Thursday, December 1, 2011
Thursday, November 10, 2011
Saturday, July 23, 2011
http://www.ibtimes.com/articles/185599/20110723/astronomers-largest-most-distant-reservoir-of-water.htm
look more into the research done for this article, try to find this on xassist
agenda
today
for next time
Monday, July 18, 2011
poster template
http://people.oregonstate.edu/studentgroups/siam/sites/default/files/OSUposter_1.pdf
agenda
-
-
-
-
-
-
-
-
-
8-
9-
10-
11-
12-
1-
2-
3-
4-
5-
6-
today
for next time
agenda
-
-
-
-
-
-
-
-
-
8-
9-
10-
11-
12-
1-
2-
3-
4-
5-
6-
today
for next time
Friday, July 8, 2011
To do every morning
STARTING THE DAY
open up window with -gmail, blogger, and google docs
open up another blogger window
open up mkeck folder in windows viewer
open up window with -gmail, blogger, and google docs
open up another blogger window
open up mkeck folder in windows viewer
HOW TO USE BLOG EFFECTIVELY
Use the blog in conjunction with google docs. Take notes on here, and save xspec input and output files, python files, and other notes on google docs.
Thursday, July 7, 2011
agenda
Run through as many models as you can
1.-simulate sources with 2-10 keV flux = 1e-14, 1e-13, 1e-12 and a power-law spectrum with photon index (gamma) = 1.0, 2.0 and an iron line at 6.4 keV with width = 0.001 keV and normalization = 1e-6 and 1e-5.
Then get errors on photon index, gaussian energy, width, norm. for 10, 20, 50, 100 ks exposures.
2-. Grab point source arf, with optical blocking filter.
It would be interesting to try iterating through the different rmfs to see what impact those different designs have but start with the current best estimate one.
3.Models to start with would be
powerlaw + diskline, ignoring 0.0-2.0 and 10.-** (i.e., ignore below 2 keV since the disk line won't have any impact below something like 4 keV and you want to go below where the diskline is contributing strongly to the spectrum to make sure the powerlaw is being fit properly). Then fit this with the input diskline model, trying to unfreeze various parameters to see if they are being constrained. That is a qualitative statement but a quantitative version would be that the parameter errors don't hit boundaries that are built into the model. xspec lets you set a "soft" and a "hard" range for each parameter. I don't recall exactly what soft means but it impacts the fitting procedure in a way that the fit is steered away from the soft boundary. The hard boundary means that the fit parameter is not allowed to go past that point. So for photon index, the default hard boundary is -3 to 10 and the soft boundary is -2 to 9. You can set this when you do "newpar", e.g.,
newpar 1 2.0 0.01 -4 -3 10 15
changes the boundaries to -4 to 15 and -3 to 10.
The default ranges for parameters for xspec models are usually physically motivated and/or based on experience... it is very rare to see a photon index < -2 or > 9. Typical values are 0-3. So if the fit goes to -2 or -3 there is a good chance that something is wrong or that the power-law is really being used to fit something that isn't really a power-law.
4-You can also do the above with absorption (i.e., due to gas between the satellite and the source, again mostly due to gas in the Milky Way and the host galaxy of the source):
model phabs * (powerlaw + diskline)
5-Also try
phabs * apec
6-model phabs * (powerlaw + diskline)
-model phabs * apec # with different values of Nh,kT, and abundance
fakeit none
-Then fits first with the apec model itself and see how constraints on Nh, kT, A come out and then fit with phabs * brem and then add in lines one at time
model phabs * brem
fit
# get errors
7. Take a simple power-law only model, run fakeit a larger number times, get the error on photon index, then plot the histogram of photon index best-fit values. From that histogram see where the 90% of the value are.
today
1 erg = 10^-7 joules!!
1 erg= 10^7 joules!!
1 erg= 10 ^7 joules!!
I need to practice my upper row typing!!!
the units of flux in are either photons*cm^-2*s^-1 or erg*cm^-2*s^-1 in xspec
-----
From the PyXspec website,
A class gives you the type, or definition of an object, and an object is a specific instance of a class.
"
This description uses the standard Python object-oriented terminology, distinguishing between classes and objects. Class is used when referring to the type or definition of an object. An object refers to a specific instance of a class and is normally assigned to a variable. For example a user may load 3 data files by creating 3 spectral data objects s1, s2, and s3, which are all instances of the class Spectrum.
The functions and stored data members that make up the definition of a class are referred to as methods and attributes respectively."
------------------------
practice programming!
http://projecteuler.net/
also, the python function type() tells you what type an object is
how to search for a file type or a file with a certain name
Use the wildcard, *
ls *text* to search for a file in a given name
ls *.doc looks for the doc extension, for example
if you want to remove a bunch of files with fake in their name, type
$ rm *fake*
-------------------------
Would making a dictionary be a better use of my time than a bunch of lists?
for next time
- try pyXspec at home (it appears not to be loaded on this computer)
- learn how to use the OS module in python!!
-go through walk through xspec tutorial on xspec website
-practice upper row typing
-review derivation for power law
-explore using dictionaries to keep models organized
Run through as many models as you can
1.-simulate sources with 2-10 keV flux = 1e-14, 1e-13, 1e-12 and a power-law spectrum with photon index (gamma) = 1.0, 2.0 and an iron line at 6.4 keV with width = 0.001 keV and normalization = 1e-6 and 1e-5.
Then get errors on photon index, gaussian energy, width, norm. for 10, 20, 50, 100 ks exposures.
2-. Grab point source arf, with optical blocking filter.
It would be interesting to try iterating through the different rmfs to see what impact those different designs have but start with the current best estimate one.
3.Models to start with would be
powerlaw + diskline, ignoring 0.0-2.0 and 10.-** (i.e., ignore below 2 keV since the disk line won't have any impact below something like 4 keV and you want to go below where the diskline is contributing strongly to the spectrum to make sure the powerlaw is being fit properly). Then fit this with the input diskline model, trying to unfreeze various parameters to see if they are being constrained. That is a qualitative statement but a quantitative version would be that the parameter errors don't hit boundaries that are built into the model. xspec lets you set a "soft" and a "hard" range for each parameter. I don't recall exactly what soft means but it impacts the fitting procedure in a way that the fit is steered away from the soft boundary. The hard boundary means that the fit parameter is not allowed to go past that point. So for photon index, the default hard boundary is -3 to 10 and the soft boundary is -2 to 9. You can set this when you do "newpar", e.g.,
newpar 1 2.0 0.01 -4 -3 10 15
changes the boundaries to -4 to 15 and -3 to 10.
