AstroSat - India's Multi-Wavelength
Astronomy Satellite
K.P. Singh
Tata Institute of Fundamental Research (TIFR), Mumbai
+ several colleagues at TIFR and
Indian Institute of Astrophysics (IIA), Bangalore
Inter-University Centre for Astronomy & Astrophysics (IUCAA), Pune
Canadian Space Agency
University of Leicester, UK
ISRO Satellite Centre (ISAC), Bangalore
Raman Research Institute, Bangalore
Vikram Sarabhai Space Centre, Trivandrum
Space Applications Centre, Ahmedabad
Physical Research Laboratory, Ahmedabad
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!  LaunchedbyPSLV-XLfromSHARonSep28,2015
Altitude:650km;Inclination:6deg.
Massof1513kg.(750kg.Payloads)+6moresmallsatellites
Power=2200wattsbysolarpanels+2x36AHLi-ionbatteries
Heatersandsensorsforthermalcontrolofallthepayloadsand
subsystemsasspecified.
!  Three-axisstabilization.
!
!
!
!
!  Orientationby4reactionwheelsand3magnetictorquers(capacity:60Am2)
!
!
!
!
+inputsfrom3dualgimbalgyros,2starsensorsand2magnetometers.
Targetacquisitioncapabilityof0.05°
Pointingaccuracyof~1arcsecwithstarsensors.
Driftrateisexpectedtobe0.2arcsec/s.
Maximumslewratewillbe0.6o/s.
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!  Solid-staterecorderwith200Gbstorage(4orbits).
!  Asatellitepositioningsystemfortimereferenceof200ns.
!  AnASICbasedsystemBusManagementUnitwith1553interfaceswill
!
!
!
!
!
!
interfacewithAttitudeandOrbitcontrolsystem,CommandProcessing,
HousekeepingTelemetry,SensorProcessing,RCSinterface,Thermal
Managementetc.
DatatransmissionbytwoX-bandcarriersviatwophasedarrayantennas,
onceinallthevisibleorbits,atarateof210(2x105Mb/s)Mb/s.House
keepingdatatransmissioninS-bandviaquadrifilarhelixantennas.
Thespacecraftcontrol,payloaddataacquisition,dataprocessingfrom
groundstationsinBengaluruviz.,ISTRACTTCNetwork,TTC-Bangalore
station.
IndianSpaceScienceDataCentre(ISSDC)forpayloaddata.
Operationallifeof>5years
Orbitalperiod:~98minutes;
Eclipseperiod:35minutes;Sunlitperiod:62minutes
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AstroSat:Co-alignedmulti-waveinstruments
SXT
UVIT (IIA+ISAC+CSA+IUCAA+TIFR)
(TIFR+UoL+ ISAC+VSSC)
LAXPC
(TIFR)
CZTI (TIFR + IUCAA
+VSSC)
SSM (ISAC+VSSC)
Cold Side with
Radiator plates
For CCD and
CZTI
Star Sensors (ISAC)
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phase, in the 2.5 -10 keV energy range.
Table 1. Performance parameters of ASTROSAT
!
ASTROSAT
Expected
Performance
Parameters
of the
scientific
Instruments
UVIT
Detector! Intensified CMOS,
used in photon
!
counting mode or
!
!!!!!!!!!!!!!!!!!!!!!!!integration mode
Imaging
Imaging!/!non/
imaging!
Twin RitcheyOptics!!
Chretian 2 mirror
system.
1300-5500
Bandwidth!
Angstroms
!
~1100
Geometric!Area!
(cm2)!
Effective!Area!! 8 - 50 (depends
on filter)
(cm2)!
28’ dia
Field!of!View!
(FWHM)!
<1000 A
Energy!
(depends
on filter)
Resolution!
Angular!
Resolution!
!
Time!resolution!
1.8 arcsec
(FUV,NUV)
2.2 arcsec (Vis)
1.7 ms
Typical!
observation!
time!per!target!
Sensitivity!
(Obs.!Time)!
30 min
Mag. 20 (5σ)
200 s
(130-180 nm)
SXT
LAXPC
CZTI
SSM
X-ray (MOS) CCD
at the focal plane.
