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E.Costa - BH in Binary Systems - Ferrara September 12 2009

Observational prospects for Polarimetry

Enrico CostaEnrico Costa

(IASF Roma)(IASF Roma)

Black Holes in Binary Systems: Observations versus Theory – Ferrara September 12 2009

More about X-ray Polarimetry


To learn more about X-ray polarimetry please see presentations at the Rome Conference (waiting for proceedings book published by CUP)

http://projects.iasf-roma.inaf.it/xraypol


Measurements in X-ray Astronomy

Photometry: Timing (Geiger, Proportional Counters, MCA, SDC)

Rockets, UHURU, Einstein, EXOSAT, ASCA, SAX, XMM, Chandra.

Imaging: Pseudo-imaging (modulation collimators, grazing incidence optics + Proportional Counters, MCA, CCD) Rockets, SAS-3, Einstein,

EXOSAT, ROSAT, ASCA, SAX, Chandra, XMM, INTEGRAL, SWIFT, Suzaku.

Spectroscopy: Non dispersive (Proportional Counters, Si/Ge and CCD, Superconducting Junctions, Bolometers)Dispersive: Bragg, Gratings. Rockets, Einstein, EXOSAT, HEAO-3, ASCA, SAX, XMM,

Chandra, XMM, INTEGRAL, Suzaku, . Polarimetry: Bragg, Thomson/Compton Rockets, Ariel-5, OSO-8


What can Polarimetry Test?

Astrophysics:Astrophysics:

Emission processes and geometry of the Emission processes and geometry of the emitting regions in a varietyemitting regions in a variety of situations of situations and classes of sources: jets, accretion, and classes of sources: jets, accretion, reflection, archeoastronomy, etc.reflection, archeoastronomy, etc.

Fundamental Physics:Fundamental Physics:

* Matter in extreme magnetic fields* Matter in extreme magnetic fields

* Matter in strong gravity fields* Matter in strong gravity fields

* Quantum gravity effects* Quantum gravity effects


Big Hopes Meager Results

Polarimetry would add to energy and time two further observable quantities (the amount and the angle of polarization) constraining any model and interpretation: a theoretical/observational break-through(Mészáros, P. et al. 1988).

The swing on the polarization vector of photon trajectories near a black hole was long ago suggested (Connors, Piran & Stark,1980) as another diagnostic; but this is still not feasible because X-ray polarimeters are far from capable of detecting the few percent polarization expected (Rees, 2001).

In 40 years only one positive detection of X-ray Polarization: the Crab In 40 years only one positive detection of X-ray Polarization: the Crab (Novick et al. 1972, Weisskopf et al.1976, Weisskopf et al. 1978) (Novick et al. 1972, Weisskopf et al.1976, Weisskopf et al. 1978) P P = 19.2 = 19.2 ± 1.0 ± 1.0 %; %; θθ = 156.4 = 156.4oo ± 1.4± 1.4o

A vast theoretical literature predicts a wealth of A vast theoretical literature predicts a wealth of results from X-ray Polarimetryresults from X-ray Polarimetry

THE TECHNIQUES ARE THE LIMIT!THE TECHNIQUES ARE THE LIMIT!Conventional polarimeters are cumbersome and have low sensitivityConventional polarimeters are cumbersome and have low sensitivity


The traditional Polarimeters

Rocket, 1972, Columbia

Ariel 5, 1974-1975, Leicester

OSO-8, 1975-1978 Columbia

odsin

nhcE

452=

The concept of The concept of Bragg PolarimetryBragg Polarimetry

At 45° a Bragg diffractor is a At 45° a Bragg diffractor is a perfect analyser of perfect analyser of polarization on a very narrow polarization on a very narrow band (<100eV) around Bragg band (<100eV) around Bragg energyenergy


The only polarized source already knownPositive measurement: of X-Positive measurement: of X-ray polarization of the Crab ray polarization of the Crab Nebula without pulsar Nebula without pulsar contamination (by lunar contamination (by lunar occultation, Weisskopf et al., occultation, Weisskopf et al.,

1978).1978). P P = 19.2 = 19.2 ± 1.0 ± 1.0 % % θθ = 156.4= 156.4oo ± 1.4± 1.4o

But this is only the average But this is only the average measurement The structure is much measurement The structure is much more complex!more complex!