The default ranges for parameters for xspec models are usually physically motivated and/or based on experience... it is very rare to see a photon index < -2 or > 9. Typical values are 0-3. So if the fit goes to -2 or -3 there is a good chance that something is wrong or that the power-law is really being used to fit something that isn't really a power-law.
4-You can also do the above with absorption (i.e., due to gas between the satellite and the source, again mostly due to gas in the Milky Way and the host galaxy of the source):
model phabs * (powerlaw + diskline)
5-Also try
phabs * apec
6-model phabs * (powerlaw + diskline)
-model phabs * apec # with different values of Nh,kT, and abundance
fakeit none
-Then fits first with the apec model itself and see how constraints on Nh, kT, A come out and then fit with phabs * brem and then add in lines one at time
model phabs * brem
fit
# get errors
7. Take a simple power-law only model, run fakeit a larger number times, get the error on photon index, then plot the histogram of photon index best-fit values. From that histogram see where the 90% of the value are.
today
1 erg = 10^-7 joules!!
1 erg= 10^7 joules!!
1 erg= 10 ^7 joules!!
I need to practice my upper row typing!!!
the units of flux in are either photons*cm^-2*s^-1 or erg*cm^-2*s^-1 in xspec
-----
From the PyXspec website,
A class gives you the type, or definition of an object, and an object is a specific instance of a class.
"
This description uses the standard Python object-oriented terminology, distinguishing between classes and objects. Class is used when referring to the type or definition of an object. An object refers to a specific instance of a class and is normally assigned to a variable. For example a user may load 3 data files by creating 3 spectral data objects s1, s2, and s3, which are all instances of the class Spectrum.
The functions and stored data members that make up the definition of a class are referred to as methods and attributes respectively."
------------------------
practice programming!
http://projecteuler.net/
also, the python function type() tells you what type an object is
how to search for a file type or a file with a certain name
Use the wildcard, *
ls *text* to search for a file in a given name
ls *.doc looks for the doc extension, for example
if you want to remove a bunch of files with fake in their name, type
$ rm *fake*
-------------------------
Would making a dictionary be a better use of my time than a bunch of lists?
for next time
- try pyXspec at home (it appears not to be loaded on this computer)
- learn how to use the OS module in python!!
-go through walk through xspec tutorial on xspec website
-practice upper row typing
-review derivation for power law
-explore using dictionaries to keep models organized
Wednesday, July 6, 2011
7-6:
http://www.phys.unsw.edu.au/~jw/paper.html
Morning- Readings
Authors: Smith, R.K., Bautz, M.W., Bookbinder, J., Garcia, M.R., Guainazzi, M., Kilbourne, C.A.
Title: Predicted X-ray backgrounds for the international X-ray observatory.
constellationx.nasa.gov/resources/Published.../IXO-bkgnd-SPIE.pdf
This paper is in my g-mail, search "ptak spie background" if more bibliographic info is needed.
Notes:
" The background that will be observed by IXO’s X-ray detectors naturally separates into two components: (1) a Cosmic
X-ray Background (CXB), primarily due to unresolved point sources at high energies (E>2 keV), along with Galactic
component(s) at lower energies that are generated in the disk and halo as well as the Local Bubble and charge exchange
in the heliosphere, and (2) a Non-X-ray Background (NXB) created by unvetoed particle interactions in the detector
itself."
" These two components have distinct effects on observations. The CXB is a sum of power-law, thermal, and charge
exchange components that will be focused and vignetted by the IXO mirrors. The NXB, in contrast, is due to particle,
not photon, interactions (although there will be some fluorescence features induced by particle interactions), and so
will not show the same effects of vignetting or trace the effective area response of the satellite."
exosphere- uppermost layer of the Earth's atmosphere (wikipedia)
Summary:
This paper summarizes the radiation background that IXO will be exposed to in it's orbit around the Earth. The background is made up of two components: the cosmic X-Ray background and the non-cosmic X-ray background. The cosmic x-ray background is made up of power-law, thermal, and charge exchange components. The non-cosmic X-ray background, on the other hand, is made up of particle interations on the telescope itself.
The cosmic x-ray backgroun is made up of local, galactic, and extra-galactic sources.
-----> Side note: Andy mentioned that O I is neutral oxygen, O II is once ionized oxygen, O III is twice ionized... O VII is helium-like, and O VIII is hydrogen-like
IXO was planned to be set in orbit in the L2 orbit, or a LaGrangian point
http://en.wikipedia.org/wiki/Lagrangian_point
A LaGrangian point is a point in a 3 body system in a which a 3rd body of low mass relative to the other bodies can orbit and experience no net force. This is pretty cool. JWST (James Webb .... Telescope) was also set to go into an L2 orbit, according to http://www.stsci.edu/jwst/overview/design/orbit
--back to reading
Components of the local cosmic background:
Solar Wind Charge Exchange:
Features line features, and not contiuum
"Solar Wind Charge Exchange (SWCX) itself arises from the Earth’s exosphere and the Solar system’s heliosphere3.
The SWCX component creates low energy (E<1.5 keV) emission lines due to electron cascades following transfers from
neutral material either in the Earth’s exosphere or the heliosphere onto highly ionized solar wind ions. "
Local Hot Bubble:
Also has line features
Modelled as a 10^6 K plasma
keyword: look direction--> which direction you look
galactic lattitude--> lattitude in galactic coordinates, in which Earth is at the origin, and the equator is in the galactic plane of the Milky Way.
Galactic Halos--> http://www.daviddarling.info/encyclopedia/G/galhalo.html
Extra-galactic background is primarily a continuum source. It is generaly agreed upon that the primary source of the extra-galactic background is unresolved AGN
The paper quotes many different flux units, including
erg/cm2/s/arcmin2. I suppose arcmin is dimensionless, so it doesn't change the dimensions. Is this and erg/cm^2/s ?
