-look up how error in values goes like 1/sqrt(N)
-read about how effective area is determined
-read about cross sections, thomson scattering, compton scattering
-read about cross section theory
-q for ptak, what models are being used in determing the spectrum of this source
http://xassist.pha.jhu.edu/pipeline4/chandra/3305/acisf03305/report/fullrun_ccd1_acisf03305_pi14-548_cl_pass1.html#src1
-q, why does effective area behave the way it does, why does it eventually decrease for increasing energies?
http://en.wikipedia.org/wiki/Ionization_energy
ionization energy is literally the energy required to ionize an atom, or to remove an electron. In general, the "nth ionization energy" is the energy needed to remove the nth electron after the previous n-1 electrons have been removed. Ionization energy can be thought of as the reluctance of an atom to give up its elecrons. As atomic number increases, the first ionization energy decreases. Ionization energy is a measure of how strongly an electron is bound, and how reactive an element is. The binding energy is the energy needed to remove an electron from an atom when the atom is adsorbed to a surface, which is different than ionization energy for a free electron.
"The binding energies of 1s electrons are roughly proportional to (Z-1)² "
http://en.wikipedia.org/wiki/Moseley%27s_law
READ ABOUT MOSELEY'S LAW, look at the lab I did on this.
TO READ XSPEC manual on-line
-think about the impressions I can make, all the crazy resources I have for getting more knowledge, making connections in the science world
-sign up for the damn GRE!!!!!!!!!!!!!
-look into college visitations! you should do some in September, at latest!!!
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http://heasarc.gsfc.nasa.gov/docs/xanadu/xspec/manual/XspecSpectralFitting.html
The main components spectral fitting are as follows:
-Observed spectra, D(I), and background counts, B(I), are obtained from a detector
-A corresopinding instrumental response, R(I, E)
- A set of Model Spectra M(E)
- These components are used in determining spectra in the following way:
1. Quoted from xspec page
· Choose a parameterized model which is thought to represent the actual spectrum of the source.
· Choose values for the model parameters.
· Based on the parameter values given, predict the count spectrum that would be detected by the spectrometer in a given channel for such a model.
· Compare the predicted spectrum to the spectrum actually obtained by the instrument.
· Manipulate the values of the parameters of the model until the best fit between the theoretical model and the observed data is found.
Then calculate the “goodness” of the fit to determine how well the model explains the observed data, and calculate the confidence intervals for the model's parameters.
----this is what the fit command in xspec does behind the scenes, and will be the data analysis pipeline I will need to setup for analyzing spectral data
-Q, how do we get to deciding what model we think acutally represents the spectrum of the source?
http://en.wikipedia.org/wiki/Convolution
The convolution of functions f and g is
f * g
picture convolution is the animation on the beginning of the wikipedia page
in the case of determining the number of counts in a given channel, the two functions are the actual, physical, input spectrum, f(E), and the response, R(E, I). R is a continuous function of E,
Thus, we compute
f*R,
and this gives the number of counts in a channel. f can be though of as several delta functions, and R is proportional the the probability that an incoming photon of energy E will be placed in a channel of energy I. Not as simple to visualize as the case of the wikipedia animation, because R is a function of two variables.
Convolution is an integral form of multiplication
BACK TO XSPEC MANUAL
"XSPEC allows the construction of composite models consisting of additive components representing X-ray sources (e.g., power-laws, blackbodys, and so forth), multiplicative components, which modify additive components by an energy-dependent factor (e.g., photoelectric absorption, edges, ...). Convolution and mixing models can then perform sophisticated operations on the result."
"The model spectrum, 
so, the Model spectrum does depend on the response file, or detector, in some way. I am thinking it depends on either the width of the channel enegies or the way in which channels is converted to energies, (such as if the detector is germanium vs. silicon)
-look up convolution in calculus book
"it is possible for the fitting process to get stuck in a local minimum and not find the global best-fit." one reason for why my fitting process could be better, to avoid this problem
"At the end of a fit, XSPEC will write out the best-fit parameter values, along with estimated confidence intervals. These confidence intervals are one sigma and are calculated from the second derivatives of the fit statistic with respect to the model parameters at the best-fit. These confidence intervals are not reliable and should be used for indicative purposes only."
