1 The Swift Gamma- Ray Burst Explorer Paolo DAvanzo INAF-Osservatorio Astronomico Di Brera (MISTICI team) Universita` degli studi dellInsubria Multiwavelength Italian Swift Team with International Co-Investigators

2 Successfully launched on the 20 th of November days in orbit All instruments operating to spec BAT First Light: 3 December 2004 XRT First Light: 11 December 2004 First BAT Burst: 17 December 2004 First XRT Afterglow: 23 December 2004 UVOT First Light: 12 January 2005 First UVOT Afterglow 15 March 2005 Calibration phase ended on Apr 5 The Swift Mission

3 OUTLINE GRB: theory and open matters Swift & REM: instruments, performances & science GRB: results Observationals procedures: BA & DS Secondary science: X-Ray Binaries Conclusions & Future

4 GRB Characteristics (BATSE+SAX) Short (10 ms < t < 1000 s) and intense (E ~ 10^54 erg) pulse of gamma rays occurring at random positions in the sky Isotropic distribution (BATSE) Afterglow era (SAX) Cosmological distances (SAX)

5 The standard model: fireball central photosphere internal external shocks engine (shocks) (reverse) (forward) gamma-ray UV/opt/IR/radio gamma-ray X-ray UV/optical IR mm radio Rees & Meszaros 1994; Paczynski & Xu 1994 Emission mechanism: synchrotron emission from power-law distribution electrons in highly relativistic outflows

6 Progenitors: long GRBs Light curvesSpectra GRB (Galama et al., 1998) First GRB – SN association GRB (Massimo Della Valle, Daniele Malesani, Stefano Benetti, Vincenzo Testa, Mario Hamuy, L. Angelo Antonelli, Guido Chincarini, Gabriele Cocozza, Stefano Covino, Paolo D'Avanzo & 7 coautori A&A 406, L33-L37 (2003)) GRB (Daniele Malesani, Gianpiero Tagliaferri Guido Chincarini, Stefano Covino, Massimo Della Valle, Dino Fugazza, Paolo Mazzali, Filippo M. Zerbi, Paolo D'Avanzo & 17 coautori ApJ 609, L5-L8 (2004)) SN - Connection

7 8 hour data gap 4 orders of magnitude Beppo-SAX takes at least 6-8 hours to perform an afterglow follow-up observation with its narrow field instruments. During this time, afterglow fades orders of magnitude. The data gap Swift was designed to fill in the gap making very early observations of the afterglows, beginning approximately a minute after the burst.

8 Burst Alert Telescope (BAT) – keV –FOV: 2 steradiants –Centroid accuracy: X-Ray Telescope (XRT) – keV –FOV: 23.6 x 23.6 – centroid accuracy:5 (UVOT) UV/Optical Telescope –30 cm telescope –6 filters (170 nm – 600 nm) –FOV: 17 x 17 –24 th mag sensitivity (1000 sec) –Centroid accuracy 0.5 BAT XRT Spacecraft UVOT BAT UVOT XRT Spacecraft Swift Mission

9 A fast moving telescope … Alt-az 60 cm f/8 RC silver-coated Alt-az 60 cm f/8 RC silver-coated 2 Nasmyth foci (one idle) 2 Nasmyth foci (one idle) 60 deg 5 sec – to any, in 60 sec 60 deg 5 sec – to any, in 60 sec 10x10 am 2 FoV 10x10 am 2 FoV … with a high throughput NIR Camera… 10x10 am 2 FoV 10x10 am 2 FoV 1.2 as pixel scale (diff.limited) 1.2 as pixel scale (diff.limited) microns (Z,J,H,Ks) microns (Z,J,H,Ks) 512x512 HgCdTe Kelvin 512x512 HgCdTe Kelvin Wobbling plate for dithering Wobbling plate for dithering

10 BAT Burst Image T<10 sec < 4' 1.Burst Alert Telescope triggers on GRB, calculates position on sky to < 4 arcmin 2.Spacecraft autonomously slews to GRB position in s 3.X-ray Telescope determines position to < 5 arcseconds 4.UV/Optical Telescope images field, transmits finding chart to ground BAT Error Circle XRT Image T<100 sec < 5'' T<300 sec T< 60 sec UVOT/REM Image Observing Scenario

11 BAT Bursts 66 GRBs detected/imaged since Dec. 17 (33.5 weeks as of 08/30/05) B A,B,C A,B A,B A,B A,B B A B A,B Average rate is ~90/year

