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Peer-reviewedCC BY 4.0The Astrophysical Journal

Unraveling the Mysteries of KS 1947+300: Study of Nonperiodic Type I X-Ray Outbursts after 2000 and 2013

  • Wei Liu1
  • Pablo Reig2,3
  • Bo Gao4
  • Xi Zhang1
  • Hongyu Gong1
  • Guangcheng Xiao5,6,7
  • Xiukun Li4,8
  • Zhongmu Li1
  • Qingzhong Liu4
8 affiliations
  1. 1Dali University
  2. 2Institute of Astrophysics
  3. 3University of Crete
  4. 4Chinese Academy of Sciences
  5. 5Jinggangshan University
  6. 6JingGangShan University
  7. 7Jiangxi Provincial Key Laboratory of Modern Agricultural Equipment
  8. 8University of Science and Technology of China
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Abstract

Type I X-ray outbursts in Be/X-ray binaries are commonly associated with enhanced accretion near periastron and are therefore expected in systems with moderate or high orbital eccentricities. KS 1947+300 is an unusual counterexample: despite its nearly circular orbit, it repeatedly exhibits type I outbursts. We investigate its long-term X-ray behavior following the giant outbursts in 2000 and 2013 using RXTE All-Sky Monitor, Swift Burst Alert Telescope, and MAXI monitoring data. We identify 22 type I outbursts and measure their durations, recurrence times, peak intensities, and orbital phases. The durations range from 3.0 to 77.8 days (0.07–1.93 orbital cycles), and the recurrence times range from 46.0 to 129.5 days. The approximate band-limited peak luminosities vary by a factor of 4.5. The full sample is consistent with a broad orbital-phase distribution, whereas the five post-2013 outbursts are concentrated near periastron. Correlation tests show that longer events are systematically brighter, but neither duration nor peak luminosity is significantly correlated with the preceding recurrence time. These observations are compatible with, but do not uniquely establish, a time-dependent eccentric and misaligned Be disk. They highlight the importance of Be-disk evolution in regulating accretion in low-eccentricity Be/X-ray binaries.

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Cite

BibTeXRIS
BibTeX
@article{liu2026unraveling,
  title = {{Unraveling the Mysteries of KS 1947+300: Study of Nonperiodic Type I X-Ray Outbursts after 2000 and 2013}},
  author = {Wei Liu and Pablo Reig and Bo Gao and Xi Zhang and Hongyu Gong and Guangcheng Xiao and Xiukun Li and Zhongmu Li and Qingzhong Liu},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = oct,
  doi = {10.3847/1538-4357/aea983},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea983},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Unraveling the Mysteries of KS 1947+300: Study of Nonperiodic Type I X-Ray Outbursts after 2000 and 2013
AU  - Wei Liu
AU  - Pablo Reig
AU  - Bo Gao
AU  - Xi Zhang
AU  - Hongyu Gong
AU  - Guangcheng Xiao
AU  - Xiukun Li
AU  - Zhongmu Li
AU  - Qingzhong Liu
PY  - 2026
DA  - 2026/10/21
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aea983
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aea983
AB  - Type I X-ray outbursts in Be/X-ray binaries are commonly associated with enhanced accretion near periastron and are therefore expected in systems with moderate or high orbital eccentricities. KS 1947+300 is an unusual counterexample: despite its nearly circular orbit, it repeatedly exhibits type I outbursts. We investigate its long-term X-ray behavior following the giant outbursts in 2000 and 2013 using RXTE All-Sky Monitor, Swift Burst Alert Telescope, and MAXI monitoring data. We identify 22 type I outbursts and measure their durations, recurrence times, peak intensities, and orbital phases. The durations range from 3.0 to 77.8 days (0.07–1.93 orbital cycles), and the recurrence times range from 46.0 to 129.5 days. The approximate band-limited peak luminosities vary by a factor of 4.5. The full sample is consistent with a broad orbital-phase distribution, whereas the five post-2013 outbursts are concentrated near periastron. Correlation tests show that longer events are systematically brighter, but neither duration nor peak luminosity is significantly correlated with the preceding recurrence time. These observations are compatible with, but do not uniquely establish, a time-dependent eccentric and misaligned Be disk. They highlight the importance of Be-disk evolution in regulating accretion in low-eccentricity Be/X-ray binaries.
SN  - 0004-637X
SN  - 1538-4357
ER  -