Hard X-ray Black Hole Surveys in Space and Time: EXIST

Concept

Josh GrindlayHarvard

International WorkshopHigh Energy Astrophysics in the Next

Decade(Tokyo)

June 21, 2006

Outline of talk• Key HEA and EXIST science questions

– Overview of EXIST as Black Hole Finder Probe (BHFP)

• Current surveys to answer them:– X-ray: Chandra, XMM, Swift-XRT, Suzaku– Hard X-ray: INTEGRAL, Swift-BAT, Suzaku/HXD & BAT-

slew– TeV: HESS, VERITAS

• Upcoming surveys:– Agile, GLAST, LSST (approved)– MAXI, Lobster/eROSSITA, HXMT, Symbol-X (uncertain?)

• “Ultimate” spectral-temporal HX survey: EXIST– Mission study for BHFP in Beyond Einstein Program…

Key HEA Survey & EXIST Science

(from the Galaxy to Pop III GRBs)• Nature/number of BHs vs. NSs, WDs in Galaxy

• Blazar spectra @TeV vs. ~100keV: origin of EBL

• Dormant AGN (tidal disruption by SMBHs)– SMBHs in every galaxy? BH masses from power spec.

• Obscured AGN and origin of CXB

• GRBs from Pop III stars: birth of First BHs & probes of IGM

Overview of BHFP-EXIST Science and Design

Hard X-ray (~3-600 keV) all-sky imaging Hard X-ray (~3-600 keV) all-sky imaging each orbit each orbit to measure:to measure: •Obscured AGN and accretion (BHs) vs. nuclear (stars) luminosity of universe•GRBs out to z ~20 and first stellar Black Holes ( ~5-20X Swift sensitivity)•Stellar Black Holes in Galaxy & IMBHs in Local Group & BHs as probes

Mission DesignMission Design parameters:parameters:•Extend ROSAT sens. (~5 x 10-13cgs) to 3-150 keV with 0.9-5’ resolution & ~10” positions•Two wide-field coded aperture telescopes: 10-600 keV (6m2 CZT) & 3-30 keV (1m2 Si)

http://EXIST.gsfc.nasa.gov

e.g., EXIST measures Cen-A every orbit: characteristic time variability (QPOs) constrain BH mass

High Energy

Telescope

HET (10-600keV)

(6 x 3 coded aperture telescopes;131o x 65o FoV)

Low Energy Telescope

LET (3-30 keV)

(4 arrays of 7 x 1 coded aperture telescopes;116o x 64o FoV)

IMDC designDec. 2004

Expected EXIST Survey Sensitivity

LET 3-30 keV; HET 10-600 keV

0.05mCrab = 5 x 10-13 cgs, (over

any band Elow 2Elow)

5σ, 1yr, 20-40% duty cycle any

source

Continuum Narrow Line

Hard X-ray Sky

Previous Hard X-ray SkyHEAO-1, BeppoSAX

2016(?) Hard X-ray SkyEXIST

≤2010 Hard X-ray SkySwift & INTEGRAL

• Hard X-ray (10-600 keV) sky not yet surveyed to ROSAT sensitivity. EXIST would be ~20X more sensitive than Swift or INTEGRAL and cover full sky

• EXIST will detect ≥3 x 104 sources, ≤10 positions, 3-600 keV spectra

• EXIST would provide unique temporal survey: full sky imaging each orbit

HXMT, eROSSITA?

Survey BHs, NSs and WDs in Galaxy

Integral and Swift/BAT discovery of hard, variable giants

Wind-fed accretion onto NS or BH:Provides variable, high NH hard sources, with Lx >1036 erg/s as seen by Integral

Complements ChaMPlane Lx~1032 erg/s, high NH sourceswhich are qLMXBs and CVs

Complements Swift discovery of transients & hard pulsars (15-150 keV)Lx >1036 erg/s & HESS (TeV)discovery of Be-binary PSRs

Simulations by J. Blondin

The Chandra Multiwavelength Plane Survey (ChaMPlane)

Josh Grindlay, Ping Zhao, JaeSub Hong, Maureen van den Berg, Silas Laycock (Harvard, CfA)

Distribution of ChaMPlane fields (●=ACIS-I, vs. o=ACIS-S) locations, exp. Times, & NH

See Grindlay et al, Hong et al, Laycock et al, Zhao et al (2005, ApJ)

Stellar mass BHs vs. CVs in Galactic Bulge?