--The Non- X-Ray Background
No X-Ray detectors have orbited at an L2 orbit, so the expected particle interactions have to be estimated.
XMM Newton has a large eliptical orbit, while Swift has a Low Earth Orbit. As a result, Swift's background is 3-4 times less that of Newton because it is shielded by the Earth's magnetosphere.
Key idea: orbit location can play a big factor in the background. IXO was set to be in an L2 orbit. I bet this will be assumed when we determine background in the future.
Section 3.2 gives a description of the known energetic particles at L2.
The stages of the solar cycle significantly influence background. Solar maximum increases the size of the heliosphere, which can deflect more galactic cosmic rays, but it can also produce more local solar wind.
What does a count rate of 0.17 * 10^-2 cts/s/arcmin^2 indicate? Is this a lot of counts? Small?
Some Solar Wind info:
"In general the solar wind average 1-10 particles/cm3, with a velocity of 400 km/s and a thermal energy of only a few eV. However, at times the thermal energy can increase to keV (although the density is then
only ~0.1 particles/cm3)."
" As a result, it is difficult to estimate what effect this will have on individual observations; obviously, during times of high incident solar
particle flux no data will be used, and the satellite might even be put in safe mode."
To model the expected non x-ray background, the author made modifications to background counts for existing satellites. For the XMS detector on IXO, NXB per unit area "is assumed to be four times that seen in the Suzaku XRS." This appears to be the same ratio commented on earlier between Suzaku and XMM.
The paper also mentions that "The Suzaku XIS background does correlate well with the Earth’s magnetic field coefficient of rigidity (COR)"
looking this up, I find
http://en.wikipedia.org/wiki/Rigidity_%28electromagnetism%29
This paper gives information on anti-coincidence counting
irs.inms.nrc.ca/publications/articles/pdf/BaergMunzenmayerEtAl-1976.pdf
if I need the reference.
For the WFI detector, the model for non-cosmic X-ray background is from the Suzaku, Chandra, and XMM-Newton CCD's.
Questions:
Why does the fraction AGN output to the X-ray background decrease as the flux-limit increases? figure 2. This does not make sense to me.
What is a GEANT simulation?
Are cosmic X-rays shielded from the detector?
Why in Figure 8 is the non cosmic background a straight line? Wouldn't it depend on the chemical makeup of the detector?
Connections to what I am currently doing:
-------------------------------------------------------------------
Now, reading
The absorption-dominated model for the X-ray spectra of type I active
galaxies: MCG–6-30-15
L. Miller,1 T. J. Turner2,3 and J. N. Reeves4
1 Department of Physics, Oxford University, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH
2 Department of Physics, University of Maryland Baltimore County, Baltimore, MD 21250, USA
3 Astrophysics Science Division, NASA/GSFC, Greenbelt, MD 20771, USA
4 Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 8EH
Accepted 2009 July 17. Received 2009 July 17; in original form 2009 May 24
This Galaxy, MCG-6-30-15 is a prime example of a galaxy which shows broad, redwing broadening, particularly below 6.4 the Fe k-alpha 6.4 keV line
"MCG–6-30-15 is the archetypal example of a type I active galaxy showing broad ‘red-wing’ emission in its X-ray spectrum at energies below the 6.4 keV Fe Kα emission line and a continuum excess above 20 keV."
It looks like this is related to the GR effects Andy was talking about with the Fe K-alpha line.
Summary- The author notes two groups with competing theories for the development of the "red-wing" emission, one (Miller et al.) pointing to clumpy absorping material, while the other, Thompson et al, argued this could not be true unless the global covering factor was very low.
Quasar- wikipedia
An AGN which is very far away. It is the active region of the accretion disk surroinding a black hole. Quasar's are extremely luminous. They can emit up to 1000 times the energy output of the Milky Way.
Occultation (wikipedia)- The occurance of an object being out of view to an observer because of another object coming into the line of sight between the observer and object. It is similar to a transit, except in a transit, the object blocking the view is smaller than the more distant object. In an occultation, the blocking object is "larger" (angular wise) than the more distant object. Planets transit stars, stars occult planets.
-bound-free transitions
see this paper for some helping on understanding bound-bound, bound-free transitions
www.astro.umd.edu/~miller/teaching/astr601/lecture21.pdf and
http://en.wikipedia.org/wiki/Atomic_spectral_line
a bound-bound transition is a transition of an electron from one bound energy state of an atomic to another, say from 2s to 2p, 2s to 3s
a bound-free transition is a transition of an electron from a bound energy to being free from the atom (it is ionized!)
Yes, this article discusses the relativistic effects on the Iron K-alpha line
"This effect is often called 'blurring.'
global covering factor --> the fraction of the sky covered by the absorber as seen from the ionizing source.
Miller et al. created a model to describe 'blurring' that based on absorption by clumpy material. He analyzed data from chandra, XMM, and Suzaku, on the energy range frmo 0.5 keV to 40 keV.
Point of paper:
so
"here we also test a model, suggested by MTR but not tested at that
time, in which the spectrum and its variability are shaped by such
high-opacity, clumpy absorption."
Recent paper about hard x-ray excess (x-ray excess)
http://arxiv.org/abs/1103.1238
http://hesperia.gsfc.nasa.gov/sftheory/xray.htm
X-Ray energies range from about 1 keV to 100 keV
1 to 10 keV ~ soft x-rays
10 keV-100 keV~ hard x-rays
"More relevant to the distinction are the instruments required to observe them and the physical conditions under which the x-rays are produced"
information on NuStar
http://hesperia.gsfc.nasa.gov/sftheory/xray.htm
Definition of covering factor, Cf, in the paper
Cf is the fraction of the source covered by the absorber, as seen by the observer
Cg is the fraction of the sky covered by the absorber, as seen by the source.
Should this be the same?
to get a feel for magnitudes
Fe-K alpha line flux is 2.54 * 10^-4 photons/s/cm^2
Reynolds chose a column density of 2*10^24 and a Photon Index of 2.2. Both of these numbers seem higher than what I have seen.
