1 / 53

X-ray afterglows of GRB

X-ray afterglows of GRB. Luigi Piro Istituto Astrofisica Spaziale, CNR Roma. Summary. Discovery of afterglows & distance scale prompt vs afterglow emission & the fireball model Environment & progenitors GHOST’s in the sky To Beam or not to Beam The future. BeppoSAX instruments.

chick
Download Presentation

X-ray afterglows of GRB

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. X-ray afterglows of GRB Luigi Piro Istituto Astrofisica Spaziale, CNR Roma X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  2. Summary • Discovery of afterglows & distance scale • prompt vs afterglow emission & the fireball model • Environment & progenitors • GHOST’s in the sky • To Beam or not to Beam • The future X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  3. BeppoSAX instruments Piro, Scarsi & Butler, 1995, SPIE; Boella et al 1996, A&AS X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  4. GB960720: the 1st GRB by BeppoSAX Piro et al. 1997 A&A X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  5. GRB970111: the 1st fast localization & follow-up of a GRB • Triggered by GRBM and localized by the WFC of BeppoSAX • fast follow-up (16 hrs after the GRB) by the NFI • MECS (2-10 keV) image (Feroci et al 1998 A&A) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  6. GRB970228: the 1st X-ray and O afterglow • Triggered by GRBM and localized by WFC Fast follow up with NFI in 8 hrs: a bright unknown X-ray source A second pointing 3 days after the GRB: fading X-ray counterpart (Costa et al 1997) Optical fading source (van Paradijs et al 1997) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  7. GB970508: the 1st redshift (I) • Triggered/ localized by BeppoSAX GRBM/WFC • Position released in 2 hrs; follow up by BSAX NFI in 5.7 hrs X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  8. GB970508: the 1st redshift (II) • Images in the 2-10 keV range by the BSAX WFC (10-200 sec after the GRB) and by the BSAX MECS (6 hrs and 3 days) OT and redshift by absorption lines z=0.83: extragalactic(Metzger et al) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  9. Afterglows: power laws everywhere ! • Light curves (Costa et al 1997) & spectrum (Frontera etal 1997) of GB970228 X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  10. Afterglows: power laws everywhere • A collection of X-ray afterglow light curves by BSAX X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  11. Afterglows: power laws everywhere • X-ray spectra of GB000926 by BSAX & Chandra at different times (Piro et al 2000): power law with no substantial spectral variations X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  12. General properties of (X-Ray) afterglows • F≈ t-dn-a • dx=1.1-1.9 (average=1.4); ax≈1.0 X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  13. R-O-X afterglow G2 g RB G1 T1 T0 T-1 The fireball scenario Observer X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  14. Internal vs external shock: prompt & afterglow emission (I) • In contrast with the afterglow, the prompt emission is characterized by strong hard-to-soft spectral evolution: e.g. GRB960720 from X- to Gamma rays (Piro et al 1997) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  15. Internal vs external shock: prompt & afterglow emission (II) • Diverse spectral behaviour (Frontera etal 1997, 2000). X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  16. NS- NS merging Hypernova The progenitors of GRB The nature of the progenitor can be inferred from the environment • NS-NS (BH-NS & BH-WD) travel far from their formation sites before producing GRB’s (Fryer et al 2000) => “clean environment”: no lines • Hypernovae/collapsar evolve much faster, going off in their formation site => “mass-rich environment” => lines X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  17. The progenitors of GRB • Deviations of the temporal and spectral behaviour (e.g. features) from the power law should betray a mass-rich environment around the GRB X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  18. X-ray Fe features • Ubiquitous feature in several classes of X-ray sources • Diagnostics of the environment nearby the central engine • Independent and direct (no host ambiguity) redshift determination X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  19. First evidence of Iron line from a GRB: BeppoSAX obs. of GB970508 (Piro et al, 2000 ApJ 514,L73) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  20. Iron line emission • The line in GB970508 (detected at 2.8 s) is consistent with emission from iron Ka with E=6.4-6.7 keV) at the redshift of the GRB (z=0.83 Kulkarni et al 1997) • These observations