PSRPSR

NW jetNW jet

SE jetSE jet

Inner torusInner torus

Outer torusOuter torus

To perform separate polarimetry of details of To perform separate polarimetry of details of the major structures we need imaging!the major structures we need imaging!

f.o.v.f.o.v.

XEUSpXEUSp.s.f..s.f.

How turbulent is the field?How turbulent is the field?

How polarized is the PSR?How polarized is the PSR?


GEM electric field

Polarization information is derived from the tracks of the photoelectron, imaged by a finely subdivided gas detector.

pixel

GEM

20 ns

α E

X photon (E)

PCB

conversion gain

collection

The new device: the Micro Pixel Detector The new device: the Micro Pixel Detector developed at INFN-Pisa for high sensitivity, developed at INFN-Pisa for high sensitivity,

imaging polarimetryimaging polarimetry


pixel electronics dimension: 80 µm x 80 µm in an hexagonal array, comprehensive of preamplifier/shaper, S/H and routing (serial read-out) for each pixel number of pixels: 2101

The collecting anode/read-out VLSI chipThe collecting anode/read-out VLSI chip


• Peaking time: 3-10 Peaking time: 3-10 µµs, externally adjustable;s, externally adjustable;• Full-scale linear range: 30000 electrons;Full-scale linear range: 30000 electrons;• Pixel noise: 50 electrons ENC;Pixel noise: 50 electrons ENC;• Read-out mode: asynchronous or synchronous;Read-out mode: asynchronous or synchronous;• Trigger mode: internal, external or self-trigger;Trigger mode: internal, external or self-trigger;• Read-out clock: up to 10MHz;Read-out clock: up to 10MHz;• Self-trigger threshold: 2200 electrons (10% FS);Self-trigger threshold: 2200 electrons (10% FS);• Frame rate: up to 10 kHz in self-trigger modeFrame rate: up to 10 kHz in self-trigger mode (event window);(event window);• Parallel analog output buffers: 1, 8 or 16;Parallel analog output buffers: 1, 8 or 16;• Access to pixel content: direct (single pixel) or Access to pixel content: direct (single pixel) or serial serial (8-16 clusters, full matrix, region of interest);(8-16 clusters, full matrix, region of interest);• Fill fraction (ratio of metal area to active area): Fill fraction (ratio of metal area to active area): 92%92%))

The presnt ASIC features

With this chip we have 100000 independent proportional counters in 2 cm2 surface


Track morphology and angle reconstruction


5.9 KeV unpolarized source 5.4 KeV polarized source

Modulation factor = (Cmax – Cmin)/ (Cmax + Cmin) ˜ 50% at 5.4 KeV

( )AT

BS

S

nnMDP

+⋅⋅= εεµ

σσ 2

1

( ) ( )02cos φφφ −⋅+= BAC

The angular distribution of photoelectron tracks gives polarization degree and angle

Using the impact point instead than the centroid the resolution is much Using the impact point instead than the centroid the resolution is much improvedimproved


5.2 keV polarized photons for two angular rotatio of the polarizer showing the good angular sensitivity.

The modulation factor measured at 2.6 keV, 3.7 keV and 5.2 keV with XPOL has been compared with the Monte Carlo previsions. The agreement is very satisfying.

Results of the last measurement campaignResults of the last measurement campaign (march (march 2007)2007)


From the laboratory to a flight prototype

Body, window, gas handling, HV etc. are conventional well established technology. Many prototype sealed detector is already built and first testing is very satisfactory.

It has been vibrated to 12 g and tested with Fe ions corresponding to It has been vibrated to 12 g and tested with Fe ions corresponding to many years of Low Eart Orbit.many years of Low Eart Orbit.