CONCEPTS TO READ ABOUT: scattering, cross sections, opacity
http://en.wikipedia.org/wiki/Opacity_%28optics%29
opacity tells you you how impenetrabile a given medium is to radiation, most commonly electromagnetic radiation.
Opaque (let's nothing through)
opacity can depend on the wavelength of radiation coming through
For example, the atmosphere is essentially opaque to x-rays, and some microwaves, I think, but it lets a lot of other e&m radiation through, namely visible.
THINK ABOUT WAVES, in particular boundaries, (reflection, transmission, absorption, scattering(new))
from the xspec website, about the phabs multiplicative model:
phabs
On page 4, he discusses estimating systematic errors to be 0.03
"...we likewise adopt here a systematic fractional error of 0.03, a likely lower limit to the calibration uncertainty given cross-instrument comparisons that show energy-dependent differences of 5-20 per cent (Stuhlinger 2007)."
POSSIBLE TO DO
I could try and replicate the values on page 4, for the galaxy MCG6-30-15, using the values on the bottom of page 4...see if MCG6-30-15 is on the xassist website
??-- This paper talks about a "mean continuum flux incident of the absorber of 0.0383 +- 0.0012 photons*s^-1*cm^-2*keV^-1 at 1 keV. I don't quite understand why energy is in the units. Do these units say "photons per second per cm^2 per keV deposited by the photon?" Is this saying that not all of the energy of the photon is deposited into the detector? Is this related to effective area? "
"optical depth to Comtpon scattering in this absorber would be tau_C approximately equal to 1.5"
?? what is tau_C ?
This paper discussed a way to model the red-wing broadening of the Fe-K alpha line in the galaxy MGC6-30-15. It used models very similar to the phabs model in xspec. It discussed two separate papers which used different models. One, by Miller et al, proposed that the broadening of the iron line can be described by interaction with clumpy material. Another group, Reynold et al, proposed that the wing is caused by relativistic effects. The paper used many concepts related to absorption, cross-sections, viewing angle, composition, and flux. I did not understand a lot of the significance of the motivation behind the models or even what their models even mean. However, it is related to the broadening of the iron-line, which is a very important feature which is to be investigated by con-x. Andy said that this line could be either caused by relativistic effects or absorption and a narrow line. This paper must be hitting at this point, so I SHOULD GET A GOOD UNDERSTANDING OF THIS PAPER!
-------------------------------------------
Another key concept Andy has discussed is degeneracy in models, especially when you have large error bars.
---------------------------------------
now, my goal is to model "Take a simple power-law only model, run fakeit a larger number times, get the error on photon index, then plot the histogram of photon index best-fit values. From that histogram see where the 90% of the value are. "
To do this,
1. Make a python program to drive xspec
2. make run_fakeit program for a powerlaw
3. make a program that can pluck out the best fit value of photon index
4. plot a hisogram of the different values of the photon index
The main step I do not know how to do is plot a histogram. Maybe I make a list, where each value in the list is a given energy. From this list, I make a plot, for a given coordinate (x,y), x corresponds to the energy, and y corresponds to the number of times x shows up in the list, I think simply list.count(x). I do not know how to make a plot of this. --> LOOK AT PH 265 notes
It looks like matplotlib will be exceptionally useful, I should learn how to use it:
http://matplotlib.sourceforge.net/
OTHER TO DO:
go to Andy's long-term plan e-mail, try making the loop he made for driving xspec work.
Morning- Readings
Authors: Smith, R.K., Bautz, M.W., Bookbinder, J., Garcia, M.R., Guainazzi, M., Kilbourne, C.A.
Title: Predicted X-ray backgrounds for the international X-ray observatory.
constellationx.nasa.gov/resources/Published.../IXO-bkgnd-SPIE.pdf
This paper is in my g-mail, search "ptak spie background" if more bibliographic info is needed.
Notes:
" The background that will be observed by IXO’s X-ray detectors naturally separates into two components: (1) a Cosmic
X-ray Background (CXB), primarily due to unresolved point sources at high energies (E>2 keV), along with Galactic
component(s) at lower energies that are generated in the disk and halo as well as the Local Bubble and charge exchange
in the heliosphere, and (2) a Non-X-ray Background (NXB) created by unvetoed particle interactions in the detector
itself."
" These two components have distinct effects on observations. The CXB is a sum of power-law, thermal, and charge
exchange components that will be focused and vignetted by the IXO mirrors. The NXB, in contrast, is due to particle,
not photon, interactions (although there will be some fluorescence features induced by particle interactions), and so
will not show the same effects of vignetting or trace the effective area response of the satellite."
exosphere- uppermost layer of the Earth's atmosphere (wikipedia)
Summary:
This paper summarizes the radiation background that IXO will be exposed to in it's orbit around the Earth. The background is made up of two components: the cosmic X-Ray background and the non-cosmic X-ray background. The cosmic x-ray background is made up of power-law, thermal, and charge exchange components. The non-cosmic X-ray background, on the other hand, is made up of particle interations on the telescope itself.
The cosmic x-ray backgroun is made up of local, galactic, and extra-galactic sources.
-----> Side note: Andy mentioned that O I is neutral oxygen, O II is once ionized oxygen, O III is twice ionized... O VII is helium-like, and O VIII is hydrogen-like
IXO was planned to be set in orbit in the L2 orbit, or a LaGrangian point
http://en.wikipedia.org/wiki/Lagrangian_point
A LaGrangian point is a point in a 3 body system in a which a 3rd body of low mass relative to the other bodies can orbit and experience no net force. This is pretty cool. JWST (James Webb .... Telescope) was also set to go into an L2 orbit, according to http://www.stsci.edu/jwst/overview/design/orbit
--back to reading
Components of the local cosmic background:
Solar Wind Charge Exchange:
Features line features, and not contiuum
"Solar Wind Charge Exchange (SWCX) itself arises from the Earth’s exosphere and the Solar system’s heliosphere3.
