Download Extreme Physics Explorer - High Energy Astrophysics

Martin Elvis, SPIE, Orlando FL, May 2006
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Extreme Physics Explorer:
A Mission to Test Basic Physics
An International, multi-agency mission of opportunity?
Martin Elvis
Harvard-Smithsonian Center for Astrophysics
Martin Elvis, SPIE, Orlando FL, May 2006
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
What is the Future of X-ray Binary Research?
 Fields go through 3 phases:
1.
Discovery: mapping basic properties
Widespread excitement rockets, UHURU to EXOSAT
2.
Understanding: detailed study & physics
Specialist interest only
3.
EXOSAT to Rossi XTE
Tool: use understanding to ask new questions
Widespread interest
begun by Chandra, XMM-Newton
 Is X-ray binary research ending phase 2?
 Is phase 3 the
testing of Extreme Physics?
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
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
Reynolds C.
Martin Elvis, SPIE, Orlando FL, May 2006
Neutron 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
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
deDeo & Psaltis, 2003 astro-ph/0302095
Martin Elvis, SPIE, Orlando FL, May 2006
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Gravitational redshift at neutron star surface
Hoogerwerf et al. 2004 ApJ 160 411
EX Hya: HETG R~500
Dvradial= 58.2 +/- 3.7 km/s
Relative velocity only
requires stability
z=0.35
+/-0.04, 10% errors
Spectrum integrated over spin period, several bursts
not absolute calibration
Martin Elvis, SPIE, Orlando FL, May 2006
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Spectroscopy: NS Equation of State
 So far M only from orbit solution
Spectroscopy adds:
 Gravitational redshift due to
neutron star: zg ~ M/R
Bhattacharya et al. 2006 ApJ
Mass (Msol)
Example:
zg
..
.
Orbit solution
 + 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
spin Doppler shift
Radius (km)
Extreme Magnetic Fields: X-ray Pulsars
Polarized by:
Thanks to Enrico
Costa
• Emission process: cyclotron
• Scattering on highly magnetized
plasma: σ║ ≠ σ┴
9 keV
3.8 keV
1.6 keV
•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)
9 keV
3.8 keV
1.6 keV
9 keV
3.8 keV
1.6 keV
Testing GR in strong field: bending of light in
Galactic Black-Hole Binaries
Thanks to Enrico
Costa
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 skyprojected 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
Martin Elvis, SPIE, Orlando FL, May 2006
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Requirements for using
Compact Objects as Physics Labs
Compact object = ‘accelerator’
X-ray telescope = ‘experiment’
Observational Requirements:
 High spectral resolution R~500
Dreaming?
•
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 10s 1% polarization
Gratings need a good (<10” HPD) mirror
 Polarization
•
Quantum critical B-field effects
Crab = 104 ct/s/sq.m
XRBs ~103 ct/s/sq.m
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
Extreme 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
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
Microcalorimeters as timing devices
 Pulse rise time ~50 msec
 Event timing to ~5 ms
 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
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
Overcoming 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
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
Microchannel Plate Mirrors
 = LOBSTER optics
George Fraser & Gareth Price 2003, priv.comm.
• 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?
7 m2 @ 1 keV
3 m2 @ 10 keV
Martin Elvis, SPIE, Orlando FL, May 2006
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
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
5m
40
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
Overcoming 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
Martin Elvis, SPIE, Orlando FL, May 2006
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Optimizing Microcalorimeter Energy resolution
 Challenging spectral resolution:
DE = 2eV, R = 500 @ 1 keV
5 arcmin
 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
50 cm
QuickTime™
TIFF (Uncompressed)
Focal Plane
are needed to see
layout
21 arcmin
Cryostat/
Polarimeter
Microcalorimeter
Hi E foci
? Lo E foci
Optical axis
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
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 1020arcmin from mcalorimeter.
Thanks to Enrico
Costa
Martin Elvis, SPIE, Orlando FL, May 2006
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
A fast evolving technique
Chip I (2003)
2101 pixel;
pitch
Thanks to Enrico
Costa
80mm; 4 mm Ø
Chip II (2004)
20000 pixel; pitch
80mm; 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
Martin Elvis, SPIE, Orlando FL, May 2006
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
MIDEX 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?
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
Challenges
 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
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
Extreme Physics Explorer A Next Generation RXTE
 10 times area
 100 times spectral resolution
 1/1000 beam size
 5ms time resolution
 polarimetry
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
Extreme 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]
Martin Elvis, SPIE, Orlando FL, May 2006
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
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 [email protected] if you want to join in
Black Hole or
`neutron’ star
QuickTime™ and a
MassTIFF (Uncompressed)
decompressor
are needed to see this picture.
donor
star
X-ray binary
The next accelerator
Astro-ph/0403554
2004, Nucl. Phys. B 134, p.78-80
Martin Elvis, SPIE, Orlando FL, May 2006
Extreme 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