The first prototype of a The first prototype of a sealed detector, built with sealed detector, built with low desorption materials low desorption materials and processes.The and processes.The window is 50window is 50µµm Be. m Be. (Bellazzini et al. (Bellazzini et al. astro-ph/astro-ph/06115120611512))

Has been tested for 2 Has been tested for 2 years showing excellent years showing excellent stability.stability.

It weights 50 g + 30 g of It weights 50 g + 30 g of PCB!PCB!


Which New Physics/Astrophysics With This

New Detector?

We are ready to convert We are ready to convert Dreams of Theoreticians Dreams of Theoreticians into Realityinto Reality


Possible Missions based on GPD• XEUS/IXOXEUS/IXO: a telescope of 6 m: a telescope of 6 m22 proposed at the Cosmic proposed at the Cosmic

Vision Announcement by ESA. A polarimeter is in the Vision Announcement by ESA. A polarimeter is in the baseline design. Due to fund shortage XEUS is now merging baseline design. Due to fund shortage XEUS is now merging with NASA mission CON-X. The new mission is named with NASA mission CON-X. The new mission is named IXOIXO and is proposed to the NSF Decadal Survey. If approved will and is proposed to the NSF Decadal Survey. If approved will be re-submitted for ESA Cosmic Vision.be re-submitted for ESA Cosmic Vision.

PathfindersPathfinders

• A national mission A national mission POLARIXPOLARIX: 3 telescopes like JET-X/SWIFT : 3 telescopes like JET-X/SWIFT (total area 1000 cm(total area 1000 cm22))

• Two telescopes onboard the Chinese Mission Two telescopes onboard the Chinese Mission HXMTHXMT (total (total area 800 cmarea 800 cm22). Advanced negotiations of ASI and CNSA.). Advanced negotiations of ASI and CNSA.

• A telescope dedicated to polarimetry on the A telescope dedicated to polarimetry on the New Hard X-New Hard X-Ray MissionRay Mission an [all]italian mission based on multi-layer an [all]italian mission based on multi-layer optics.optics.

Running for an Italian Mission: POLARIX


• POLARIX was proposed on 2007 in response to an POLARIX was proposed on 2007 in response to an Announcement of opportunity of ASI for 2 small Announcement of opportunity of ASI for 2 small missions.missions.

• 5 missions selected for the A phase study.5 missions selected for the A phase study.

•A phase study completed on december 2008A phase study completed on december 2008

• Waiting for the selection of the 2 missions to fly Waiting for the selection of the 2 missions to fly (maybe)(maybe)


POLARIX Institute teamEnrico CostaEnrico Costaaa, Ronaldo Bellazzini , Ronaldo Bellazzini cc, Gianpiero Tagliaferri, Gianpiero Tagliaferridd, A.Argan, A.Arganaa, Luca , Luca

BaldiniBaldinicc, Stefano Basso, Stefano Bassodd, Johan Bregeon, Johan Bregeoncc, Alessandro Brez, Alessandro Brezcc, Oberto , Oberto CitterioCitteriodd, Vincenzo Cotroneo, Vincenzo Cotroneodd, Sergio Di Cosimo, Sergio Di Cosimoaa, Sergio Fabiani, Sergio Fabianiaa, ,

Marco FerociMarco Ferociaa, Massimo Frutti, Massimo Fruttiaa, Francesco Lazzarotto, Francesco Lazzarottoaa, Luca , Luca LatronicoLatronicocc, Giorgio Matt, Giorgio Mattee, Massimo Minuti, Massimo Minuticc, E.Morelli, E.Morelliff, Fabio Muleri, Fabio Muleria,ba,b, , Luigi PaccianiLuigi Paccianiaa, Giovanni Pareschi, Giovanni Pareschidd, Michele Pinchera, Michele Pincherac c ,, Alda RubiniAlda Rubiniaa, ,

Carmelo SgroCarmelo Sgrocc, Paolo Soffitta, Paolo Soffittaaa, Gloria Spandre, Gloria Spandrecc

(a)(a) Istituto di Astrofisica Spaziale e Fisica Cosmica, Istituto di Astrofisica Spaziale e Fisica Cosmica, INAF, INAF, Roma, Italy;Roma, Italy;