The SWCX component creates low energy (E<1.5 keV) emission lines due to electron cascades following transfers from
neutral material either in the Earth’s exosphere or the heliosphere onto highly ionized solar wind ions. "
Local Hot Bubble:
Also has line features
Modelled as a 10^6 K plasma
keyword: look direction--> which direction you look
galactic lattitude--> lattitude in galactic coordinates, in which Earth is at the origin, and the equator is in the galactic plane of the Milky Way.
Galactic Halos--> http://www.daviddarling.info/encyclopedia/G/galhalo.html
Extra-galactic background is primarily a continuum source. It is generaly agreed upon that the primary source of the extra-galactic background is unresolved AGN
The paper quotes many different flux units, including
erg/cm2/s/arcmin2. I suppose arcmin is dimensionless, so it doesn't change the dimensions. Is this and erg/cm^2/s ?
--The Non- X-Ray Background
No X-Ray detectors have orbited at an L2 orbit, so the expected particle interactions have to be estimated.
XMM Newton has a large eliptical orbit, while Swift has a Low Earth Orbit. As a result, Swift's background is 3-4 times less that of Newton because it is shielded by the Earth's magnetosphere.
Key idea: orbit location can play a big factor in the background. IXO was set to be in an L2 orbit. I bet this will be assumed when we determine background in the future.
Section 3.2 gives a description of the known energetic particles at L2.
The stages of the solar cycle significantly influence background. Solar maximum increases the size of the heliosphere, which can deflect more galactic cosmic rays, but it can also produce more local solar wind.
What does a count rate of 0.17 * 10^-2 cts/s/arcmin^2 indicate? Is this a lot of counts? Small?
Some Solar Wind info:
"In general the solar wind average 1-10 particles/cm3, with a velocity of 400 km/s and a thermal energy of only a few eV. However, at times the thermal energy can increase to keV (although the density is then
only ~0.1 particles/cm3)."
" As a result, it is difficult to estimate what effect this will have on individual observations; obviously, during times of high incident solar
particle flux no data will be used, and the satellite might even be put in safe mode."
To model the expected non x-ray background, the author made modifications to background counts for existing satellites. For the XMS detector on IXO, NXB per unit area "is assumed to be four times that seen in the Suzaku XRS." This appears to be the same ratio commented on earlier between Suzaku and XMM.
The paper also mentions that "The Suzaku XIS background does correlate well with the Earth’s magnetic field coefficient of rigidity (COR)"
looking this up, I find
http://en.wikipedia.org/wiki/Rigidity_%28electromagnetism%29
This paper gives information on anti-coincidence counting
irs.inms.nrc.ca/publications/articles/pdf/BaergMunzenmayerEtAl-1976.pdf
if I need the reference.
For the WFI detector, the model for non-cosmic X-ray background is from the Suzaku, Chandra, and XMM-Newton CCD's.
Questions:
Why does the fraction AGN output to the X-ray background decrease as the flux-limit increases? figure 2. This does not make sense to me.
What is a GEANT simulation?
Are cosmic X-rays shielded from the detector?
Why in Figure 8 is the non cosmic background a straight line? Wouldn't it depend on the chemical makeup of the detector?
Connections to what I am currently doing:
-------------------------------------------------------------------
Fundamental Questions in Astrophysics: Guidelines for ... - tiera.ru
Now, reading
The absorption-dominated model for the X-ray spectra of type I active
galaxies: MCG–6-30-15
L. Miller,1 T. J. Turner2,3 and J. N. Reeves4
1 Department of Physics, Oxford University, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH
2 Department of Physics, University of Maryland Baltimore County, Baltimore, MD 21250, USA
3 Astrophysics Science Division, NASA/GSFC, Greenbelt, MD 20771, USA
4 Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 8EH
Accepted 2009 July 17. Received 2009 July 17; in original form 2009 May 24
This Galaxy, MCG-6-30-15 is a prime example of a galaxy which shows broad, redwing broadening, particularly below 6.4 the Fe k-alpha 6.4 keV line
"MCG–6-30-15 is the archetypal example of a type I active galaxy showing broad ‘red-wing’ emission in its X-ray spectrum at energies below the 6.4 keV Fe Kα emission line and a continuum excess above 20 keV."
It looks like this is related to the GR effects Andy was talking about with the Fe K-alpha line.
Summary- The author notes two groups with competing theories for the development of the "red-wing" emission, one (Miller et al.) pointing to clumpy absorping material, while the other, Thompson et al, argued this could not be true unless the global covering factor was very low.
Quasar- wikipedia
An AGN which is very far away. It is the active region of the accretion disk surroinding a black hole. Quasar's are extremely luminous. They can emit up to 1000 times the energy output of the Milky Way.
Occultation (wikipedia)- The occurance of an object being out of view to an observer because of another object coming into the line of sight between the observer and object. It is similar to a transit, except in a transit, the object blocking the view is smaller than the more distant object. In an occultation, the blocking object is "larger" (angular wise) than the more distant object. Planets transit stars, stars occult planets.
-bound-free transitions
see this paper for some helping on understanding bound-bound, bound-free transitions
www.astro.umd.edu/~miller/teaching/astr601/lecture21.pdf and
http://en.wikipedia.org/wiki/Atomic_spectral_line
a bound-bound transition is a transition of an electron from one bound energy state of an atomic to another, say from 2s to 2p, 2s to 3s
a bound-free transition is a transition of an electron from a bound energy to being free from the atom (it is ionized!)
Yes, this article discusses the relativistic effects on the Iron K-alpha line
"This effect is often called 'blurring.'
global covering factor --> the fraction of the sky covered by the absorber as seen from the ionizing source.
Miller et al. created a model to describe 'blurring' that based on absorption by clumpy material. He analyzed data from chandra, XMM, and Suzaku, on the energy range frmo 0.5 keV to 40 keV.
Point of paper:
so
"here we also test a model, suggested by MTR but not tested at that
time, in which the spectrum and its variability are shaped by such
high-opacity, clumpy absorption."
Recent paper about hard x-ray excess (x-ray excess)
http://arxiv.org/abs/1103.1238
http://hesperia.gsfc.nasa.gov/sftheory/xray.htm
X-Ray energies range from about 1 keV to 100 keV
1 to 10 keV ~ soft x-rays
10 keV-100 keV~ hard x-rays
"More relevant to the distinction are the instruments required to observe them and the physical conditions under which the x-rays are produced"
information on NuStar
http://hesperia.gsfc.nasa.gov/sftheory/xray.htm
Definition of covering factor, Cf, in the paper
Cf is the fraction of the source covered by the absorber, as seen by the observer
Cg is the fraction of the sky covered by the absorber, as seen by the source.