ChaMPlane survey and optical-IR followups: a mixture of magnetic CVs, NSs and BHs in SgrA* and Bulge…

Quantile diagram (see Hong et al 2004) for ~900 sources within 7’ of SgrA*: spectral classification & IDs (Hong et al 2006)

IR variable (red star in 0.5” Chandra circle) for a “Muno source” in H1 class: Possible CH-Cam BH-LMXB?(Laycock et al 2006)

Optical IDs with OGLE variables In “Stanek Window” : probable Wind-fed CVs, symbiotics (IPs?)(van den Berg et al 2006)

Survey Stellar BHs & IMBHs in Local Group with EXIST

• EXIST detects all bright stellar BHs in transients (Lx(>10 keV) ~1037-38 erg/s) throughout Galaxy, LMC/SMC and M31. Reveal population of obscured HX sources found with INTEGRAL/Swift: discrete sources at >20 keV

• Isolated stellar BHs in Galaxy and IMBHs in Local Group accreting via Bondi-Hoyle (with ~10-4 efficiency) from GMCs nearly Compton thick

• Faint BH transients in Central Galactic Bulge?: BHs in nuclear cusp (cf. Alexander & Livio 04) detected if Lx(>10 keV) ~1035

erg/s CI Cam type outbursts (~1-2d?) of Bulge BH vs. WD binaries around SgrA* SgrA*

Chandra viewof central Bulge(~ 2o x 1o)

New Swift/BAT Slew Survey (BATSS) (being developed at CfA for Swift/BAT science & EXIST testing)

BAT slews ~60X/day between pointings; photon data could be sent down (1min/slew) for imaging all-sky survey (15-150 keV), ~1h/day fast timing gives:

•GRBs & Long (High z) GRBs (30% more coverage)

•New transients & pulsar monitoring (~70mCrab/orbit)

•Stacked sky images for fainter transients (~20mCrab/d~90%sky)

•New persistent sources

•Test scanning for EXIST

70sec BAT slew image across CygX-1 (S/N~19) to a GRB (which was the z =6.3 event!)

BATSS enables ~30% more GRBs & ~90% sky/day

BATSS coverage & sensitivity vs. time(e.g. 10days in May, 2006…)

~30% increased detection probability for GRBs, transients,or steady sources is relatively constant w.r.t. GRB/transient duration. BUT only BATSS would provide photon timing; normal BAT data binned in 5min integ.Enables first all-sky PSR monitoring Survey since BATSE

TeV Blazar surveys: constrain EBL & IRB

(but only if constrain HX spectrum and variability)

Ongoing HESS and (soon) VERITAS surveys discover new Blazars for comparison with X-ray & HX spectra

New blazars detected by HESS at large z !

H2356-309 (z=0.165), 1ES1101-232 (z=0.186)

Reconstructing EBL (HESS collab., submitted to Nature)

X- Blazar surveys• Agile & GLAST will discover flaring

Blazars (~30MeV-30 GeV)• Swift/BAT, INTEGRAL give partial HX

coverage• Swift/XRT, Suzaku, Chandra, XMM

give partial X-ray coverage

Need ~5-300 keV imaging & monitoring to constrain SSC

GLASTMkn 421 flares– 0.5h – 2d

Blazar SSC models

Synch. IC

EXIST

VERITASGLAST

SSC model for Mkn 501 (Coppi & Aharonian 1999)EXIST will provide the continuous HX spectral-monitoringcontinuous HX spectral-monitoring to study Blazars and non-thermal AGN to constrain diffuse IR (~10-100μ) background from obscured AGN and thus nuclear vs. accretion nuclear vs. accretion luminosity of the universeluminosity of the universe

Complements GRB science: star formation vs. redshift from Complements GRB science: star formation vs. redshift from LGRBs vs. zLGRBs vs. z

Blazar Spectral variability: Extragalactic Background Light (EBL) & Stellar vs. Accretion Extragalactic Background Light (EBL) & Stellar vs. Accretion

Luminosity of UniverseLuminosity of UniverseEBL: Hard x-ray (synchrotron)

spectral breaks (~5-200keV) for BlazarsBlazars at known redshift allow SSC -ray (~10 GeV - 10 TeV) spectral breaks measured by GLAST and HESS/VERITAS to constrain origin of diffuse IR background

Time-variability: spectral breaks required from simultaneous HX measurements. Wide-field HX imaging needed to match GLAST

Dormant SMBHs revealed by Tidal disruption

(and BH masses from AGN power spectra)

Artists conception of tidal disruption of star in RXJ1242-1119 detected with ROSAT (1991) and confirmed with Chandra (Komossa et al 2004).

