Version History

new features for v1.1.3:

  • Added same_target mode for stacking multiple exposures of one target in observed frame.

  • Stacked FITS outputs now record command provenance in header HISTORY cards.

v1.1.2 (latest)

  • Major performance refactor for on-the-fly stacking, reducing peak RAM and total runtime.

  • Significant bootstrap speedup (bootstrap runtime now close to a single-stack run in typical use).

  • Reduced redundant I/O for faster processing throughput.

  • Added do_cache mode to store/reuse per-source rest-frame intermediate files, improving rerun speed.

  • Fixed bkggrpflg indexing in background-group handling.

  • Miscellaneous maintenance and documentation updates, including read-the-docs integration.

Download link is here.

Earlier Versions

v1.1.1

This release (v1.1.1) includes slight improvements to the code:

  1. better treatment for extremely low data by properly assigning photon counts in each shift (individual count can be float; only round to integer for the final stacked spectrum) [Thanks Y. Zhang for helpful discussion];

  2. fix stacking Swift-XRT / XMM MOS issues [Thanks S. Mondal for helpful discussion];

  3. speed up initial file reading process;

  4. input bkg files can be none now.

Download link is here.

v1.1.0

Stacking extended sources is now supported, with methods inspired from Eq. 9 to Eq. 12 of X. Zhang+2024. However, some slight differences are:

  • Eq. 10, the bkg spectra are scaled not only by REGAREA, but additionally by the averaged exposure per pixel, which effectively results in an exactly same scaling formula as for the point sources (BACKSCAL * EXPOSURE * AREASCAL). Note, the averaged exposure = BACKSCAL / REGAREA * EXPOSURE.

  • Eq. 11 and Eq. 12, the separate stacking of ARF and RMF are replaced by the stacking of RSP=ARF * RMF in one step.

Overall, for extended sources, the only difference is how the response weighting factors are computed under FLX mode.

Download link is here.

v1.0.0

Public version used for X-ray spectral stacking, with method detailed in Appendix A of S. Chen, J. Buchner, T. Liu et al. 2025, A&A, The average soft X-ray spectra of eROSITA active galactic nuclei.

Download link is here.