The two fits plotted over each other look like this:



Still attempting to figure out how to plot y error bars....

For 0931, one off-chip source located at 143.04074, 36.50115, had a high x-ray flux, so we took a closer look at it. We are investigating to see if it falls under the category of an XBONG.

Our source is slightly extended (I'm trying to extract a radial profile, but am having trouble with the syntax in bash..) It's chandra counts in the 0.5-2.0keV range were 165, and in the 5-10keV range were 65 (230 over the whole range). It has a redshift of z=0.15, and when assuming a powerlaw dependence and a photon index of 1.9 (characteristic of x-bongs, for which gamma ranges between 1.6-2.4, this leads to an x-ray luminosity of approx. 2.2e43 erg/s.

The source has a ROSAT counterpart cataloged, with a countrate of 4.78e-2+/-1.38, which using WEBPIMMS for ROSAT PSPC, leads to a luminosity of 2.075*10^43erg/s.

We decided to extract spectra from the chandra source, using the ciao routine specextract.

I attempted to fit the spectra based on the discussion of similar sources by Civano et al. 2007, in which they fit a mekal model with the lower energies of the spectra, and then a powerlaw for the higher energies. I as of yet haven't figured out how to fit different source models in different regimes, but here is an image of the data in the 0.5-10.0keV range fit first with the xsmekal source model, parametrized only by the redshift and with "switch"=0, and with an absorbed powerlaw, with gamma=1.6 and nH of 0.0142e-22.

The mekal fit looks as follows (unsure of why it appears to fall off and not intersect the high energy data points, I think this is something weird that happens from the log_scale command..)


And the powerlaw:


The statistics from these fits over the 0.5-10keV range are as follows:
mekal, rstat = 0.632163888096
powlaw, rstat = 0.619105037196

The next step is to get the y errors, and overplot or consolidate in one plot the two fits, which I have had no luck with so far...

The colors of the sources close to the SNR are:

275.23312 -14.32476 (the further source)
IR:

closest source was 2.039001" away , at RA: 275.233684, DEC: -14.324909, with theses colors: j_mag:12.093, h_m: 11.612, k_mag: 11.402, and j-h=0.4810, h-k=0.2100, j-k=0.6910
errors were: j_msigcom:0.023, j_snr:323.8, h_msigcom:0.028, h_snr: 94.2,k_msigcom: 0.030, k_snr: 91.3- snr's are insanely high, unfortunately, not sure if this debunks any of this....
FLAGS: ph_qual: AAA, rd_flg:222, bl_flg: 111, cc_flg:000

optical:
closest source was 2.052775", at RA: 275.233659, DEC:-14.324989, with these colors, b1_mag: 15.48, r1_mag: 13.54,
errors: e_ra: 82, e_dec:69, there were no flags


For 275.23763 -14.33405 (the source closer, to the right side of the snr flux peak),
In the IR:

There were two sources found within a radius of 5"
The closest was 1.079200" away, RA: 275.237796, DEC: -14.334303, with these colors: j_mag:16.008, h_m: 14.235, k_mag: 12.635, j-h=1.7730, h-k=1.600, j-k=3.37300
errors were: j_msigcom:0.096, j_snr:8.8, h_msigcom:0.075, h_snr: 8.4, k_msigcom: null, k_snr: null
FLAGS: ph_qual: BBU, rd_flg:220, bl_flg: 110, cc_flg:0c0

No optical counterpart

At the SNR peak, 275.24215 -14.33351, though no IR counterpart, there was an optical counterpart, with these properties:
b1_mag: null, r1_mag:18.83,
errors: e_ra: 10, e_dec:999, no flags.

Got the positions of the outlying sources for G16.7.
Compared the positions of the sources on the central chip with 2mass. Of the 9 sources detected on the chip, 7 had possible matches in the IR within 5 arcseconds; they all had possible matches within 9 arcseconds.

Outlined visually the positions of the chandra sources for 0931 and 1532, centered on the RASS source position, with the correct log(fx/fopt), and the offsets calculated from the RASS source.

