A2327: looking at bursts from brown dwarfs
- a2327- may08:17,18,19.. using wapps.
Looking at TVLM513
- a2414- jun09:7,8,9,10,11,12,13,14,15 using
wapps. Looking at TVLM513
- a2430- dec09; 1,2,3,4,5,6 using mocks.
Looking at 2MASS-J0746
A2327 used the 800 MHz mode of the wapps to
monitor bursts from a brown dwarf. The emission should be 100 %
circularly polarized. The datataking setup was:
- use the wapp spectrometer with 100 MHz bw/band, 3 level
sampling, 2048 channels, full stokes. The data was sampled at 1
- Do a 15 second cal on , 15 second cal off 12 seconds of time
from the source then track the source for 600 seconds. The cycle
took about 667 seconds.
- Input the cal scan, data scan and convert them from cross
correlations to uncorrected stokes.
- Create an rfi mask for the cal using calOn/caloff (this
removes the bandpass). Use corblauto
to excluse channels that are more than 3 sigma from the mean.
- Call the corstokes
to scale to kelvins with the cals and then phase correct the
signal path using the cal data (hi correlated cal). There was no
mueller matrix correction since the matrix we have is out of
- Convert the data from Kelvins to Janskys using the gain curve
- Computing the total power.
- We have and array of 2048 channels by 600 seconds. Use corrms()
along each chan) to make a mask where there is no rfi. Average
the good chanels to get the total power.
For each day 2 sets of plots were made:
- First set of plots. IQUV, vs data sample and frequency band.
- The horizontal axis is data sample (1 second). I have left
out the 67 second gaps between each 10 minute dataset. The
vertical axis is milliJy.
- There are 8 frequency bands with 4 per page.
- The data is plotted I:page1,2 Q:page3,4,U:page5,6,
- Red vertical lines are drawn at the start of each 10 minute
- I data
- The median value for I has been removed.
- The variation is the za dependence of the gain (the SEFD
is higher at large za).
- U,V data
- The 5125 MHz band had a problem with the correlations.
There was a high frequency variation (probably the
interleaving for the 100 MHz). You probably should not
believe what you see in this band.
- 2nd set of plots. Stokes V vs Time at the Bursts.
- Each frequency band has been color coded.
- Each frequency is offset for display. The lowest frequency
is at the bottom, the highest frequency is at the top.
- The horizontal axis is seconds from the first dataset of the
nite. The xtitle shows the utc start data,time and seconds for
midnite for the origin of the x axis (start of first data set
for the night).
- A blue dotted vertical line is where the bursts (and the
opposite sense burst) should occur. The phase and period
was taken from the 4725 MHz data on 17may08 and 18may08 (ast).
The label pulseSecs: xxx,xxx tells when the two pulses
occurred from the start of the nites data.
I'm using positive and negative burst
rather the left and rigtht circular. We need to use the heliax in
the bowl to see which one comes out where in the data
A2327: may08 data (top)
- 7051.3 seconds or 1.958703 Hrs. (using 17may,18may pulse at
- Time between burst and opposite sense burst: 497 seconds.
- Pulse Start Times.
- the file shows the AST start times for the pulses using the
17may08 and 18may08 positive pulse.
A2414 - jun09 (top)
Looked at tvlm513 7,8,9,10,11,12,13,14,15
using the wapps. See setup for a2327 above.
The type of plots were similar to those of a2327. Some newer
- When plotting the entire days i,q,u,v:
- For some day a 2nd polynomial was also fit to each 10 minute
scan. this helped finding pulses and interference. If
any pulses last for a long time it could corrupt them (so the
pulse should be compared to the unfit data).
- When plotting the pulses, the expected pulse arrival time
- This was computed for the entire set of days using the
first pulse of 08,12jun09 (and knowing the approximate period
a2430 - dec09 (top)
a2430 continued a2327 measurements. The mock setup
The sources looked at were:
- 7 x172Mhzx1024 channel Full stokes data
- 1 millisecond sampling. 10 minutes on source, then
calon,caloff (off source).
- Src1: 2MASS0036.. No
bursts were seen
- Src2: 2MASS0746..
bursts were seen on multiple days. Somedays we were unlucky and
the burst occurred during he calOn,off
Plotting the data by day: