Searching for Transients with LOFAR/CS1 Casey Law (Amsterdam)

You know LOFAR... What is CS1? Possible layout of LOFAR stations Low-band antenna in CS1 Core Station 1 is a prototype LOFAR station Located in LOFAR core 96 LBAs and HBAs

Good for commissioning, good for science! Early LBA observations: Frequencies from MHz Resolutions from deg Bandwidth ~ 4 MHz Correlating 16 dipoles A eff ~ 128 m 2 dipoles have all-sky sensitivity produce all- sky maps

Ultimate goal: The Radio Sky Monitor Imaging survey at 30, 120 MHz 1 sec sensitivity: 500, 50 mJy Covers 1/4 of sky daily The RSM in action Sky coverage of the RSM

What will this produce? Image ~300 deg 2 /s Studies sky on range of timescales Lightcurves of all sources Public access to database

Image srcdet db class alert Transient Detection Pipeline (Posters by J. Swinbank and B. Scheers) Real-time pipeline in Python Starts with image cubes, produces source lists, alerts.

The Search Data: LBA, near 45 MHz Bandwidth = 4 MHz 24 hours Method: Image for times of 4, 8 min,..., 4, 8 hrs Area of ~1200 deg 2 Run source detection Search for good candidates Image of North Celestial Pole at 45 MHz. All 3C sources visible, some SNRs, M82. Search area shown in green.

Example lightcurves: 3C 390.3: 1 hour integrations 30 min integrations

Results For 10  threshold, no transients. Nondetection limits transient rate, f. For Poisson statistics, P(N det =0) = e -fN For 95% confidence, P(N det =0) = Constraint on transinents in LOFAR CS1 survey.

Comparison to Previous Results STARE (Katz et al. 2003) MOTER (Amy et al Green Bank 300ft (Gregory & Taylor 1986) FIRST/NVSS (Levinson et al. 2002) STARE Green Bank MOTER FIRST/NVSS

Summary 1.The TKP is actively developing tools to exploit LOFAR. 2.LOFAR/CS1 is able to do science today! 3.A 24 hour study of a 1200 deg^2 field found no transients. 4.Upper limits starting to constrain transient sky.