Spectral and timing variability of the transient ultraluminous X-ray source NGC 4631 X-4

arXiv:2606.23498 · astro-ph.HE · Submitted 2026-06-22 · Read on arXiv

Sinan Allak, Wei Yu, Lorenzo Ducci, Andrea Santangelo, Aysun Akyuz, Faruk Soydugan, Valery Suleimanov

astro-ph.HE

Submitted: 2026-06-22

Comments: Accepted for publication in Astronomy & Astrophysics (A&A)

DOI: 10.1051/0004-6361/202660387

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Terminology

• Consistency — 3× in this paper · explained in 3 episodes
• Robustness — 3× in this paper · explained in 5 episodes
• Accretion Physics — 2× in this paper · explained in 2 episodes
• Calibration — 2× in this paper · explained in 7 episodes
• XRT Photon Counting — 1× in this paper

Sources

• Identification of three new ultraluminous X-ray sources in NGC 4631 and NGC 1097: Evidence for stellar-mass black holes
• Discovery of a 9.67-s pulsar in an ultraluminous X-ray source in NGC 4631 with XMM-Newton
• Ultra-luminous X-ray sources: extreme accretion and feedback

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