HETG

Follow-on Science Instrument

Contract NAS8-01129

Monthly Status Report Numbers 029-030

July - August 2004

Science Theme: Supernova Remnants III

Prepared in accordance with DR 972MA-002; DPD #972

Prepared for

National Aeronautics and Space Administration

Marshall Space Flight Center, Alabama 35812

 

Center for Space Research; Massachusetts Institute of Technology; Cambridge, MA 02139



Supernova Remnant Progress, Part III (Sept.’03 – August’04)

 

Summary of Supernova Remnant Observations and Activities

In the last 12 months progress has continued in the analysis and understanding of our GTO observations of Supernova Remnants, the first four in the Table below. Among the main highlights are the publication of our E0102 results (Flanagan et al. 2004), new O III long-slit data on E0102, detailed modeling of radial variation, progress in global modeling of E0102, and spectral models for Type 1a, e.g., N103B. Specific progress is described in the following pages.

Obs

Cycle

HETGS

Obsid(s)

Exp.

Time

(ks)

SNR

Name

Loc.,

Dist.

(kpc)

Ang.

Dia.

Dia.

(pc)

Age

(y)

Comments

2

1045, 2410,

2416

117

N103B

LMC, 50

31”

7.5

1,500

Strong Si and Fe lines.

Type 1a or Core collapse?

 

 

 

 

 

 

 

 

Oxygen-rich SNRs w/HETGS:

2

1046

70

Cas A

Gal., 3.4

340”

5.6

320

 

1

121, 1828

100

N132D

LMC, 50

115”

27.9

1,350

Bright Filaments, “O blob”

1,

4

120, 968

3828

137

138

E0102

SMC, 60

44”

12.8

1,000

Weak Fe lines

90 deg roll from Cycle 1 obs.

 

 

 

 

 

 

 

 

Other Known O-rich SNRs:

 

 

 

Puppis A

Gal., 2.0

 

3300”

32.0

~ 5,000

 

 

 

 

G292.0+1.8

Gal., 4.8

540”

12.5

< 1,600

 

 

 

 

B0540-69

LMC, 50

68”

16.5

~ 1,700

PWN; 8” dia. O III ring.

 

 

 

0103-72.6

SMC, 60

170”

49.4

~20,000

Older version of E0102 ?

Park et al. Astro-ph/0309271

 

 

 

NGC 4449

3900

<0.03”

< 0.6

~ 100

Patnaude and Fesen, ApJ 2003



 

 

Optical Confirmation of E0102 Velocities

In our past work described in Flanagan et al. 2004, we were able to analyze the HETG observation of SNR E0102 to obtain the color-coded-velocity image shown at left. This image gives the velocity of the Ne-X ion emission: red represents motion away from us in the range 500 to 2200 km/s, and green and blue are velocities towards us of order 900 km/s and 1800 km/s, respectively.

In January of 2004 optical (~5000 Å) long-slit spectra were taken for us by astrophysicist You-Hua Chu; these data are plotted at right. The slit ran from lower left to upper right on the color image and corresponds to bottom-to-top on the data at right. The vertical dashed line at about “110” on the x-axis corresponds to rest-frame O III emission; velocities away from us are to the right and velocities towards us are to the left of that dashed line.

Some clear similarities between the X-ray Ne-X and optical O III data are seen. For example, the “blue” region in the X-ray corresponds to the signal bumps seen in the data at Offsets of 4 to 6; the “green” to Offsets of –10 to –7. On the other hand, the optical data shows no or very reduced emission to the right of the dashed line, which should correspond to the “red” emission seen in the X-ray image. This may be an indication of a “dust” plane; see pages 3 and 4 in Dewey’s poster at the HEAD ’04 meeting.


 

E0102 Second Observation: Azimuthal Variations

 

Our second observation of E0102 with the HETG was taken at a different roll angle – with the dispersion direction running roughly North-South. The images at left show the zeroth-order image and the dispersed O VII F,I,R line complex. The indicated rectangular and square regions are in the SE and SW of the remnant.

 

There is a clear variation in the intensity of the emission around the ring and in the dispersed image at far right is appears that the intensity variation is more extreme for the forbidden line (left-most ring image) as opposed to the resonance line. Analysis carried out by Kathy Flanagan on these two regions gives quantitative measure of this effect. The two plots below show allowed values of T and tau for the SW and SE regions. The red curves are derived from the forbidden-to-resonance ratio and the are clearly different for the two regions. This work was presented at the COSPAR meeting in July.

 

 



E0102 in 3D: De-projection of Line Images

 

The dispersed images of E0102 contain much information on both large scales, the amount of emission in each line, and on small scales of the detailed images of the lines. In particular the cross-dispersion profile of lines is very sensitive to the distribution of the emission in space.

 

Assuming the line emission comes from a 3D object of revolution shown at left with a radial variation in intensity, the parameters of the model could be fit to the line data. The result is an intensity distribution which is a function of the actual radius rather than the project-on-the-sky radius.

 

 

 

 

 

Using the values of fits to various lines Kathy Flanagan constructed the plot at right which shows how the model values of T and tau vary with 3D radius (the values next to each data point.) These values indicate that the plasma is hotter and “older” the further out it is in radius. This qualitatively agrees with the idea of the reverse shock moving in toward smaller radii: the inner regions are then “younger” (small tau) and have cooler electron temperatures. (This work was also presented at the COSPAR meeting.)



E0102 in 3D: A Coarse Model

 

Modeling of the E0102 data on a gross or coarse scale was begun using a model consisting of the sum of cylinders of emission from the various ions seen in the data (O VII, O VIII, Ne IX, Ne X, Mg XI, Mg XII, Si XIII) and an outer blastwave component of a spherical shape, e.g., see the images at right.

 

Adjusting the intensity of the cylinders for rough agreement with the data gave a reasonable overall fit to the data. The size of each ions’ cylinder was set based on the measured radii given in Flanagan et al. 2004.

 

 

 

Similarly to the previous 3D fitting, the result gives a de-projected model of the emission as a function of radial coordinate in 3D. These emission values were analyzed to obtain the density of the various ions vs radius as well as the self-consistent local electron density. These density values are plotted at right.

 

For more details see pages 5 to 15 in Dewey’s poster at the HEAD ’04 meeting.

 

 



 

N103B and Type Ia Models

 

We have observed the SNR N103B with the HETG and the dispersed spectra show lines of O, Ne, and Fe. To better put the measured spectrum in context, we’ve been working to calculate model spectra for Type Ia SNR based on model files from Carles Badenes, see Badenes … 2003. The images above show a “true color” Chandra image of N103B (left) and color representations of four of Badenes models (right.) An example of the spectrum calculated from the models is also shown above. The spectrum is shown at both high resolution and smoothed to CCD quality resolution. This and related work will be the focus of an upcoming poster at the XDAP meeting in November 2004 by Dewey and Houck.