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Searching for Transients with LOFAR/CS1

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 .

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Searching for Transients with LOFAR/CS1

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

  2. 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 

  3. Good for commissioning, good for science!  •  Early LBA observations: • Frequencies from 10 - 90 MHz • Resolutions from 2 - 0.2 deg • Bandwidth ~  4 MHz • Correlating 16 dipoles        Aeff ~ 128 m2 dipoles have  all-sky sensitivity... ... produce all-sky maps

  4. 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

  5. What will this produce? •  Image ~300 deg2/s • Studies sky on range of timescales • Lightcurves of all sources • Public access to database

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

  7. 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 deg2 • 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. 

  8. Example lightcurves: • 3C 390.3: • 1 hour integrations • 30 min integrations

  9. Results For 10 threshold, no transients. Nondetection limits transient rate, f. For Poisson statistics, P(Ndet=0) = e-fN For 95% confidence, P(Ndet=0) = 0.05. Constraint on transinents in LOFAR CS1 survey.

  10. Comparison to Previous Results STARE (Katz et al. 2003) MOTER (Amy et al. 1989 Green Bank 300ft (Gregory & Taylor 1986) FIRST/NVSS (Levinson et al. 2002) Green Bank FIRST/NVSS STARE MOTER

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

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