Tidal disruption of stars spiraling into Dormant SMBHs with mass ~107 Mo:if 1% of Lacc in HX band, ~10-5 events/year/Mpc3 allow EXIST to see ~10-30 flares/yr out to ~200Mpc! (Grindlay 2004). HX spectral comp. “confirmed”with PL spectral decay of RX1242

Sub-giants with WD cores aregravitational wave LISA triggers.

Possible soft (~5keV) prompt (~1d) burst detectable out to ~30 Mpc

directly with EXIST (LET) and with MAXI or LOBSTER; LISA trigger

Measure 106-7M SMBH content/evolution of nearby

galaxies(understand BH-Bulge mass relation & BH-galaxy

evolution!)

Obscured AGN and origin of the CXB

NGC1068NGC1068NGC6240NGC6240(Vignati et al 99)(Vignati et al 99)

EXIST will find >1-10 obscured AGN/square degree and obtain first all-skyall-sky measure of Seyfert 2 QSO 2 luminosity function

and constrain obscuration vs. z for supermassive BHs. Provide required all-sky survey for rare (Type 2 QSOs) and Lx dependence of NH

EXIST survey

HEAOHEAO

SwiftSwift

SAX/PDSSAX/PDS

Chandra & XMM surveys find >40% unresolved CXB from obscured AGN

Birth of Stellar BHs at z~5-20 • “Long”-GRBs are from SNIb,c & likely due to stellar BH formation

• Likely that first stars were ~100Mo and collapse to BHs GRBs

• “Short”-GRBs from merging NSs in globulars (Grindlay et al 2006) suggests Short GRBs enhanced at z of globular cluster formation?

EXIST detects GRBs to z~20from PopIII BHs at re-ioniz.epoch suggested by WMAP.

Photometric z from Lum-Epeak

need response to E>300keV,And from Lum-Variability (PaczynskiRelation) need large area det.

X-ray flashes and high z GRBs need response to E~5 keV

~5sr instantaneous GRB coverageAnd increased sensivity: Rare (high z?) events; 3-5GRBs/d!

Flux vs. detected Epeak for GRBs from z=1 (top +) to 10 (bottom +) for Epeak =30, 100, 300, 1000keVif emitted at z=1 vs. sensitivities (Band 2004).

Highest z stellar universe uniquely from GRBs

• Swift GRB at z = 6.3 shows high z universe is accessible• Broader energy band, higher sensitivity needed for z~20

PopIII• IR from space needed for z!

• GRBs provide “back-light” for IR spectroscopy of IGM, gas, galactic structure back to re-ionization: EXIST + JWST?

Record-setting z vs. time: GRBs are gaining fast!

Zenith (Yaw)

Orbit Normal (Pitch)

Velocity (Roll)

Solar Panels(fold-down)

Thermal Radiator

EXIST: Current Baseline Mission Design Concept

• Survey the hard X-ray sky 50x deeper than previous, with 10 source positions (5)

• Cover the 3 to 600 keV band with two telescope systems: HET: 10 - 600 keV (5.6 m2 CZT ) and LET: 3 - 30 keV (1.1 m2 Si)

(GSFC ISAL & IMDC runs Oct. & Dec. '04)

Low Energy Telescopes

(LET: 3-30 keV)

High Energy Telescopes

(HET: 10 – 600 keV)

EXIST Mission Design Parameters

Orbit Normal

Zenith Nod direction, ┴ scan

(+/-20o ea. ~10min)

Orbital scan direction(orbital velocity vector)

•Free-Flyer (500km, i 5-7º, low bkgnd)

•Zenith pointer - scanning & nodding for full sky coverage each orbit (95min)

•18 coded aperture HE telescopes (6m2 total area CZT pixel

det.)

•28 coded aperture LE telescopes (1m2 total area Si drift

det.)