indicate that a mass M few Afe-1 Ms should be located at a distance  1016 cm. => Massive progenitor (Woosley 1993, Paczynsky 1998, Vietri & Stella 1998). • A line with a similar significance found by ASCA in GB970828 (Yoshida et al 1999) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  21. line at Eobs=5 keV. With z=0.96 (Djorgovski et al 2000) =>Erest=9.3 keV: iron recombination continuum (Weth et al 2000, Paerels et al 2000) GB970828 by ASCA X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  22. GB991216 X-ray light curve • Localized by BATSE/PCA (Takeshima et al 2000): very bright X-ray afterglow • OT found (Halpern et al. 2000) • Chandra TOO (1st) at T0+1.5 days XTE/ASM XTE/PCA Chandra X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  23. Iron features in GB991216 (I) E=4.5 keV E=3.5 keV, S=4.7s (Piro et al. Science, Nov.3 2000) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  24. Iron features in GB991216 (II) • Line at E=3.5 keV => Fe Ka neutral, He-like, H-like (Erest=6.4, 6.7, 6.9 keV) • Feature at E=4.5 keV: Fe recombination edge in emission(Erest=9.28 keV) => • Fe H-like => z=1.00+\-0.02: consistent with the most distant absorption system found in O (Vreeswick et al GCN496; candidate host galaxy by Djorgovsky et al) • The medium is photoionized (i.e. must be illuminated by GRB photons) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  25. Fe Ka Line & recombination edge • Both expected in a medium highly photoionized by the radiation field of the GRB (Weth et al 2000 computed the time evolution) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  26. The mass of iron • The total n. of Fe atoms NFe=LLtrec, where trec =30 T71/2 n10-1 is the recombination time, with kT>1 keV (from the width of the edge). • A lower limit on n10<15 can be derived by requiring Fe to be in H-like stage: ionization parameter x=Lx/nR2>104 with R>1 l.d. • M>5 XFe-1 M ; MFe > 0.01 M • Massive progenitor X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  27. Moving ejecta from the progenitor • the iron abundance of the line emitting medium XFe > 60 (it derives from the requirements t>1 and x>104) • the line width(0.23+/-0.07 keV) => the medium is moving with v=0.1 c • density & velocity non consistent with winds (unless exotic processes accelerate clouds) • very high Fe abundance and velocity => ejecta from a SN explosion occured shortly before the GRB (SupraNova model of Vietri & Stella) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  28. Other scenarios • a disk formed during the common envelope phase being shock-heated (and accelerated to v=0.1 c) by the GRB expanding shell (Boettcher & Fryer 2000, see also Vietri, Perola, Piro & Stella 2000) • Problem: the gas is expected to be in thermal equilibrium => no recombination edge in emission (cfr typical plasma sources in thermal equilibrium as cluster of galaxies) • other models (Meszaros& Rees 2000) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  29. What’s next: is Fe line a common feature of GRB (I) ?:GB000214 Antonelli et al. 2000 X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  30. What’s next: is Fe line a common feature of GRB (II) ? • Residuals from a power law fit to BeppoSAX X-ray afterglows with known z plotted in the rest frame (Piro & Stratta 2000); preliminary results: X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  31. AGN: Fe lines and reflection bump Both features produced by optically thick medium (Piro et al 1990, Matt et al. 1991) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  32. GRB vs AGN • From the comparison with AGN it follows that the line in GRB’s cannot be produced by an optically thick (Compton scattering) medium: no high energy bump visible X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  33. What’s next: is Fe line a common feature of GRB (III) ? • On the other hand upper limits from ASCA (Murakami’s talk in Rome). Possible explanations: • because line disappears at later times (region smaller than 1-2 l.d.) • because of the highly variable ionizing continuum and of the non-linear dependence of the line intensity on it X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  34. What can we expect in the X-ray “prompt” spectrum re the edge? • If the medium is also located in the line of sight => the iron edge should be first seen in absorption (and then in emission in the afterglow) (Weth et al. 2000) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  35. What can we expect in the X-ray “prompt” spectrum re the edge? (II) • A transient iron edge has been indeed observed by BeppoSAX in the prompt emission of GB990705 Amati et al. 2000 Science,Nov 3 