It seems that in both cases the ROSAT source was probably not detected. The sources located closest to the expected RASS position are discussed below:

For 0931:
The RASS position is 142.829998,36.3730554
The WD position is 142.84526595, 36.36928494
RASS-WD offset: .7760754592'

The closest source to the RASS source position is located at 142.8057, 36.378942, at a distance of 1.2219', and a distance of 1.997426' from the WD. It has a u magnitude of 22.57+/-0.53, a g magnitude of 21.89+/-0.10, and thus a u-g value of .68, or with errors, between .25-1.11. It's log(f_x/f_opt)=.873428. Though it is the closest source detected, and perhaps at a plausible distance, it seems unlikely that it is in fact the ROSAT source because its chandra count rate of 5.8e-3, is much lower than the predicted chandra count rate of the RASS source, of 3.678e-2-1.559e-1.
The SDSS match to the chandra source, J093113.37+362244.0, objid: 587735240642789732, was offset from the chandra source position by 0.17028447"

For 1532,
The RASS position is 233.098415 47.446660
WD position is 233.10621952, 47.45025013
WD-RASS offset: 0.3829797676'

The closest source to the RASS position was at 233.1842, 47.401489, a distance of 4.412', and 4.3119980'away from the WD. It's u magnitude is 21.97+/-0.20, it's g magnitude was 21.03+/-0.03, and thus the u-g was .94, or somewhere in .77-1.11 when accounting for errors. The log(f_x/f_opt)=0.84207. It seems an unlikley RASS counterpart not only because of it's large distance, but also because its chandra count rate of 1.67e-2 was less than the predicted flux of the RASS source, 2.956e-2-1.092e-1.
Its optical counterpart, J153244.22+472405.2, objld: 587733442656731241, was offset from the chandra source by .17425710".

It looks to me as though, due to the difference in fluxes and pretty high positional offsets, that for both 0931 and 1532, the RASS source was not detected with chandra, even when recalculating the expected counts accounting for RASS errors in counts.


For 0931+3622 and 1532+4724

Compiled a visual of the chandra sources relative to the WD, with offset, u-g values, log(f_x/f_opt) [log(f_x/f_opt)=f_x+m_v/2.5+5.47, cts, and expected count range.

Got estimates for counts from Webpimms again, this time accounting for the uncertainty in ROSAT counts. Results were as follows:

0931: n_H=1.42E+20 (.009-.025cps)
0.9e-2cps:
.06KeV: I-2.106e-3
S-3.678e-2
.1KeV: I-1.151e-2
S-5.611e-2

2.5e-2cps:
.06KeV: I-5.850e-3
S-1.022e-1
.1KeV: I-3.198e-2
S-1.559e-1

So counts should be in a range for the I array of (2.106e-3 - 3.198e-2) and for S array of (3.678e-2 - 1.559e-1)

1532: n_H=1.7 (.007-.017cps)

0.7e-2:
.06KeV: I-1.831e-3
S-2.956e-3
.1KeV: I-9.543e-3
S-4.496e-2
1.7e-2cps:
.06KeV: I-4.447e-3
S-7.179e-2
.1KeV: I-2.318e-3
S-1.092e-1

So for the I array the cps should be within (1.831e-3 - 2.318e-3) and for the S array within (2.956e-3 - 1.092e-1)

275.23312 -14.32476.



With USNO B1.0 with gator;
Distance: 2.052775"
RA: 275.233659, DEC:-14.324989, e_ra: 82, e_dec:69, b1_mag: 15.48, r1_mag: 13.54, no flags.

With USNO B1.0 with "Integrated Image and Catalog Archive Service"



With USNO A2.0:



Visual from DSS survey:


With 2Mass with Gator:
One source was found within 5" of the chandra source, at a distance of 2.039001:
RA: 275.233684, DEC: -14.324909, err_maj: 0.06, err_min: 0.06, err-ang: 90, j_mag:12.093, j_msigcom:0.023, j_snr:323.8, h_m: 11.612, h_msigcom:0.028, h_snr: 94.2, k_mag: 11.402, k_msigcom: 0.030, k_snr: 91.3, FLAGS: ph_qual: AAA, rd_flg:222, bl_flg: 111, cc_flg:000, j-h=0.4810, h-k=0.2100, j-k=0.6910

I think there is defiantly evidence of a matching source in the optical and infrared here, so not the pulsar...

