Rob Fender, Ben Stappers and Ralph Wijers on behalf of LOFAR and the Transients Key Science Project

Transcription

1 Quiquid variat notandum Rob Fender, Ben Stappers and Ralph Wijers on behalf of LOFAR and the Transients Key Science Project RAMJW 1

2 LOFAR: surveyor and transient monitor (SCUBA-2, ALMA fields of view smaller than one pixel) Large collecting area x vast field of view x multiple beams = unprecedented survey speed (while maintaining arcsec resolution) Very deep and wide surveys / all-sky monitoring for transients RAMJW 2

3 LOFAR Transients science working groups JETS (Sera Markoff) Accreting binaries, YSOs, rapid AGN variability synchrotron PULSARS (Ben Stappers) Pulsar / friends of pulsars survey / monitoring FLARE STARS (Rachel Osten) Active stars, brown dwarfs coherent PLANETS (Philippe Zarka) Solar system and extrasolar planetary radio bursts SERENDIPITY & TRANSIENT DETECTION (Michael Wise) Source classes and source detection RAMJW 3

4 Compact objects; explosive/dynamic events. Timescales of ns to years. Known sources: pulsars (also magnetars), gamma-ray bursts, flare stars, supernovae, planets. Likely unknown source classes as well. RAMJW 4

5 (Wν) 2 SD 2 /T Large portions of phase space empty and unexplored! (Cordes et al. 2004) RAMJW 5

6 Large FoV for rare events Large instantaneous sensitivity for weak source classes RAMJW 6

7 Timescales of ns - seconds. Internal source variability and singular bursts. Probed only by nonimaging (timeseries) techniques. Propagation effects in ISM (e.g. scattering and dispersion) very important. RFI contamination. Pulsar-like surveys Imaging surveys (Fender RAMJW et al. 2008) 7

8 CI Cam Explosive particle acceleration in GRB afterglows, microquasar jets, supernovae long-lived low-frequency synchrotron emission Time-resolved census of particle acceleration in our galaxy BUT low frequencies not optimum for early warning RAMJW 8

9 Funny radio sources... GCRT J1745 (Spreeuw et al. 2008) GRB prediction (Van der Horst) RAMJW 9

10 Extrasolar planets Note that the lowest frequencies are required Scaling Jupiter s emission for Hot Jupiters experiencing much stronger stellar winds, we could discover radio bursts to distances of 10s of pc Inclination independent method for finding planets Provide physical information: rotation rate / magnetic field strength unavailable by any other means RAMJW 10

11 Extragalactic radio bursts Freq (MHz) 5ms burst at 1.4 GHz originated at >0.5 Gpc LOFAR should detect 1000s of such events, perhaps one per day dispersed to durations of minutes in LOFAR band LOFAR high band Time delay (sec) 90 RAMJW 11

12 The bursts will allow us to probe the physics of the IGM/ICM all the way back to EoR we can measure dispersion measure and (maybe) rotation measure to probe the electron and magnetic field content / turbulence If these burst are associated with LIGO events such as a NS-NS merger LOFAR may provide the first electromagnetic localisation of a gravitational wave event Combining LIGO and LOFAR measurements will provide two completely independent measurements of distance on cosmological scales, test RAMJW 12 theories of gravity etc.

13 The LOFAR Radio Sky Monitor We will monitor entire visible sky ~daily to mjy level at 50/150 MHz Localisation of transient sources to arcsec or better Instant reporting of events Transient buffer boards allow us to look back in time in other RAMJW 13 directions

14 All Northern Sky Survey will find more than 1000 pulsars, 50% more than currently known. Will be so sensitive it will find entire local population allowing studies of luminosity function in detail. So many new pulsars exotic objects like pulsar-pulsar and pulsar-bh binaries possible Sufficiently sensitive to find pulsars in external galaxies for the first time. RAMJW 14

15 Transient Buffers Some instrument flags an event location. What did LOFAR see there 20 sec ago? Buffer boards store sec-min of data Freeze buffer on trigger Read out raw data Analyse/beamform for any spot on the sky T back = 1 sec / (bandwidth/100mhz) Possible expansion goal: do better (memory cheap) RAMJW 15

16 Pipeline detects transient Public alert on LOFAR Transients VOEventNet channel yes >>99% certain? no Alert communicated only to 'partners' and is not made public In both cases we will communicate as much information as possible [coords, spectrum, polarization, preliminary classification] in VO-compatible xml format -- See John Swinbanks talk for more lots of public alerts for 'free' but follow-up / partner observations proprietary RAMJW 16

17 RSM data Transients pipeline Transient detected [localised to ~arcmin / alert via VOEventNet or 'sub prime' channel] External trigger (e.g. MAGIC, MAXI..) Full array override radio spectrum / arcsec localization RAMJW 17

18 Collaborating facilities 'Multi-messenger' science with LOFAR Other radio: WSRT / e-merlin / e-evn / MWA / ASKAP/MeerKAT Optical/infrared: The Liverpool Telescope / PAIRITEL X-ray / Gamma-ray: Fermi, Swift, INTEGRAL GW / Particle: LIGO / VIRGO MAGIC / VERITAS / HESS ANTARES/ICECUBE/KM3NET RAMJW 18

19 Data products and policy All alerts immediately public Subthreshold alerts private to collaborations Most light curves in database and immediately or very soon public What that means still TBD due to resources Ideally browsable/searchable public database In any case Transients Centre at UvA for visitors RAMJW 19

20 A New Twist: AARTFAAC Combine superterp LBA antennae in hardware correlator ERC-AIG funded extension (1 M hardware) Runs parallel to LOFAR proper 24/7 all-sky imaging, low-res R.m.s. 3-5 Jy/(s.4MHz) at MHz Look for the rarest, brightest flares, add to the alert streams RAMJW 20

21 State of Progress Imaging pipeline exists, being used, tested, augmented Pulsar and transients pipelines: prototypes exist, to be turned into testable production versions this year RAMJW 21

22 Conclusions LOFAR is a giant leap in transients surveying Wide range of transients science A lot has been done on pipelines Still quite a lot to do on pipelines Let the fun begin!.. RAMJW 22

23 TKP Synergy Opportunities LOFAR-internal: Sharing sky Sharing compute resources Sharing TBBs Sharing science LOFAR-external: Joint programs/proposals with other pathfinders Cross-triggering via VOEvents RAMJW 23

24 TKP Synergy: Sharing Sky You add, we subtract However: Cadence Area RFI rejection Computing RAMJW 24

25 TKP Synergy: Sharing TBBs Two extremes: 1. CR and TRA each 50% of TBBs full-time 2. CR and TRA each 50% of time all TBBs Option 1 is win-win if rarest, brightest events are best science for both But: other things possible, e.g. each 50% of each TBB full-time RAMJW 25

26 TKP Synergy: Sharing Computing Piggybacking modes: Analyse all incoming data for transients Secondary science: no control over obs. Settings, so usually sub-optimal Science is significant, so always a win IF resources OK Significant commissioning issue RAMJW 26

27 TKP Synergy: ASKAP/MeerKAT Joint programmes are being set up for transients with both ASKAP and MeerKAT LOFAR: more sky, better for non-thermal transients ASKAP/MeerKAT: better resolution, more and faster thermal transients RAMJW 27