issue) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  36. GRB: the largest explosions since the Big Bang • GRB990123: the brightest event ever observed by BeppoSAX (in the top 0.3% observed by BATSE) • at z=1.6, assuming isotropy): E= 4x1054 erg • M=E/c2 = 2 Sun Mass !!!! • To Beam or not to beam ? X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  37. Jet vs spherical expansion: break in the afterglow light curve F The break must be achromatic G-1(t4)=q Spher. Jet t4 t q t1 t2 t3 t4 t5 X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  38. Simultaneous O and X-ray light curves of GB990510 • Break in the O at t= 1day (Harrison et al 99) • BeppoSAX light curve well fitted by simple power law (but also compatible with breakKuulkers et al 2000) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  39. The brightest OT (R=19.3 Dall et al GCN 804) found 1 day after the GRB (from IPN Hurley et al. GCN804) BeppoSAX follow up from T0+1.9 to T0+2.7 days GB000926: 1st evidence of jet from an achromatic break in X-rays ? • Chandra obs T0+2.7 days after the GRB (14 ksec) • Another Chandra obs at T0+10 days (Kulkarni’s programme) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  40. GB000926: fast decaying X-ray afterglow X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  41. GB000926: 1st evidence of jet from an achromatic break in X-rays ? O data from Halpern et al, Dall et al., Hjort et al, Veillet et al, Price et al X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  42. Jet’s in GRB • GB000926: dx=-3.7+/-1.4 the steepest observed in X-rays, steeper than do before the break, (marginally) consistent with do=-2.3-2.5 (Halpern et al, Hjort et al. Fynbo,Veillet et al),do=-3.2+-0.4 (Rol et al GCN850) • achromatic break (from O to X-rays) at t=2 days => (Sari et al 99)q»10° • However, late time X-ray behaviour shows deviations from this scenario…. X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  43. Jet’s in GRB (II) • Other candidate jets from optical (GB990123, GB99216,..). However on average GRB are not highly collimated: no break at t<2days (q>10°) (Stratta & Piro 2000) X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  44. X-ray afterglows > 90% Optical afterglows ~ 40% - 50% Radio afterglows ~ 35% - 40% GRB localized and observed in X-rays • As of Nov.8, 2000: • Fast&precise localizations: 34 GRBM+WFC BeppoSAX, 1 XTE/ASM, 3 (+1) BATSE/XTE; plus: 1 OT (from IPN), 1 XTE(ASM)+IPN • 27 fast follow-up by BeppoSAX(1 triggered by XTE/ASM, 1 by OT) • 4 by ASCA (970828 triggered by XTE/ ASM) • 3 by Chandra: (GB991216 by BATSE/XTE; GB000210 by BSAX ; GB000926 by OT • 1 by Newton-XMM (GB001025) 26 X-ray afterglow candidates out of 30 GRB follow up obs in X-rays X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  45. GHOST’s in the sky • Grb Hiding Optical Source / Transient: GRB with X-ray but no O afterglow • Optical searches with same sensitivity & reaction times as in the cases with OT • OT heavily absorbed by star forming region ? • Key path to disclose GHOST’s from X-rays: • ID of X-ray afterglow (i.e. unknown decaying source) • arcsec position X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  46. GRB000210: BeppoSAX & Chandra • GRB localized by BeppoSAX • Simultaneous obs of the X-ray afterglow with Chandra X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  47. GB000210 X-ray light curve Piro et al X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  48. a constant optical source (the galaxy?) coincident with the X-ray afterglow (Gorosabel et al. GCN.783) Deeper observations & spectroscopy are being gathered GB000210 in the optical band X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  49. Gamma Ray Bursts: The Future 1999 • BeppoSAX - XTE/BATSE ~15 GRB/yr Locations, X-ray afterglows • HETE 2 (2000) ~40 GRB/yr Locations • BALLERINA (2002 ?) ~70 GRB/yr Locations, X-ray afterglows • SWIFT (2003) ~200-300 GRB/yr Locations, X-ray and optical afterglows In the same period: Chandra • X-ray spectroscopy of a few bright X-ray afterglows • PROBE INTO THE CENTRAL GRB ENVIRONMENT Newton/XMM • X-RAY REDSHIFT (LINE; ABSORPTION) + INTEGRAL, AGILE, GLAST BURST PROPER / HARD X, GAMMA RAYS 2006 X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

  50. The far future • Still missing in the approved missions: high resolution spectroscopy: study of GRB and their environment in the early Universe. • This could be achieved via a dedicated mission based on e.g. X-ray bolometers pointing the GRB in a few minutes or by a huge area telescope - like the 35 sqm foreseen on XEUS- pointing around a day after the GRB X-ray afterglows of GRB, L. Piro (IAS/CNR):Jerusalem Dec. 2000

More Related