Should this be the same?
to get a feel for magnitudes
Fe-K alpha line flux is 2.54 * 10^-4 photons/s/cm^2
Reynolds chose a column density of 2*10^24 and a Photon Index of 2.2. Both of these numbers seem higher than what I have seen.
CONCEPTS TO READ ABOUT: scattering, cross sections, opacity
http://en.wikipedia.org/wiki/Opacity_%28optics%29
opacity tells you you how impenetrabile a given medium is to radiation, most commonly electromagnetic radiation.
Opaque (let's nothing through)
opacity can depend on the wavelength of radiation coming through
For example, the atmosphere is essentially opaque to x-rays, and some microwaves, I think, but it lets a lot of other e&m radiation through, namely visible.
THINK ABOUT WAVES, in particular boundaries, (reflection, transmission, absorption, scattering(new))
from the xspec website, about the phabs multiplicative model:
phabs
A photoelectric absorption using cross-sections set by the xsect command. The relative abundances are set by the abund command.
![M(E) = exp[-n_H*sigma(E)]](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_ulMbreB-Jmgf054twf_gPtSNKfRf7SrqcIh9aU0jaribt7hhAUcOJaoJYDkNMs0igZ0dws8CtoHAUg-UaA90RVCWRhRV-O3Yp6EaiMFUZ0iu5poSauN3R_SeC7ZZCOku_YD3hgS93rYWkyAafD0A=s0-d){kind=small}
HUGE!
CROSS-SECTIONS WIKIPEDIA
This paper looked at the range of energies of 0.5 keV to 50 keVs, across multiple data sets from several telescopes. How could they do this? How do they know calibrations, background cancelling, and other factors were the same?
order of magnitude feel: normalization for the powerlaw was 0.01695
On page 4, he discusses estimating systematic errors to be 0.03
"...we likewise adopt here a systematic fractional error of 0.03, a likely lower limit to the calibration uncertainty given cross-instrument comparisons that show energy-dependent differences of 5-20 per cent (Stuhlinger 2007)."
POSSIBLE TO DO
I could try and replicate the values on page 4, for the galaxy MCG6-30-15, using the values on the bottom of page 4...see if MCG6-30-15 is on the xassist website
??-- This paper talks about a "mean continuum flux incident of the absorber of 0.0383 +- 0.0012 photons*s^-1*cm^-2*keV^-1 at 1 keV. I don't quite understand why energy is in the units. Do these units say "photons per second per cm^2 per keV deposited by the photon?" Is this saying that not all of the energy of the photon is deposited into the detector? Is this related to effective area? "
"optical depth to Comtpon scattering in this absorber would be tau_C approximately equal to 1.5"
?? what is tau_C ?
This paper discussed a way to model the red-wing broadening of the Fe-K alpha line in the galaxy MGC6-30-15. It used models very similar to the phabs model in xspec. It discussed two separate papers which used different models. One, by Miller et al, proposed that the broadening of the iron line can be described by interaction with clumpy material. Another group, Reynold et al, proposed that the wing is caused by relativistic effects. The paper used many concepts related to absorption, cross-sections, viewing angle, composition, and flux. I did not understand a lot of the significance of the motivation behind the models or even what their models even mean. However, it is related to the broadening of the iron-line, which is a very important feature which is to be investigated by con-x. Andy said that this line could be either caused by relativistic effects or absorption and a narrow line. This paper must be hitting at this point, so I SHOULD GET A GOOD UNDERSTANDING OF THIS PAPER!
-------------------------------------------
Another key concept Andy has discussed is degeneracy in models, especially when you have large error bars.
---------------------------------------
now, my goal is to model "Take a simple power-law only model, run fakeit a larger number times, get the error on photon index, then plot the histogram of photon index best-fit values. From that histogram see where the 90% of the value are. "
To do this,
1. Make a python program to drive xspec
2. make run_fakeit program for a powerlaw
3. make a program that can pluck out the best fit value of photon index
4. plot a hisogram of the different values of the photon index
The main step I do not know how to do is plot a histogram. Maybe I make a list, where each value in the list is a given energy. From this list, I make a plot, for a given coordinate (x,y), x corresponds to the energy, and y corresponds to the number of times x shows up in the list, I think simply list.count(x). I do not know how to make a plot of this. --> LOOK AT PH 265 notes
It looks like matplotlib will be exceptionally useful, I should learn how to use it:
http://matplotlib.sourceforge.net/
OTHER TO DO:
go to Andy's long-term plan e-mail, try making the loop he made for driving xspec work.
Tuesday, July 5, 2011
7-5:
xassist website
http://xassist.pha.jhu.edu/
http://xassist.pha.jhu.edu/pipeline4/chandra/3305/acisf03305/report/fullrun_ccd1_acisf03305_pi14-548_pass1_cl_src1.html
http://xassist.pha.jhu.edu/pipeline4/chandra/3305/acisf03305/report/index.html
-------------
I am trying to get a better grasp of what the different models actually are modeling.
http://heasarc.nasa.gov/xanadu/xspec/manual/Models.html
-Apec model
An emission spectrum, from collisionally-ionized, reduced gas.
For motivation, see:
http://atomdb.org/
-Bremms
A thermal bremstrahlung spectrum
http://adsabs.harvard.edu/abs/1975ApJ...199..299K
http://adsabs.harvard.edu/cgi-bin/bib_query?1961ApJS....6..167K
-Diskline model
a line emission from a relativistic accretion disk see the paper below for motivation.
http://adsabs.harvard.edu/abs/1989MNRAS.238..729F
http://xassist.pha.jhu.edu/
http://xassist.pha.jhu.edu/
http://xassist.pha.jhu.edu/pipeline4/chandra/3305/acisf03305/report/index.html
-------------
I am trying to get a better grasp of what the different models actually are modeling.
http://heasarc.nasa.gov/xanadu/xspec/manual/Models.html
-Apec model
An emission spectrum, from collisionally-ionized, reduced gas.
