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Extreme Physics Explorer: A Mission to Test Basic Physics. An International, multi-agency mission of opportunity?. Martin Elvis Harvard-Smithsonian Center for Astrophysics. What is the Future of X-ray Binary Research?. Fields go through 3 phases: Discovery : mapping basic properties

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Extreme Physics Explorer: A Mission to Test Basic Physics


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extreme physics explorer a mission to test basic physics
Martin Elvis, SPIE, Orlando FL, May 2006

Extreme Physics Explorer: A Mission to Test Basic Physics

An International, multi-agency mission of opportunity?

Martin Elvis

Harvard-Smithsonian Center for Astrophysics

what is the future of x ray binary research
Martin Elvis, SPIE, Orlando FL, May 2006What is the Future of X-ray Binary Research?
  • Fields go through 3 phases:
    • Discovery: mapping basic properties

Widespread excitement rockets,UHURU to EXOSAT

    • Understanding:detailed study & physics

Specialist interest onlyEXOSAT toRossi XTE

    • Tool: use understanding to ask new questions

Widespread interestbegun byChandra, XMM-Newton

  • Is X-ray binary research ending phase 2?
  • Is phase 3 the

testing of Extreme Physics?

black holes magnetars neutron stars
Martin Elvis, SPIE, Orlando FL, May 2006

Reynolds C.

Black Holes, Magnetars & Neutron Stars

are cosmic laboratories for Extreme Physics:

  • Gravity at the event horizon -- Black Holes

Frame dragging, metric in strong gravity -- AGNs, BH binaries

  • Magnetic fields with energy densities greater than an electron -- Magnetars BQED=4.4x1013 g
  • Densities of nuclear matter or beyond -- ‘neutron’ stars
neutron star surfaces
Martin Elvis, SPIE, Orlando FL, May 2006Neutron star surfaces…
  • … explore extreme physics
  • … have a hard surface enabling precision measurements
  • … have a thin atmosphere that imprints sharp atomic features in their spectra
    • Enables spectroscopic tests of extreme physics
  • … are intrinsically X-ray sources

Space-Time curvature

deDeo & Psaltis, 2003 astro-ph/0302095

gravitational redshift at neutron star surface
Martin Elvis, SPIE, Orlando FL, May 2006

Hoogerwerf et al. 2004 ApJ 160 411

z=0.35

Gravitational redshift at neutron star surface

Cottam J. Paerels F. & Mendez M., 2002, Nature, 420, 51

EX Hya: HETG R~500Dvradial= 58.2 +/- 3.7 km/s

Relative velocity only requires stability

not absolute calibration

+/-0.04, 10% errors

Spectrum integrated over spin period, several bursts

spectroscopy ns equation of state
Martin Elvis, SPIE, Orlando FL, May 2006

Mass (Msol)

Radius (km)

Lattimer & Prakash 2000 Phys. Rep. 333, 121.

Spectroscopy: NS Equation of State

Example:

  • So far M only from orbit solution

Spectroscopy adds:

  • Gravitational redshift due to neutron star: zg ~ M/R Bhattacharya et al. 2006 ApJ
  • + Doppler shift vs. phase
    • ~12 km/s
    • R x sin i
  • Map R vs. M of EoS Van den Heuvel
  • zg~ 0.3 czg~100,000 km s-1
  • 1% errors ~1000 km/s -> R ~ 300
    • DE ~ 20 eV @ 6 keV
    • DE = 2eV @ 1 keV

zg

.

.

.

Orbit solution

spin Doppler shift

extreme magnetic fields x ray pulsars
Extreme Magnetic Fields: X-ray Pulsars

Thanks to Enrico Costa

  • Polarized by:
  • Emission process:cyclotron
  • Scattering on highly magnetized
  • plasma: σ║≠σ┴
  • Swing of polarization angle vs. phase measures:
    • orientation of rotation axis on the sky &
    • inclination of the magnetic field
  • the case 45°, 45° (from Meszaros et al. 1988)
testing gr in strong field bending of light in galactic black hole binaries

Thanks to Enrico Costa

Testing GR in strong field: bending of light in Galactic Black-Hole Binaries

Polarimetry gives the orientation of an accretion disk on th sky

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)

Sunyaev & Titarchuk, 1985

If the field is strong enough polarization is 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.

Simulated observation

requirements for using compact objects as physics labs
Martin Elvis, SPIE, Orlando FL, May 2006Requirements for using Compact Objects as Physics Labs

Compact object = ‘accelerator’

X-ray telescope = ‘experiment’

Observational Requirements:

  • High spectral resolutionR~500
    • precise measurements of zg, B
  • High time resolution Dt = 100msec
    • Resolve 10 phase bins in msec period
  • Large area 5-10 sq.m: to collect enough photons:
    • few x 103 counts in few x 103

~1 eV spectral bins x 10 phase bins

    • 106 photons to measure 10s1% polarization
    • Gratings need a good (<10” HPD) mirror
  • Polarization
    • Quantum critical B-field effects

Dreaming?

