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Bright broad-band afterglows of gravitational wave bursts from mergers of binary neutron stars

Bright broad-band afterglows of gravitational wave bursts from mergers of binary neutron stars Xuefeng Wu Purple Mountain Observatory Chinese Center for Antarctic Astronomy Chinese Academy of Sciences. Collaborators: He Gao, Xuan Ding, Bing Zhang, Zi-Gao Dai,

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Bright broad-band afterglows of gravitational wave bursts from mergers of binary neutron stars

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  1. Bright broad-band afterglows of gravitational wave bursts from mergers of binary neutron stars Xuefeng Wu Purple Mountain Observatory Chinese Center for Antarctic Astronomy Chinese Academy of Sciences Collaborators:He Gao, Xuan Ding, Bing Zhang, Zi-Gao Dai, Yizhong Fan, & Daming Wei Beijing Gravitational Waves Workshop Tsinghua University; July 1 - 2, 2013

  2. Introduction: see Bing Zhang’s talk BH NS-NS coalescence Normal EOS Remnant? NS Stiff Electromagnetic (EM) emission signal accompany with a GWB is essential for GW identification. The brand new channel of GW signals combining with old channel of EM emission would lead us better understand our universe. http://physics.aps.org/articles/v3/29

  3. EM signals for a BH post-merger product SGRB Multi-band transient ~hours, days, weeks, or even years Li-Paczyński Nova Li & Paczyński, 1998 Opical flare ~ 1 day Ejecta-ISM shock Nakar& Piran, 2011 Radio ~years Metzger & Berger, 2012

  4. Short GRBs γ-ray Light curve

  5. Li-Paczynski Nova / Kilonova Metzger et al. (2010)

  6. Radio Afterglows Rosswog, Piran & Nakar (2012)

  7. What if the central product is magnetar rather than a black hole?

  8. Why Magnetar ? Stiff EoS Theoretical reason

  9. Why Magnetar ? Stiff EoS Theoretical reason Lattimer (2012) Stiff equation-of-state: maximum NS mass close to 2.5 M

  10. Why Magnetar ? Stiff EoS Theoretical reason NS with mass > 2 Msun has been discovered (e.g., PSR J0348+0432, M=2.01+/-0.04 Msun) NS-NS systems: total mass can be ~ 2.6 Msun Observational reason Zhang, 2013 (Ref therein) Lattimer & Prakash (2010)

  11. Why Magnetar ? Stiff EoS Theoretical reason NS with mass > 2 Msun has been discovered (e.g., PSR J0348+0432, M=2.01+/-0.04 Msun) NS-NS systems: total mass can be ~ 2.6 Msun Observational reason Based on the observations of the SGRB X-ray afterglows. Zhang, 2013 (Ref therein) GRB 090515 Rowlinson et al. 2010 Rowlinson et al. 2013

  12. Why Magnetar ? Stiff EoS Theoretical reason NS with mass > 2 Msun has been discovered (e.g., PSR J0348+0432, M=2.01+/-0.04 Msun) NS-NS systems: total mass can be ~ 2.6 Msun Observational reason Based on the observations of the SGRB X-ray afterglows. Zhang, 2013 (Ref therein) A postmerger magnetar would be initially rotating near the Keplerian velocity P~1ms. GRB 090515 Rowlinson et al. 2010 Rowlinson et al. 2013

  13. Inferred physical parameters of magnetar Some inferred initial rotation periods are as long as ~10 ms!

  14. Initial period of NS from merger- theoretical expectation The expected rotation period is ~1 ms! (Fan, Wu & Wei 2013)

  15. Signature of gravitational wave? • The total energy radiated in wide energy band during the X-ray plateau phase is much smaller than that expected for a merger-formed magnetar (E_k ~ P-2). Two possible solutions: • The radiation efficiency of the outflow is very low. But this possibility is disfavored by the extremely dim forward shock emission of some events. • (b) Strong gravitational wave radiation (?) (Fan, Wu & Wei 2013)

  16. The observed “too-short” duration of the X-ray plateau can be accounted for! (Fan, Wu & Wei 2013)

  17. Is it possible to have an ellipticity ~ 0.01? • The super-strong interior magnetic field (~1017 G) may be able to deform the magnetar significantly (Dall’Osso et al. 2009). • (b) Ellipticity up to 0.1 is possible for a quark star • (Lin 2007; Johnson-McDaniel & Owen 2013) (Fan, Wu & Wei 2013)

  18. Mass Ejection during NS-NS Merger Initial velocity: 0.1 – 0.3 c Ejected mass: 0.0001 – 0.01 Msun Hotokezaka,et al., arXiv:1212.0905

