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. Observations 864: January 2000, 49.75 ks
4899 and 4900: May 2004, ks and ks, with 57.6 ks gap (with HETG)
obtained source file and event file for each observation
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

8. Energy Spectra

9. 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
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

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