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Discovery of powerful millisecond flares from Cyg X-1

Discovery of powerful millisecond flares from Cyg X-1. Marek Gierli ński University of Durham , England Andrzej Zdziarski N. Copernicus Astronomical Center, Warsaw, Poland. Cyg X-1 variability from years to milliseconds. Cyg X-1: a tame source. Persistent source

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Discovery of powerful millisecond flares from Cyg X-1

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  1. Discovery of powerful millisecond flares from Cyg X-1 Marek GierlińskiUniversity of Durham, England Andrzej Zdziarski N. Copernicus Astronomical Center, Warsaw, Poland

  2. Cyg X-1 variabilityfrom years to milliseconds

  3. Cyg X-1: a tame source • Persistent source • Spectral states: hard and soft • Variability nothing like as dramatic as in transients • Cyg X-1 is a well-behaved black hole PCA+HEXTE Powerful millisecond flares from Cyg X-1

  4. 2001/2002 soft state(400 days) Seven years of Cyg X-1 ASM BATSE Powerful millisecond flares from Cyg X-1

  5. Spectral transitions – days to weeks • Typical transition between states takes about a week • There are faster events with timescales of a day Cui, Feng & Ertmer 2002 Powerful millisecond flares from Cyg X-1

  6. Kilosecond outbursts 20-300 keV 20-300 keV Stern, Beloborodov & Poutanen 2001 Powerful millisecond flares from Cyg X-1

  7. Not much variabilityabove 100 Hz Power spectrum of Cyg X-1 Revnivtsev, Gilfanov & Churazov 2000 Powerful millisecond flares from Cyg X-1

  8. Other black holes too Sunyaev & Revnivtsev 2000 Powerful millisecond flares from Cyg X-1

  9. Cyg X-1 high-frequency PDS Revnivtsev, Gilfanov & Churazov 2000 Powerful millisecond flares from Cyg X-1

  10. Very short eventsfrom Cyg X-1

  11. X-ray archaeology: 1973 Rothschild et al. 1974 Powerful millisecond flares from Cyg X-1

  12. Shots • Flares or ‘shots’ are weak, each of them 2–3 times brighter than the continuum • Superposition of hundreds of ‘shots’ • Timescales of ~10 and ~100 ms (sum of two exponentials) Feng, Li & Chen 1999 Powerful millisecond flares from Cyg X-1

  13. So, you don’t expect suddendramatic events from Cyg X-1…

  14. 20 …until this happened • Enormous flare on 31 July 2002 (during extended soft state) • PCA count rate increased by factor 20 in 100 ms PCA 2–60 keV(4 PCUs) Powerful millisecond flares from Cyg X-1

  15. Is it real? • An external event not from Cyg X-1? • Perhaps an energetic particle hit the PCA detector? • Or is it a solar flare? • Or is it a gamma-ray burst? 27 August 1998:SGR 1900+14 flarerecorded by PCA looking somewhere else Powerful millisecond flares from Cyg X-1

  16. Multiple detection • The flare was detected by four units of PCA (PCU1 was switched off) and one HEXTE cluster Powerful millisecond flares from Cyg X-1

  17. Even BATSE can see it! PCA 16-12-1996 BATSE Powerful millisecond flares from Cyg X-1

  18. It really comes from Cyg X-1 • HEXTE (15–150 keV) contains two detector clusters switching between the source and background 1.5 deg away • When cluster B detected the flare, cluster A looked at background and did not see anything • The flare comes from Cyg X-1 source background Powerful millisecond flares from Cyg X-1

  19. Flare properties

  20. More flares • We’ve scanned all the PCA data from Cyg X-1 • Found 13 strong flares with cpeak- c > 10 • 12 flares in the hard state, 1 in the soft state 16-12-1996 14-02-1988 31-07-2002 Powerful millisecond flares from Cyg X-1

  21. exp(-|t/|) Flare profile (soft state)   20 ms   0.7 PCA 20HEXTE Powerful millisecond flares from Cyg X-1

  22. Increase 10in 2 ms Very short precursor 2 ms ~ 40GM/c3 Powerful millisecond flares from Cyg X-1

  23. 30 flux increaseLpeak ~ 1.4 1038 erg/s Spectral hardening  ~ 1.8 Spectral hardening  ~ 1.3 Flare anatomy (soft state) Flux (3–30 keV)  (2–15 keV)  (6–60 keV) Powerful millisecond flares from Cyg X-1

  24. 10 flux increaseLpeak ~ 0.9 1038 erg/s Spectral softening  ~ 0.3 Flare anatomy (hard state) Flux (3–30 keV)  (2–15 keV)  (6–60 keV) Powerful millisecond flares from Cyg X-1

  25. Flare spectrum (soft state) Flare spectrum SAX/OSSEsoft state Model luminosityLbol ~ 0.3LEdd PCA/HEXTEcontinuumaround flare Powerful millisecond flares from Cyg X-1

  26. Flare spectrum (hard state) Flare spectrum Model luminosityLbol ~ 0.25LEdd PCA/HEXTEcontinuumaround flare SAX/OSSEhard state Powerful millisecond flares from Cyg X-1

  27. Not only Cyg X-1 XTE J1118+480 Powerful millisecond flares from Cyg X-1

  28. Not only Cyg X-1 GX 339–4 Powerful millisecond flares from Cyg X-1

  29. Rapid flare in Sgr A* Shortest timescale ~30GM/c3 Baganoff et al. 2001 Powerful millisecond flares from Cyg X-1

  30. Conclusions • We have discovered several strong millisecond X-ray flares from Cyg X-1 and other black holes • Shortest observed timescales correspond to ~40GM/c3or half of the Keplerian period on the marginally stable orbit • The flares must be due to a sudden release of accretion energy in the inner region of the disc • Magnetic flares? e.g. Beloborodov 1999; Poutanen & Fabian 1999; Machida & Matsumoto 2003 • Challenge for theorists! Powerful millisecond flares from Cyg X-1

  31. Magnetic flares in plunging region Machida & Matsumoto 2003 Powerful millisecond flares from Cyg X-1

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