275.23763 -14.33405:



USNO B1.0 with Gator:
No sources were found within 5".

USNO B1.0 with "Integrated Image and Catalog Archive Service":
again, just for the visual, not much info here:


border="0" alt=""id="BLOGGER_PHOTO_ID_5239658620774324546" />

USNO A2.0 with same archive as above:



With DSS (just visual, no information)



2Mass with Gator:
2 sources were found within 5":
The closest was at a distance of 1.079200
RA: 275.237796, DEC: -14.334303, err_maj: 0.08, err_min: 0.08, err-ang: 90, j_mag:16.008, j_msigcom:0.096, j_snr:8.8, h_m: 14.235, h_msigcom:0.075, h_snr: 8.4, k_mag: 12.635, k_msigcom: null, k_snr:null, FLAGS: ph_qual: BBU, rd_flg:220, bl_flg: 110, cc_flg:0c0, j-h=1.7730, h-k=--, j-k=--

The farther was a distance of 3.970672
RA: 275.237272, DEC: -14.333003, err_maj: 0.07, err_min: 0.06, err-ang: 4, j_mag:15.931, j_msigcom:0.094, j_snr:9.4, h_m: 13.073, h_msigcom:0.064, h_snr: 24.5, k_mag: 11.663, k_msigcom: 0.043, k_snr:71.8, FLAGS: ph_qual: BAA, rd_flg: 222, bl_flg: 111, cc_flg:ccc, j-h=2.8580, h-k=1.4100, j-k=4.2680

There seems consistently to be no source matching the chandra source in the optical surveys for this source (unfortunately, that would be convenient). I'm not sure what to make of the infrared sources, if they are in fact supportive of the pulsar being located here, even if not visible in the optical..?

275.24215 -14.33351 peak of extended source
275.23763 -14.33405 right side source
275.23312 -14.32476 above right source

There are many more, but these are the closest to the SNR

Starting with the peak of the extended SNR source, here's the result from several surveys (These are not as fun as SDSS)

275.24215 -14.33351:

So the positions of the sources nearest the SNR are:

USNO B1.0 with Gator:
At the position of the SNR, 275.24215 -14.33351, one source found within 5":
Distance: 3.711696"
RA: 274.241739, DEC:-14.332559, e_ra: 10, e_dec:999, b1_mag: null, r1_mag:18.83, no flags.

USNO B1.0 with "Integrated Image and Catalog Archive Service, the interface is pretty hard to make any certain conclusions from:




USNO A1.0 with the same "Integrated Image and Catalog Archive Service"



DSS seems to be pretty simple, but as the fields are dense, and the sources are close together, just looking at the results aren't too illuminative:
These are the images returned, in order of the positions listed above(the peak of the SNR flux, the source to the right, and the source above and to the right):




This so far is the best DSS query I can find- there is one on the MAST website, but it is not finding any results for the given positions in it's cross correlation query...
Just from looking at these, it seems a pretty good match for the source above at 275.23312, -14.32476, though I can't say much regarding the other two (it would have been nice to have a bright optical source associated with the xray source to the immediate right of the SNR..) Will keep trying to see if there is a better way to compare to DSS.


2Mass with Gator: no sources found within a five" radius.

This is slightly unsatisfying, as the optical catalogs don't agree conclusively. It appears that there is a possible match in the USNO B1.0 survey, but not so in A2.0.
Also, there could be a match in DSS, but it's hard to say, as it is only a picture.
At least we cannot conclusively say there ISN'T a match, unfortunately.

For G16.7, not sure what energy range I should be looking at, I am starting with .5-8 KeV for the exercise...

Tried detection methods,vtpdetect and wavdetect (as well as celldetect), on the data near the SNR to see if the detection was more accurate due to the extended nature of the source. Both methods over counted the number of sources, calling large regions "sources" that visually didn't look to be, and not defining regions of that were obviously sources. Decided to find peaks flux by hand, several ways, first smoothing the data with a Gaussian to find center. I called the peaks of flux the locations of the sources on the chip on which the SNR was detected, to compare to other catalogs.

Is it ok to just stick to the sources closer to the pointing acis? there are many other sources on the outer chips but I thought that these aren't candidates for the neutron star, or anything related to this system.