Crab = 104 ct/s/sq.m

XRBs ~103 ct/s/sq.m

extreme physics explorer
Martin Elvis, SPIE, Orlando FL, May 2006Extreme Physics Explorer

A mission designed to study physics in the extreme environments provided by neutron stars and black holes

  • Not an X-ray astronomy mission
    • A physics mission
    • though utilizing X-ray astronomy techniques
  • Achieves:
    • Large collecting area
    • High time resolution
    • High spectral resolution
    • Sensitive polarimetry
  • Targets:
    • Galactic neutron star and black hole binaries,

including magnetars, transients

    • Long observations
microcalorimeters as timing devices
Martin Elvis, SPIE, Orlando FL, May 2006Microcalorimeters as timing devices
  • Pulse rise time ~50 msec
  • Event timing to ~5ms
  • Energy resolution <5 eV
    • R>200 @ 1keV
  • Con-X, NEW, DIOS goal 2 eV
    • R=500 @1 keV = RGS, HETGS
  • QE ~ 1 (down to ~0.5 keV)
  • Ideal for neutron stars

BUT:

  • Count rate limit ~103 Hz
    • Event duration ~100 msec
    • Constellation-X cannot observe X-ray binaries with XRS
  • SMALL~1 cm2 area
overcoming microcalorimeter limitations 1 area
Martin Elvis, SPIE, Orlando FL, May 2006Overcoming microcalorimeter limitations: 1. Area
  • Galactic X-ray neutron star binaries emit ~103 ct/s/sq.m
  • Need ~107 counts/observation
  • Observation should be small fraction of hours-days binary orbit: ~104s -> Area ~1 - 5 sq. m.
  • = mirrors.
  • Con-X mirrors weigh 280 kg m-2
    • too much for a MIDEX
  • But: Good imaging is bad for microcalorimeter timing: Need to spread out the signal.
  • ~1 arcminute HPD optics are about right.
    • SOLUTION: microchannel plate mirrors: 3.7 kg m-2
microchannel plate mirrors
Martin Elvis, SPIE, Orlando FL, May 2006

George Fraser & Gareth Price 2003, priv.comm.

7 m2 @ 1 keV

3 m2 @ 10 keV

Microchannel Plate Mirrors
  • = LOBSTER optics
    • Well developed (U. Leicester)
    • Not XEUS Micropore optics
  • Lightweight: 3.7 kg m-2
    • 1/10 area/mass ratio of next lightest X-ray mirrors (ASCA/Suzaku foils)
    • Plate-like, robust: fold/deploy easily
      • Units ~1.7m dia.
      • Deploy to 5m dia.
  • 1 arcmin HPD:
    • Demonstrated Bavdaz et al 2002 SPIE
    • Not so bad: low background, confusion: can reach 10’s of AGNs
  • High aperture utilization
  • Thermal control?
long focal length
Martin Elvis, SPIE, Orlando FL, May 2006

5m

40

Long Focal Length
  • Needs ~40m focal length to get area
    • f-number is fixed for grazing incidence mirrors
    • 1arcmin ~ 1.5cm @ focal plane: good size for microcalorimeters
  • Flight-tested light-weight deployable optical benches exist
    • Able Engineering: UARS, GGC WDIND, GGS POLAR, Cassini, Lunar Prospector, IMAGE
  • Slow slewing: long observations
overcoming microcalorimeter limitations 2 count rate
Martin Elvis, SPIE, Orlando FL, May 2006Overcoming microcalorimeter limitations: 2. Count rate
  • Count rate limit is per pixel:
    • 32x32 array can count at 1 MHz - for uniform illumination
    • C.f. 105 ct/s 10sq.m X-ray binary
  • C.f. Con-X: 32x32, 2eV;NEW 32x32 2eV; DIOS 16x16 6eV
  • Slightly larger arrays allow for aspect jitter:
    • 5 arcsec rms -> ~10 arcsec 90% -> 5 pixels -> 42x42 array
  • Pixel size ~ 500 mm (~ 2 arcsec)
    • 50 meter focal length (to get needed area)
      • 1 arcsec ~0.25 mm
      • 1 arcmin beam size ~9 mm dia.
    • ~ 2 x Con-X = DIOS
      • DE = 2.36x 2m1/4 (kT2C/a)1/2 , C=heat capacity = a(pixel size)2
      • Trade-off: technical difficulty of larger arrays vs. DE
optimizing microcalorimeter energy resolution
Martin Elvis, SPIE, Orlando FL, May 2006

5 arcmin

50 cm

21 arcmin

Cryostat/ Microcalorimeter

Polarimeter

Hi E foci

?