(XMM & Swift
heritage)
Proportional
counter
CdZnTe
detector array
Positionsensitive
proportional
counter
Imaging
Non-imaging
Imaging
Imaging
Conical foils
(~Wolter-I) mirrors.
2-m focal length
0.3 - 8 keV
Collimator
2- D coded
mask
1- D coded
mask
3 - 80 keV
10 - 100 keV
2.5 - 10 keV
~250
10800
1024
~180
~128@1.5 keV
~22@6 keV
∼ 40’ dia
8000@5-20
keV
0
1 x 10
1000 (E>10
keV)
60 x 60
~11 @ 2 keV
~53 @ 5 keV
100 x 900
∼5-6%@1.5
keV
∼2.5%@6keV
∼2 arcmin
(HPD)
12%@22 keV
5% at 100
keV
25% @ 6 keV
~(1-5) arcmin
(in scan
mode only)
8 arcmin
~12 arcmin
2.4 s, 278 ms
10 µs
1 ms
1 ms
0.5 - 1 day
1 - 2 days
2 days
10 min
~10-13 ergs cm-2
0.1 milliCrab
0.5 milliCrab
-1
s
(3σ)
(3σ)
(5 σ)KPS@MSSL2015
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(1000 s)
(1000s)
~28 milliCrab
(3σ)
(600s)7
ASTROSAT UVIT: Configuration
Doors
Main-baffles
Secondary Mirror
Sec. Baffle
Primary Baffle
~3100 mm
TiCone (interface
With S/C)
Primary mirror (375 mm)
Thermal cover (this encloses
Detectors and filter-wheels)
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UVIT:J.HutchngsPASP(2011),123,833EffectiveApertures
(estimates)
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UVIT:J.HutchngsPASP(2011),123,833EffectiveApertures
(estimates)
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ASTROSATSCIENCE:UVITSimulations
630 SRIVASTAVA, PRABHUDESAI, & TANDON
M51 galaxy
GALEX (spatial scale
reduced to put it at 3
times its distance)
vs
Astrosat FUV Image
From stacking of
several short
exposure images to
correct for drift
PASP (2009), 121, 621
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LAXPC: Large Area Proportional Counters
X-ray timing (10 µsec) low spectral resolution studies
A broad energy band (3 - 80 keV) with high detection efficiency
• Three co-aligned identical Counters
• Each with a multi-wire-multi-layer configuration filled with 90%Xe +10%
Methane gas at 1520 torr. Energy resolution (13%@22 keV)
• A 50 micron thick aluminized Mylar window for X-ray entrance
• Mylar film support -- by a honeycomb shaped window support
collimator with 5 x 5 degs field of view
• A narrow field of view of 1x1 degs provided by mechanical collimators
made of a sandwich of 50µ Sn + 25µ Cu + 100µ Al co-aligned with the
window support collimator and sitting above it.
• Blocking shield on sides and bottom : 1mm Sn + 0.2 mm Cu
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made"up"of"46"anode"cells"each"with"cross6section"of"1.5"cm"X"1.5"cm"surrounds"the"main"X6ray"detection"
volume" on" 3" sides" to" reject" events" due" to" charged" particles" and" interaction" of" high" energy" photons" in" the"
detector."The"alternate"anode"cells"of"Layer"1"and"2"are"linked"together"and"thus"4"outputs"are"obtained"from"
Layer"1"and"Layer"2.."The"anode"cells"in"each"of"the"Layer"3,"4"and"5"are"linked"together"to"provide"one"output"
from"each"layer."Thus"there"are"7"anode"outputs"that""are"operated"in"mutual"anticoincidence"to"reduce"the"
non6cosmic"X6ray"background"The"Veto"layer"is"divided"in"3"parts"providing"3"Veto"Layer"outputs."The"left"side"
60 anode cells 3 cm x 3 cm x 100 cm in 5 layers each 15 cm deep (12 anodes/layer).
and"right"side"veto"anodes"are"linked"together"to"provide"one"output"from"each"one"and"the"third"veto"output"
Mutual
& layer by layer anticoincidence + Veto layers of 46 anodes cells (1.5x1.5 cm)
is"from"the"bottom"layer"veto"anodes"linked"together.""
