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Re: Flashers
I remind you all that this was first put up as "I see a lot of this
annoying thing, can someone tell me what it is?" I am not making any
claim. I figure this list is like the lunch room at Fermilab. I feel free
to sit down and say "Can anyone explain what I am seeing today?" You come
here at your own risk. If I cause you to do some work with some wild
error, then no one is forcing you. You are free to stay away.
Now that the first few simple explanations don't seem to work it is time
for some real data.
At 02:41 PM 5/18/03 -0700, you wrote:
>The lack of reasonable explanations is probably due to lack of
>reasonable description.
It seems the nature of this medium that everything that is posted is not
always read. So one has to repeat it several times. Also due to this
being a mail list, it is assumed that those that read it know what is going
on. This is not a publication that stands alone. I assumed that everyone
reading here knew that the tass cameras take simultaneous V, Ic
images. Further, I assumed that everyone knew that we require
simultaneous V, Ic detections for a star measurement to make it to the
output file. Not good assumptions, it turns out. ;^(
OK, I realize that one is suspicious of the original images. For various
reasons, it will take me some time to dig them out. It is true, we are
looking at what comes out of the end of a pipeline, and there may be
something in the software that produces these bumps. However, I have
looked at a lot of images and we are doing things to reject the crummy
images. As you shall see, I have looked at the data around the
images. There may be some grand common cause, but I have not figured it
out yet. As the six out of 18 statistic below indicates, there are enough
of these to be annoying.
First some background:
I am looking at a data set that contains 9,709,345 V, Ic measurement pairs
of 1,851,566 stars. Most of the measurements were taken between -6 and +18
degrees declination. The Mark IV camera is turned on at dusk and scans
from -4 (center of field) to +16 in six fields. It then returns to -4 and
repeats the process through the night. This covers all the sky that
crosses the meridian from -6 to +18 with one measurement pair a
night. There is some overlap of the fields so it is possible that a star
will be measured as many as 4 times a night. This rarely happens, though
quite a few get measured twice an evening at slightly different times. The
data spans about 100 days of observation.
The data was processed by the Michael Richmond pipeline version TARP
1.0. One can get more than you want to know about this at the tass web
site. I think Michael will be the last to claim that all 62,065 lines of
code are perfect. But that is what I am trying to do these days. Look at
the result and question anything funny.
As a first look, I have selected the 18 stars with WS statistic > 1000. 10
of these were previously presented and all turned out to be known
variables. Two others are also probably in this category. There are six
that show "flashes". That is they show one or more measurements which are
brighter than the others.
The first of the six has one bright point. It happens to be the first on
the list below though it was one of the last in time for this star. You
will note a slightly different position. This is about a pixel on the Mark
IV which has 7.5 arc second pixels. This could be explained by some shift
in the position computation with brightness. Pixels should not be
saturated at mag 9. The bright point is of order 2 mag brighter. One
sigma for all the data is more like 0.1 mag at this magnitude.
For these data, the first number is a sequential star number for the
processing run. Mostly the run is sorted by RA. Next is the number of
measurements for this star. Then RA and dec in decimal degrees,
date/fractional_day, V, vmag, v_err, v_flags, I, ... See the pipeline
documentation on the web site for details.
783941 19 129.3065 11.7692 2452679.73662 V 9.896 0.004 0 I 9.102
0.002 0
783941 19 129.3081 11.7724 2452609.92696 V 11.644 0.014 0 I 10.946
0.007 0
783941 19 129.3082 11.7718 2452618.90236 V 11.585 0.010 0 I 10.965
0.005 0
783941 19 129.3082 11.7716 2452614.91324 V 11.645 0.010 0 I 10.969
0.005 0
783941 19 129.3082 11.7716 2452615.91063 V 11.552 0.011 0 I 10.958
0.005 0
783941 19 129.3083 11.7715 2452683.72567 V 11.674 0.011 0 I 10.989
0.005 0
783941 19 129.3083 11.7718 2452619.89993 V 11.611 0.010 0 I 11.000
0.005 0
783941 19 129.3083 11.7716 2452654.80499 V 11.702 0.012 0 I 11.010
0.005 0
783941 19 129.3083 11.7714 2452651.81306 V 11.684 0.011 0 I 11.009
0.005 0
783941 19 129.3084 11.7721 2452617.90528 V 11.625 0.010 0 I 10.984
0.005 0
783941 19 129.3084 11.7716 2452624.88652 V 11.607 0.011 0 I 10.990
0.005 0
783941 19 129.3084 11.7720 2452616.90789 V 11.639 0.010 0 I 10.983
0.005 0
783941 19 129.3085 11.7721 2452678.73941 V 11.656 0.011 0 I 10.978
0.005 0
783941 19 129.3085 11.7718 2452643.83490 V 11.570 0.011 0 I 10.957
0.005 0
783941 19 129.3086 11.7720 2452662.78314 V 11.662 0.012 0 I 10.940
0.005 0
783941 19 129.3086 11.7719 2452690.70657 V 11.611 0.011 0 I 10.971
0.005 0
783941 19 129.3086 11.7717 2452648.82126 V 11.632 0.011 0 I 10.968
0.005 0
783941 19 129.3087 11.7717 2452666.77211 V 11.766 0.013 0 I 10.981
0.005 0
783941 19 129.3087 11.7719 2452647.82429 V 11.593 0.011 0 I 10.993 0.006 0
For comparison I paged down the processed list until I found a star close
to the star above and with a similar number of measurements and similar
brightness. The data is below. You will note that there is a measurement
of this nearby star at the same time as the flasher above. It is not
significantly different from the other measurements for this star. It is
in the same image and at near the same RA and a degree away in
declination. There appears to be nothing funny common to all the data on
this day/time.