For motivation, see:
http://atomdb.org/
-Bremms
A thermal bremstrahlung spectrum
http://adsabs.harvard.edu/abs/1975ApJ...199..299K
http://adsabs.harvard.edu/cgi-bin/bib_query?1961ApJS....6..167K
-Diskline model
a line emission from a relativistic accretion disk see the paper below for motivation.
http://adsabs.harvard.edu/abs/1989MNRAS.238..729F
Friday, July 1, 2011
7/1:
-review how a powelaw spectrum is produced
-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!!!
---------------------------------
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
-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!!!
---------------------------------
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
Administratitve TO DO:
MAKE THIS INTO A PAGE LATER:
-Have Andy fill out tracker form, take it to main gate office
-Check into IT Access to make to see if I can login to SATERN account yet
-Have Andy fill out tracker form, take it to main gate office
-Check into IT Access to make to see if I can login to SATERN account yet
Thursday, June 30, 2011
astronomy statistics
Here is a website with a lot of good links.
http://user.pa.msu.edu/linnemann/public/workshop/stat_resources.html
http://user.pa.msu.edu/linnemann/public/workshop/stat_resources.html
Wednesday, June 29, 2011
6/29
A lot of stuff today. Andy worked with me almost all day, which was astounding. He also gave me several papers to review and a very good process to go to build up to be doing the error analysis we want to be doing. I better go to catch the bus.
Overall goal now is to get very familar with xspec, get intuitive feel for how changing the different parameters of the models changes the fit, how exposure times change the errors, fit parameters, and other factors. devote completely to xspec, terminal, statistics. Keep on the track he wrote down.
Overall goal now is to get very familar with xspec, get intuitive feel for how changing the different parameters of the models changes the fit, how exposure times change the errors, fit parameters, and other factors. devote completely to xspec, terminal, statistics. Keep on the track he wrote down.
6/30:
Recommended by Andy:
numerical recipes in C++
http://www.nr.com/
reading, section 15.5 non-linear models
I. confidence limits
[cofidence limits] summarizes the probability distribution of errors in parameter estimation.
" The full probability distrubtion is a function defined on the M-dimensional space of parameters a
numerical recipes in C++
http://www.nr.com/
reading, section 15.5 non-linear models
I. confidence limits
[cofidence limits] summarizes the probability distribution of errors in parameter estimation.
" The full probability distrubtion is a function defined on the M-dimensional space of parameters a
Tuesday, June 28, 2011
6/28
links
confidence interval wikipedia
http://xassist.pha.jhu.edu/pipeline4/xmm/0304850901/xmm0304850901/report/fullrun_mos1_xmm0304850901_pi300-10000_pass1_cl_src3.html
-total angular momentum
http://www.chemglobe.org/ptoe/_/14.php
using help in general is very useful for getting help (woaaaaaah)
confidence interval wikipedia
http://xassist.pha.jhu.edu/pipeline4/xmm/0304850901/xmm0304850901/report/fullrun_mos1_xmm0304850901_pi300-10000_pass1_cl_src3.html
-total angular momentum
http://www.chemglobe.org/ptoe/_/14.php
using help in general is very useful for getting help (woaaaaaah)
Monday, June 27, 2011
6/27/2011: First day
Well, a ton of information. Whew, I will have to get good sleep to stay on top of everything.
Recap of day
-Met Dr. Ptak
-Talked about limitations of CCD astronomy, spectral resolution (error goes like 1/sqrt(N)
- N is the number of electrons, which is determined by photon energy/ ionization energy (ionization energy is energy needed to remove one electron from an atom).
- talked about effective area, about how it is similar to optical telescopes
-looked at Chandra website, Education, in order understand how x-ray telescopes work, with their diffration gratings
-talked about the point spread function, which shows how much a point source is spread out from thermal noise, electronic noise
-When looking at spectra, looked actual data for x-ray flux and the model for x-ray counts, using a simple POWER LAW fit
F(E)= N*E^(-a)
-this is related to counts, as F(E)/E= Counts= N*E^(-a)-1= N*E^-(c), where c=a+1
taking log of both sides,
log P(E) is proportional to -c*log(E) + log(n)
SO, it should be linear. However, it is not. (See journal).
GOALS:
model X-Ray sources, analyze errors
Dr. Ptak mentioned another good idea was to develop program to automatically run modelling, given different response functions
-Calorimeters have better spectral resolution than CCD's, CCD's work by ionization of atoms on the detector, usually Si, Ge.
Photon energy is proportional to ionization energy
LOOK UP: Gaussian, Poission distributions!!
review Standard deviation, look this up in data analysis book!
Potential to do: simulate radiactive emission of Cl-38 to model spectra of Cl-38, using random library. I am not very sure how to start doing this.
-Dr. Ptak then brought up some basic optics to show how the focal length of the lense (10m) and the pixel size impacts the angular resolution.
This allows you to figure out the source size on the detector, pi*(angular resolution)^2 (angular resolution is radius?)
Dr. Ptak then installed heasoft. He used many shortcuts in the terminal to make the process quicker.
In order to get HEASOFT to work, he had to add 3 keywords into several files. I believe this was included in the log of programming of today, in the folder documents/6-27
He mentioned that arf essentially is the mirror, while rmf is essentially the detector.
keep reading about what arf, rmf are.
LOOK UP: what files did Dr. Krane use to collect data?
phabs= photon absorption
FOR TOMORROW:
play with terminal
look up cross-section theory
play with x-spec
get card from office secretary on 2nd floor
read about fits, file extensions
read about gaussian, poisson distributions.
review everything we went over today
TO ASK Dr. Ptak
1. What was he doing exactly when he was doing this step process?
XSPEC12>step 2 2.4 2.6 10
C-Statistic Delta PhoIndex
C-Statistic 2
404.28 0.093251 0 2.4
404.39 0.20187 1 2.42
404.54 0.35127 2 2.44
404.73 0.54097 3 2.46
404.96 0.77047 4 2.48
405.23 1.0389 5 2.5
405.54 1.3458 6 2.52
405.88 1.6904 7 2.54
406.26 2.0718 8 2.56
406.68 2.4893 9 2.58
407.13 2.9422 10 2.6
XSPEC12>step 2 2.4 2.8 10
ask about how to add the blank files keywords to the files (the programming wasn't saved).
