So are there counterparts to the NCP transient in the HBA/RSM data?

Gosia Pietka

Transcript

1. So are there counterparts to the NCP transient in the HBA/RSM data? G. Pietka, R. Fender, T. Hassall, A. Stewart Amsterdam, January 8, 2014
2. RSM low DM directions • Concentrate search for FRBs to RSM pointings with a low DM • This means 7 out of 48 pointings ~ 220 deg2 • 6 Zenith scans • 2 x 10 min snapshots per scan. An ideal low DM RSM strip
3. RSM low DM directions • RSM short-timescale imaging • Using one band (149 MHz) out of the 4 used in the RSM. • Eg. 2 Mins 6 Zenith scans x 2 snapshots x 5 (2min) epochs = 60 x 2min epochs An ideal low DM RSM strip
4. Estimating FRB Rates in RSM ν NCP =60 MHz t NCP =660s ν RSM =149 MHz t∼ν−4 ⇒ t RSM =17s 25 Jy FRB candidate lasting 11 minutes found in NCP data at 60 MHz: At the frequency of RSM data, the pulse width will be scaled according to the scatter broadening: Assume NCP Transient is Real (and duration was scattering-dominated):
5. FRB Rates in 10s RSM Images FoV NCP =175deg2 Nr of epochs NCP =1897 FoV RSM =219deg2 Nr of epochs RSM =720 Flux limit = 4 Jy Flux limit =1Jy R RSM (1Jy) = 219deg2×720 epochs 175deg2×1897 epochs ×( 1Jy 4 Jy ) −3/2 =3.8 R∝F−3/2 α=0 First for spectral index , 25 Jy NCP source will be 25 Jy also in the RSM data. So we would expect 3.8 NCP-Like transients in 10s RSM Low DM search
6. FRB Rates in 10s RSM Images R RSM (1Jy) =3.8×[( ν NCP ν RSM ) α ] −3/2 =3.8×f R∝F−3/2 Take the range of spectral index values -3 ≤ α ≤ 0 Expected number of NCP-Like transients in 10s RSM Low DM search for a range of spectral index values α f RSM Rate 0 1 3.8 -1 0.25 0.97 -2 0.065 0.248 -3 0.017 0.063
7. FRB Rates in 10s RSM Images α=−3 For spectral index F NCP =25 Jy F RSM =1.63 Jy Source at the RSM detection limit of 1 Jy in the NCP band will be 15 Jy bright. R RSM (1Jy) = 219deg2×720 epochs 175deg2×1897 epochs ×R NCP(15Jy) N NCP(15Jy) =N NCP(4Jy) ×( 15 4 ) −3/2 N NCP(15Jy) =0.14
8. FRB Rates in 10s RSM Images R RSM (1Jy) = 219deg2×720 epochs 175deg2×1897 epochs ×0.14 R RSM (1Jy) =0.07 For the spectral index α=−3
9. FRB Rates in 2min RSM Images R RSM (1Jy) = 219deg2×60 epochs 175deg2×1897 epochs ×( 1Jy 4 Jy ) −3/2 =0.3 α=0 For spectral index However, there are other possible transient candidates in 2 minute images...
10. 2 Minute RSM Snapshots TraP Transient Candidate #929 July 13, 17.14 July 13, 17.16 Example of type of events reported by TraP that need to be tested and understood
11. 2 Minute RSM Snapshots TraP Transient Candidate #929 July 13, 17.14 July 13, 17.16
12. #929 Detection in 10s Images
13. #929 Detection in 10s Images
14. Deep 10 Minute Image of the Field • No source visible in deeper 10 minute image. • But artifacts in short time scale imaging not well understood.
15. Conclusions • ~20s time scale NCP like events expected in the RSM field • Rate of NCP like events in a spectral index range -3 and 0 expected in the RSM low DM 10 s data: 0.07 - 4 • Possible transient candidate selected by TraP in the RSM data • More tests need to be done ...
16. If No Transients in RSM Data Rate=− −ln 0.05 FoV ×Nr of epochs Rate 10s =− −ln 0.05 FoV ×Nr of epochs =− −ln 0.05 219deg2×720 =1.9×10−5 deg−2 Rate 2mins =− −ln 0.05 FoV ×Nr of epochs =− −ln 0.05 219deg2×60 =2×10−4 deg−2