University of Amsterdam Jess Broderick University of Southampton Martin Bell, Valeriu Tudose, Dan Calvelo, Dan Plant, Richard Plotkin, Dario Carbone, Adam Stewart, Gosia Pietka, Antonia Rowlinson, John Swinbank, Evert Rol, Bart Scheers, Jason Hessels, James Miller-Jones, Rob Fender, Ralph Wijers and the LOFAR Transients KSP
x 6 hour observaCons • April 2010 – November 2011 • 7 – 20 staCons • Field of view: ~20 deg2 • Noise: 4-‐15 mJy/beam • 2 transient candidates: – 1 turns out to be artefact at edge of image (Cimager performed poorly at image edge) – 1 with higher conﬁdence, but what is it?
VLSS/NVSS sky model maybe not adequate for longest baselines • Standard cookbook parameters with few tweaks • One good image from one observaCon • Averaged from 21 sub-‐ bands • Post BBS ﬂagging of 25% – to be reduced! • Flux: 4.4 Jy • Noise: 138 mJy/beam PKS 1510-‐089: current status
rays down to low radio frequencies • LOFAR 6 hour HBA test observaCons in August • Sky model: gsmuCls.py script, 3C 454.3 removed • First image with 6 sub-‐bands: 119.1-‐152.3 MHz • Remote staCons ﬂagged • Individual images combined in image plane • ResoluCon 195x168 arcsec • StaCon beam correcCon at center of ﬁeld
recorded • Most nearby Type Ia SN in decades (6.4 Mpc) • No detecCon at high radio frequencies • LOFAR 4 hour HBA observaCon • 4 days aoer discovery (Aug 28) • Sky model from imaging pipeline used WSRT at 1.4 GHz (Horesh et al. 2011)
HBA observaCons: – Jun 25: 19 core + 7 Dutch remote – Aug 16: 18 core + 8 Dutch remote – Sep 11: 20 core + 8 Dutch remote • Sky model: PyBDSM & shapelets on 74 MHz VLA map • SS433 not included in sky model • Shortest baselines (< 50 m) excluded from BBS because of unsaCsfactory W50 model – not ﬂagged in imaging • Dutch remote staCons ﬂagged completely because of unsaCsfactory model on long baselines • Beam correcCon applied at ﬁeld center
accurate to 10-‐20% • Marginal detecCon of variability? • No obvious transients when comparing observaCons • Future work: – Sky model improvements – ConCnued observaCons – Re-‐analysis of April HBA data (2 x 2 hours) – Analyze LBA data – Image data with AWimager and use self-‐calibraCon
sub-‐bands, average at 128 MHz • Images for each sub-‐band combined in image plane • Remote staCons not included • ResoluCon: 3x6 arcmin • Sky model: – PyBDSM on a WENNS mosaic: 1050 model sources – Cyg A model based on VLA image at 325 MHz (3 arcsec) • Noise: 12-‐20 mJy, depending on closeness to bright sources (sidelobe related artefacts)
model • Start with core staCons for iniCal model, then remote ones with self calibraCon? • ContribuCon of A-‐team sources and demixing • Take direcCon dependent eﬀects into account • Try global solver to improve calibraCon (mulCple sub-‐ bands)
for RFI • Add model transients to real data to test the AOﬂagger • Example: 2 Jy source on for half hour in 6 hour observaCon of PSR B0329+54 ﬂagged • Test the limits of pipeline parameters in terms of amplitude and duraCon of sources • InvesCgate various parameters to minimize unwanted ﬂagging of bright transients • SoluCon: separate pipelines for transient searches?
the various ﬁelds • Several new commissioners have been trained • TKSP input in general commissioning important • AWimager tesCng: – TKSP-‐speciﬁc tests – Imaging Busy Week (Jan 30 – Feb 3) • TesCng of source extractors (PYSE / PyBDSM) • Quality control metrics for trip/trap + sky model tesCng • MSSS preparaCon • Imaging team increased, but volunteers welcome!