(b)(b) UUniversitaniversita’’ di Roma Tor Vergata, Dipartimento di Fisica, Roma, Italy di Roma Tor Vergata, Dipartimento di Fisica, Roma, Italy; ;

(c)(c) Istituto Nazionale di Fisica Nucleare, Pisa, ItalyIstituto Nazionale di Fisica Nucleare, Pisa, Italy; ;

(d)(d) Osservatorio Astronomico di Brera, Osservatorio Astronomico di Brera, INAF, INAF, Merate (Lc), ItalyMerate (Lc), Italy; ;

(e)(e) UniversitUniversita’a’ di Roma Tre, Dipartimento di Fisica, Roma , Italy di Roma Tre, Dipartimento di Fisica, Roma , Italy;;

(f)(f) IIstituto di Astrofisica Spaziale e Fisica Cosmica, stituto di Astrofisica Spaziale e Fisica Cosmica, INAF, INAF, Bologna (BO), Bologna (BO), ItalyItaly..

Recycling old stuff: JET-X (optics ready Recycling old stuff: JET-X (optics ready since1996) / SwiftXRT(2004) opticssince1996) / SwiftXRT(2004) optics

Source Source separationseparation: 20”: 20”

• Wolter I profile – Au coating Wolter I profile – Au coating (pathfinder of XMM)(pathfinder of XMM)

• 2 mod. (JET-X) / 1 mod (Swift) – 12 shells/mod. 2 mod. (JET-X) / 1 mod (Swift) – 12 shells/mod.

• F.L. = 350 cm - Max diam = 30 cmF.L. = 350 cm - Max diam = 30 cm

• AAeff eff @ 1 keV= 150 cm@ 1 keV= 150 cm22 /module /module

• HEW= 15 arcsecHEW= 15 arcsec


Mirror Mirror EffectiveEffective Area Area

• red points ==> measurementsred points ==> measurements

• green line ==> ray tracing green line ==> ray tracing


Filter Filter WheelWheel

DetectorDetector

bafflebaffle

Be windowBe window

Polarized Polarized Xray sourceXray source

Muleri et al Muleri et al 20072007

Positions of the filter wheelPositions of the filter wheel•ClosedClosed•OpenOpen•Diaphragm (faint source Diaphragm (faint source close to a bright source)close to a bright source)•Grey filter (bright source)Grey filter (bright source)•Calibration source 1 (Calibration source 1 (5555Fe)Fe)•Calibration source 2 (Cu Calibration source 2 (Cu fluorescence)fluorescence)•Polarized sourcePolarized source

Bragg diffraction (45Bragg diffraction (45oo))From Graphite: From Graphite: PVC Fluorescence (2.6 keV) from PVC Fluorescence (2.6 keV) from FeFe55 55 P = 99.9%P = 99.9%From FLi From FLi 5.89 keV diffracted at 47.65.89 keV diffracted at 47.6o o P = P = 87.9 %87.9 %

The focal plane device


Prima Prima Science Science PlatformPlatform

PolariX PolariX Plug&Play Plug&Play PayloadPayload

The BUS based on PRIMA

The bus was designed by Thales Alenia Space The bus was designed by Thales Alenia Space of Turin. Combining the heritage of SAX, of Turin. Combining the heritage of SAX, INTEGRAL with recurrents from PRIMA and INTEGRAL with recurrents from PRIMA and GLOBALSTAR. Commonalities with SIMBOL-XGLOBALSTAR. Commonalities with SIMBOL-XE.Costa - BH in Binary Systems - Ferrara September 12 2009

POLARIX Data Policy & Data RightsMission OperatioMission Operation:Commissioning Phasen:Commissioning Phase 1 month 1 month

Science Verification PhaseScience Verification Phase 2 months 2 monthsNominal Observation PhaseNominal Observation Phase 12 months12 months

Data Rights:Data Rights: Commissioning PhaseCommissioning Phase POLARIX Team POLARIX TeamScience Verification PhaseScience Verification Phase POLARIX Team POLARIX TeamNominal Observation PhaseNominal Observation Phase 25% Core Program – 25% Core Program –