Here are the links that to some of the pages Andy showed me, just to make sure I have a link to them.
This is a link that will show me the locations of different buildings at Goddard
http://wikimapia.org/#lat=38.993005&lon=-76.853571&z=16&l=0&m=b
This is a link to arf, rmf, and other files for the a source from data taken from NGC 253, this is the SOURCE 3 data.
This link gives the equation for determining cross section absorption
http://xassist.pha.jhu.edu/pipeline4/xmm/0110900101/xmm0110900101/report/fullrun_mos2_xmm0110900101_pi300-10000_pass1_cl_src3.html
Recap of day
-Met Dr. Ptak
-Talked about limitations of CCD astronomy, spectral resolution (error goes like 1/sqrt(N)
- N is the number of electrons, which is determined by photon energy/ ionization energy (ionization energy is energy needed to remove one electron from an atom).
- talked about effective area, about how it is similar to optical telescopes
-looked at Chandra website, Education, in order understand how x-ray telescopes work, with their diffration gratings
-talked about the point spread function, which shows how much a point source is spread out from thermal noise, electronic noise
-When looking at spectra, looked actual data for x-ray flux and the model for x-ray counts, using a simple POWER LAW fit
F(E)= N*E^(-a)
-this is related to counts, as F(E)/E= Counts= N*E^(-a)-1= N*E^-(c), where c=a+1
taking log of both sides,
log P(E) is proportional to -c*log(E) + log(n)
SO, it should be linear. However, it is not. (See journal).
GOALS:
model X-Ray sources, analyze errors
Dr. Ptak mentioned another good idea was to develop program to automatically run modelling, given different response functions
-Calorimeters have better spectral resolution than CCD's, CCD's work by ionization of atoms on the detector, usually Si, Ge.
Photon energy is proportional to ionization energy
LOOK UP: Gaussian, Poission distributions!!
review Standard deviation, look this up in data analysis book!
Potential to do: simulate radiactive emission of Cl-38 to model spectra of Cl-38, using random library. I am not very sure how to start doing this.
-Dr. Ptak then brought up some basic optics to show how the focal length of the lense (10m) and the pixel size impacts the angular resolution.
This allows you to figure out the source size on the detector, pi*(angular resolution)^2 (angular resolution is radius?)
Dr. Ptak then installed heasoft. He used many shortcuts in the terminal to make the process quicker.
In order to get HEASOFT to work, he had to add 3 keywords into several files. I believe this was included in the log of programming of today, in the folder documents/6-27
He mentioned that arf essentially is the mirror, while rmf is essentially the detector.
keep reading about what arf, rmf are.
LOOK UP: what files did Dr. Krane use to collect data?
phabs= photon absorption
FOR TOMORROW:
play with terminal
look up cross-section theory
play with x-spec
get card from office secretary on 2nd floor
read about fits, file extensions
read about gaussian, poisson distributions.
review everything we went over today
TO ASK Dr. Ptak
1. What was he doing exactly when he was doing this step process?
XSPEC12>step 2 2.4 2.6 10
C-Statistic Delta PhoIndex
C-Statistic 2
404.28 0.093251 0 2.4
404.39 0.20187 1 2.42
404.54 0.35127 2 2.44
404.73 0.54097 3 2.46
404.96 0.77047 4 2.48
405.23 1.0389 5 2.5
405.54 1.3458 6 2.52
405.88 1.6904 7 2.54
406.26 2.0718 8 2.56
406.68 2.4893 9 2.58
407.13 2.9422 10 2.6
XSPEC12>step 2 2.4 2.8 10
ask about how to add the blank files keywords to the files (the programming wasn't saved).
Here are the links that to some of the pages Andy showed me, just to make sure I have a link to them.
This is a link that will show me the locations of different buildings at Goddard
http://wikimapia.org/#lat=38.993005&lon=-76.853571&z=16&l=0&m=b
This is a link to arf, rmf, and other files for the a source from data taken from NGC 253, this is the SOURCE 3 data.
This link gives the equation for determining cross section absorption
http://xassist.pha.jhu.edu/pipeline4/xmm/0110900101/xmm0110900101/report/fullrun_mos2_xmm0110900101_pi300-10000_pass1_cl_src3.html
Monday, June 20, 2011
Topics, Concepts to Research
1. Moseley's Work
2. K, L, M Shells in electrons
3. Electron transitions (K-alpha, beta, etc.)
4. J-vector, quantum numbers
5. spin, implications to atomic energy levels
2. K, L, M Shells in electrons
3. Electron transitions (K-alpha, beta, etc.)
4. J-vector, quantum numbers
5. spin, implications to atomic energy levels
Goal of Blog
-Keep log of X-Ray telescope internship
-keep note of thesis ideas I have
-->keep lists of topics/ concepts to research, books/articles to read, and questions I have.
---->To do this, I should take note of it in the journal, and then write it up more neatly on the computer.
I think I should try and keep the following progression for writing about my work:
1. Journal (Rough Draft)
2. Word Document (final draft)
3. Blog (published draft)
To save time, skip the word document step if it is not necessary. I need to practice trying to communicate my ideas, discoveries to others. This will allow others to read what I have been doing, and give good documentation that will help me in writing my thesis and communicating more clearly what I have done to others. I feel like I can have better organization with writing about my progress on-line.
-keep note of thesis ideas I have
-->keep lists of topics/ concepts to research, books/articles to read, and questions I have.
---->To do this, I should take note of it in the journal, and then write it up more neatly on the computer.
I think I should try and keep the following progression for writing about my work:
1. Journal (Rough Draft)
2. Word Document (final draft)
3. Blog (published draft)
To save time, skip the word document step if it is not necessary. I need to practice trying to communicate my ideas, discoveries to others. This will allow others to read what I have been doing, and give good documentation that will help me in writing my thesis and communicating more clearly what I have done to others. I feel like I can have better organization with writing about my progress on-line.
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