1600 wires – tension 80 gm per wire
"
ASTROSAT LAXPC
"
"
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A"50"micron"thick"aluminized"Mylar"film"serves"as"the"gas"barrier"as"well"as"the"X6ray"entrance"window"for"the"
detector."The"detector"is"filled"with"a"mixture"of"90%"Xenon"+"10"%"Methane"at"a"pressure"of"1520"torr."The"
ASTROSATLAXPCunit(~125Kg)
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SXT:FPCA+Optics(~65Kg)
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SXT:Optics–ReplicatedThinfoilmirrorsmadein
TIFR(followingSuzaku)
2 m focal length;
~2 arcmin HPD;
40 shells (130 – 260
mm dia);
Only 12 Kg !
Mirror roughness 7 – 10
Angstroms : Exp. Ast.
(2011), 28,11
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Modified from Swift; Using
spare MOS CCD22 from XMM:
600 x 600 pix, 40 microns
• Four Fe-55 calibration (corner) sources
• One Fe 55 calibration door source
• Thin Optical Blocking Filter
• CCD Assy. including TEC
• PCB with front-end electronics
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ReadoutModesoftheCCD
(1)  Photon Counting Mode (PC), [The Default Mode - includes the
calibration sources]
(2)  Photon Counting Window Mode (PCW),
(3)  Fast/Timing Mode (FM),
(4)  Bias Map Mode (BM), and
(5)  Calibration Mode (CM).
! X-ray spectral information available in all the modes.
! Time resolution in the PC, PCW, CM modes is 2.4 s, and 0.278 s in the FM
mode.
! FM reads only the central 150x 150 pixels of the CCD.
! For observing very strong cosmic sources, the PCW mode should be used
to avoid pile-up followed by the Calibration mode where four small windows
(each of size=80 x 80 pixels) covering only the corners are used for the
corner radioactive sources in the CM. ( A central 100x100 window is also
used in the CM).
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SXT Flight FPCA CCD
Door and Corner X-ray Calibration
Sources
Optical LED Image
Very good – only 2 hot pixels
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SXTFM:Electronics:NIM:A(2009),604,747;Energy
Calibrationspectrummeasuredusinginternalsources:SinglePix
events,alltypesofevents.CCD@-80C
4.5 keV
(Ti-F)
4.15,
4.75
keV Mn-K Esc
1.48 keV
(Al-F)
1.74 keV
(Si-K)
2.6 keV
(CL-F)
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FMCALIBRATIONat-80C:Measuredwith
InternalFe-55sourcesandresponsemodeled
Target Energy
Res.
%ge
(FWHM, eV)
Al –Flo 1487 eV
90 +- 8
6.0+-0.5
Si –K 1740 eV
92 +- 6
5.1+-0.3
Cl –Flo 2621 eV
104+-5
4.0+-0.2
Mn-Kα esc 4155eV 120+-5
2.0+-0.15
Ti -Flo 4511 eV
2.8+-0.15
126+-6
Mn-Kβ esc 4750 eV 128+-7
2.7+-0.15
Mn-Kα 5895 eV
135+-9
2.3+-0.15
Mn- Kβ 6490 eV
140+-10
2.1+-0.15
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ASTROSAT CZT-Imager
Size: 482 x 458 x 603 mm
Heat pipes
CFRP support
Weight - 50 kg
Power – 60 Watts
Collimator fov: 6o x 6o
976 cm 2 (64 CZT modules x 15.25 cm2
in 4 quadrants);
No. of pixels: 16384; 2.4 mm X 2.4 mm
(5 mm thick) ; ASIC based
(128 chips of 128 channels)
Radiator
Optical cube
Alpha tag source
CZT bottom hsg.
Handling brackets
CAM (Tantalum)255
pseudo-random Hadamard
Collimator
Side joining plates
CZT top hsg.
CZTI: Calibration & Veto
!  An X-ray source (Am241) mounted in a gap of 8 cm
between the base of the collimator slats and detector
plane in each quadrant for calibration.
!  VETO Detector: CsI (Tl) 20 mm thick x 165 mm x 165 mm
detector viewed by two photomultipliers in a flat geometry. Just
under the CZT modules.
"  LLD: 50 keV. Variable by command: 256 steps of ~ 10 keV.
