1. Capella Grating Data and the Emission Line Project - An Update
Priya Desai (CfA)
Nancy Brickhouse
Jeremy Drake
Dave Huenenmoerder
Randall Smith
Andrea Dupree
Vinay Kashyap
I’d like to thank my collaborators
Nancy Brickhouse ,randal Smith ,Dave etc.
I’d also like to take this opportunity to thank Harvey and the CDO
Make sure you thank Harvey and Gu!!
Add andrea
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X-Ray Gratings Workshop

2. X-Ray Gratings Workshop
Outline
What is the Emission Line Project (ELP)?
Some results and existing problems – Using Capella grating data
Future Plans
I would like to give a brief over view and motivation behind this project and then focus on some of the work that has been done under the emission line project umbrella
I will conclude by talking about where we see this project going in the future.
July 11
X-Ray Gratings Workshop

3. What is the Emission Line Project?
Collaborative effort organized by CXC
To use the calibration data to identify potential atomic data problems that can be addressed theoretically or in the laboratory-mostly Capella
Primary Goals:
- to improve the plasma spectral models used to
analyze and fit X-ray spectra.
- catalog of observed spectral lines
The ELP is a is a project aimed at benchmarking and improving plasma models of X-ray spectral observations using high resolution, high signal-to-noise Chandra calibration spectra. The Emission Line Project (ELP) is a collaborative effort, organized by the Chandra X-ray Observatory Center, to improve the plasma spectral models used to analyze and fit X-ray spectral observations. One of the goals is to produce a catalog of observed spectral lines with comparison to current plasma spectral models on an ion-by-ion basis.
We are focusing on Capella becaues of the really good signal to noise.
The first phase of the Emission Line Project will take advantage of high quality spectra of three stellar coronal targets (Procyon, Capella, and HR 1099) that will be obtained for the purposes of calibrating the Chandra transmission gratings. soliciting letter proposals from individuals or groups who are interested in participating in the Chandra Emission Line Project (ELP) by providing funds for research To support the critical evaluation of relevant theoretical atomic data.
To support relevant fundamental laboratory spectroscopy and laboratory atomic physics. Of these grants (average grant $10 K), 5 were laboratory, 8theoretical, 2 database. Final reports to date show typically 1 to 3refereed publications partially supported with these funds.
The primary goal of the Emission Line Project (ELP) is to produce a catalog of observed spectral lines with comparison to current plasma spectral models on an ion-by-ion basis. The line source targets Procyon, Capella, and HR 1099 are specially chosen because they exhibit emission corresponding to a wide range of plasma temperatures from K. The stellar spectra are rich in emission lines from high ionization states of cosmically abundant elements. The ELP is organized by the Chandra X-Ray Center in an effort to improve the plasma spectral models used to analyze and fit X ray spectral data.
Staus so far:
 Fifteen Chandra ELP grants were awarded for a one-year period from NASA administered by the CXC. Of these grants about half were theoretical, a few laboratory and a couple database. Final reports to date show atleast a couple of refereed publications partially supported with these funds. Furthermore, the projects which produced atomic data are making their data available to the Astrophysical Plasma Emission Database (APED)(which can be accessed with CIAO).
        Small ELP grants ($6 to $15 K) were awarded for specific calculations or measurements from researchers primarily funded some other way. The idea was to use the small grants to leverage research on critical problems for applications. The NRC Committee is considering recommendations to help facilitate the interaction between data producers and data users.
        Data Analysis of Chandra calibration data (Capella, Procyon, and HR 1099) for use in benchmarking plasma spectral codes is also underway.Work in progress includes constructing comprehensive line lists,studying the effects of line blending in diagnostic regions,analysis of the line free regions to determine continuum levels.
July 11
X-Ray Gratings Workshop

4. Publications related to the ELP
Chen, G.X., Smith, R.K., Brichouse, N.S.,Wargelin, B.J., Phys Rev A, 2006, 74,
Gu, M.F., Gupta, R., Peterson, J.R., Sako, M. , 2006, ApJ, 649, 979
Keenan, F.P., Drake, J.J., Chung, S., Brickhouse, N. S., Aggarwal, K.M., 2006, ApJ, 645, 597
Ishibashi, K., Dewey, D.,Huenenmorder, D., Testa, P., ApJ, 644, L1171
Desai, P., et al ,2005, ApJ, 625, L59
Ness, J.U., Brickhouse, N.S., Drake, J.J., Huenenmorder, D., 2003, ApJ, 598, 1277
Campbell,S.M., Brickhouse, N.S.,2001, AAS, C
Ayres, T. R., 2001,ApJ, 549, 554A
These are papers specific to Chandra data there area lot of Lab astrophysics wher the authors are paybg close attention to the Capella data.
By no means is this list complete and any papers I have not included was not intentional.
A more complete list can be found at our website :
Please let me know of publications that I may have missed out so I can update the website.
Some publications the first light papers had line fluxes ..but now we have more that 10 times that much exposure time ..
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X-Ray Gratings Workshop