POLARIX TeamPOLARIX Team 75% Open Time - GOs75% Open Time - GOs

Data Policy:Data Policy:• Guest Observer Program, based on a public AO.Guest Observer Program, based on a public AO.• Proposal peer review and selection by a Time Allocation Proposal peer review and selection by a Time Allocation Committee.Committee.• All data public 1 year after release of data, software & All data public 1 year after release of data, software & calibrations.calibrations.• All data accessible to POLARIX Team for Calibration & Health All data accessible to POLARIX Team for Calibration & Health Monitoring.Monitoring.• Prompt alerts (e.g., GCN, IAU Circ., ATel) by POLARIX Team Prompt alerts (e.g., GCN, IAU Circ., ATel) by POLARIX Team also for proprietary data (with involvement of the PI and release also for proprietary data (with involvement of the PI and release of only the info for follow-up observations).of only the info for follow-up observations).• Target of Opportunity allowed in GOP .Target of Opportunity allowed in GOP .

Sensitivity


An approved mission GEMS


GSFC developed e photoelectric polarimeter different from ours. A SMEX mission based on it has been approved by NAS for a lauch in 2014.

GEMS is more sensitive of POLARIX but not imaging.

Integrates photons within 12’ f.o.v.Needs rotation.Background is not negligible for faint sources


The link of Polarimetry with Hard X-ray Astronomy

A certain connection does exist between physics of hard X-ray emitters A certain connection does exist between physics of hard X-ray emitters and expectations of polarization. and expectations of polarization.

Non thermal processes, can be singled out by the presence of hard Non thermal processes, can be singled out by the presence of hard tails tails (e.g. in some clusters and in some shell like SNR) (e.g. in some clusters and in some shell like SNR) but also from the but also from the existence of linear polarization. existence of linear polarization. The latter also provides a geometric The latter also provides a geometric information (e.g. the orientation of magnetic fields or the direction of information (e.g. the orientation of magnetic fields or the direction of particle acceleration). particle acceleration).

Alternatively the presence of hard component and the absence of Alternatively the presence of hard component and the absence of polarization can provide the evidence for disordered systems (e.g. polarization can provide the evidence for disordered systems (e.g. disordered magnetic fields for synchrotron, or diffuse source of seed disordered magnetic fields for synchrotron, or diffuse source of seed photons in an inverse compton). photons in an inverse compton).

Because of these overlaps and because of a reduced mismatching of Because of these overlaps and because of a reduced mismatching of observing times, observing times, a polarimeter and a hard X-ray instrument can a polarimeter and a hard X-ray instrument can efficiently combine, resulting in a very performing mission. efficiently combine, resulting in a very performing mission.

This is the case of HXMT of the Chinese Space AgencyThis is the case of HXMT of the Chinese Space Agency


The HXMT Mission

• A possible implementation of this commonality Hard X/Polarimetry• Is foreseen with the idea to introduce two telescopes with a

polarimetr on the Chineese Mission HXMT

• Hard X-ray Modulation Telescope (HXMT)– Proposed in 1993

- April 2000 pre phase A study– Main participating institutions:

• Chinese Academy of Sciences• Tsinghua University• Chinese Academy of Space Technology Research

– PI and Co-PI: Ti-Pei Li and Shuang-Nan Zhang– Selected in 2005 as the first Chinese space astronomy mission. – Launch 2012 with on board an X-ray polarimeter.

The Italian Team on HXMT

• The same team of POLARIX and HXMT

Plus

• Filippo Frontera and his team at Ferrara University


A piggy-back solution


In order to semplify AIV the two In order to semplify AIV the two polarimeters (optics and focal plane) polarimeters (optics and focal plane) will be integrated within a cf tube will be integrated within a cf tube and mounted, as piggy-back and mounted, as piggy-back instruments, on the two sides of the instruments, on the two sides of the HXMT bus free from solar panels.HXMT bus free from solar panels.


