FLOW the french LOFAR consortium P. Zarka, M. Tagger + ~30 participants

 Long-lived interest for LOFAR in France : CNRS « Prospective » : « LOFAR » proposal ~20 scientists from 14 labs Support with limited funding, for involvement in : (1) scientific case (2) enabling observations (ITS/NDA) (3) software (RFI) developments (4) hardware participation  After reorganization of LOFAR consortium (1) & (2) done/in progress (3) generic LOFAR/SKA/FASR… (4) cancelled/reoriented SKA, FASR  More significant participation difficult to introduce among many other national priorities… History (1/2)

 OP expression of interest 1/2006 : official visit to ASTRON  Meudon workshop 3/2006 ( > 30 participants positive signals from agencies FLOW consortium FLOW science case (10/2006) ( Proposal to funding agencies : a LOFAR station in Nançay + join the LOFAR collaboration  ASTRON visit to Nançay 7/2007  RFI measurements planned 10/2007 History (2/2)

 Topology and geopolitics of french funding agencies : complex but ~ centralized : INSU (astronomy) + IN2P3 (particle physics) + Région Centre + thematic/interdisciplinary programs Funding Situation  “Green light” 3/2007 : 40% funding secured today, complement expected over next 2 years  Procurement of Nançay station under way  So far, so good …

 Very strong interest in most topics adressed by LOFAR : EOR, galaxies and clusters, AGN and X-ray binaries, young stars, Planets and exoplanets (PI-ship of TKP (exo)Planets SWG), Sun, atmospheric phenomena (sprites, elves…)  Excellent complementarity with existing or planned instruments : XMM, HESS, Planck, GLAST, Simbol-X, ECLAIRs, Taranis… Science (1/2)

CNES+ASI, launch kev Formation flight with Simbol-X

 Minority of radio-astronomers  Many specialists of other wavelengths attracted by the prospects of LOFAR Goutelas spring school 6/2007 ( COST action submitted (for e-LOFAR)  Some interest (to be explored…) in “other” sciences … Science (2/2)

 Involvement in workshop & Science case for an extended LOFAR ( ) Long Baselines (1/4)

 VLBI observations of Jupiter ITS-NDA : Broadband observations, baseband digitization bits VLBI feasibility Ok/ionospheric decorrelation at 700 km & 22 MHz (60000 ), over  t~1 sec Long Baselines (2/4)

ANALOG BEAM-FORMING 72 RHC antennas DIGITIZATION 0-40 MHz 80 Msamples/sec NDA DIRECT DIGITIZATION 60 linear antennas 0-40 MHz 80 Msamples/sec Storage LOFAR/ITS Timing: GPS Timing: Crystal + NTP Offline Correlation Long Baselines (3/4)

210  peak for 1 s integration Long Baselines (4/4)  Nigl, Zarka, Kuijpers, Falcke, Bähren, Denis, A&A 471, 1099–1104, 2007 (+ Astron & OP Newsletters)  Work in progress CS-1/NDA (% time Ok, weaker sources…) ITS NDA Correlation

Next Step ?

 LOFAR station back end + specific antennas : ~10 times more antennas (~small core)  Aim = increase sensitivity (“weight” in correlation) by ~10, with cost increase <  2 LOFAR “Super” Station (LSS) concept  Use LBL channel (with specific input filter) ?  Switch standard / super – station ! add 96 mini-phased arrays of N~10 antennas each, analog phasing identical for all 96  input to RCUs

 Standard mode = as part of LOFAR array additional high weight visibility measurements in (u,v) plane improve ionospheric calibration over extended array ? (especially at early stage of project) more sensitive station usable even when ionospheric conditions poor (fringes rotate fast), with short integration times (idem E-VLBI)  Non-standard mode = correlate separately outer+european stations when core used alone (ex: EoR - strong competition for LOFAR use and not all modes use all stations) LSS provides core-like high-weight visibilities  More generally, 2 large sub-arrays better to : confirm weak source detection (e.g. exoplanets) decorrelated ionospheric perturbations, RFI, instrumental effects increase transients detection efficiency ? improve high-resolution astrometry ? LSS : Interest (1/2)

 Standalone use possible (LSS area 3-4  NDA) : Jupiter, Sun, Pulsars, various RS student training … local data center ? LSS : Interest (2/2)

 Characteristics / performance / cost of LSS antennas ? bandwidth : MHz, MHz, MHz … ? + FoV, polarization … ≠ LOFAR LBA  Ok / standard use of LSS ?  Correlation between inhomogeneous stations Ok ? usual for VLBI core/outer/foreign stations for LOFAR phase 1  Sub-arrays tractable by Blue Gene ?  Standalone use requires to extract locally data output from LOFAR back-end LSS : Technical issues

 Original instrumental development  Scientific interest (why we want them at all) impact for Key Science ? for high-resolution studies ? new scientific objectives ?  Need for a specific science case draft document workshop in preparation (before end 2007)  European/International contributions ? LOFAR participants + contacts with Austria & Ukraine LSS : Context (1/2)

 Feasibility study group in Nançay technical evaluation comparison LSS / several colocated standard stations instrument simulations …  Funding application for prototype possible in march 2008 much easier than for a second station ! interest of LOFAR European participants ? several LSS in Europe ? (a few LSS operated together with  f  LBL+LBA ranges = new instrument !) LSS : Context (2/2)