Extracted positions of sources on the chip and am in the process of comparing them to other catalogs

For 1532, (233.1062, 4745025)

At the position 233.18429 47.401489, which was closest in proximity to the expected position and the closest in flux to the Pimms estimate (though as discussed below, still much lower than the estimate) the corresponding image looks like this:


it's type is classified as a star, it's u value is 21.97 and it's g value is 21.03.
(u-g=.94)
The other chandra source, located at 232.95798 47.3968, has the following SDSS counterpart:

classified as a star and with u=22.33 and g=21.66.
(u-g=.67)
The first seems like the most probable match, not sure if the discrepencies in the flux between the Pimms estimate of the RASS flux for chandra are large enough to conclude these sources aren't matches (for both 0931 and 1532, the counts are ~an order of magnitude in difference)

Looked at the positions of the chandra sources in SDSS. The results for 0932+027 are:


143.0399 36.50026: This is the image of the source that matched the flux estimate from RASS,however it is classified as a galaxy in SDSS- not sure how accurate that is, but I'm guessing that means we are looking at a galaxy. Its spectra looks like:



It's u=19.19 and g=17.72-
(We have log fx/fv = log fx + mv/2.5 + 5.47, but what exactly should I do as we only have u and g, also, does the median log(fx/fg) (-0.23) and 2sigma (-1.72 to +1.26) range derived from the DA set apply to DB's, or are these two DB's the way that this will be tested...?... also do )
(u-g=1.47)
(also, looks as though these are absorption lines to me, wouldn't a QSO be showing emission lines?)

Also this has already been cataloged, cross identified with ROSAT, with values of cps 0.04776 and HR1=-.61 and HR2 as -1. This is ~3 times the RASS count rate associated with our source, so again it appears to not to be the little guy.

The next image is at 142.80575 36.378942, closest in proximity to the given position of the WD, which I initially thought was a less probable candidate for a match because of it's low flux compared to the PIMMs estimate (see below), but now I'm not sure...


It is also identified as a GALAXY, with no spectroscopic information, and a u value of 22.57 and a g value of 21.89, u-g=.68 (again not sure how accurate the type specification is, not what we exactly I am expection to see for u-g).... If it is a galaxy, it is probably not a DB white dwarf (deep thoughts).

The next proximate match after these two is at 142.67369 36.56530948, and looks like this:

Also catogorized as a GALAXY, u=19.44 g=19.08, u-g=.36. Specta looked as follows:

I'm not quite sure what conclusions to draw from looking at spectra, looks like emission lines, which would also indicate a QSO- I know we are looking for a black body with lines indicating helium, but I'm not sure if these spectra are normalized in some way (this is probably very obvious but I'm not very used to interpreting spectra...) Also, this is kindof irrelevent if this is a galaxy, again.

The last two chandra sources didn't see any objects within 2 arcseconds, and manually looking around the area, the closest sources were catogorized as galaxies.....

Messed with parameters of celldetect and dmextract, region shapes, single and multiple chip exposure maps, to see if I could get closer results for the two threads; still pretty big discrepancies between the two.

Made table to see the general difference between results from celldetect and dmextract, as compared to each sources distance off the pointing axis of the observation. Values in table were position, counts (in the .5-8KeV range), error in counts, exposure time, flux (counts/exposure time- approximation), Del_counts (dmextract-celldetect results), Del_Pointing i.e.{[(RA1-RA2)*3600*cos(DEC1)]^2+[(DEC1-DEC2)*3600]^2}^(1/2)

Though the sample set too small to see if there is a direct correlation, it looked as though generally counts were more alike closer to pointing axis.

Compared these fluxes (which as expected differ somewhat depending on the extraction method) to Webpimms estimates based on ROSAT count rates.