Telescope Effective AreaA major improvement is the use of Iridium as a reflector. The constraint of A major improvement is the use of Iridium as a reflector. The constraint of a maximum length of 2.5 meters has fixed the detector focal length to 2.1 a maximum length of 2.5 meters has fixed the detector focal length to 2.1 meters. The Ir provides an improvement at higher energies.meters. The Ir provides an improvement at higher energies.


Sensitivity of polarimeter aboard HXMT

A new proposal NHXM


A summary of facts• In Italy the Observatory of Brera/Merate has developed since the time of BeppoSAX technology for X-ray optics based on replica from superpolished mandrels.• In last ten years OAB has spent with the support of ASI a large effort to develop multi-layer optics to extend to hard X-ray range (20 – 80 keV) the response of telescopes.• A mission with 4 hard X-ray telescopes and pixelled detectors in the focus (HEXIT-SAT) was identified as one of priorities by ASI.• Following an AOO from CNES Italy and France started the development of the mission SIMBOL-X based on two satellites in formation flight one hosting the optics and one hosting the detectors (a stack of Si and CdTe arrays). ASI kept also open the “national” option of HEXIT-SAT (renamed NHXM) by performing a parallel phase A study.• In May 2009 CNES has withdrown from SIMBOL-X• On suggestion of ASI, the italian team of SIMBOL-X is studying a mission based on NHXM but also dedicating a telescope to polarimetry.

NHXM


NHXM is based on 4 telescopes (60 shells) with 10m focal length. It is designed to be consistent with VEGA launcher. The focal plane is moved in orbit to the right distance by a deployable system.In the focus of 3 telescopes it will have a Silicon Detector stacked on a CdTe (or CZT) detector to perform spectra, imaging and timing from 0.5 to 80 KeV with 12’ f.o.v. and <20” resolution.

NHXM vs POLARIX: area

20 inner shells Pt/C M/L 40 outer shells W/Si M/L

One telescope is already better than all POLARIXThe possibility to have some extra-shell is studied

NHXM vs POLARIX: angular resolution

The intrinsic space resolution of the detector is suitable (~150µm).An extra-blurring is due to inclined penetration of photons in the gas and finite absorption thickness and this scales with the focal length.

Resources

From POLARIX study.

MassDetector 0.4 kgFW, Buffle, Box 2.9 kgBack End Electronics 3.5 kg

total on the plane 6.75 kgControl Electronics (if separate) 4.8 kg

total 11.3 kg

PowerBack End Electronics 12.9 WControl Electronics (if separate) 18.4 W

total 31.3 W

Bits: a lot! But can be handled …..

A baseline solution


To use in the focus of NHXM the same detector already used for POLARIX and HXMT. The performance of the detector proposed for POLARIX is maximized in the 2-5 keV range.

Two detectors on a sliding device


This can be partially matched with NHXM targets because the same physics can be addressed either going to high energies or searching for polarized fraction at lower energies.

But this is not true in general for some important targets of NHXM imaging/spectroscopy: e.g. obscured objects (galactic or extragalactic), cyclotron lines, hard tails.

We are investigating solutions that use the whole range of the telescopes:• One Low Energy Polarimeter: 10 mm thick 1 atm 80%DME• One Medium Energy Polarimeter: 30 mm thick 3 atm 80%Ar

Advantages and disadvantagesDisadvantages

• Introduces a moving device: potential source of failure. A recovery solution should be studied. With a wise design moving parts could stay within 200÷300 g.

• The time must be shared between two detectors. • Argon GPD has been tested as a polarimeter only at 1 atm. A

first prototype (2 atm 20 mm) is in production and should be available by september.

Advantages• Completes the low energy response of GEMS and covers a band

that GEMS will never cover.• Is better tuned with the imaging/spectra science• Is much more powerful for energy dependent polarimetry• Uses the same components of LEP. The readiness level is

basically the same except for the performance of GEM with ions in an argon based mixtures.

Ingredients to sensitivity: μ×(εA)½

MDP LEP

MDP MEP


Which Polarimetry of Galactic BH?


Relatively poor literature.

