Still attempting to figure out how to plot y error bars....
Monday, October 13, 2008
For 0931, one off-chip source located at 143.04074, 36.50115, had a high x-ray flux, so we took a closer look at it. We are investigating to see if it falls under the category of an XBONG.
Our source is slightly extended (I'm trying to extract a radial profile, but am having trouble with the syntax in bash..) It's chandra counts in the 0.5-2.0keV range were 165, and in the 5-10keV range were 65 (230 over the whole range). It has a redshift of z=0.15, and when assuming a powerlaw dependence and a photon index of 1.9 (characteristic of x-bongs, for which gamma ranges between 1.6-2.4, this leads to an x-ray luminosity of approx. 2.2e43 erg/s.
The source has a ROSAT counterpart cataloged, with a countrate of 4.78e-2+/-1.38, which using WEBPIMMS for ROSAT PSPC, leads to a luminosity of 2.075*10^43erg/s.
We decided to extract spectra from the chandra source, using the ciao routine specextract.
I attempted to fit the spectra based on the discussion of similar sources by Civano et al. 2007, in which they fit a mekal model with the lower energies of the spectra, and then a powerlaw for the higher energies. I as of yet haven't figured out how to fit different source models in different regimes, but here is an image of the data in the 0.5-10.0keV range fit first with the xsmekal source model, parametrized only by the redshift and with "switch"=0, and with an absorbed powerlaw, with gamma=1.6 and nH of 0.0142e-22.
The mekal fit looks as follows (unsure of why it appears to fall off and not intersect the high energy data points, I think this is something weird that happens from the log_scale command..)
And the powerlaw:
The statistics from these fits over the 0.5-10keV range are as follows:
mekal, rstat = 0.632163888096
powlaw, rstat = 0.619105037196
The next step is to get the y errors, and overplot or consolidate in one plot the two fits, which I have had no luck with so far...
Our source is slightly extended (I'm trying to extract a radial profile, but am having trouble with the syntax in bash..) It's chandra counts in the 0.5-2.0keV range were 165, and in the 5-10keV range were 65 (230 over the whole range). It has a redshift of z=0.15, and when assuming a powerlaw dependence and a photon index of 1.9 (characteristic of x-bongs, for which gamma ranges between 1.6-2.4, this leads to an x-ray luminosity of approx. 2.2e43 erg/s.
The source has a ROSAT counterpart cataloged, with a countrate of 4.78e-2+/-1.38, which using WEBPIMMS for ROSAT PSPC, leads to a luminosity of 2.075*10^43erg/s.
We decided to extract spectra from the chandra source, using the ciao routine specextract.
I attempted to fit the spectra based on the discussion of similar sources by Civano et al. 2007, in which they fit a mekal model with the lower energies of the spectra, and then a powerlaw for the higher energies. I as of yet haven't figured out how to fit different source models in different regimes, but here is an image of the data in the 0.5-10.0keV range fit first with the xsmekal source model, parametrized only by the redshift and with "switch"=0, and with an absorbed powerlaw, with gamma=1.6 and nH of 0.0142e-22.
The mekal fit looks as follows (unsure of why it appears to fall off and not intersect the high energy data points, I think this is something weird that happens from the log_scale command..)
And the powerlaw:
The statistics from these fits over the 0.5-10keV range are as follows:
mekal, rstat = 0.632163888096
powlaw, rstat = 0.619105037196
The next step is to get the y errors, and overplot or consolidate in one plot the two fits, which I have had no luck with so far...
Subscribe to:
Posts (Atom)