"  Uniformity: ~ 10%,
"  Response time: 5 µs
"  Typical dead-time: 20 µs; A few hundred µs for saturated
peaks
NIM:A (2010), 616, 55
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CZTI: Modes
Normal mode
SAA mode
Shadow mode
Reduced data mode
"  Fixed no. of events
"  Block veto spectrum
"  2 word event report
!  Secondary spectral
!
!
!
!
1s
0-9 packets/quadrant
100s 1 packet/quadrant
100s 1 packet/quadrant
1s
1s
1s
100s
0-9 packets/quadrant
0-9 packets/quadrant
0-9 packets/quadrant
2 packets/quadrant
Charged Particle Monitor – to monitor the SAA entry
and exit to lower voltages of the LAXPC
CsI + Si-pin photodiode; LLD of 1 MeV & can be reset
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CPMdetectsSAA(Oct.1,2015)
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of" the" incident" photon." " The" position" (P)" of" the" incident" photon" on" the" detector" plane" is" given" by" P=(VL6
VR)/(VL+VR)"*C1+C2,"where"VL"and"VR"are"the"amplitudes"of"the"left"and"right"output"pulses"and"C1"and"C2"are"
Scanning Sky Monitor
the"calibration"constants"of"that"particular"anode"on"which"the"photon"is"incident.""
" (SSM)
The"SSM"detector"plane"consists"of"two"layers"of"wire6cells,"central"eight"of"the"top"layer"being"active"anode"
cells."The"two"edge"cells"of"the"top"layer"and"the"ten"cells"in"the"bottom"layer"are"all"connected"together"to"
form"the"background"or"veto"layer."The"information"that"we"get"about"every"photon"that"is"incident"on"the"
detector"are"1."Time"of"arrival,"2."Energy"and"3."Position"of"incidence.""All"the"three"parameters"are"measured"
using"the"electronics"system"of"SSM."
"
Design of Mask
Six"different"coded"mask"patterns"could"be"generated"for"the"constraints"set"in"the"specifications"of"SSM,"with"
50%"transparency.""They"are"joined"sideways"and"the"resulting"complete"mask"plate"is"shown"in"figure"4.""The"
design" of" the" coded" mask" and" the" deconvolution" software" is" developed" in" collaboration" with" Prof." D."
Bhattacharya"of"IUCAA."
Three rotating Units: PSPC + coded mask
The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.
Figure!6.5!:!The!coded!mask!plate!with!six!different!mask!pattern!used!in!each!of!the!three!SSM!cameras.!
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AstroSatStatus&SwitchONSequence
!  ChargeParticleMonitor(CPM)forSAAmonitoringisONand
!
!
!
!
!
!
!
working
LowVoltageSystemsforPEswitchedonforSXT,CZTI&
LAXPC:StatusOK
SXTcameraventinggoingondailyfor10mins
CZTIHighVoltage-5thOct,andfirstlight–Oct6th(Crab
simultaneouswithSwift)
SSMOn:12thOct.
SXT:TECONforCCD(Oct9)andTelescopeDooropening(15
Oct)andCameraDoorOpeningandfirstlight(Oct27)
LAXPCHVONandfirstlight(Oct17)
UVITON(Nov26th)
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Astrosat–PostlaunchMissionPlan
!  1styear
"  First6months–PVPhase(4X-ray;2UV)
"  Next6months–GTPhase(4X-ray;2UV)
!  2ndyear
"  5%Canada,3%UK,5%TOO,2%Cal,35%OpenforGO(India),
50%Instruments’GT
!  3rdyear
"  5%Canada,3%UK,5%TOO,2%Cal,45%OpenforGO(India),
30%Instruments’GT,10%OpenforInternationalGO
!  4thyear
"  5%Canada,3%UK,5%TOO,2%Cal,65%India(GO),20%
InternationalGO
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ASTROSAT –
several multi-wave instruments
co-aligned for
#  SimultaneousOpt-NUV–FUV-softX-ray-hardX-ray
measurements
#  LargeX-raybandwidth,betterhardX-raysensitivity
thanRXTE
#  LowbackgroundX-raydetectors:nearEquatorial
Launch
#  BrightsourcecapabilityinsoftX-rays
#  UVimagingcapabilitybetterthanGALEX
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ASTROSAT:AcomparisonwithotherX-ray
Satellites
Energy (keV)
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SciencewithX-rayInstruments
!  Accretion–WhiteDwarfs(CVs),NeutronStar
BinariesandBlackHoles(galactic,extragalactic–
AGN).