5. X-Ray Gratings Workshop
Some Results
Fe XVIII and Fe XIX EUV to X-ray discrepancies
Line Identifications
Ne IX G -ratios in Capella
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X-Ray Gratings Workshop

6. X-Ray Gratings Workshop
Capella :X-rays
LETG 355 ks
-- Fe XVIII(resonance)
HETG/MEG
300 ks
Fe XVIII
We are constructing an emission line catalog based on the Capella grating spectrum, in part to benchmark the spectral models.
Left figure shows 1 Angstrom around 14 A. Right shows a 20 A section of the EUV from 90 to 110 A.
Note LETG is one spectrometer w/ VERY broad bandpass.richness
Note HETG MEG and HEG are simultaneous, w/ med res having more area.
LETG has the highest area but lowest spectral res at 14 A.
The EUV/X-ray line ratios provide a temperature diagnostic based on REALLY strong lines.
HETG/HEG
300 ks
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X-Ray Gratings Workshop

7. Fe XVIII and Fe XIX X ray to
EUV discrepancies
All X-ray/EUV line ratios are larger than predicted (by all codes).
Fe XVIII
For the strongest lines,
the codes agree: discrepancies are 30% for Fe XVIII and a factor of 2 for Fe XIX.
Fe XIX
X-ray
The figure shows a comparison of X-ray, EUV and from FUSE FUV line ratios for Fe XVIII and XIX lines.
Observed intensity ratios of EUV to Xray lines are found to be a factor of 2 smaller.
Both the strongest EUV and Xray lines are resonance lines which means that they are allowed transitions that should be straight forward to calculate the error bars are tiny and would nt even show up on this plot.
So we concluded that they may be an atomic physics problem. We don’t think is a calibration problem
EUV
FUV
Why Capella ?
Atomic Physics
Desai et al. 2005

8. Interstellar Absorption?
Partially ionized Hydrogen => more Helium
NH=1.6e18
NH=7.2e18
NH=1.6e19
Ionized
The n=2->2 transition lines (lines shown in this plot are EUV lines of L shell ions. They are overestimated bya factor of 2??
Correction factor due to ISM absorbtion at Nh=1.8e18 is a fairly small effect.
They suggest that the absorbtion column density is much higher. They suggest that Ism along Capella’s line of sight is partially ionized and therefore has a larger effective absortbion than if the medium were neutral
Gu et al. 2006
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X-Ray Gratings Workshop

9. Interstellar Absorption?
NH=1.8e18cm-2
NH=7.2e18
Its not a atomic physics model but a problem with the ISM model.
Our(Linsky’s) model assumes ISM is neutral: ie that there is neutral hydrogen which is the primary absorber and neutral He is .09H or about 10% of the Hydrogen amount. There is NO He II. Say fe16 is a good system because it has a few lines around 335 adnd 360 angs and a series of lines between angs
NhI=1.8e18
NheII=0.09*NhI
NheII=0
But if not neutral then; Nh=NhI+NhII <- non zero
Therefore NHe=NheI+NheII+NheIII <-zero
NheI could be higher because presence of ionized NhII could lead to more neutral and ionized Helium.
Abundance assumption : Nhe=. 1*Nh(=NhI)
Nhe=.1*(NhI+NHII)
Nhe>.1NhI
If HII fraction is ,assume its .8;
Then Nh=NhI+. 8*Nh
0.2Nh=NhI
Nh=1.8e18/.2= 9e18
Nhe=.1*(9e18)
Nhe=NheI+NheII
If NheII/Nhe=.5 then
NheI=NheII
NheI=0.5*0.1*9e18=.
NheII=.5*.1*9e18
So hI(neutral), heI(neutral) and heII contribute to absorbtion.
NH=1.6e19
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X-Ray Gratings Workshop

10. X-Ray Gratings Workshop
Fe XVI line ratios
Predicted line ratio (335.1/360.8)
NH=1.8e18
NH=7.2e18
Its not a atomic physics model but a problem with the ISM model.
Our(Linsky’s) model assumes ISM is neutral: ie that there is neutral hydrogen which is the primary absorber and neutral He is .09H or about 10% of the Hydrogen amount. There is NO He II.
NhI=1.8e18
NheII=0.09*NhI
NheII=0
But if not neutral then; Nh=NhI+NhII <- non zero
Therefore NHe=NheI+NheII+NheIII <-zero
NheI could be higher because presence of ionized NhII could lead to more neutral and ionized Helium.
Abundance assumption : Nhe=. 1*Nh(=NhI)
Nhe=.1*(NhI+NHII)
Nhe>.1NhI
If HII fraction is ,assume its .8;
Then Nh=NhI+. 8*Nh
0.2Nh=NhI
Nh=1.8e18/.2= 9e18
Nhe=.1*(9e18)
Nhe=NheI+NheII
If NheII/Nhe=.5 then
NheI=NheII
NheI=0.5*0.1*9e18=.
NheII=.5*.1*9e18
So hI(neutral), heI(neutral) and heII contribute to absorbtion.
NH=1.6e19
July 11
X-Ray Gratings Workshop

