Final Project Report 

to the 

National Aeronautics and Space Administration 

Grant No. NAG 8-535 

"Observational Study of Ion-Electron Equilibration 

and of Cloud Evaporation in Supernova Remnants 

Under the HEAO-2 Guest Investigator Program" 

for the period June 1, 1935 to September 30, 1985 

Richard G. Teske 

Department of Astronomy 

The University of Michigan 

Ann Arbor, Michigan 48109 

(NASA-CE-179922) CBSERVATICNAL STUDY OF N87-I3365 

IGN-ELECIRON EQUILIBFATIOM AND OF CLOUD 

EVAPOEBTICN IN SUPERNOVA REPlWAN'IS UNDER THE 

HEAO-2 GUEST INVEE?IGATOX PRGGEAM Final llnclas 

Project Fieport, 1 Jun. 1985 - 30 Sep. 1986 G3/90 44606 
I. Summary of Accomplishments 

This project had two goals. The first was to make 

observations of three selected supernovae remnants (Cygnus Loop, 

IC 443 , and Puppis A) in the forbidden coronal iron lines [Fe X] 

A6374 and [Fe XIVl X5303, compare the resulting data quantitatively 

with €instein images of the same objects, and attempt to determine 

(a) the process by which ion and electron energies are 

equilibrated behind the shock front in the ISM and (b) whether 

cloud evaporation occurs within the hot remnant interiors. The 

second goal was to make preparations to model spatially-resolved 

X-ray emission for Sedov-Taylor blast wave models of SNR under 

conditions of non-equlibrium ionization. The computations will be 

intended to provide results that can be directly compared with 

Einstein HRI and IPC data. 

Observations of all three target SNR were obtained (Table 

l), but those on the Cygnus Loop are poor ar,d must be repeated. 

Reduction, analysis, and publication of the Puppis A data is 

complete. Reduction and analysis of the IC 443 and Cygnus Loop 

data was incomplete at the end of the report period. 

The computer program for predicting the spatial distribution 

of HRI and IPC counting rates was complete at the end of the 

report period, and final testing of it had begun. 

1 
11. Observations 

A log of observing trips and their outcome is given as 

Table 1. 

a. Puppis A 

A specially-designed image reducing camera was constructed 

for obtaining the Puppis A images at Cerro Tololo Inter-American 

Observatory in January 1985. The data were of excellent quality 

and show for the first time the structure of the coronal gas in 

an SNR on a scale approaching 2.6" arc. A preliminary report was 

presented at the Charlottesville AAS meeting (Teske 1985). The 

coronal iror, line observations were compared with the Einstein HRI 

mosaic of Puppis A prepared by Petre et aL. (1982); two separate 

investigations have resulted. In the first, Teske and Petre 

(19863) addressed the question of whether the "eastern X-ray knot" 

is an example of a cool cloud evaporating into the hot SNR 

interior. We concluded that the knot is a "complicated combination 

of the effects of shock heating plus evaporation. The initial 

encounter of the ICM shock front with a denser region of the 

interstellar medium (a 'cloud') has led to shock heating and the 

production of strong forbidden iron and X-ray emission. 

Subsequently, evaporation of the cloud increased the emission 

measure in the cloud vicinity, causing an augmentation of the iron 

and X-ray brightness there." 

In the second investigation, Teske and Petre (1986b) 

examined the spatial surface brightness profiles of the red and 

green iron lines and of the HRI count rates, across the Puppis A 

shock front. both the opticai and X-ray data are consistent in 

2 
showing a nearly flat gradient of ionization behing the shock. We 

were unable to match the observed forbidden line surface 

brightness distributions with a single Sedov-Taylor model, and 

have ascribed the failure - together with the flat ionization 

gradient which is not predicted by the similarity solution - to the 

inhomogeneous structure of the gas behind the shock front at the 

location observed. We believe that this result has "important 

implications for the determination of SNR shock front models by 

means of fitting X-ray data with Sedov-Taylor models." 

b. IC 443 

In 1983 and 1984 I secured a few CCD frames of IC 443 observed 

through the red filter. These were of poor quality because of an 

uncertainly-identified noise source (probably in a read-write 

buffer of the MIT MASCOT instrument [Meyer and Ricker 19801). A 

Michigan undergraduate has examined the data under my supervision 

and reduced what was reliable; we have published the result 

(Gensheimer and Teske 1986). 

