DOI: 10.5281/zenodo.14739970
title: Dynamic Spectra associated with the paper "Transient Blurring of the Scintillation Arc of Pulsar B1737+13"

description: contents of the 0README file (as of 2025-02-26)

This is a very basic documentation file for the dynamic spectrum repositorythat we have created to accompany the publication of our paper

"Transient Blurring of the Scintillation Arc of Pulsar B1737+13"authors: Yen-Hua Chen, Sammy Siegel, Daniel Baker, Ue-Li Pen, and Dan Stinebring

We plan to submit this to the Astrophysical Journal. This Zenodo DOI will bereferenced in that paper when it is published.

This document was written by Dan Stinebring on Feb. 4, 2025 and finalized on Feb. 26, 2025.

An arXiv version of our paper can be found here: https://arxiv.org/abs/2412.10323

First, these dynamic spectra, are the data behind the "Transient Blurring ..."paper and ALSO the data that were analyzed in this earlier paper:

Hemberger and Stinebring 2008 "Time Variability of Interstellar Scattering and Improvements to Pulsar Timing"https://ui.adsabs.harvard.edu/abs/2008ApJ...674L..37H/abstract

Second, we have done a decent job preparing this data set, but we are not claiming thatthis work is complete or free of problems. In particular, there is un-mitigated radio frequency interference (RFI) in the data still, although the "Cleaned" version ofthe data set is definitely an improvement on the "Raw" version in this regard. Onthe other hand, the Cleaned version was done by setting affected rows and columns ofthe dynamic spectrum (DS) array to not-a-number (NaN) values. More sophisticated RFI excision/treatment options could be applied to the Raw data files.

The Cleaned files differ from the Raw files in two other aspects. First, the FITS headershave been fixed up (astropy.io.fits.verify)https://docs.astropy.org/en/stable/io/fits/usage/verification.htmlso that they are strictly conformant with the FITS standard.

Second, the subintegration-to-subintegration modulation present in the Raw data setsdue to the relatively small number of pulse periods included in each10s subint for this P = 0.803 s period pulsar has been removed. This wasdone by dividing by a singular value decomposition (mode 0) model of the DSarray. An example of the procedure followed in doing this is given inthe Jupyter notebook: SVDExample.ipynb in the top-level directory.You will need to rename the file that is accessed in that notebook since thefile naming convention has now changed.

Regarding that file name change: internally (before Jan. 20, 2025) we were usinga naming convention like this:

B1737+13.wapp1.53830.0.dyn.fitsB1737+13.wapp2.53830.0.dyn.fitsB1737+13.wapp3.53830.0.dyn.fitsB1737+13.wapp4.53830.0.dyn.fits...

We changed this to be clearer and easier to search ...B1737+13_53830.36_1175MHz_AO.fitsB1737+13_53830.36_1360MHz_AO.fitsB1737+13_53830.36_1400MHz_AO.fitsB1737+13_53830.36_1440MHz_AO.fits...

and that is the pattern that we have used for filenames in both the Cleaned and Raw directories, with a _raw.fits appended to each file in the Raw directory.

DIAGNOSTIC PLOTS----------------These are included to give you a quick look at the 144 data files in the dataset. However,the program used to produce the plots is legacy IDL software from Dan Stinebring's lab(~ 1998 - 2005) and does not have many of the state-of-art enhancements provided inDaniel Reardon's scintools software suite:  https://github.com/danielreardon/scintools

So, look at these plots if they are useful to you, but don't consider themresearch-ready for any further purposes.

NOTE again: the Cleaned files have NaNs marking excised channels and subints. You will needto deal with those in some fashion when proceeding with your own analysis. The Rawfiles do not have any NaNs in them, but they have significant unexcised RFI atsome epochs.

The Diagnostic Plots show all four 50-MHz bands on one page. There are 36 pages per PDFbecause there are 36 epochs of observation with nearly weekly spacing. The header at thetop of each plot sub-panel lists the pulsar (B1737+13), the MJD, and the year-frac of thatepoch.

The IDL command used to created the combined PDF for both the raw & cleaned files is similar to thisIDL> dyn_ss_plot,files_clean,/nohanning,/fullsec,outfile='0Output/Diagnostic',nrows=2,ncols=2,/compact

The raw files have numerous non-standard aspects to their FITS headers. As noted above, the cleaned files havehad these problems fixed by the astropy verify() method

https://docs.astropy.org/en/stable/io/fits/usage/verification.html   (accessed 2025-02-26)

e.g. (from other astropy fits documentation)

from astropy.io import fitsfilename = fits.util.get_testdata_filepath('verify.fits')

Non-standard FITS keywords--------------------------T_INT   =                 10.0      subintegration time                                               NBINS   =                  128      number of pulse phase bins (used in producing dynamic spectra)                                          NCHANS  =                 2048      number of frequency channels                                          ORIGIN  = 'Arecibo '                   telescope of origin (this is actually a standard FITS keyword)                                        SCINTCUB= 'Scintcube'                  Program used to create dynamic spectrum (IDL code; Stinebring lab)                                        SPECTROM= 'WAPP    '                   Spectrometer used at Arecibo                                        TTOT    = 3600.00000000000000000000    total integration time (s)