11. X-Ray Gratings Workshop
Fe XVI line ratios l
335.4 /360.8
NH=1.8e18cm-2
335/63.7
NH=7.2e18cm-2
335.4/63.7
Its not a atomic physics model but a problem with the ISM model.
Our(Linsky’s) model assumes ISM is neutral: ie that there is neutral hydrogen which is the primary absorber and neutral He is .09H or about 10% of the Hydrogen amount. There is NO He II.
NhI=1.8e18
NheII=0.09*NhI
NheII=0
But if not neutral then; Nh=NhI+NhII <- non zero
Therefore NHe=NheI+NheII+NheIII <-zero
NheI could be higher because presence of ionized NhII could lead to more neutral and ionized Helium.
Abundance assumption : Nhe=. 1*Nh(=NhI)
Nhe=.1*(NhI+NHII)
Nhe>.1NhI
If HII fraction is ,assume its .8;
Then Nh=NhI+. 8*Nh
0.2Nh=NhI
Nh=1.8e18/.2= 9e18
Nhe=.1*(9e18)
Nhe=NheI+NheII
If NheII/Nhe=.5 then
NheI=NheII
NheI=0.5*0.1*9e18=.
NheII=.5*.1*9e18
So hI(neutral), heI(neutral) and heII contribute to absorbtion.
NH=1.6e19cm-2
July 11
X-Ray Gratings Workshop

12. Blending with FeXIX in the Ne IX triplet region
Label F,I,R
Model Fe XIX lines from HULLAC(1% accuracy)
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X-Ray Gratings Workshop

13. Blending with FeXIX in the Ne IX triplet region
ATOMDB
With EBIT λ measurements (Brown et al. 2002, 5-10 mÅ)
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X-Ray Gratings Workshop

14. Fe XIX Model Wavelengths Kotochigova et al. 2005
With this Fe XIX model we can match the positions of all
features in the spectrum.
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X-Ray Gratings Workshop

15. Recent Results New Ne IX G-ratio calculations (Chen et al. 2006, PRA)
On the right is plotted the same ratio againa s a functtion of temperatur but in the EBIT experiment the ration is really a function of beam energy.No NxX in this system to recompine hence the clines don’t curve
G-ratio agrees with LLNL EBIT
measurements of Wargelin
(PhD Thesis 1993)
Derived T from Capella
in better agreement

16. New Calculated G-ratios
Ness et al Ne IX G- ratios don’t predict the correct temperature
Chen et al improved calculations bring it more in line with observations
July 11
X-Ray Gratings Workshop

17. X-Ray Gratings Workshop
Future Plans
A lot of work in theory and lab astro
Catalog of emission lines
Access to Users
Line Catalog consisting of measured wavelengths, fluxes, FWHM, identifications not all of it is available for Chandra users
10times the signal to nois ewe can go deeper and weaker lines and new issues that come out of that too.
July 11
X-Ray Gratings Workshop

19. Blending with Fe XIX in the Ne IX Spectral Region
Ignore the blue shaded regions
Neix triplet region –is a density and temperature diagnostic
Focus on the fit of the pink line with the observed spectrum
Model Fe XIX wavelengths
from HULLAC (1% accuracy)
With EBIT λ measurements
(Brown et al. 2002, 5-10 mÅ)

20. Fe XIX Model Wavelengths from Dirac-Fock-Sturm Method Kotochigova, in progress
With this Fe XIX model we can match the positions of all
features in the spectrum.

21. Ne IX “R-ratio” and “G-ratio”
Classic He-like diagnostics
“R-ratio” = f/i is density-sensitive.
“G-ratio” = (f + i)/r is temperature- sensitive.
f = forbidden s2 1S0 - 1s2s 3S1
i = intercombination 1s2 1S0 - 1s2p 3P2
1s2 1S0 - 1s2p 3P1
r = resonance s2 1S0 - 1s2p 1P1

22. But there still is a problem!
Fe XVI calculations
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X-Ray Gratings Workshop

23. Improved wavelength calculations
Provides substantial cleaning up of the
Angs Ne IX region
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X-Ray Gratings Workshop

24. X-Ray Gratings Workshop
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25. X-Ray Gratings Workshop
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26. X-Ray Gratings Workshop
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27. X-Ray Gratings Workshop
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