Pimms estimates were as follows (temperature range between .06-.1KeV, as calculated in "The Coolest X-Ray Emitting White Dwarfs"):

0931: n_H=1.42e20, .017 cps ROSAT, temp=.1keV:
ACIS I= 2.175e-2 cps
ACIS S= 1.06e-1 cps
0.06KeV:
ACIS I=3.978e-3 cps
ACIS S=6.946e-2 cps

1532: n_H=1.7e20, .012 cps ROSAT, temp=.1keV:
ACIS I= 1.636e-2 cps
ACISS= 7.707e-2 cps
0.06KeV:
ACIS I=3.139e-3 cps
ACIS S=5.068e-2 cps

For 0931 (located at 142.8454132 36.3692741), the closest match to this estimated flux was at 143.03993 36.500260. This source is on the ACIS I array and has a flux of approximately 2.8e-2 cps (cdetect) or 4.04e-2 cps (dmextract). The closest source to the expected position of the WD was at 142.80575 36.378942; this is on the ACIS S array and it's flux (approx 5.1e-3 or 5.8e-3) is an order of magnitude lower than the estimated chandra flux, so it seems more probable to me that the former is the more probable source (not sure if that is an ok assumption- is the astrometry good enough that proximity is more indicative of possible matching.....?)

For 1532 (located at 233.1062 47.45025) both sources detected were found on the ACIS S array; the closest both in flux and position to estimates was one at 233.18429 47.401489 with a flux of approx. 9.396e-3 (cd) or 1.167e-2 (dme) cps, so if in fact one of these is a match, it seems like the most probable of the two.

These estimates were based on my assumption that the ROSAT data was taken with the HRI. Were it with the PSPC, with the same other parameters, the estimates would be:

0931: ACIS I- 5.108E-03 cps
ACIS S- 2.489E-02 cps

1532: ACIS I- 3.998E-03 cps
ACIS S- 1.883E-02 cps

I'm in the process of comparing these sources with SDSS using image list and cross ID, to see if there are matches.

Also retrieved and played around a bit in ds9 with G16.7. Next steps are to get counts, try by hand and with celldetect or wavedetect (extended source), make exposure map, play with gator and other matching catalog exercises...

-Ran the other detection methods on the dataset:
vtpdetect found many spurious sources and was defining large areas as sources, which could be expected as it is geared for very faint and extended sources
-wavdetect- takes much longer and creates larger files, so it's easier to crop field and choose a chip to centralize the cluster core, which- counts found are much lower than the same source's counterpart using the other detection methods; also not ideal because it requires the input of parameters like wavelet length and false source detection rates, the best values for which I am not sure of.... also geared towards closely spaced and extended sources, which ours aren't for the most part.

Went back to try to make celldetect work, and I realized that the sources that I believed to be spurious were in fact valid, for the most part. Viewing in Ds9 was cropping the field and centralizing on one ccd chip, creating white space at the edges though the field continued.
Readjusting binning and resolution parameters allows for the entire array to be viewed.

This is good news for me because it seems to be the best suited detection method. However, using the other methods, I've noticed a pretty severe discrepancy in net counts for corresponding sources, which worries me about the validity of the counts. Also the count rate, NET_RATE, and exposure time, EXP_TIME data model outputs are not yet implemented in the celldetect version and are just arrays of zeros.
To find count rate, I went back and manually (using dmextract) extracted the net counts and exposure times to find the count rate. As the net counts found with dmextract and celldetect were different enough, I think this may be a pretty inaccurate way to do this. (for the possible matching source, net counts found manually were 62.5, whereas with celldetect 48.5). The exposure time with this method was 5102.559, and thus the count rate was 1.23*10^-2.

Because of this, finding the minimum count rate that we could expect to detect (to know if perhaps the source is present, with a flux too low to be detected) is proving variable based on detection method. For celldetect with a 3 sigma, the default seemingly the best value, the lowest rate is around 5.037e-3. Our two sources should theoretically be detectable, as their count rates are: 0931+3622 (1.5-2.5 *10^-2) and 1532+4727 (.9-1.9*10^-2). I computed this value using the full energy range (.5-8KeV) I am working on the minimum count rate for a much softer range (.1-1 Kev)
(should I be looking as low as .06-.1 KeV?- was the energy range given in "The Coolest X-Ray Emitting WD's" This seems very soft...?)
For our two sources, it still looks as though only 153225.49+472700.9 could match a source anywhere near it's supposed position- I haven't yet computed it's theoretical xray count rate.. will do that in the morning.....