• Polarization from disks: BH not much different from NS.• Polarization from reflection • Rotation of the polarization angle for GR effects (typical of BH, depending on the spin)• Polarization of jets.


An extreme case of reflectionSgrB2 is a giant molecular cloud at 100pc projected distance from SgrA

Integral Image of GC, Revnivtsev 2004Integral Image of GC, Revnivtsev 2004

The spectrumof SgrB2 is pure reflection The spectrumof SgrB2 is pure reflection spectrumspectrum

Reflection of what? Reflection of what? No bright enough No bright enough source is theresource is there

The emission from SgrB2 The emission from SgrB2 is extended and brighter is extended and brighter in the direction of in the direction of SgrA,Murakami 2001SgrA,Murakami 2001


Archaeology of the Galactic Center How bright it was 300 – 500 years

ago?

We can derive the date and intensity of the supposed flare when the GC was 105 to 106 times brighter than now.

Polarimetry complemets space resolved spectroscopy and extended band

spectroscopy

R.Sunyaev predicted in 1993 that some sources in the area could be reflecting X-rays emitted from the GC in the past when it was a real AGN

X-ray polarimetry can proof or disproof this hypothesis. SgrB should be highly polarised with the electric vector perpendicular to the line connecting the two sources.

The degree of polarization would measure the angle and provide a full 3-d representation of the clouds. Churazov et al.2002


What can we do with HXMT?HXMT can detect a polarization of 20% in 10HXMT can detect a polarization of 20% in 1066 s s

Not only the amount of polarization is a relevant information. Not only the amount of polarization is a relevant information. The perpendicular to the polarization plane should “point” the The perpendicular to the polarization plane should “point” the source of the reflected radiation. If SgrB2 is polarized at 70% source of the reflected radiation. If SgrB2 is polarized at 70% (that means 60° < q < 120° the BH should be within a cone of (that means 60° < q < 120° the BH should be within a cone of ± 3°. A very tight constraint to the association!± 3°. A very tight constraint to the association!

Polarization of accretion disks

The first complete theory of polarization from an accretion disk as a function of optical thickness and view angle was given by Sunyaev & Titarchuk, 1985

In general polarimetry gives the orientation of an accretion disk In general polarimetry gives the orientation of an accretion disk on th skyon th sky

Testing GR in strong field: bending of light in a galactic Black-Hole

The Polarization angle from an accretion disk in the ‘Newtonian’ case is either parallel to the major axis of the sky-projected disk (positive) or parallel to the sky-projected disk symmetry axis (negative) A,B,C,D, refers to different viscosity regimes and soft-X-ray photons which are the seeds (Lightman & Shapiro, 1976).

But if the field is strong enough the polarization properties are altered by gravitational effects.

The polarization plane rotates continuously with energy because of General Relativistic effects. This is a signature of the presence of a black-hole (Stark& Connors, Connors& Stark, 1977, Connors, Piran & Stark, 1980). This effect is definitely measurable.


A modern approach to the same problem


Two days observation with NHXM (not much different for POLARIX or HXMT).

If the Dovciak, Muleri, Karas, Goosman and Matt model (MNRAS 2008) is correct the observational consequences are impressive. Notice that similar results have been found by Schnittman and Krolik (ApJ 2009).Of course GRS1915+105 is a very favourable case because of high inclination of the disk to the observer. But it is known (from radio jets) and this is an excellent constraint.

IXO


XPOL, a GPD polarimeter was foreseen for XEUS. With the merging of XEUS with CON-X XPOL survived aboard IXO.

