Neutron star observations in
hard X-rays
Hard X-rays are
emitted by
• Accretion powered
pulsars
•Magnetars
•Young rotation
powered pulsars
Missions
•Ginga
•RXTE
•Integral/Swift
•BATSE/GBM
•Beppo-SAX
•Suzaku
2-37 keV
2-25, 20-100, keV
15-150 keV
15/7-50 keV
0.1-100 keV
0.5-150 keV
•Nu-Star
5-80 keV
•Astro-H
•Astrosat
0.5-200 keV
0.5-150 keV
•POLIX
•LOFT
5-30 keV
2-50 keV
Magnetars
•Magnetars 1013-15 Gauss (SGR, AXP)
•Short lived evolutionary track of the magnetars after
birth  good fraction of all neutron stars are probably
born as magnetars
•Highly variable in their X-ray emission properties.
•Huge outbursts once every few decades
•Active phase: bursts with random time difference and
random intensity occur
•X-ray pulses and the pulse profile shows long term
variations, sometimes with associated spectral
changes.
•A a very challenging class  motivated many
theoretical work.
Magnetars
•Strong hard X-ray emission with multiple spectral
components, pulsating differently between them and
differently with the soft component.
•Association with the highest magnetic field radio
pulsars,
•Quasi-periodic oscillations
clue to the internal and crustal structures of the
neutron stars.
•The spin phase dependence of the short bursts of
magnetars.
Magnetar hard X-ray emission
Magnetar hard X-ray emission
Magnetars
•Hard X-ray pulse profiles, pulse profiles of different
spectral components and long term variabilities of all of
these.
•Measurement of hard X-ray spectrum of several
magnetars
•Study of the long term variations of the pulse profiles
and the spectra,
• Test the magnetar models
Young Neutron Stars
•Only a small fraction of the spin-down energy is emitted in the
radio band. Much larger fraction of the spin-down energy in high
energy band, X-rays and Gamma-rays.
•Soft X-ray and amma-ray emission seen in many objects.
•Recently, pulse hard X-ray emissions have been detected in
several pulsars.
•Pulsar modes to be tested over the widest energy band possible.
Rotation Powered Pulsars
Hard X-ray emission
Energy dependent pulse profiles
Accretion Powered Pulsars
Spin-evolution, Quasi-period Oscillations
Orbital evolution, orbital glitches
Broad band spectrum
Energy dependence of pulse profiles
Luminosity dependence of pulse profiles
Cyclotron lines
Cyclotron lines: pulse phase dependence
Cyclotron lines: luminosity dependence
Cyclotron lines: luminosity dependence of the pulse phase dependence
Cyclotron lines: pulse profile dependence of the pulse phase dependence
Energy dependent pulse profiles
Luminosity dependent pulse profiles
Orbital evolution of X-ray binaries
LMC X-4
CenX-3
SMC X-1
4U 1538-52
Double Compact Binaries
Gravitational Wave Emitters
Short Gamma-ray Bursts
XTE J1808-5635
Cyg X-3
XTE J 1810-271
EXO 0748-676
XTE J1710-281
4U 1822-37
Her
X-1
Her
X-1
Cycltron lines
Luminosity dependence
Pulse phase dependence
Dips in Pulse Profiles : Partial Covering Absorption
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Dips in Pulse Profiles : Partial Covering Absorption
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NuSTAR
NuStar
Broad band spectrum with good energy resolution
of moderate/faint objects
Long exposure required: limited number of sources
Limited scope for pulse phase resolved studies
ASTRO-H
ASTRO-H
c
Astro-H
Broad band spectrum with good energy resolution
of moderate/faint objects
Micro-calorimeter
Very broad band
Long exposure required: limited number of sources
Limited scope for pulse phase resolved studies
ASTROSAT
IXAE
Indian X-ray Astronomy Instrument
Onboard IRS-P3, 1996
Large Area X-ray Proportional Counter
ASTROSAT Ground Trace
Pulsar Cyclotron lines
Cyclotron lines studies with LAXPC
Chandreyee Maitra 2012
Thermonuclear X-ray Burst Reprocessing
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Reprocessing in EXO 0748-676: XMM-Newton Observations
Hard X-ray Quasi Periodic Oscillations
Astrosat
Good for moderate/bright sources
time/phase resolved studies
Multi-wavelength observations
Stable background
X-ray Polarimetry
Polarised X-rays
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Accreting X-ray Pulsars
Image: NASA
Meszaros et al. 1988
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POLIX
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X-ray Polarimeter
Polarisation is unexplored in High Energy Astrophysics
X-ray emission from the following processes should be polarised
Measurement Technique
•Cyclotron
Anisotropic Thomson Scattering
•Synchrotron
•Non-Thermal Bremsstrahlung
•Scattering from non-spherical plasma
These objects should produce polarised X-ray radiation
•Accretion powered pulsars
Crab nebula is the only source for
which X-ray polarisation measurement
•Rotation powered pulsars
exists. This was made in 1976 !!
•Magnetars
Approved mission: GEMS
•Pulsar wind nebulae
•Non-thermal supernova remnants
•Black holes, micro-quasars and active galactic nuclei
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Test Setup
CNC CONTROLLER
CNC ROTARY TABLE
DETECTORS
rotation axis
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Test Results
Rishin et al. 2010
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Engineering Model
The mechanical configuration
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Development Status
Rishin et al. 2012
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Thomson X-ray Polarimeter
Proposal submitted to ISRO
Included in ISRO’s 5 yr plan
Key features of the polarimeter
•Minimum detectable Polarisation of 2%
at 5 sigma level for a 50 mCrab source
•No of sources: 50
•Weight: 110 kg
•Data rate: 300 Mb per orbit
Collimator
Scatterer
Detectors
Spacecraft requirements
•Spinning platform/satellite, 0.5-5 rpm
•Very long exposures required, one week to one month
•Pointing accuracy required: 0.1 degree
•Equatorial orbit, less than 10 degree
•Altitude: 500—600 km
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HXMT, SVOM, LOFT