region  perhaps no emergent radio emission mitigating effect: radio coherent, upboosted photons incoherent Short bursts: merging NS-NS, NS-BH  vacua that high-brightness radiation can get through  plausible radio bursts through reactivation of magnetosphere n+1 ~ 3.5

20. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 20 Isolated pulsar Re-activation of pulsar action in mergers? Hansen & Lyutikov 2000 Lyutikov 2006

21. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 21 Transient Surveys Fast Too fast to be sampled by raster scanning (<1 day) Sub-second transients: –Produced by compact sources (size < c  t) –Coherent radiation –Influenced by diffractive interstellar scintillations  imposed -t structure on intrinsic signal Sampled by “staring” for long dwell times Large solid angle coverage needed for rare events –Likelihood of detection –Completeness level Very high data rates for full FoV analysis Slow Durations long enough to be handled with imaging raster scans

22. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 22 Survey Metrics “Survey speed” for Steady Sources: Payoff = number of objects detected to some flux density level in some fixed amount of time Steady sources, homogeneously distributed, etc. »Integration time per source = dwell time in survey  Get same metric by looking at rate at which volume or solid angle surveyed:  SS = FoV (A/T) 2 Processed bandwidth enters in linearly  SS = FoV (A/T) 2 B Extended survey metric that includes other factors: f c = fraction usable antennas N FoV = number of pixels (PAFs ) N sa = number of subarrays m = signifcance level (min. S/N)

23. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 23 Survey Metrics Survey speed for Transient Sources: W = transient duration,  = dwell time in survey scan Slow transients: integration time =  Fast transients: (days  ns) integration time = W  New factor on survey metric that accounts for integration time and time-capture probability FoMTS = FoMSS  integration time factor  P t Integration time factor Probability that  1 event occurs from source when pointed at a =  W,  = event rate/sourcex =  / W K(a,x)  1 See SKA memo by JMC to appear at www.skatelescope.org

24. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 24 For: 1 GHz 1 sec integration 0.3 GHz bw 25 K, 60% Sensitivity vs. instantaneous FoV $$$$$ $$ ¢¢¢¢¢

25. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 25 Wide FoV Non-Imaging Surveys Pixelization of the field of view Correlation approach favored over beam forming Number of pixels Sky coverage Raster scanning (slow transients) Staring (fast transients) Analysis Full search analysis on each pixel Extensive for pulsars and fast transients –E.g. 1024 frequency channels  64  s samples from each pixel Frequency-time plane analysis for all cases to discriminate RFI from celestial signals

26. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 26 Example Synoptic Cycle for SKA A 10-day total cycle: variable scanning rates –Fast for extragalactic sky (away from Galactic plane) E.g. 1 deg 2 single pixel FoV Full sky survey (80% of 40,000 deg 2 ) T scan = 5 days T ~ 10 sec = time per sky position S min ~ 15  Jy at 10  with full sensitivity and on axis Multiple pixel systems (PAFs) increase sensitivity (for fixed total time) Subarrays reduce sensitivity but speed up the survey –Slow for deep extragalactic fields and Galactic plane –Galactic center: staring mode –Repeat scans many times –Break out of scanning mode for targeted observations (10%?) –Break out for targets of opportunity Issues for pulsars (~steady amplitudes): –Need minimum contiguous dwell time for Fourier transforms (e.g. 100 – 1000 s for large-area blind surveys) –Need frequent re-observation coverage for long-term timing followup Calibration requirements Are there solutions for HI, pulsars, transients, SETI and magnetism? –Yes (to zeroth order)

27. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 27 Summary A complete inventory requires attention to the time domain on many scales A multi-wavelength enterprise but some radio-unique areas too Target classes for transients Relativistic objects (stellar, AGN) Planets, brown dwarfs ETI Evaporating black holes? What else? Keys to discovery at radio wavelengths Time-frequency (t- ) analysis Wide-field sampling (  ) Low-mid-high sensitivity (s min ) Blind surveys of the radio sky Expand A e  T Comprehensive matched filtering (computing) Start now Arecibo, GBT, Parkes,WSRT,EVLA  ATA,LOFAR, LWA,MWA,ASKAP,MeerKAT  SKA Fast transients: obtain & process data as in pulsar surveys, SETI +? Slow transients: raster scan the sky repetitively Develop the SKA as a Radio Synoptic Survey Telescope (RSST) Causes: internal instabilities extrinsic triggers external modulations lensing scintillations

28. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 28 Extra Slides

29. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 29 Arecibo/ALFA (30% of sky in 2000 hr) or SKA/SP (80% of sky in 5 days) SKA/PAF (80% of sky in 5 days) low rate high rate “W” limited

30. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 30 Science and Implementation of RSST SKA mid-frequencies: 0.3 to >3 GHz Hydrogen 0.3 – 1.4 GHz »(galaxy evolution, dark energy) Pulsars and Gravity »(GR, GWaves, EoS, Magnetospheres) ~0.8 – 3 GHz Transients (ns to years)0.3 – 8 GHz »Relativistic objects »Exoplanets »SETI Magnetic Universe1 – 2 GHz Synoptic and Commensal Surveys Sensitivity + Wide FoV + Frequency-time flexibility Spectral line + pseudo-continuum + time-domain surveys Need multiple backend processors Compatibility issues (configuration, cadences, scan types) »HI galaxy evolution ~10 km baselines »Pulsar/transient full-FoV search < 1 km

31. 2 Oct 2007Jim Cordes Modern Radio Universe Manchester 31 Small and Big Science Discovery space can be explored with both low sensitivity and high sensitivity instruments W space: ns  years space: MHz   -rays rate space: >>1 s -1 to 1 d -1 hemisphere -1 flux densities:  Jy to GJy Fast transients require matched filtering in the -t plane High-resolution, high-performance processing Minimal systems can make useful observations Low-f: LOFAR, LWA, MWA Mid-f: Arecibo, GBT, EVLA, ATA, ASKAP, MeerKAT High-f: GBT, EVLA, ALMA?