  19. Magnetar as the central product Jet-ISM shock (Afterglow) SGRB Late central engine activity ~Plateau & X-ray flare SGRB X-ray Radio Optical X-ray Magnetic Dissipation X-ray Afterglow Ejecta 1000 ~10000 s Shocked ISM X-ray Zhang, 2013 Ejecta-ISM shock with Energy Injection (EI) MNS Multi-band transient ~hours, days, weeks, or even years Poynting flux Gao, Ding, Wu, Zhang & Dai, 2013

  20. Magnetar as the central product Jet-ISM shock (Afterglow) SGRB Late central engine activity ~Plateau & X-ray flare SGRB X-ray Radio Optical X-ray Magnetic Dissipation X-ray Afterglow Ejecta 1000 ~10000 s Shocked ISM X-ray Zhang, 2013 Ejecta-ISM shock with Energy Injection (EI) MNS Multi-band transient ~hours, days, weeks, or even years Poynting flux Gao, Ding, Wu, Zhang & Dai, 2013

  21. Magnetar as the central product Jet-ISM shock (Afterglow) SGRB Late central engine activity ~Plateau & X-ray flare SGRB X-ray Radio Optical X-ray Magnetic Dissipation X-ray Afterglow Ejecta 1000 ~10000 s Shocked ISM X-ray Zhang, 2013 Ejecta-ISM shock with Energy Injection (EI) MNS Multi-band transient ~hours, days, weeks, or even years Poynting flux Gao et al, 2013 Rowlinson et al. 2013

  22. Magnetar as the central product Jet-ISM shock (Afterglow) SGRB Late central engine activity ~Plateau & X-ray flare SGRB X-ray Radio Optical X-ray Magnetic Dissipation X-ray Afterglow Ejecta 1000 ~10000 s Shocked ISM X-ray Zhang, 2013 Ejecta-ISM shock with Energy Injection (EI) MNS Multi-band transient ~hours, days, weeks, or even years Poynting flux Gao et al, 2013

  23. Magnetic Dissipation X-ray Afterglow Zhang, B., 2013, ApJL, 763,22 The proto-magnetar would eject a wide-beam wind, whose dissipation would power an X-ray afterglow as bright as~ (10−8–10−7) erg cm−2 s−1. The duration is typically 103–104s. Flux (ergcm-2s-1) t With , one can roughly estimate that the optical flux could be as bright as 17th magnitude in R band.

  24. Magnetar as the central product Jet-ISM shock (Afterglow) SGRB Late central engine activity ~Plateau & X-ray flare SGRB X-ray Radio Optical X-ray Magnetic Dissipation X-ray Afterglow Ejecta 1000 ~10000 s Shocked ISM X-ray Zhang, 2013 Ejecta-ISM shock with Energy Injection (EI) MNS Multi-band transient ~hours, days, weeks, or even years Poynting flux Gao, Ding, Wu, Zhang & Dai, 2013

  25. Ejecta-ISM shock with Energy Injection Gao, Ding, Wu, Zhang & Dai, 2013, arXiv:1301.0439 Energy conservation equation ISM (n) when Dynamics depends on and , namely and

  26. Ejecta-ISM shock with Energy Injection For given different leads to different Dynamic cases. Some of them could be even relativistic If Non-relativistic

  27. Ejecta-ISM shock with Energy Injection X-ray: Opt: Radio:

  28. Ejecta-ISM shock with Energy Injection X-ray: Opt: Radio:

  29. Ejecta-ISM shock with Energy Injection X-ray: Opt: Radio:

  30. Ejecta-ISM shock with Energy Injection X-ray: Opt: Radio:

  31. Ejecta-ISM shock with Energy Injection X-ray: Opt: Radio:

  32. Ejecta-ISM shock with Energy Injection X-ray: Opt: Radio:

  33. Late Re-brightening in SGRB 080503

  34. Late Re-brightening in SGRB 080503 --- Li-Paczynski Model Perley et al. 2009, ApJ, 696, 1871

  35. Late Re-brightening in SGRB 080503 --- Refreshing Shock Model Ek,0 = 7x1050 erg Ek,inj = 30 Ek,0 ~ 2x1052 erg ε_e = (ε_B )^0.5 ε_B = 5x10−2 , p = 2.5 n = 10-3 cm−3 z = 0.5 Hascoet et al. 2012, A&A, 541, A88

  36. Late Re-brightening in SGRB 080503 --- Gao, Ding, Wu, Zhang & Dai (2013) Model Ding, Gao, Wu, Zhang & Dai 2013, in preparation

  37. Relativistic PTF Transient PTF11agg --- Another GWB magnetar candidate? Cenko et al. (2013)

  38. Event Rate by VLA Bright Radio Transient Survery • Field of 3C 286 • 23-year archival observation • 1.4 GHz • event rate (>350 mJy ) is • < 6×10−4 degree−2 yr−1, • or < 20 yr −1 • Bright GWB afterglow rate • uncertainties: • NS-NS merger • Fraction of forming a massive • millisecond magnetar Bower & Sauer. 2011, ApJL, 728, 14

  39. Thank You

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