The Swift GammaRay 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 1
The Swift Mission
• 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
2
OUTLINE
•
•
•
•
•
•
GRB: theory and open matters
Swift & REM: instruments, performances & science
GRB: results
Observationals procedures: BA & DS
Secondary science: X-Ray Binaries
Conclusions & Future
3
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)
4
The standard model: fireball
Hypernova
Merging Neutron Stars
Young (few
Old (few billion
yrs)
Merging
Outside galaxies
Neutron
Stars
UV/opt/IR/radio
million yrs)
Inside or near
Hypernova
galaxies
gamma-ray
gamma-ray
X-ray
UV/optical
IR
mm
radio
central
engine
photosphere
internal
(shocks)
external shocks
(reverse)
(forward)
Emission mechanism: synchrotron emission from power-law distribution electrons in highly
relativistic outflows
Rees & Meszaros 1994; Paczynski & Xu 1994
5
Progenitors: long GRBs
Light curves
GRB 021211
Spectra
(Massimo Della Valle, Daniele Malesani,
Stefano Benetti, Vincenzo Testa,
Mario Hamuy, L. Angelo
Antonelli,
Young
(few
Guido Chincarini, Gabriele
Cocozza,
million yrs)
Stefano Covino, Paolo D'Avanzo
& 7near
coautori
Inside or
Hypernova
A&A 406, L33-L37
(2003))
galaxies
SN Hypernova
- Connection
GRB 980425
(Galama et al., 1998)
First GRB – SN
association
GRB 031203
(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))
6
8 hour data gap
4 orders of magnitude
The data gap
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.
Swift was designed to fill in the gap making very early observations of the
afterglows, beginning approximately a minute after the burst.
7
Swift Mission
•
•
•
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”
UVOT
BAT
BAT
XRT
UVOT
XRT
Spacecraft
Spacecraft
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A fast moving telescope …
• Alt-az 60 cm f/8 RC silver-coated
• 2 Nasmyth foci (one idle)
• 60 deg 5 sec – to any , in 60 sec
• 10x10 am2 FoV
… with a high throughput NIR Camera…
• 10x10 am2 FoV
• 1.2 as pixel scale (diff.limited)
• 0.9-2.3 microns (Z’,J,H,Ks)
• 512x512 HgCdTe chip @77 Kelvin
• Wobbling plate for dithering
9
Observing Scenario
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 Burst Image
XRT Image
UVOT/REM Image
BAT Error
Circle
T<10 sec
 < 4'
T<100 sec
 < 5''
T<300 sec
T< 60 sec
10
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
050803
050819
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
050814
050830
050726
041228
050117
Average rate is ~90/year
050124
GRB Fluence
Date
20
05
7/
1/
20
05
6/
1/
20
05
5/
1/
20
05
4/
1/
20
0
/1
/
12
050306
4
050223
20
05
0.1
3/
1/
050219A,B
1
20
05
050215B
10
2/
1/
050215A
100
20
05
050202
1000
1/
1/
050128
GRB Fluence (10^-7)
050126
11
Short
GRB
XRF
XRF
XRF
XRF
XRF
XRF
Short
GRB
XRF
Short
GRB
12
RESULTS
13
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)
Merging Neutron Stars
Old (few billion
GRB 050509B & GRB 050724
yrs)
Host Galaxies
Merging
Outside galaxies
Host Galaxies
Neutron
• early type elliptical
of
Stars
vs.
• red color spectrum
long GRB
• no emission lines
XRT position
Low star formation rate
Population of very old stars
GRB 050709
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
15
The fartest GRB ever observed
z = 6.3!
ESO press release
12 Sep 2005
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Observational procedures (I)
REM
17
Observational procedures (II)
• Burst Advocate
• Rem Duty Scientist
18
Science with Swift & REM
GRB!
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.
2.
3.
4.
Multifrequency monitoring of AGNs
X-Ray Binaries
Flare Stars
Others...
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X-Ray Binaries
SXRT
sporadic outbursts
• long quiescent periods
•
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Doppler tomography
image reconstruction
• monitoring at different orbital phases
• bidimensional maps
•
spectral
lines
… and corresponding
velocity coordinates
familiar spatial coordinates…
21
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 external
region
• HeI emission from internal
region
COMPANION STAR
• Hα emission from low
velocity regions
• HeI emission from high
velocity regions
22
Origin of the quiescent emission (I)
The companion fills its Roche Lobe
and could be subject to irradiation
from the NS
23
fase 0
fase 0.25
fase 0.5
fase 0.75
Origin of the quiescent emission (II)
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
1% of the incident X-Ray flux should be
reprocessed to Hα photons
LHα = f1f2LX = 5 x 10-3 LX = 0.5% LX
f1= solid angle
f2= 0. 3 (Osterbrock 1987)
D'Avanzo et al. 2005, A&A, accepted
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ms X-Ray Pulsars
Campana, D'Avanzo et al.,
2004, ApJ
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 J1900.12455
377 Hz/2.65 ms
1.39 hrs
n
TNG approved proposal (P.I.: P. D’Avanzo)
ESO – VLT proposal (in prep.)
25
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
26
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
27