!  Physicsofastronomicaljets(Blazars),magnetic
fields(Cyclotronlines)etc.
!  Physicsofhotcoronalplasmas:HardX-ray
componentsandflares
!  Synchrotron,InverseComptonemissionprocesses
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ASTROSATSCIENCE:X-raySimulations
Hercules
X−1 (Astrosat)
4U
1636−536
Exposure==12.5
50 ks
Exposure
ks (F)
ASTROSAT−Simulation
3C454.3
SED of AGN:
Blazars,
Seyferts
100
1000
100
10
Model: phabs*powerlaw (nH = 6.5E+20 cm−2, Indx = 1.6, Norm = 2.6E−02)
Black: SXT(0.3−8.0keV):
27.5 cps
wabs*NPEX*cyclabs
Red:
LAXPC(3−80keV):
753.4
cps
[Enoto et al., PASJ, 60, 57, 2008]
Green: CZTI(10−100keV): 1.8 cps
SXT
wabs*(bbodyrad+bbodyrad+comptt)
3
LAXPC
[Fiocchi et al., ApJ, 651, 416, 2006]
10
10
1
Count Green:
Rates CZTI(10−100keV): 74.3 cps
SXT: 3.07
ct/s wabs*NPEX
Histogram:
model:
3
CZTI: 4.4 ct/s
Data points: Simulated data
LAXPC: 121.7 ct/s
0.1 1
0.01
0.1
−1 keV
−1
Counts
Counts ss−1
keV−1
Black: SXT(0.3−8.0keV): 1.3 cps
Red: LAXPC(3−80keV):
Exposure:
10 ks 1697.0 cps
CZTI
3
Flux
−4
10
0.01
10−3 0.1
0.01
Simulation
MCV
10−4
10−3
Simulation
XRB,
Cyclotron lines
from neutron
stars in X-ray
binaries.
normalized counts s−1 keV−1
1
2
SXT(0.5−10 keV): 1.78E−10 ergs−11cm−21s−1 2
Dotted lines
: model
components
CZTI(10−100
keV):
3.95E−10
ergs−1 cm−2 s−1
1
:
1st
blackbody
LAXPC(3−80 keV): 4.39E−10 ergs−1 cm−2 s−1
2 : 2nd blackbody
3 : Comptonization
Ref: Wehrle et al., ApJ, 758, 72 (2012)
11
1
2
10
10
10
Energy
(keV)
Energy
(keV)
Energy (keV)
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100
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Acc. Disks in AGN – UV/X-ray continuum
Laha, GCD, AKK, SC 2013
IRAS 13349+2438
Done et al. 2013
Disk
Disk
PG 1244+026
OM
Mrk 509
FUSE
HST/COS
EPIC-pn
Mehdipour et al. 2011
Disk dominated AGN!
High/Soft
State of AGN!!!
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Non-ThermalEmissioninClustersof
Galaxies:Motivation
The X-ray emitting thermal plasma in a virialized cluster loses
most information on how the formation proceeded due to the
dissipative processes driving the plasma towards a MaxwellBoltzmann momentum distribution characterized by its
temperature only.
Non- equilibrium distributions of cosmic rays preserve the
information about their injection and transport processes much
better, and thus provide a unique window of current and past
structure formation processes. Information about these nonequilibrium processes is encoded in the spectral and spatial
distribution of cosmic ray electrons and protons. Radiative loss
processes of these non-thermal particle distributions produce
characteristic radio synchrotron, hard X-ray inverse Compton,
and hadronically induced γ-ray emission.
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Motivation(contd.)
Non-thermal Radio emission is seen as:
Radio Relics: Have a high degree of polarisation, are
irregularly shaped and occur at peripheries of the clusters
-- can be attributed to merging or accretion shock waves.
Radio Haloes: Resemble the regular morphology of the Xray emitting intra-cluster plasma and are poorly
understood.
Where is the non-thermal X-ray and γ-ray emission ?