Lo E foci

Optical axis

Optimizing Microcalorimeter Energy resolution
  • Challenging spectral resolution: DE = 2eV,R = 500 @ 1 keV
  • Easier to achieve over limited bandwidth: thinner converter, lower heat capacity
  • Divide high and low energy signal between two detector arrays, few arcmin apart
  • Tilt outer shells by ~5 arcmin

~10% of 1 keV graze angle

    • Degradation of beam shape small compared with 1 arcmin HPD
    • Also enables ~doubling of maximum count rate
    • Keep polarimeter on axis - avoid instrumental polarization

Focal Plane layout

one polarimeter option micro pattern gas detector
Martin Elvis, SPIE, Orlando FL, May 2006

Thanks to Enrico Costa

One Polarimeter Option: Micro Pattern Gas Detector
  • Costa et al.
  • Polarization from tracks of photoelectron: 50% modulation, 5.4 keV
  • imaged by a finely subdivided gas detector, PIXI
  • High time resolution: few msec
    • High count rate: few 104 ct/s
  • Put in ‘warm’ focal plane 10-20arcmin from mcalorimeter.
a fast evolving technique
Martin Elvis, SPIE, Orlando FL, May 2006

Thanks to Enrico Costa

A fast evolving technique

Chip I (2003)2101 pixel; pitch80mm; 4 mm Ø

Chip II (2004) 20000 pixel; pitch80mm; 11 × 11 mm2

Chp III (2006) 105600 pixel: pitch 50 mm 15 × 15 mm2

Morover in Chip III each pixel has independent trigger and capability to convert only triggered channels →very fast read-out, few msec

midex scale mission mass
Martin Elvis, SPIE, Orlando FL, May 2006MIDEX Scale Mission Mass
  • Feasible mass budget:
    • 10 m2 microchannel plate mirror: 37 kg
    • Mirror support assembly: 37 kg
    • Optical bench (extending to 40m): 40 kg
    • Optical bench canister: 50kg
    • Calorimeter & cryostat: 123 kg
    • Spacecraft: 200 kg
    • 20% reserve: 83 kg
    • TOTAL: 585 kg
  • Easily within MIDEX range
    • Add small polarimeter, ASM mass
    • Use excess to achieve a high orbit
      • gives long continuous coverage
    • Geostationary?
      • Continuous data contact:
        • 104 ct s-1 x 64 bits/event = 0.1 Mbaud continuous
      • But high background?
        • Not important for bright X-ray binaries
        • May overload telemetry?
challenges
Martin Elvis, SPIE, Orlando FL, May 2006Challenges
  • 2 eV 42x42 microcalorimeter array
  • Mass production of microchannel plate optics
  • Deployment of MCP optics
  • Data rate: 0.1 MB continuous
  • 40 meter optical bench
  • Polarimeter
  • Small cryostat; no cryogen?
  • All Sky Monitor for transients?
  • Science case development
    • Spectro-timing, Polarimetric tests not fully developed
    • Need simulations for specific sources
    • Form Science Working Group
extreme physics explorer a next generation rxte
Martin Elvis, SPIE, Orlando FL, May 2006Extreme Physics Explorer -A Next Generation RXTE
  • 10 times area
  • 100 times spectral resolution
  • 1/1000 beam size
  • 5ms time resolution
  • polarimetry
extreme physics explorer a mission of opportunity
Martin Elvis, SPIE, Orlando FL, May 2006Extreme Physics Explorer -A Mission of Opportunity?
  • NASA Appeals to: Fundamental Physics; RXTE community
      • SAO [mirror partner, ops/data center]
      • GSFC [mcalorimeter]
  • DoE? Fundamental Physics connection (&much cheaper than JDEM!)
  • Potential International partners:
    • With likely funding:
      • Canada want a mission; Kaspi (McGill) pushing X-ray binaries
      • Netherlands (SRON)want to fly a mcalorimeter as XEUS prep.
    • Funding less clear:
      • UK (Leicester) microchannel plate mirror
      • Italy (ASI) U. Rome [polarimeter]
extreme physics explorer23
Martin Elvis, SPIE, Orlando FL, May 2006

Black Hole or

`neutron’ star

Mass donor star

X-ray binary

Extreme Physics Explorer
  • Time is ripe for X-ray emitting Compact Objects research to move to 3rd phase: Extreme Physics
  • Physics-Astrophysics collaboration on Extreme Physics?
  • Need theoretical predictions of spectral features
  • email elvis@cfa.harvard.edu if you want to join in

The next accelerator

extreme physics explorer24
Martin Elvis, SPIE, Orlando FL, May 2006Extreme Physics Explorer
  • MIDEX scale: 500kg, deployed optics, 40m focal length, GEO orbit?
  • Microchannel plate Mirror:
    • Area ~5-10 m2 at ~0.5 - ~10 keV [goal 20keV?]
      • ~10 x RXTE(PCA), ~500 x Chandra(HETG, LETG)
      • Arcminute imaging
    • Long focal length ~40m
  • Microcalorimeter: 2 42x42 arrays, 500mm pixels
    • Low E: DE=2eV R=500 @ 1 keV, v +/-30 km/s
    • High E: DE=6eV R=1000 @ 6 keV
  • Polarimeter:
    • TBD: several candidate technologies