In January and February 1986 I secured good frames of this 

SNR in each Fe line, with the image reducer. By the end of the 

report period the data were being reduced. 

c. Cygnus Loop 

Data-taking on the Cygnus Loop have been plagued by problems - 

principally by bad weather. This object is observable all night 

only during the period of worst weather at the McGraw-Hill 

Observatory. In August of 1925 ciouds, rain, and equipment failure 

3 
interfered; in August of 1986 clouds were present for all of the 7 

nights assigned to me. Four poor quality frames were obtained with 

the MIT MASCOT in June 1985; I am still working on them and intend 

eventually to publish. An extend observing run has been requested 

for June/July 1987 which I hope will complete the data-taking on 

this object. 

d. Other SNR 

In January and February 1986 I obtained three frames on 

Tycho's remnant in the [Fe XIV] green line. There is no clear 

signal down to 20% of the night sky level. Two green line frames 

of the Monoceros Loop,were made at locations selected after 

discussion with Dr. D. Leahy ( e.g. Leahy, Naranan, and Singh 

1985) but again there is no obvious signal in the data. I have 

started to develop two computer routines which are intended to 

"dig out" faint information from the frames. One depends on 

calculation of local median values of the non-stellar abackground 

for showing the presence of faint nebulosities; the other looks 

for faint surface brightness structures by means of an F-test 

(see, e.q. Petro et a2. 1984; Bevington 1969). These have not yet 

been applied to real data. 

In July 1986 I was assigned 5 nights on the CTIO 1.5 m 

reflector. During the only two clear half-nights I secured green 

line frames on fields containing SN 1006, RCW 103, SN185 = RCW 86, 

and Kepler's remnant. These are not yet analyzed. 

\ 

\ 4 
111. Computation of X-ray Surface Brightness Distributions 

Most of the work described in this section has been 

accomplished by graduate student Mr. Diab Jerius under my 

supervision. 

My code for computing Sedov-Taylor blast wave models (Teske 

1984) has been updated and installed in the astronomy department’s 

VAX 11/750 computer. Two versions are available: one assumes that 

ion-electron equilibration takes place on a time-scale shorter 

than the ionization time of prevalent ionic species; the other 

assumes that ion and electron energies are equilibrated by Coulomb 

collisions. Both versions assume that the sole ionization process 

behind the shock is collisional ionization via electron impact, 

and that the sole inverse processes are radiative and 

dielectronic. Account is taken of photoionization ahead of the 

shock by assuming that all atomic species come through the shock 

with four electrons already lost. 

Ionization and recombination rates are calculated for ten 

atomic species by routines very kindly sent to me by A. J. S. 

Hamilton; the species are C, N, 0, Ne, Mg, Si, S, Cay Fey and Ni. 

To these we have added rates for Ar (Shull and van Steenberg 

1982), A1 (Mewe and Gronenschild 1981), and Na (Mewe and 

Gronenschild 1981). 

Model SNR are divided into 99 shells (100 boundaries). The 

output of the blast wave programs is a file of positions, 

temperatures, densities, and ionic fractional abundance5 on each 

boundary. A separate, post-processing code prepared by Mr. Jerius 

uses the file as input data to compute the radial distribution of 

emergent X-radiation, as it would iook projected against the sky, 

5 

~ ~~ ~~ 
from the extreme edge almost to the center. The emergent spectrum 

for 3 5 X I 130 Angstrom ( 0.1 5 Eh,> 5 4.1 keV) is computed for 99 

positions distributed along the projected remnant radius. Our 

ultimate aim is to convolve these 99 spectra with the IPC and HRI 

curves of effective area us photon energy to obtain predicted 

surface brightnesses. 

Computed emissivities include contributions from free-free, 

free-bound, and two-photon continua; to them we have added the 

emission from 358 spectrum lines. At each stage of code 

preparation we have been careful to check the results with hand 

calculations and, if possible, with results published by others. 

At the end of the report period we were still at it. The goal is 

to be at least 95% sure there are fewer than 1% errors. 

Atomic data for computing the line emissivities has been 

taken from the references marked with an asterisk in Table 2. The 

list given in the Table is not exhaustive; while it contains the 

major references searched by us, not all references we actually 

looked at are contained in it. 

We plan to compute X-ray surface brightness models for the 

HRI and IPC observations of Puppis A and the Cygnus Loop, and to 

publish these soon. We intend to present this work at the 

symposium on The Interaction of Supernova Remnants with the 

Interstellar Medium to be held in June, 1987, in Penticton. 

6 
Observing Trips and their Outcome 

Month Observatory Nights Assigned Program Object(s) 

/Nights Usable 

-----__-____---------------~--------------------- 

Jan '85 CTIO 5/5 Puppis A 

June '85 McGraw-Hill 2/7 Cygnus Loop 

Aug '85 McGraw-Hill 013 Cygnus Loop 

Jan '86 McGraw-Hill 2 1/2 / 5 IC 443, Tycho 

Feb '86 McGraw-Hill 117 IC 443, Monoceros B 

July '86 CTIO 215 SN 1006, RCW 86, RCW 103,Kepler's 

Aug '86 McGraw-Hill 0/7 Cygnus Loop 

_--------------------_--___I_____-_I_____-___ 

7 
TABLE 2. 

References Searched for Atomic Data for X-ray Line Emissivities 

Abu Salbi, N., and Callaway, J. 1981, PAYS. Rev A, 24, 2372. 

