Open bilby-bot opened 2 years ago
In GitLab by @git.ligo:colm.talbot on Jan 17, 2022, 20:28
Hi @git.ligo:ecm and Tom, this is interesting to see. I'm not sure exactly where such an example would be best to live, but I agree that it could be very informative.
I have a few minor comments:
IMRPhenomT
is fast and of a similar quality to SEOBNRv4
.In GitLab by @git.ligo:ecm on Jan 19, 2022, 10:28
Hi @git.ligo:colm.talbot
thank you for the quick feedback!
no tapering is done on the waveform here
Tapering is included at template generation stage with SEOBNRv4. This can be checked in figure [14] of our notebook. The orange template is clearly tapered. Actually, the lack of tapering would probably affect the posterior of all parameters, not only geocent_time. So, this seems unlikely to us that tapering is the culprit.
Our question is: what is the time-alignment convention that should be followed by the template in Bilby?
I'm not sure exactly where such an example would be best to live
We were thinking to: https://git.ligo.org/lscsoft/bilby/-/tree/master/examples/gw_examples/injection_examples
Eric and Tom
In GitLab by @git.ligo:ecm on Jan 17, 2022, 17:58
Dear Bilby developers,
together with Tom Colin (intern student), we have put together a Jupyter notebook based on Tuto 3.2 of the ODW 2021 [https://github.com/gw-odw/odw-2021/blob/master/Tutorials/Day_3/Tuto_3.2_Parameter_estimation_for_compact_object_mergers.ipynb] that does a simplified analysis of GW150914 using a time-domain approximant using the same model (SEOBNRv4). Our objective is to get consistent posterior distributions. Here is our notebook:
Notebook
We align the template in time so that it matches well that of the frequency domain approximant. The time alignment code is:
which leaves a small time shift with the time-domain waveform obtained from the frequency-domain generator (using the exact same model). See sanity check in the notebook.
Questions:
We conclude that the time alignment procedure is wrong. We struggle to understand how to align. Could you please give us a hint?
Notes:
For the time-domain approximants, we coded the two following functions (see cell [19]):
def lalsim_SimInspiralTD(...): def _base_lal_cbc_td_waveform(...): def lal_binary_black_hole_td(...):
which are the exact symmetric of the following frequency-domain functions already included Bilby:
def lalsim_SimInspiralFD(...): https://git.ligo.org/lscsoft/bilby/-/blob/master/bilby/gw/utils.py#L735
def _base_lal_cbc_fd_waveform(...): https://git.ligo.org/lscsoft/bilby/-/blob/master/bilby/gw/source.py#L247
def lal_binary_black_hole(...): https://git.ligo.org/lscsoft/bilby/-/blob/master/bilby/gw/source.py#L14
Those could be added to the Bilby code as well.
Best, Eric and Tom