12 XRF Short GRB XRF Short GRB XRF Short GRB

13 RESULTS

14 Progenitors: short GRBs (I) GRB B: first detection of the X-ray afterglow of a short GRB (N. Gehrels et al., 2005 Nature) GRB : first detection of the optical afterglow of a short GRB (S. Covino, D. Malesani, G.L. Israel, P. DAvanzo & 29 coauthors, 2005 A&AL, submitted) GRB : again a detection of the optical afterglow of a short GRB (S.D. Barthelmy, G. Chincarini, D.N Burrows, N. Geherels, S. Covino, A. Moretti, P. Romano, P.T. OBrien, C.L. Sarazin, C. Kouvelotou, M. Goad, S. Vaughan, G. Tagliaferri, B. Zhang, A. Antonelli, S. Campana, P. DAvanzo & 12 coauthors, 2005 Nature, submitted) Host Galaxies

15 Progenitors: short GRBs (II) GRB B & GRB Host Galaxies early type elliptical red color spectrum no emission lines Low star formation rate Population of very old stars XRT position GRB Host Galaxy late type irregular blue color spectrum Hα emission line BUT... off-core (3 kpc) position of the OT, consistent with a system of age 10^9 y vs. Host Galaxies of long GRB

16 The fartest GRB ever observed z = 6.3! ESO press release 12 Sep 2005

17 Observational procedures (I) REM

18 Observational procedures (II) Burst Advocate Rem Duty Scientist

19 Science with Swift & REM GRBs observed rate now is about 2 burst per week but also latitude/longitude constraints have to be taken into account. This is leaving free Swift & REM observing time that is largely used for: Any program requesting fast multi-frequency observations 1.Multifrequency monitoring of AGNs 2.X-Ray Binaries 3.Flare Stars 4.Others... GRB!

20 X-Ray Binaries sporadic outbursts long quiescent periods SXRT

21 Doppler tomography image reconstruction monitoring at different orbital phases bidimensional maps spectral lines familiar spatial coordinates… … and corresponding velocity coordinates

22 Centaurus X-4 – quiescent optical emmission H α HeI 5875 HeI 6678 circular ring-like structure in emission emission from the companion visible hot spot Irradiation hypothesis: DISC H α emission from external region HeI emission from internal region COMPANION STAR H α emission from low velocity regions HeI emission from high velocity regions

23 Origin of the quiescent emission (I) fase 0 fase 0.25 fase 0.5 fase 0.75 The companion fills its Roche Lobe and could be subject to irradiation from the NS

24 Origin of the quiescent emission (II) D'Avanzo et al. 2005, A&A, accepted EW = 4.4 ± 0.5 Å log F Hα = log EW(Hα) (B-V) 2 – 1.188(B-V) (Soderblom et al., 1993) F Hα = 7 x 10 6 erg cm -2 s -1 L X = 4 x erg s -1 (Campana et al., 2004) F X = L X /(4πa 2 ) = 5 x 10 8 erg cm -2 s -1 a = 3.6 solar radius L Hα = f 1 f 2 L X = 5 x L X = 0.5% L X f 1 = solid angle f 2 = 0. 3 (Osterbrock 1987) 1% of the incident X-Ray flux should be reprocessed to Hα photons

25 ms X-Ray Pulsars Source nameX period (Hz/ms) Orbital period (h) Optical counterpart in quiescence SAX J Hz /2.49 ms2.01 hrsI=21 XTE J Hz /2.30 ms0.70 hrsR>23.1, I>21.6 XTE J Hz /5.41 ms0.73 hrsn XTE J Hz /5.24 ms0.67 hrsn XTE J Hz /3.18 ms4.30 hrsR > 23 IGR J Hz /1.67 ms2.46 hrsI > 21 HETE J Hz/2.65 ms1.39 hrsn Campana, D'Avanzo et al., 2004, ApJ ESO – VLT proposal (in prep.) TNG approved proposal (P.I.: P. DAvanzo)

26 Conclusions (I) Exciting Swift results on: –GRB progenitors –Host Galaxy morfology –High z GRB New light on quiescent optical emission of SXRTs Opportunity to investigate the link between ms X-Ray Pulsars and ms Radio Pulsars

27 Conclusions (II) Our results on GRB led to: –42 GCN circulars –3 published papers –3 submitted papers –2 papers in preparation Our results on SXRT led to: –1 paper published –1 approved TNG proposal –3 ESO proposals in preparation