Whoops...... by ***** I mean ~1.1Kev . It is found by extracting a spectrum in energy space of the region around the source and finding the peak energy from a histogram of count rate as a function of energy using dmextract... Not sure how valid this is because the short exposure and low counts of our data may not contain much useful spectrum info...

(Tying to) build an exposure map (converting the counts image into an image in flux units for chips 2,3,5,6,7,8 of j0931+3622, in our case, which supposedly helps account for dither motion, especially near the edge of the detector) in several steps- using "asphist" function and the asol1.fits file to compute aspect histograms and map aspect information during the event; then using "mkinstmap" and the msk1.fits and pkb0.fits files to make an instrument map during the event (for simplicity assuming a monoenergetic distribution of source photons at an energy level or ***** found from using dmextract to make a histogram of count-rate as a function of energy, not sure if this is an ok assumption...), then with mkexpmap and aspect info, projecting the instrument map onto the sky....

first had to learn basic for loops in the bash shell. The basic syntax is:

for var in list

do;

commands;

done

In the process of doing this I have found the Calibration Database is not properly accessible, so I am currently (and slowly, stupid internet) attempting to download and reinstall it to continue..
Not sure if having an exposure map will even help because I'm not sure if dithering edge effects are what are causing spurious detection, but thought I would try to go through the process...

Found position and fluxes for J093_3622 and J1532+4727:

8916: J093+3622

RA DEC NET_COUNTS

142.8321 36.3673    26.3125

142.8057 36.3789   25.750

8917: J1532+4727

RA DEC NET_COUNTS

233.1843 47.4015   48.557

we can now compare to optical data of these events.

Looking into issue of off-field spurious events- think it may be due to the recursive blocking nature of celldetect but I'm not sure. Trying to fix the cell parameter to see if that helps. So far little luck- the parameter must be 1 or a multiple of 3: 1 doesn't find both events (and counts the same event twice, offset by one pixel), 3 still comes up with 6 spurious events, 9 makes 11 spurious events, etc. Attempting to fix a cell and then vary the S/N threshold not particularly successful either. So probably not an effective solution. Trying to build an exposure map as it is supposed to help with edge effects...

Compiled table for the isolated neutron star data, comparing results in the standard, soft, and hard x-ray regimes from visually identifying events and getting counts with dmextract, and using celldetect. Events are mostly much stronger in the softer xrays, and only are detected once (6701) in the hard xray. 

 Generally celldetect corresponded well with visual results, and the counts extracted with dmextract, with a few deviations: in the standard and soft xray regimes of 6696, 6701, 6703, 6705 (I'm not sure offhand which event these folders correspond to, I will check) there appeared events (with relatively lower counts) that weren't detected with the thread. 

Playing around with some of the parameters of celldetect, namely in for this case the signal to noise threshold from the default value of 3 to 2, has more success- however I'm concerned that this would introduce more invalid source detection from the hot pixel cosmic ray issues;

will look more into those issues, and how present these errors may be- superficial reading of the help manual makes me think that the standard data processing that has already been applied would be sufficient.. 

Also found that celldetect in a few instances returned "events" whose positions were off the data's field. Confirmed that celldetect returns these same positions a second time. Not sure what that is about..

created corrected energy level files for the chandra data, played around with those. Estimated fluxes and positions with dmextract, played with region types, tried running celldetect and compared results. 

Continuing to attempt proper installation of Ciao. Reinstalled one million times- installs fine without the "tools" binary, which includes all the necessary data modeling tools- when installing with the "tools" binary, testing ciao returns the error "cannot execute binary." Confused.

read about imaging functions; attempted to use some (i.e. dmcopy, dmextract etc.), but got error "dmcopy: command not found." uninstalled and reinstalled ciao...

started table of counts and positions of events, went through primary data from the isolated neutron star data. continued reading about science threads.

copied isolated neutron star data, looked at some of the fits files with ds9 to get preliminary fluxes and positions

researched some of the ciao data reduction and analysis threads

began to install calibration software library, ran out of disc space

read about the different background effects on ACIS data

looked at some of the chandra fits files with ds9

Installed (successfully I hope) the binaries for ciao

played around with aliases

licensed IDL

updated Xcode, emacs

June 23rd, 2008

messed around with software packages