Taking values given off a run from xspec,
Model powerlaw<1>*phabs<2> Source No.: 1 Active/On
Model Model Component Parameter Unit Value
par comp
1 1 powerlaw PhoIndex 1.10697 +/- 4.16336E-03
2 1 powerlaw norm 1.13978 +/- 8.08390E-03
3 2 phabs nH 10^22 1.10989 +/- 6.33133E-03
looks like the +/- values must be the confidence intervals it is talking about. the error command must be more accurate, I believe this is what Andy said.
SPEC uses a bracketing algorithm followed by an iterative cubic interpolation to find the parameter value at each end of the confidence interval.
This must be the error in each value?
Parameter Confidence Range (4.7)
1 1.0981 1.11587 (-0.00886957,0.00890067)
look these up
examples of how bracketing algorithms are used to find roots
www.caam.rice.edu/~caam453/lecture38.pdf
confusing, but gives
ode-math.com/PDF_Files/Appendices/AppendixJ.pdf
okay, interpolation is pretty straight forward, it is essentially determining a continuous shape in data by "filling in" values inside the range of data points.
-look up photoelectric absorption, edges
"This differs from the previous formulation in that the operations that control the fitting process make fewer assumptions about how the data are formatted, what function is being minimized, and which algorithm is being employed. At the calculation level, XSPEC requires spectra, backgrounds, responses and models, but places fewer constraints as to how they are represented on disk and how they are combined to compute the objective function (statistic). This has immediate implications for the extension of XSPEC analysis to future missions."
Why exactly?
Parameter Confidence Range (4.7)
1 1.0981 1.11587 (-0.00886957,0.00890067)
"Responses, which abstractly represent a mapping from the theoretical energy space of the model to the detector channel space,"
I like this definition
look up cross-correlation techniques
--------------------
Running XSPEC
Models to try
phabs*powerlaw
plot model to see different values of column density, nH, to see how this influence the X-Ray spectra
powerlaw + diskline
phabs*(powerlaw + diskline)
phabs*apec
model will have a big difference between CCD and calorimeters
wikipedia has good links for:
inverse compton scattering
http://en.wikipedia.org/wiki/Thomson_scattering
http://en.wikipedia.org/wiki/Plasma_physics
unknown fact of the day: the most phase of matter in the universe is plasma
-definition of plasma
Plasma is loosely described as an electrically neutral medium of positive and negative particles (i.e. the overall charge of a plasma is roughly zero). It is important to note that although they are unbound, these particles are not ‘free’. When the charges move they generate electrical currents with magnetic fields, and as a result, they are affected by each other’s fields. This governs their collective behavior with many degrees of freedom.[1][9] A definition can have three criteria:[10][11]
http://en.wikipedia.org/wiki/Effective_temperature
http://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram
boltzmann constant is on the order of 8.16*10^-5 eV/k
Bremsstrahlung means braking radiation, not breaking. It arises from the deceleration of a charged particle as it gets deflected by another charged particle. A photon is emitted in this process, which satisfies of conservation of energy. Whatever energy the particle lost became the energy of the photon.
--bosons vs. fermions
spin 1 vs. spin 1/2
don't care about Pauli vs. Pauli governs order
---------------------
Running XSPEC
Running XSPEC
Models to try
phabs*powerlaw
plot model to see different values of column density, nH, to see how this influence the X-Ray spectra
powerlaw + diskline
phabs*(powerlaw + diskline)
phabs*apec
Figure out how to run pyxspec
-->http://heasarc.nasa.gov/xanadu/xspec/python/html/install.html
TO DO: install python on linux side
http://en.wikipedia.org/wiki/Emissivity
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