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Non-thermalprocessesin
Cosmic rays in clusters of galaxies – II. Ra
clusters
KPS@SAAO 2015
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lines. Occ
On macros
diffusion p
scopically
can be reg
tangled ma
E < 2×1
the order o
Berezinsky
to diffuse
filling dist
tion is an a
the ICM.
The C
CR energy
36individual
ticle as we
HardX-ray(20-80keV)Tails:
Balloon+Satellitebasedmeasurements
Beppo-SAX: Nevalainen et al. 2003
Relaxed
Fig. 3.— The non-thermal signal and 1σ uncertainties in PDS 20 – 80 keV band after subtraction of the contributions
from the background, thermal gas and AGN in the field, and after propagating uncertainties due to these subtractions.
The dotted vertical line separates the relaxed clusters (left) from the rest (right).
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Swift/BAT:JointlywithXMMNewton
Ajello et al. 2009, 2010
20 Clusters studied:
Perseus, A3266, A754, Coma, A3571, A2029, A2142,
Triangulum, Ophuchius, A2319;
A85, A401, Bullet, PKS 0745-19, A1795, A1914, A2256,
A3627 (Norma), A3667, A2390.
All best described by multi-temp thermal model except
Perseus and Bullet (4.4σ) which show hard X-ray excess
consistent with Chandra Observations for Bullet, and AGN:
NGC 1275 in Perseus.
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t the results. The spectral fitting results are
ble 2.
Newton and Suzaku Spectral Fits Without
Considering Systematic Errors
usly fit the Suzaku HXD-PIN and XMMspectra for the PIN FOV. First, we consider
perature fit, in order to establish whether the
hermal component actually improves the fit
d a best fit temperature
± 0.06 keV,
Wik et of
al.8.45
2009;
l agreement with similar fits to the PIN data
nd XMM dataAlso
(8.37 see:
± 0.12 keV) individue dip at 15 keV
is a known problem with
Suzaku
model (Mizuno et al., Suzaku Memo 2008observations
of by the
spectrum is individually
described
X-ray excess
perature, the existence
of excess emission
emission
in the
s unlikely. While
all of these
temperatures
cluster average
A 3112temperature
r than the cluster-wide
al. in this and
es et al. 1993),T.theLehto
energyetrange
ly extends to energies
2010 below 2 keV and thus
w temperature gas.
$ Basically:
a power-law Cannot
non-thermal
component
prorule
out
better description
of the spectra, according
the presence of
oving the overall fit (Table 2), but only for a
NT
emissionand
!! power law
0. Allowing the
temperature
PIN. Shown as solid lines are the best fit models for a single temperature
thermal component. The thermal model (“APEC", green) is nearly coincident
with the data, though falling below it at higher energies. Also included for all
joint fits are the the total spectrum for the “XMM Point Sources" (red) and the
Cosmic X-ray Background (“CXB", purple), the latter of which only applies
to the PIN spectrum since the CXB is subtracted from the XMM data along
with the NXB.
Suzaku+XMM:ComaCluster
(A1656)
ry along with each component’s normaliza8.42 ± 0.06 keV and Γ = −1.6, though Γ is
d. If we fix Γ to this best-fit value, the IC
ificant at the 2.2σ level without considering
matic uncertainties. However, this photon
F IG . 5.— Suzaku HXD-PIN spectrum (E > 12 keV) and the combined
XMM spectrum (E < 12 keV) corresponding to the spatial sensitivity of the
PIN. Shown as solid lines are the best fit models for a single temperature thermal component plus a non-thermal component. The thermal model (“APEC",
green) is nearly coincident with the data, though falling below it at higher
energies. The non-thermal model (“Power Law", light blue) is the faintest
model component for both spectra, and the photon index is fixed at Γ = 2.0.
The other two components are described in Figure 4.
KPS@SAAO 2015
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for E > 40 keV results in a best-fit power law component very
39
only very
standard
ent backing from
χ2red
PF−test a
kT [keV]
FluxHXR b
CLHXR σc
Method 1
0.93
2 · 10−4
8.56+0.37
−0.35
10.1 ± 2.5
4.0
Method 2
1.05
7 · 10−5
8.50+0.48
−0.45
8.2 ± 1.3
6.4
Ophiuchus:2ndbrightestX-ray
cluster(kT~9-10keV)
Integral Detection at 4 to 6.4σ level: Eckert et al. 2007
10−4
10−3
0.01
0.1
Consistent with Suzaku (Fujitsa
et al. 2008), Beppo-SAX, Swift/
BAT upper limits !
