Fiona Harrison: NuSTAR Results: From the Galactic Center to Local Starbursts

NuStar
  • Explorer class
  • PI-led
  • Will have guest investigator program
  • First focusing telescope in high-energy X-ray band
  • 100x improvement in 3-79 keV
  • Previous telescopes: detector was larger than collecting area of telescope
  • ~18" resolution, 12.5' fov
Our CMZ: Multicolor cmz vs INTEGRAL
  • NUstar FOV = Integral resolution
  • Survey Muno field (CMZ surey covering negative longitudes)
Sgr A*
  • Flares show it obviously
  • ~1hr/day
  • detection of flare at >10 keV
Gamma ray pulse in Galactic Center
  • enhanced X-ray emission
  • pulsations detected
  • 3.7 second pulsations
  • 3" distant magnetar: SGR J1745-29
  • Associated with disk of massive stars near Sgr A*?
HESS J1640-465
  • being observed right now
  • TeV source
  • possible evidence from NuStar for a pulsar
Nearby Starburst Galaxies
  • Observations coordinated with Chandra
  • NGC 253, Arp 299, M82, NGC 3310, NGC 3256
  • AGN may only be visible at high energies b/c of absorption at lower energies
  • sampling range in mass, sfr
NGC 253
  • Lehmer et al 2013
  • Where is the nucleus? Crowded core, hard to determine
  • Chandra obscured X-ray source "off-center" compared to Radio
  • dynamical center determined; Chandra sees one source near it + variability driven by that source + nustar spectrum by assuming all variability associated with it + classical ULX source: binary star + BH + Either IMBH or super-eddington accretion
  • nuclear emission overestimated due to ULXs
Arp 299
  • Only "B" nucleus visible at high X-ray energies
  • Only one nucleus currently active

Questions:

  • Farhad: Will Nu-Star look at gamma-ray bubble?
  • A: Two problems: 1. too extended, too much time, can't contribute much
  • Is there a possibility of other magnetars not yet detected?
  • A: Various types of magnetars. Undetectable in quiescence. Difficult to constrain overall population. Raises questions: unlikely by chance; do we not understand magnetar population
  • What is the diffuse emission detected with INTEGRAL? In Sgr E?
  • A: We don't see hard x-ray emission coincident with INTEGRAL source. Centroid of INTEGRAL source offset from diffuse emission

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