Doubt related to polarization analysis

[Rafaely15]

Dear author,
I have two questions.

1. Is it possible to perform polarization analysis (stokes Q, stokes U, stokes V) in the .xml file itself? If so, do you have an example?

2. When I started trying to perform the analysis in Python, I couldn't retrieve the generic metrics created in the \pluggins folder. Is there any way to retrieve them and raytrace them?

I created a bumblebee metric, and my xml is given by, See attachment.

My XML is 0.xml, my metrics file is .bumblebeekerr.C and mypagethorneBB.C.

I tried to implement and analyze it using the Python notebook you provided as an example, but it only shows orange. Perhaps I didn't fully understand how it should be used.

bumblebee_disk.zip

polarizacao_bumblebee.ipynb

I'm sorry for bothering you so much.

I look forward to hearing from you, thank you.

[paumard]

Dear Ana, thanks for your message. First answering your first question: we have just added a new example file with polarization. Just request the Stokes parameters in <Quantities/>:

<Quantities>Spectrum SpectrumStokesQ SpectrumStokesU SpectrumStokesV</Quantities>

The FITS file will contain a cube with the requested Stokes parameters. The order is which they are stored is written in the FITS header.

[paumard]

Concerning the second issue, I cannot really test your plug-in as the include and lib directories are empty in you zip file.

To load a plugin, you can list it in the GYOTO_PLUGINS environment variable or you can load it with gyoto.core.requirePlugin().

When loading a plugin you can give the fully qualified path to the file: gyoto.core.requirePlugin("/path/to/libgyoto-myplugin.so"). Maybe the easiest for your case.

Else you can load it with only the plugin name: gyoto.core.requirePlugin("myplugin") in which case Gyoto will first try to let the operating system's runtime linker find it for you (i.e. add the directory to your LD_LIBRARY_PATH environment variable) and if that fails will try to load it from a few predertermined (at compilation time time) places. Those places are displayed when you run:
gyoto.core.listRegister()

Cheers

[Rafaely15]

I'm sorry, I thought I had put everything correctly. I'll send you the correct format.

When I add the line you mentioned, some errors appear that I can't yet identify how to solve. Could you help me?

The XML file I'm testing the simulation on is named "testpolarizacao.xml."

I've attached the revised files.

The error that appears is:

anarafaely@speed-Precision-7960-Tower:~/Gyoto/plugins/bumblebee_disk$ gyoto testpolarizacao.xml testpolarizacao5.fits
WARNING: unable to load optional plug-in libgyoto-lorene.so
Reading parameter file: testpolarizacao.xml
Copyright (c) 2011-2019 Frédéric Vincent, Thibaut Paumard,
Odele Straub and Frédéric Lamy.
GYOTO is distributed under the terms of the GPL v. 3 license.
We request that use of Gyoto in scientific publications be properly
acknowledged. Please quote:
GYOTO: a new general relativistic ray-tracing code,
F. H. Vincent, T. Paumard, E. Gourgoulhon & G. Perrin 2011,
Classical and Quantum Gravity 28, 225011 (2011) [arXiv:1109.4769]

j = 1/200h2= -1.42405e-308
In gyoto.C: Error during ray-tracing: WorldlineIntegState.C:378 in virtual int Gyoto::Worldline::IntegState::Boost::nextStep(Gyoto::s

tate_t&, double&, double): h2 < delta_min
h2= -1.42405e-308
ǵ8%�U.C: Error during ray-tracing: WorldlineIntegState.C:378 in virtual int Gyoto::Worldline::IntegState::Boost::nextStep(Gyoto::state_t&, double&, double): h2 < delta_min
h2= -1.42405e-308
ǵ8%�U.C: Error during ray-tracing: WorldlineIntegState.C:378 in virtual int Gyoto::Worldline::IntegState::Boost::nextStep(Gyoto::state_t&, double&, double): h2 < delta_min

bumblebee_disk.zip

[Rafaely15]

I tested your example and it generated black files when I opened them in DS9, and I made a mini script to check in Python in Fits but it doesn't plot anything, how do you check the Stokes result?

what I tested was your example "example-equat-hot-spot-polar.xml"

[paumard]

Hi, were you able to make progress on your own or do you still need help?

If you run gyoto on example-equat-hot-spot-polar.xml with the default resolution of 100, the image indeed appears almost completely black, except a few pixels around 39 59. If you switch to log scale in ds9 you will realize that there is a fairly large area around 80 50 which is also not black.

[paumard]

Hi again, I have looked at your example and found that you have uncovered a recently introduced bug in Gyoto that I have circumvented (a proper fix will take more time). You can pull Gyoto again and set <NoCheckBasis/> in your xml file. It will produce the 4 planes as intended. However only the first plane, which corresponds to total intensity, is non zero. Your Astrobj will have to provide the polarized version of radiativeQ to get actual polarization. An example is given in EquatorialHotSpot.