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On the nature of the Long-duration radio transients

On the nature of the Long-duration radio transients. Eran Ofek CALTECH. Collaborators: B. Breslauer, A. Gal-Yam, D. Frail, S.R. Kulkarni, P. Chandra, M. Kasliwal, E. Waxman, N. Gehrels. Einstein Fellows symposium October 2009. Talk Layout. A new class:

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On the nature of the Long-duration radio transients

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  1. On the nature of the Long-duration radio transients Eran Ofek CALTECH Collaborators: B. Breslauer, A. Gal-Yam, D. Frail, S.R. Kulkarni, P. Chandra, M. Kasliwal, E. Waxman, N. Gehrels Einstein Fellows symposium October 2009

  2. Talk Layout A new class: Long-duration radio transients Summary of observational facts What are they? Speculations… New observations

  3. Bower et al. (2007) 944 epochs, 1/week, for 22 years @ 5GHz 7 transients, fluxes: 0.3-1.7mJy Time scale < 1 week, >20 min Optical counterparts: g>27.6, R>26.5, K>18 No X-ray in ROSAT Galactic latitude: b~37o Circular polarization <30%

  4. Long-duration radio transients Lack of counterparts Ofek et al. 2009 K>20.4 mag

  5. A Search for Radio transients The FIRST-NVSS survey Levinson et al. (2002) Gal-Yam et al. (2006) Comparison of the NVSS and FIRST radio surveys Area: ~2500 sq. deg Flux limit: 6mJy @ 1.4 GHz 1 transient candidates (SN in NGC4216)

  6. Yet, some more… Kida et al. (2008)… 6 bright (>1 Jy) transients detected by the Nasu Pulsar Observatory, No localization Similar time scales (~<1 day)

  7. Long-duration radio transients Rates

  8. Long-duration radio transients Log N – Log S Ofek et al. 2009

  9. Long-duration radio transients Surface density of progenitors 7 events within ~8’ in Bower et al. (2007) If catastrophic If repeaters rate Number of progenitors in the Universe >4x1016 Sky surface density S>60 deg-2 (@95% CL) @ b~37o

  10. Progenitors – Extragalactic? Ovaldsen et al. (2007) analytic

  11. Progenitors? - Galactic Many Galactic progenitors are ruled out: Flare stars, X-ray binaries, pulsars, magnetars, Evaporating BHs, microlensing, Floating planets, solar flares reflected from asteroids…

  12. Isolated-old NSs? Large population in the Galaxy: 108-109 High velocities @ birth Large scale height Abundant at high Galactic latitudes Large energy reservoir: rotational, magnetic, accretion

  13. Ofek 09, Ofek et al. 09 Isolated-old NSs? All Birth rate Init. Vel. Dist.

  14. Isolated-old NSs? Distance distribution at the direction of the Bower et al. field

  15. Ofek et al. 2009 Energetics – NSs? Repetition time scale: Mean luminosity: 1025 erg s-1 Total energy: 1043 erg Magnetic: ~1041 erg Rotational: ~1044 erg NSs Energy reservoir Accretion: ~1045 erg

  16. Isolated-old NSs? Fireball model – Incoherent synchrotron radiation

  17. Isolated-old NSs? Fireball model – Incoherent synchrotron radiation

  18. Ofek et al., in prep. New observations 30 VLA hours (August 2008) Target: 150 fields at low Galactic latitude 11 epochs

  19. New observations 30 VLA hours (August 2008) Target: 150 fields at low Galactic latitude 11 epochs Followup: VLA + Swift/XRT + P60/P200/Keck Excpectation: ~1 event, detect: 0 (above 2 mJy) Several fainter events still under investigation. For 3 most promising - no optical counterparts i~24 + for one source - no XRT source within 2 days

  20. Predictions If transients are NSs… Repetition time scale ~ 3 month Spectral slope – syn. Self absorption More abundance towards the Galactic center, but details depends on flux limit and distance Pulsations? – search for pulsars at 5 GHz Linear polarization, if incoherent syn. radiation

  21. End

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