This repository contains the analysis software and processed data products for Stevens et al. 2018, "A NICER Discovery of a Low-Frequency QPO in the Soft- Intermediate State of MAXI J1535-571", ApJL, 865, L15. If you use this research or software, you must cite the paper.

If you would like to apply this software for your own sources, please get in touch with me! I strongly recommend using Stingray because it has much more functionality and is designed for broader use cases.

1. analyze_all_segments.py: Computes information about sequential 64 seconds segments of the light curves (e.g., count rate, spectral hardness, rms).

2. segment_info.ipynb: Reads in the file from analyze_all_segments.py to visualize the evolution of different parameters and look for correlations. Makes plots like Figure 1 in the paper.

3. power_and_cross.py: Computes the power spectrum and cross spectrum.

4. psd_fitting.ipynb: Writes scripts to fit the power spectrum to get the centroid and FWHM of the QPO.

5. lag-energy.ipynb: Computes and plots the lag-energy spectrum from the cross spectrum computed in step 3.

The input event lists are in in/ (the local path to those event lists will vary based on your local data directory structure) and the processed data products are in the out/ directory. Public NICER data can be downloaded from HEASARC.

get_total_counts.ipynb will compute the total number of photon counts for a set of observations (going off the length of the event list in the FITS header). nicer_v1.02rbn.rsp is the NICER response matrix binned up to the energy resolution used for the lag-energy spectrum (the same as in in/chbinfile.txt and in/chan_group.txt). xcor_tools.py has helper methods used in the analysis steps.

Copyright (c) 2017-2018 Abigail L. Stevens

The contents of this repository are licensed under a BSD 3-Clause License (Revised). See LICENSE for details, and here for more explanation.