ABSTRACT The ultra‐luminous x‐ray pulsar (ULXP) NGC 7793 P13 has been regularly monitored with XMM‐Newton , NuSTAR , and Swift for the last 8 years. Here, we present the latest results of this monitoring campaign with respect to the pulse period evolution and spectral variability. We find that since the source recovered from an x‐ray low state in 2020–2022 the spin‐up rate has increased significantly compared with before the off‐state, even though the x‐ray luminosity has not shown an equivalent increase. We find that the x‐ray and optical/UV flux are anti‐correlated, and speculate that this variability might be driven by a large accretion disk, precessing at a super‐orbital period of 7–8 years. We study the spectral behavior in the XMM‐Newton and NuSTAR data, and find very little changes in the spectral shape, despite the large flux variability. This spectral consistency provides further indication that the observed flux variability is a geometric effect and not due to intrinsic changes of the accretion rate.

Felix Fürst

Dominic J. Walton

Matteo Bachetti

Hannah Earnshaw

Murray Brightman

Astronomische Nachrichten

ASTRONOMISCHE NACHRICHTEN 由 H. C. SCHUMACHER 于 1821 年创立，是世界上仍在出版的最古老的天文学期刊。著名的天文发现和在天文学和天体物理学方面的重要论文发表在 300 多卷期刊上，出色地代表了过去 180 年来天文学研究的进展。今天，ASTRONOMICAL NOTES/ASTRONOMISCHE NACHRICHTEN 发表了关于观测和理论天体物理学领域以及太阳系和太阳物理学相关主题的文章。此外，还涵盖了有关天基和天基天文仪器的论文，以及有关数值天体物理技术和超级计算机建模的论文。论文可通过电子版短视频序列完成。 ASTRONOMICAL NOTES/ASTRONOMISCHE NACHRICHTEN 还出版会议记录的特刊。

Founded by H. C. Schumacher in 1821, "Astronomische Nachrichten" is the oldest astronomy journal still in publication today. It has published numerous significant astronomical discoveries and important papers in the fields of astronomy and astrophysics across more than 300 volumes, excellently representing the progress of astronomical research over the past 180 years. Today, "Astronomical Notes/Astronomische Nachrichten" publishes articles on observational and theoretical astrophysics, as well as topics related to the solar system and solar physics. Additionally, it covers papers on ground-based and space-based astronomical instruments, as well as research on numerical astrophysical techniques and supercomputer modeling. Papers can be presented through electronic short video sequences. "Astronomical Notes/Astronomische Nachrichten" also publishes special issues of conference proceedings.

《Astronomische Nachrichten》由H. C. Schumacher于1821年创立，是世界上仍在出版的最古老的天文学期刊。该期刊发表了许多著名的天文发现和在天文学及天体物理学领域的重要论文，涵盖了300多卷，出色地代表了过去180年来天文学研究的进展。如今，《Astronomical Notes/Astronomische Nachrichten》主要发表关于观测和理论天体物理学的文章，以及与太阳系和太阳物理学相关的主题。此外，期刊还包括有关天基和地基天文仪器的论文，以及数值天体物理技术和超级计算机建模的研究。论文可以通过电子版短视频序列进行展示。《Astronomical Notes/Astronomische Nachrichten》还出版会议记录的特刊。

Category	Quartile
物理与天体物理	4
物理与天体物理, 天文与天体物理	4

The Surprising Long‐Term Evolution of the ULXP NGC 7793 P13

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ASTRONOMY & ASTROPHYSICS	3