•Mass, power, telemetry: 9500kg, 3KW, 3Mbs

•Delta IV launch (to i ~5o orbit)

•Mission lifetime: 5 years

Detector packaging: DCU, DCA, DM, Sub-Tel & HETBuilding a very large area CZT detector/telescope

Detector Crystal Array (DCA) 2x2 DCUs (4x4 cm2) + FPGA Board

Detector Module (DM) 7x7 DCAs (28x28 cm2) + MicroProcessor Board

Sub-Tel Module 2x2 DMs (56x56 cm2); each of 18!Active & Passive shields

Detector Crystal Unit (DCU) Crystal (2x2 cm2) (with Interposer Board?) + 2 x 128 channel ASIC (with micro-via tech?)

HET3x6 Sub-Tels (5.6 m2)

Baseline Mission parameters: EXIST/HET & LET

Parameters EXIST/HET EXIST/LET

Energy 10 – 600 keV 3 - 30 keV

Modules 3x6 4x7

Mask (W) 5mm thick, 2.5 mm pix0.05mm thick, 0.2mm

pix.

Detector (CZT)Area (Mod./Tot.)

5 mm thick, 1.25mm pix56x56 cm2 /5.6 m2

1mm thick, 0.16 mm strip.

20x20cm2/ 1.1 m2

F.C. FoV (Mod./Tot.)

21º x21º / 65º x131º 16º x16º /64º x112º

Ang. Res./5σ Loc. 5.7/ 1.2 0.95/ 11

Mask-Det. Sep. 1.5 m 0.72 m

Temporal Res. < 0.1 ms < 0.1 ms

Shields(GRB spectra to

10MeV)

CsI/passive side,CsI rear shields

Passive

Sensitivity(5σ)

0.05mCrab (<150 keV, ~1yr)

0.5mCrab (>150 keV, ~1yr)

0.15mCrab

Advancing the Mission Design

• The contiguous layout of HET sub-tel modules allows very efficient shield sharing and makes the overall instrument design simple and straightforward.

• The current mission design already meets the mission parameters required for science goals.

• However, the current layout introduces some unnecessary constraints on spacecraft design due to asymmetric packaging for launch.

• Goal: Redistribute sub-tel modules symmetric for launch and increase total area in LET (and HET).

New (General Dynamics) Design Concept Symmetric, smaller solar panels & increased LET Area &

FoV

Stowed

Delta IV (5m Fairing)

On Orbit

Zenith

Velocity

Orbit Normal

Solar Panels

LET

HET

Spacecraft Bus

Side and Top Views of New Design

Instrument Layout & FoV Comparison

Baseline DesignHET: 5.6m2 (18 mods)LET: 1.1m2 (28 mods)

HET

65

131

64

112

154

64

160

65

New ConfigurationHET: 6.0m2 (19 mods)LET: 1.3m2 (32 mods)

HET

LETLET

Mission parameters for the new configuration

Parameters EXIST HET EXIST LET

Energy 10 – 600 keV 4 - 30 keV

Modules 8+5+8=19 6+10+10+6=32

Mask (W) 5mm thick, 2.5 mm pix0.05mm thick, 0.2mm

pix.

Detector (CZT) 5 mm thick, 1.25mm pix1mm thick, 0.16 mm

strip.

Det. Area (Mod./Tot.)

56x56 cm2 /5.96 m2 20x20cm2/ 1.28 m2

F.C. FoV (Mod./Tot.)

21º x21º / 65º x 154º16º x16º / (32º64º) x

160º

Ang. Res./5σ Loc. 5.7/ 1.2 0.95/ 11

Mask-Det. Sep. 1.5 m 0.72 m

Temporal Res. < 1 ms < 1 ms

ShieldsCsI/passive side,CsI rear shields

Passive

Sensitivity(5σ)

0.05mCrab (<150 keV, ~1yr)

0.5mCrab (>150 keV, ~1yr)

0.05mCrab

• A wide dynamic range (>~103-4) to achieve high sensitivity impose challenges for coded-aperture imaging.

• The main factor for limiting the performance in coded-aperture telescopes is noise caused by unknown systematics in the system.

• These systematics include non-uniformity in the detectors such as detector gaps, dead pixels, efficiency variations, background variations, etc.