−2
0
2
4
normalized counts/sec/keV
χ
er of the
V (white)
V image.
he cluster
osition of
Chandra
The errors are quoted at the 1σ level. c Confidence level for the
detection of the non-thermal component.
5
10
20
channel energy (keV)
50
Fig. 7. JEM-X/ISGRI combined spectrum in the 3-80 keV band.
The solid line is a fit to the 3-20 keV part of the spectrum with
a single-temperature MEKAL model. The bottom panel shows
the residuals from the model. The hard X-ray excess is clear.
spectrum and the residuals from the thermal
40NXB by ±5% (cros
KPS@SAAO
2015
10/30/15
Fig. 7. HXD PIN spectra,
including
the effect
of varying the normalization of the
The NXB has been subtracted. The fit (solid line) is for the normal NXB. The lower panel plots
model
with temresiduals divided by the 1σ errors.
ComaClusterwithAstroSat
KPS@MSSL2015
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41
BulletCluster:NuStar(266ks):
Wiketal.2014
NuSTAR Observations of
Very hot kT ~ 15.3 keV, and no evidence for a NT component above 20 keV
Fig. KPS@SAAO
5.— The ratio
spectrum (crosses, using the
42 nominal
2015of the
10/30/15
background model; all spectra from Figure 3 have been combined
for clarity) to each model. The red/dark and green/light shaded regions are the same as in Figure 4. Although difficult to tell, the 2T
h
o
n
b
n
k
fl
t
w
h
o
U
t
e
a
a
m
t
b
o
t
i
c
Chandra:TheBulletCluster
8
E. T. Million and S. W. Allen
non-thermalsurfacebrightnessandPLindex
Figure 2. (a) left panel: Spatial map of the surface brightness (in erg cm 2 s 1 arcsec2 ) of non-thermal-like X-ray emission in the Bullet
Cluster, 1E 0657-56 (z = 0.297). A power-law component is only included in regions where it is statistically required at greater than
90 per cent significance (Section 3.2). The 1.34 GHz radio surface brightness contours from Liang et al. (2000) are overlaid in black.
(Radio point sources have been removed). (b) right panel: Map of the photon index of the power-law components, with the radio surface
brightness contours overlaid. Only regions with ‘non-thermal’ surface brightness greater than 10 16 ergs s 1 cm 2 arcsec 2 are shown
in this map. Each spatial region has ⇠ 104 net counts in the 0.6 7.0 keV Chandra band.
KPS@SAAO 2015
eter). The nominal temperatures of the additional emission
components are typically high, with kT2 >
⇠ 15 keV.
3.2
10/30/15
Detailed spatial mapping of the ‘non-thermal’
components
43
Chandra:TheBulletCluster
RESULT:
Spatial correlation between the regions of the
brightest non-thermal radio halo emission,
brightest thermal X-ray emission, and
strongest non-thermal-like X-ray signatures
in the central regions of 1E 0657-56
KPS@SAAO 2015
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44
Summary&Challengesahead
The presence of non-thermal hard X-ray emission in clusters of galaxies
remains controversial.
Existing limits on this component suggest a small magnetic field of the order
of 0.1µG, which is in stark contrast to the
Faraday rotation measurements which demand much stronger intracluster
magnetic field of order of a few µG (Clarke,Kronberg,Bo ̈hringer,2001;Carilli and
Taylor,2002).
Several possible explanations: Two most likely options in this regard could be
the simplest ones: either the reports of detections of nonthermal X-rays are
not correct, or they are correct but the nonthermal X-rays are not of IC origin.
To establish the presence or absence of this component, we will need:
Hard X-ray telescopes with: High Spatial resolution,
Wide field, Low-to-medium energy/spectral resolution &
Large area
KPS@SAAO 2015
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45
Thanks!
Website : astrosat.iucaa.in
KPS@MSSL2015
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46