XEUS/IXO baseline includes 4 differnt detector in the focalplane:

•A Wide Field Imager based on APS array

•A Narrow Field Non Dispersive Spectrometer based on microcalorimeter

•A fast Timing Experiment based on SDD

•A Polarimeter based on Gas Pixel Detector


Characteristics X-Ray Polarimeter

Detector Type Gas Pixel Detector

Pixel size 50 µm (on hexagonal pattern)

Number of pixels 105600

Array Size (mm2) 15 × 15

Field of View 1.5 × 1.5 arcmin 2

Energy range 1.9 - 6.0 keV (2% efficiency 10 % Mfactor)1.7 – 10.0 keV (5% Mfactor, 0.5% efficiency)

Energy Resolution ∆E /E = 0.2 × (6 KeV/E)½

Non X-Ray detector Background 1 x 10-2 counts/cm2 s roughly flat

Angular Resolution:Telescope :5’’Detector : (150 um = 1’’)Inclined penetration (400 um = 2.7 ‘’)

5.8’’

Count rate/source with 10% pile-up 20k independent on of the position with 10% dead time (no pile-up)

Timing accuracy 10 µs

Typical/ Max telemetry 15kbs-1/1.5 Mbs-1

Operating Temperature Detector 10 ± 2 °C Electronics 20± 20 °C

Cooling Requirements at operating temperature 0.5 W

Type of coolers peltier

Cooler Mass 100 g

Instrument Mass, excl coolers 14.3

Instrument Power excl coolers 33 W

Total Mass 14.4 kg

Total Power 33.5 W(in operation)

XPOL on IXO


XPOL will represent the deepest application of polarimetry in terms of sensitivity.It will also benefit of high angular resolution of the order of 5”. Angular resolution is important for extended objects. In terms of BH candidate sorces angular resolution can allow for:• Resolving jets from microquasars• Detect Ultra Luminous Sources singuling out from other sources in the galaxy.

Key Performance Requirements for IXO instrumentation

Mirror Effective Area

3 m2 @1.25 keV

0.65 m2 @ 6 keV with a goal of 1 m2

150 cm2 @ 30 keV with a goal of 350 cm2

Black hole evolution, large scale structure, cosmic feedback, EOSStrong gravity, EOSCosmic acceleration, strong gravity

Spectral Resolution

ΔE = 2.5 eV within 2 x 2 arc min (0.3 – 7 keV) . ΔE = 10 eV within 5 x 5 arc min (0.3 - 7 keV)

ΔE < 150 eV @ 6 keV within 18 arc min diameter (0.1 - 15 keV)

E/ΔE = 3000 from 0.3–1 keV with an area of 1,000 cm2 for point sources

ΔE = 1 keV within 8 x 8 arc min (10 – 40 keV)

Black Hole evolution, Large scale structureMissing baryons using tens of background AGN

Mirror Angular Resolution

≤5 arc sec HPD (0.1 – 10 keV)

30 arc sec HPD (10 - 40 keV) with a goal of 5 arc sec

Large scale structure, cosmic feedback, black hole evolution, missing baryonsBlack hole evolution

Count Rate 1 Crab with >90% throughput. ΔE < 200 eV (0.1 – 15 keV)

Strong gravity, EOS

Polarimetry 1% MDP on 1 mCrab in 100 ksec (2 - 6 keV) AGN geometry, strong gravity

Astrometry 1 arcsec at 3σ confidence Black hole evolution

Absolute Timing 50 μsec Neutron star studies



1 mcrab (2-10 keV) = 2.4 10-11 erg s-1 cm-2

ULX with IXO/XPOL


3 bright ULX from Winter et al., ApJ 649:730 (2006) – 200 ks

IC0342 XMM2: 0.3323 c/s, 0.09 mCrab => MDP=6.3 %.M81 XMM1: 0.3244 c/s, 0.09 mCrab => MDP=6.3 %.Holm 9 XMM1: 0.6627 c/s, 0.18 mCrab => MDP=4.9 %.

JETS

XTEJ1550-564 Western Jet: 0.0365 c/s, 0.01 mCrab, 0.28317, => 25.08700% with 105 s

A message to the Community


Polarimetry has been for 40 years a game for a few addict players. The big expectations from a bunch of theoreticians did not find an adequate crop of data.The situation will likely change in a near (in terms of space business scale) future.So please whenever you create or improve a scenario or a model please try to evaluate the implications in terms of observable polarization.

The chance is high that these predictions will be verified (or falsified) in a near future.

observational prospects for polarimetry - infn sezione di ... · observing times, a polarimeter and...

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