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Analysis of Off-Nuclear X-Ray Sources in Galaxy NGC 4945

Analysis of Off-Nuclear X-Ray Sources in Galaxy NGC 4945. Sarah Harrison Massachusetts Institute of Technology under the direction of Grzegorz Madejski and Martin Mueller. X-Ray Astronomy. clusters of galaxies, AGN, quasars, XRBs, SNR accretion: main mechanism of power in XRBs.

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Analysis of Off-Nuclear X-Ray Sources in Galaxy NGC 4945

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  1. Analysis of Off-Nuclear X-Ray Sources in Galaxy NGC 4945 Sarah Harrison Massachusetts Institute of Technology under the direction of Grzegorz Madejski and Martin Mueller

  2. X-Ray Astronomy • clusters of galaxies, AGN, quasars, XRBs, SNR • accretion: main mechanism of power in XRBs

  3. The Eddington Limit • maximum luminosity for many accreting astrophysical systems • accretion: material falls onto compact object and gravitational potential energy is released in form of EM radiation • EM radiation exerts force on surrounding material (Thompson scattering) • Eddington Limit: outward force of radiation balances inward gravitational force, preventing further increase in accretion rate (can use to calculate mass)

  4. Mechanisms of X-Ray Production • thermal bremsstrahlung • synchrotron radiation (magnetic bremsstrahlung) • blackbody radiation

  5. Objectives • examine off-nuclear sources in galaxy NGC 4945 • energy spectra • luminosity • light curves (time series) • search for ultraluminous sources/ massive black holes

  6. The Chandra X-Ray Observatory • launched July 9, 1999 • Advanced CCD Imaging Spectrometer (ACIS) • photon information provided: location, energy, time stamp

  7. Programs Used: ds9, CIAO, xspec extracted spectra and light curves for 5 brightest sources in each observation fit spectra using absorbed power law, bremsstrahlung, and blackbody models Observations • 864: January 2000, 49.75 ks • 4899 and 4900: May 2004, 78.64 ks and 95.8 ks, with 57.6 ks gap (with HETG) • obtained source file and event file for each observation

  8. Energy Spectra

  9. most of sources best fit with absorbed bremsstrahlung and absorbed power law models matches models for accreting black holes and neutron stars luminosity range indicates black holes Results • created table of 5 brightest sources in 864, 4899, and 4900, their spectral parameters and luminosities • luminosities ranged from 2-9 * 1038 erg/s • ULXs: 3 * 1039 erg/s

  10. Light Curves and Variability • reports net count rate of a single source versus time (binned in 3000 s intervals) • used to assess variability of sources • rescaled because of grating used in 4899 and 4900

  11. Conclusions • most sources are accreting black hole XRBs with luminosities below 9 * 1038 erg/s • inaccuracies because of grating used in observations 4899 and 4900 (lower count rate) • further analysis of source variability may provide information about about physical process of accretion • comparison with Hubble data (optical)

  12. Acknowledgments • Grzegorz Madejski and Martin Mueller • Department of Energy • SLAC/KIPAC • Adam and Stephanie

  13. Happy Birthday HUGH!!!!!!

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