• EXIST’s scanning/nodding motion designed for surveying the sky is also a key to reduce the unknown systematics.

• We demonstrate imaging performance of EXIST by a series of progressively realistic simulations. Swift/BAT slew imaging tests are in progress; and demonstration of EXIST detectors and imaging planned with ProtoEXIST balloon experiments.

Ensuring EXIST Imaging Performance

Artifacts due to gaps start appearing at ~0.5 mm gap in the sky image generated by a simple correlation without any correction

Example: Imaging noise caused by detector gapsExample: Imaging noise caused by detector gaps(click for movies)(click for movies)

Scanning motion automatically averages out the coding noise without need for additional correction

Assuming a fraction of unknown dead pixels in the detector,1 day exposure of one sub-tel in EXIST HETs

Simulated Simulated ScanningScanning vs. Pointing with vs. Pointing with dead-dead-pixelspixels

5 detection limit with no other sourceor with a 1.5 Crab source

Dynamic Rangewith a 1.5 Crab source

Assuming a partially coded source in the FoV & unknown 1 mm crystal gap,apply a CLEAN procedure for the partially coded source

ScanningScanning vs. Pointing with a vs. Pointing with a partially-coded partially-coded sourcesource

5 detection limit with no other sourceor with a 1.5 Crab source

Dynamic Rangewith a 1.5 Crab source

BAT slew imaging provides on-orbit test

And new Swift/BAT survey science…

~70sec scan detects CygX-1 @19 vs. 14 for pointing with BATNoise reduced due to averaging effects of scan

Prototyping EXIST

• Balloon program to develop ProtoEXIST(Harvard, GSFC, Caltech, Stanford collaboration)

• Phased development (ProtoEXIST1

ProtoEXIST2)(2.5mm 1.2mm pixel pitch & direct-bonded ASIC)

• Demonstrate detectors & packaging, scanning imaging and (if ULDB?!) early

EXIST survey science

The current test board (poptart) allows testing 4 Detector Crystal Units (DCUs = crystal + IPB+ASIC)

1 DCU:2cm x 2cmX 0.5 cm CZT

Custom ASIC 64ch, 3 x 9mm pkg., ~150microW/channel

Prototype Detector Performance

Parasitic Capacitance of Input traces on Interposer board

(IPB)(from simulations)

FWHM measurements of a bare IPB using pulser

Internal to ASIC

Radiation Tests on prototype DCUs for ProtoEXIST1

~4.7 keV FWHM from 120 keV (57Co)

~4.5 keV FWHM from 60 keV (241Am)

We expect ~3 keV FWHM from the next batch (Aug ’06) of DCUs with improved (lower capac.) IPBs.

(vs. ~1.5 keV for direct-bonded ASICs in ProtoEXIST2 and EXIST)

Detector Crystal Arrays (DCAs) for ProtoEXIST1

Detector Crystal Unit (DCU)

TopSocket Board

BottomFPGABoard

FPGA(controls/reads out8 ASICs on DCA)

ASIC

Assembled ProtoEXIST1 DCA (design complete; under fab.)

Enable tiling of4cm x 8cm CZT arrays

with 0.4mm gaps

Detector Module for ProtoEXIST1(256cm2 close-tiled array of 8 DCAs)

Detector Crystal Arrays (DCAs)

HV bias

Detector Module for ProtoEXIST1

Near gapless Packaging of 16cm x16cm

CZT arrays

EXIST sub-tels willhave 56 cm x 56 cm

CZT arrays.

Summary

• INTEGRAL and Swift imagingimaging have revealed the rich HX sky (obscured binaries, AGN, high z GRBs…!)

• Broad band (≥3 – 300 keV), large area and wide FoV are key. Unique all-sky imaging each orbit

• HX surveys have enormous synergy with GeV-TeV (GLAST-VERITAS) studies of Blazars (and EBL)

• Both obscured and dormant SMBHs best studied with wide-wide-field field very sensitive HX imager

• Highest z universe uniquely measuredmeasured via GRBs

• EXIST under study for BHFP – could could launch in ~2016– See EXIST website (http://EXIST.gsfc.nasa.gov) for Study &

team

• ProtoEXIST1 balloon in 2008, ProtoEXIST2 in 2010… ProtoEXIST1 balloon in 2008, ProtoEXIST2 in 2010…