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Peer-reviewedCC BY 4.0The Astrophysical Journal

The Demographics of Sagittarius A* X-Ray Flares over 25 yr with Chandra

  • Zach Sumners1,2
  • Nicole M. Ford1,2
  • Daryl Haggard1,2
  • Joseph M. Michail3
  • Joey Neilsen4
  • Michael A. Nowak5
  • Mayura Balakrishnan1,2
  • Sophia Sánchez-Maes6
  • Sebastiano D. von Fellenberg7,8
  • S. P. Willner3
  • Sera Markoff9,10
  • Howard A. Smith3
1 more authors
  • Joseph L. Hora3
10 affiliations
  1. 1McGill University
  2. 2Trottier Space Institute
  3. 3Center for Astrophysics ∣ Harvard & Smithsonian
  4. 4Villanova University
  5. 5Washington University in St. Louis
  6. 6University of Maryland
  7. 7University of Toronto
  8. 8Max Planck Insitute for Radioastronomy
  9. 9University of Amsterdam
  10. 10University of Cambridge
Open at sourcePDFDOICite

Abstract

We present the Chandra 25 yr Sagittarius A* (Sgr A*) X-ray flare catalog: a systematic analysis of 6.8 Ms of Sgr A* monitoring spanning the Chandra X-ray Observatory’s mission lifetime. This is the most complete Chandra Sgr A* X-ray flare catalog to date, consisting of 100 flares with 2–10 keV unabsorbed luminosities in the range of ∼4–575 × 10 ³³ erg s ⁻¹ . Eighteen flares are reported for the first time, including the second brightest Sgr A* flare observed by Chandra. The expanded dataset supports previous indications of a correlation between X-ray flare hardness and luminosity. Spectral modeling corroborates this finding, showing a statistically significant change in the X-ray spectral index, from Γ ∼ 3 to 2 with increasing flare brightness. Previously established correlations between flare duration, fluence, and maximum count rate are strengthened via the greater sample size. These results likely reflect variations in the underlying particle distribution that produce weak and strong flares, and the new catalog serves as a rich archive for ongoing observational and numerical investigations into the physical mechanisms responsible for producing Sgr A*’s X-ray flares.

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Cite

BibTeXRIS
BibTeX
@article{sumners2026demographics,
  title = {{The Demographics of Sagittarius A* X-Ray Flares over 25 yr with Chandra}},
  author = {Zach Sumners and Nicole M. Ford and Daryl Haggard and Joseph M. Michail and Joey Neilsen and Michael A. Nowak and Mayura Balakrishnan and Sophia Sánchez-Maes and Sebastiano D. von Fellenberg and S. P. Willner and Sera Markoff and Howard A. Smith and Joseph L. Hora},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = sep,
  doi = {10.3847/1538-4357/ae9c3d},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/ae9c3d},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - The Demographics of Sagittarius A* X-Ray Flares over 25 yr with Chandra
AU  - Zach Sumners
AU  - Nicole M. Ford
AU  - Daryl Haggard
AU  - Joseph M. Michail
AU  - Joey Neilsen
AU  - Michael A. Nowak
AU  - Mayura Balakrishnan
AU  - Sophia Sánchez-Maes
AU  - Sebastiano D. von Fellenberg
AU  - S. P. Willner
AU  - Sera Markoff
AU  - Howard A. Smith
AU  - Joseph L. Hora
PY  - 2026
DA  - 2026/09/30
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/ae9c3d
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/ae9c3d
AB  - We present the Chandra 25 yr Sagittarius A* (Sgr A*) X-ray flare catalog: a systematic analysis of 6.8 Ms of Sgr A* monitoring spanning the Chandra X-ray Observatory’s mission lifetime. This is the most complete Chandra Sgr A* X-ray flare catalog to date, consisting of 100 flares with 2–10 keV unabsorbed luminosities in the range of ∼4–575 × 10 ³³ erg s ⁻¹ . Eighteen flares are reported for the first time, including the second brightest Sgr A* flare observed by Chandra. The expanded dataset supports previous indications of a correlation between X-ray flare hardness and luminosity. Spectral modeling corroborates this finding, showing a statistically significant change in the X-ray spectral index, from Γ ∼ 3 to 2 with increasing flare brightness. Previously established correlations between flare duration, fluence, and maximum count rate are strengthened via the greater sample size. These results likely reflect variations in the underlying particle distribution that produce weak and strong flares, and the new catalog serves as a rich archive for ongoing observational and numerical investigations into the physical mechanisms responsible for producing Sgr A*’s X-ray flares.
SN  - 0004-637X
SN  - 1538-4357
ER  -