783955 18 129.3085 12.3744 2452643.83490 V 12.211 0.017 0 I 11.338
0.007 0
783955 18 129.3086 12.3738 2452624.88652 V 12.169 0.016 0 I 11.339
0.006 0
783955 18 129.3088 12.3744 2452654.80499 V 12.112 0.015 0 I 11.356
0.007 0
783955 18 129.3088 12.3723 2452666.77211 V 12.398 0.021 0 I 11.351
0.007 0
783955 18 129.3088 12.3735 2452662.78314 V 12.235 0.017 0 I 11.347
0.007 0
783955 18 129.3088 12.3734 2452678.73941 V 12.236 0.016 0 I 11.366
0.007 0
783955 18 129.3088 12.3733 2452679.73662 V 12.338 0.018 0 I 11.379
0.007 0
783955 18 129.3088 12.3732 2452619.89993 V 12.189 0.014 0 I 11.346
0.006 0
783955 18 129.3089 12.3739 2452647.82429 V 12.278 0.018 0 I 11.374
0.007 0
783955 18 129.3089 12.3739 2452618.90236 V 12.101 0.015 0 I 11.319
0.006 0
783955 18 129.3090 12.3737 2452648.82126 V 12.241 0.017 0 I 11.359
0.007 0
783955 18 129.3091 12.3736 2452651.81306 V 12.329 0.017 0 I 11.395
0.006 0
783955 18 129.3091 12.3740 2452616.90789 V 12.126 0.014 0 I 11.353
0.006 0
783955 18 129.3092 12.3741 2452609.92696 V 12.259 0.021 0 I 11.253
0.007 0
783955 18 129.3092 12.3733 2452683.72567 V 12.340 0.018 0 I 11.419
0.007 0
783955 18 129.3093 12.3730 2452690.70657 V 12.200 0.017 0 I 11.343
0.007 0
783955 18 129.3098 12.3750 2452614.91324 V 12.291 0.016 0 I 11.364
0.006 0
783955 18 129.3101 12.3729 2452615.91063 V 12.253 0.018 0 I 11.337
0.006 0
The last of the six has two high points. For this star position of the
bright points seem to be within the error in comparison to the other
positions. Again the points happen to come first on the list but vary
through time as a plot will show. Sorry, you will have to plot these to
see them.
960657 12 168.0465 2.7291 2452678.84684 V 11.016 0.009 0 I 10.243 0.004 0
960657 12 168.0469 2.7276 2452648.92867 V 10.649 0.008 0 I 9.840 0.004 0
960657 12 168.0470 2.7303 2452740.67971 V 11.923 0.013 0 I 11.128 0.006 0
960657 12 168.0471 2.7293 2452763.61215 V 11.791 0.013 0 I 11.335 0.006 0
960657 12 168.0471 2.7293 2452690.81400 V 11.917 0.014 0 I 11.165 0.006 0
960657 12 168.0472 2.7296 2452654.91238 V 11.805 0.012 0 I 11.310 0.006 0
960657 12 168.0473 2.7297 2452651.92051 V 11.802 0.012 0 I 11.129 0.005 0
960657 12 168.0475 2.7300 2452677.84950 V 11.984 0.014 0 I 11.179 0.006 0
960657 12 168.0475 2.7295 2452762.61029 V 11.995 0.014 0 I 11.267 0.007 0
960657 12 168.0477 2.7298 2452647.93183 V 12.009 0.014 0 I 11.196 0.006 0
960657 12 168.0478 2.7295 2452620.00721 V 11.878 0.012 0 I 11.231 0.006 0
960657 12 168.0478 2.7288 2452739.67689 V 11.795 0.015 0 I 11.043 0.006 0
This time the next star on the list was comparable. I notice that it
contains points taken on the same day as the pulser above, but at different
time, so they appear to be in different images. This means that the bright
points are in the overlap region between two images.
960658 14 168.0471 1.6509 2452648.92698 V 12.650 0.023 0 I 11.916 0.009 0
960658 14 168.0474 1.6509 2452763.61046 V 12.497 0.021 0 I 11.934 0.009 0
960658 14 168.0475 1.6501 2452677.84781 V 12.388 0.019 0 I 11.796 0.009 0
960658 14 168.0475 1.6513 2452643.94062 V 12.459 0.021 0 I 11.859 0.009 0
960658 14 168.0476 1.6511 2452654.91068 V 12.536 0.020 0 I 11.871 0.008 0
960658 14 168.0477 1.6512 2452755.63427 V 12.463 0.023 0 I 11.826 0.009 0
960658 14 168.0479 1.6508 2452762.60860 V 12.536 0.021 0 I 11.839 0.010 0
960658 14 168.0479 1.6514 2452651.91881 V 12.554 0.020 0 I 11.861 0.009 0
960658 14 168.0480 1.6504 2452690.81231 V 12.536 0.021 0 I 11.859 0.009 0
960658 14 168.0480 1.6510 2452678.84514 V 12.549 0.021 0 I 11.873 0.009 0
960658 14 168.0481 1.6514 2452679.84233 V 12.402 0.020 0 I 11.873 0.009 0
960658 14 168.0484 1.6515 2452647.93013 V 12.560 0.021 0 I 11.860 0.009 0
960658 14 168.0486 1.6502 2452620.00539 V 12.459 0.018 0 I 11.867 0.008 0
960658 14 168.0491 1.6497 2452666.87784 V 12.719 0.033 0 I 11.930 0.011 0
OK, any comments? Yes, I know, more data is needed. More data is always
needed. ;^) I am looking at a lot of this stuff. There is no good way to
transfer it to you until I can get it into shape to put on Mike Sallman's
data base. But I want to find problems first, that is why I am making
these posts.
Tom Droege