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NICER Mission Overview

Astrophysics on the International Space Station - Understanding ultra-dense matter through soft X-ray timing

  • Science: An International Space Station (ISS) payload dedicated to the study of neutron stars. A fundamental investigation of extremes in gravity, material density, and electromagnetic fields
  • Launch: June 3rd, 2017 at 17:07 EDT, on a SpaceX Falcon 9 rocket
  • Primary Mission Duration: 18 months, with an additional 6 months long Guest Observer program
  • Platform: ISS ExPRESS Logistics Carrier (ELC), with active pointing over 2π steradians
  • Instrument: X-ray (0.2-12 keV) "concentrator" optics and silicon-drift detectors. GPS position and absolute time reference to better than 300 ns.
NICER on ISS

ISS Accommodations

An established platform and a benign environment

The ISS offers:

  • Established infrastructure (transport, power, comm, etc.) that reduces risk
  • Generous resources that simplify design and reduce cost.
  • A stable platform for arcminute astronomy

NICER's design:

  • Is tolerant of ISS vibrations
  • Is insensitive to the ISS contamination and radiation environments, with safe-stow capability
  • Provides high (> 65%) observing efficiency.
tracking

Instrument Description

High-throughput, low-background soft X-ray timing and spectroscopy

  • Bandpass: 0.2-12 keV
  • Effective area:
    >2000 cm2 @ 1.5 keV,
    600 cm2 @ 6 keV
    2x XMM-Newton for soft X-ray timing
  • Energy resolution:
    85 eV @ 1keV,
    137 eV @ 6 keV
    Similar to XMM and Chandra
  • Time-tagging resolution:
    <300 nsec (absolute)
    ~25x better than RXTE
    ~100-1000x better than XMM
  • Spatial resolution: 5 arcmin diam. non-imaging FOV
  • Background: Dominated by diffuse cosmic XRB (soft)
    (Slides: Impact of Soyuz gamma-ray altimeter on NICER background, Krizmanic et al. 2017, in prep)
  • Sensitivity: 3x10-14 ergs s-1cm-2 (0.5-10 keV, 5 σ in 10 ksec)
    ~30x better than RXTE,
    ~4x better than XMM
Effective area curve
Labled diagram
3D graph of NICER capabilities vs other missions

NICER offers a combination of capabilities not available in any existing mission.

Lightcurves for XMM and NICER

"Best effort" XMM and NICER lightcurves for key target PSR J0437-4715.

Science Objectives

Neutron Stars - Unique environments in which all four fundamental forces of Nature are simultaneously important

pulsar
  • To address NASA and National Academy of Sciences strategic questions
  • To resolve the nature of ultradense matter at the threshold of collapse to a black hole
  • To reveal interior composition, dynamic processes, and radiation mechanisms of neutron stars.
Objective Measurements
Structure - Reveal the nature of matter in the interiors of neutron stars Neutron star radii to +5%. Cooling timescales
Dynamics - Reveal the nature of matter in the interiors of neutron stars Stability of pulsars as clocks. Properties of outbursts, oscillations, and precession
Energetics - Determine how energy is extracted from neutron stars. Intrinsic radiation patterns, spectra, and luminosities.
Diagram of a neutron star
Neutron Star and Strange Quark Star

Science Measurements

Reveal stellar structure through lightcurve modeling, long-term timing, and pulsation searches

Thermal Lightcurve Model

Lightcurve modeling constrains the compactness (M/R) and viewing geometry of a non-accreting millisecond pulsar through the depth of modulation and harmonic content of emission from rotating hot-spots, thanks to gravitational light-bending...

Energy vs. Pulse Phase

... while phase-resolved spectroscopy promises a direct constraint on radius R

Counts vs. Pulse Phase

Simulations demonstrate how well an assumed neutron star radius can be recovered. The +5% (3σ) measurement goal is attained in less than 1 Msec.

The resulting allowed regions in the M-R plane rule out proposed families of neutron star equations of state. The best mass measurements alone can't distinguish among competing models.

Graphs showing number of photons and Solar Mass versus Neutron Star Radius

Neutron Star Science Synergies

Interplay between multiwavelength capabilities amplifies scientific returns from all

Diagram showing interplay between NICER, Fermi, Future X-ray polarimeter, Radio, MAXI, and other all-sky monitors

Guest Observer Program

Sample science enabled by the NICER GO program

Black holes of all sizes are probed through soft continuum spectroscopy to constrain spins in stellar-mass binaries, power spectra of QPOs to definitely establish ultraluminous X-ray sources as intermediate-mass black holes, and relativistic reflection lines to discriminate among AGN models.

Power vs Frequency

Redshifted Fe Lines

Redshifted Fe lines from galaxy clusters reveal star-formation history and poorly understood feedback processes that drive galaxy evolution. (Left) A z = 1.18 line is seen well above the diffuse X-ray back-ground (blue).

Plus...

  • Temporal and spectral variability studies of bright coronal stars can be conducted on much shorter timescales than previously possible
  • The interplay of accretion processes and gravitational radiation in double-degenerate systems can be studied through QPOs in "polars" and long-term timing of SN Ia progenitors
  • Emission lines and soft excesses in high-mass X-ray binaries probe field strengths, accretion geometry, and long-term spin evolution.