Help with Data Challenge 3

Open Data Workshop
1

I am using the tool q_transform from pycbc to transforms the time series signal into a frequency-time plot and I am stuck with the following -

  1. how does changing q values affect the plot or what is the significance of the range of q values? (I tried various q ranges to be able to see the signal in the plot below but I was unable to spot it)
  2. I do not understand how to read the x-axis with the UTC time. For example, in the following plot, if I want to narrow my window to 5.6s - 6.4s, how do I format the outseg argument?
    image (3)
    image (3)1920Ă—1080 418 KB
1 Like
2

Hi! Thank you for your question!

Are you using the q_transform from pycbc or gwpy?

  1. The q-value should correspond to the number of cycles in the LIGO band. You can see some notes in the following places:

quickview app - Click “see notes” under the q-transform plot.

intro tutorials

  1. For pycbc, you could try something like the code below.
    For gwpy, you might look instead at the Quickview notebook 
t0 = 1204
data = pycbc_strain.time_slice(t0-10, t0+10)
times, freqs, power = data.qtransform(.001, logfsteps=100,
                                                qrange=(3, 10),
                                                frange=(10, 1024)
                                         )
plt.figure(figsize=[15, 3])
plt.pcolormesh(times, freqs, power**0.5)
plt.xlim(t0-2, t0+2)
plt.ylim(10,1024)
plt.yscale('log')
plt.clim(0,20)
plt.colorbar()
plt.show()
3

Hi Jonah,
I am using q_transform from gwpy (apologies for the incorrect statement earlier). Thank you for the resources, they were helpful.

4

Hello, for q-transform in challenge I am getting this. Quit a long glitch?

image
image865Ă—476 139 KB

For this data set, how to find starting time for bilby analysis?

5

@Arunan23 Thank you for your questions!

Yes - that looks like a glitch! Probably scattering arches, as described in this paper

For bilby, you want to give bilby a few seconds of data, with the merger time in the center. So - maybe a 4 or 16 second window, with the merger time in the center.