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The Swift Gamma-Ray Burst Explorer

Paolo D’Avanzo

INAF-Osservatorio Astronomico Di Brera

(MISTICI team)

Universita` degli studi dell’Insubria

Multiwavelength Italian Swift Team with International Co-Investigators

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• Successfully launched on the 20th of November 2004 • 267 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

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OUTLINE

• GRB: theory and open matters

• Swift & REM: instruments, performances & science

• GRB: results

• Observationals procedures: BA & DS

• Secondary science: X-Ray Binaries

• Conclusions & Future

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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)

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The standard model: fireball

central photosphere internal external shocksengine (shocks) (reverse) (forward)

gamma-ray

UV/opt/IR/radio

gamma-rayX-rayUV/optical

IRmmradio

Rees & Meszaros 1994; Paczynski & Xu 1994

Hypernova

HypernovaYoung (few million yrs)Inside or near galaxiesHypernovaHypernova

HypernovaYoung (few million yrs)Inside or near galaxiesMerging

NeutronStars

Merging Neutron Stars

Old (few billion yrs)Outside galaxiesMerging

NeutronStars

Merging NeutronStars

Merging Neutron Stars

Old (few billion yrs)Outside galaxies

Emission mechanism: synchrotron emission from power-law distribution electrons in highly relativistic outflows

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Progenitors: long GRBsLight curves Spectra

GRB 980425(Galama et al., 1998)

First GRB – SN association

GRB 021211

(Massimo Della Valle, Daniele Malesani, Stefano Benetti, Vincenzo Testa,

Mario Hamuy, L. Angelo Antonelli, Guido Chincarini, Gabriele Cocozza,

Stefano Covino, Paolo D'Avanzo & 7 coautoriA&A 406, L33-L37 (2003))

GRB 031203

(Daniele Malesani, Gianpiero TagliaferriGuido Chincarini, Stefano Covino,

Massimo Della Valle, Dino Fugazza,Paolo Mazzali, Filippo M. Zerbi,Paolo D'Avanzo & 17 coautori

ApJ 609, L5-L8 (2004))

Hypernova

HypernovaYoung (few million yrs)Inside or near galaxiesHypernovaHypernova

HypernovaYoung (few million yrs)Inside or near galaxies

SN - Connection

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8 hour data gap

4 or

ders

of

mag

nit

ude 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.

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• Burst Alert Telescope (BAT)– 15-150 keV– FOV: 2 steradiants – Centroid accuracy: 1’ - 4’

• X-Ray Telescope (XRT)– 0.2-10.0 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’– 24th mag sensitivity (1000 sec)– Centroid accuracy 0.5”

BAT

XRT

Spacecraft

UVOT

BAT

UVOT

XRT

Spacecraft

Swift Mission

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A fast moving telescope …A fast moving telescope …• Alt-az 60 cm f/8 RC Alt-az 60 cm f/8 RC silversilver-coated -coated • 2 Nasmyth foci (one idle)2 Nasmyth foci (one idle)• 60 deg 5 sec60 deg 5 sec – to any – to any ,, in 60 sec in 60 sec• 10x10 am10x10 am22 F FooVV

… … with a high throughput NIR Camera…with a high throughput NIR Camera…• 10x10 am10x10 am22 F FooVV• 1.2 as pixel scale (diff.limited)1.2 as pixel scale (diff.limited)• 0.9-2.3 microns (Z’,J,H,K0.9-2.3 microns (Z’,J,H,Kss))• 512x512 HgCdTe chip @77 Kelvin512x512 HgCdTe chip @77 Kelvin• Wobbling plate for ditheringWobbling plate for dithering

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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 20-70 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 secT< 60 sec

UVOT/REM Image

Observing Scenario

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BAT Bursts• 66 GRBs detected/imaged since Dec. 17 (33.5 weeks as of 08/30/05)

041217 050315 050410 050502B 050603 050715 050730 050815

041219A,B,C 050318 050412 050505 050607 050716 050803050819

041220 050319 050416A,B 050507 050701 050716 050805 050820A,B

041223 050326 050418 050509A,B 050712 050721 050807 050822

041224 050401 050421 050525 050713A,B 050724 050813 050824

041226 050406 050422 050528 050714B 050726 050814 050830

041228

050117

050124

050126

050128

050202

050215A

050215B

050219A,B

050223

050306

GRB Fluence

0.1

1

10

100

1000

12/1

/200

4

1/1/

2005

2/1/

2005

3/1/

2005

4/1/

2005

5/1/

2005

6/1/

2005

7/1/

2005

Date

GR

B F

lue

nc

e (

10

^-7

)

Average rate is ~90/year

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XRFShortGRB

XRF

ShortGRB

XRF

XRFXRF

XRF

XRF

ShortGRB

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RESULTS

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Progenitors: short GRBs (I)

GRB 050509B: first detection of the X-ray afterglow of a short GRB(N. Gehrels et al., 2005 Nature)

GRB 050709: first detection of the optical afterglow of a short GRB(S. Covino, D. Malesani, G.L. Israel, P. D’Avanzo & 29 coauthors, 2005 A&AL, submitted)

GRB 050724: 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. O’Brien, C.L. Sarazin, C. Kouvelotou, M. Goad, S. Vaughan, G. Tagliaferri, B. Zhang, A. Antonelli, S. Campana, P. D’Avanzo & 12 coauthors, 2005 Nature, submitted)

Host Galaxies

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Progenitors: short GRBs (II)

GRB 050509B & GRB 050724Host Galaxies

• early type elliptical

• red color spectrum

• no emission lines

Low star formation ratePopulation of very old stars

XRT position

GRB 050709Host Galaxy

• late type irregular

• blue color spectrum

• Hα emission lineBUT...

off-core (3 kpc) position of the OT,consistent with a system of

age 10^9 y

vs.Host Galaxies

oflong GRB

Merging NeutronStars

Merging Neutron Stars

Old (few billion yrs)Outside galaxiesMerging

NeutronStars

Merging NeutronStars

Merging Neutron Stars

Old (few billion yrs)Outside galaxies

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The fartest GRB ever observed

z = 6.3!ESO press release

12 Sep 2005

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Observational procedures (I)

REM

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Observational procedures (II)

• Burst Advocate

• Rem Duty Scientist

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Science with Swift & REM

GRBs observed rate now is about 2 burst per week but also GRBs observed rate now is about 2 burst per week but also latitude/longitude constraints have to be taken into account.latitude/longitude constraints have to be taken into account.

This is leaving free Swift & REM observing time that is largely used for: This is leaving free Swift & REM observing time that is largely used for:

Any program requesting fast multi-frequency observationsAny program requesting fast multi-frequency observations

1.1. Multifrequency monitoring of AGNsMultifrequency monitoring of AGNs2.2. X-Ray BinariesX-Ray Binaries3.3. Flare StarsFlare Stars4.4. Others...Others...

GRB!

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X-Ray Binaries

• sporadic outbursts• long quiescent periods

SXRT

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Doppler tomography

• image reconstruction• monitoring at different orbital phases• bidimensional maps

spectral lines

familiar spatial coordinates…

… and corresponding velocity coordinates

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Centaurus X-4 – quiescent optical emmission Hα HeI 5875 HeI 6678

• circular ring-like structure in emission• emission from the companion• visible “hot spot”

Irradiation hypothesis: DISC• Hα emission from externalregion• HeI emission from internal region

COMPANION STAR• Hα emission from low velocity regions• HeI emission from high velocity regions

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Origin of the quiescent emission (I)

fase 0 fase 0.25 fase 0.5 fase 0.75

The companion fills its Roche Lobeand could be subject to irradiation

from the NS

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Origin of the quiescent emission (II)

D'Avanzo et al. 2005, A&A, accepted

EW = 4.4 ± 0.5 Å

log FHα = log EW(Hα) + 0.113(B-V)2 – 1.188(B-V) +7.487(Soderblom et al., 1993)

FHα = 7 x 106 erg cm-2 s-1

LX = 4 x 1032 erg s-1

(Campana et al., 2004)

FX = LX/(4πa2) = 5 x 108 erg cm-2 s-1

a = 3.6 solar radius

LHα = f1f2LX = 5 x 10-3 LX = 0.5% LX

f1= solid anglef2= 0. 3 (Osterbrock 1987)

1% of the incident X-Ray flux should be reprocessed to Hα photons

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ms X-Ray Pulsars

Source name X period

(Hz/ms)

Orbital period

(h)

Optical counterpart in quiescence

SAX J1808.4-3658 401 Hz /2.49 ms 2.01 hrs I=21

XTE J1751-305 435 Hz /2.30 ms 0.70 hrs R>23.1, I>21.6

XTE J0929-314 185 Hz /5.41 ms 0.73 hrs n

XTE J1807-294 191 Hz /5.24 ms 0.67 hrs n

XTE J1814-338 314 Hz /3.18 ms 4.30 hrs R > 23

IGR J00291-5934 599 Hz /1.67 ms 2.46 hrs I > 21

HETE J1900.1-2455

377 Hz/2.65 ms 1.39 hrs n

Campana, D'Avanzo et al., 2004, ApJ

ESO – VLT proposal (in prep.)

TNG approved proposal (P.I.: P. D’Avanzo)

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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

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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