*Clark, R. E. H., Magee, N. H. Jr., Mann, J. B., and Merts, A. L. 

1982, Ap. J., 254, 412. 

Clark, R. E. H., arid Sampson, D. H. 1978, At. Data and Nuclear 

Data Tables, 22, 527. 

*Davis, J., Kepple, P. C. and Blaha, M. 1976, J.Q.S.R.T., 16, 

1043. 

*Davis, J., Kepple, P. C., and Blaha, M. 1977, J.Q.S.R.T., 13, 

535. 

*Gaetz, T. J., and Salpeter, E. E. 1983, Ap. J. Suppl., 52, 155. 

Gau, J. N., and. Henry, R. J. W. 1977, Phys. Kzv. A, 16, 986. 

Goett, S. J., Clark, R. E. H., and Sampson, D. H. 1980, At. Data 

and Nuclear Data Tables, 25, 185. 

Itikawa, Y., Hara, S., Kato, T., Nakazaki, S., Pindzola, M. S., 

and Crandall, D. H. 1983, Report of Institute of Plc~s)7ul 

Physics, Nag.oya Urciversity: **Recomme)7-CZed Oata on Excitation 

of Curbon and Oxygen Ions by Electron Collisions.” 

Itikawa, T., Takayanagi, K., and Iwai, T. 1984, At. Data and 

Nuclear Data Tables, 31, 215. 

*Kato, T. 1976, Ap. J. Suppl., 30, 397. 

Magee, N. H., Mann, J. B., Merts, A. L., and Robb, W. D. 1977, 

Los Alms Report LA-6691-MS. 

Mason, H. E., Doschek, G. A., Feldman, U., and Bhatia, A. K. 

1979, Astron. Ap., 73,74. 

Merts, A. L., Mann, J. B., Robb, W. D., and Magee, N. H. 1980, 

Los Alarms Report LA-8267-MS. 

Mewe, R., and Gronenschild, E. H. B. M. 1981, Astron. Ap. SuppL., 

45, 11. 

Nakazaki, S., and Hashino, T. 1982, -7. Phys. B, 15, 2295. 

Nakazaki, S., and Hashim, T. 19Pj2, J. Phys. 5, 15, 2767. 

Pradhan, A. K., Norcross, D. W., and Hummer, D. G. 1981, Ap. J., 

246, 1031. 

Raymond, J. C,, and Smith, B. W. 1977, AP. J. SuppL., 3s2 419. 

8 
T&& 2 I Continued 1 

Rugge, H. R., and Walker, A. B. C., Jr. 1978, Ap. J., 219, 1068. 

*Smith, B. W., Raymond, J. C., Mann, J. E., and Cowan, R. D. 1985, 

Ap. J. , 298, 898. 

*Shull, J. M. 1981, Ap. 3. 5uppl. , 46, 27. 

Tucker, W. H., and Koren, M. 1971, Ap. J., 168, 283. 

van Wyngaarden, W. L., Bhadra, K., and Henry, R. J. W. 1979, 

Phys. Rev. A, 20, 1409. 

Walker, A. B. C., Jr., Rugge, H. R. , and Weiss, K. 1974, Ap. J., 

194, 471. 

Younger, S. M. 1980, J.Q.S. R.T. ,23, 489, 

* References from which atomic data were taken for computation of 

line emissivities. 

9 
., , 

REFERENCES 

Eevington, P. R. 1969, Data Reduction and Error Analysis for the 

Physical Sciences (New Ynrk: McGraw-Hill Reek Ccmpany). 

Gensheimer, P. and Teske, R. G. 1986, Pubs. Astron. SOC. Pacific, 

In Press 

Leahy, D. A., Naranan, S., and Singh, K. P. 1985, M. N. R. A. S., 

213, 15P. 

Mewe, R., and Gronenschild, E. H. B. M. 1981, Astron. Ap. SuppL., 

45, 11. 

Meyer, S. S., and Ricker, G. R. 1980, Applications of Digital 

Irnage Processing to Astronomy, S. P. I. E. 264, 38. 

Petre, R., Canizares, C. R., Kriss, G. A., and Winkler, P. F. 

1982, Ap. J. , 258, 22. 

Petro, L. D., Foukal, P. V., Rosen, W. A., Kurucz, R. L., and 

Pierce, A. K. 1984, Ap. J., 283, 426. 

Shull, J. M., and van Steenberg, M.. E. 1981, Ap. J. SuppZ., 45, 

95. 

Teske, R. G. 1984, Ap. J., 277, 832. 

Teske, R. G. 1985, €3. A. A. S., 17, 596 (Abstr). 

Teske, R. G., and Petre, R. 1986a, Ap. J., In Press. 

Teske, R. G., and Petre, R. 1986b, Ap. J., Submitted. 

10