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arXiv · 2407.00150

The restless population of bright X-ray sources of NCG 3621

A. Sacchi·M. Imbrogno·S. E. Motta·P. Esposito·G. L. Israel·N. O. Pinciroli Vago·A. De Luca·M. Marelli·F. Pintore·G. A. Rodríguez Castillo·R. Salvaterra·A. Tiengo
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Abstract

We report on the multi-year evolution of the population of X-ray sources in the nuclear region of NGC 3621 based on Chandra, XMM-Newton and Swift observations. Among these, two sources, X1 and X5, after their first detection in 2008, seem to have faded below the detectability threshold, a most interesting fact as X1 is associated with the AGN of the galaxy. Two other sources, X3 and X6 are presented for the first time, the former showing a peculiar short-term variability in the latest available dataset, suggesting an egress from eclipse, hence belonging to the handful of known eclipsing ultra-luminous X-ray sources. One source, X4, previously known for its "heart-beat", i.e. a characteristic modulation in its signal with a period of $\approx1$ h, shows a steady behaviour in the latest observation. Finally, the brightest X-ray source in NGC 3621, here labelled X2, shows steady levels of flux across all the available datasets but a change in its spectral shape, reminiscent of the behaviours of Galactic disk-fed X-ray binaries.

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A. Sacchi, M. Imbrogno, S. E. Motta, P. Esposito, G. L. Israel, N. O. Pinciroli Vago, A. De Luca, M. Marelli, F. Pintore, G. A. Rodríguez Castillo, R. Salvaterra, A. Tiengo. 2024-06-28. The restless population of bright X-ray sources of NCG 3621. https://doi.org/10.1051/0004-6361%2F202450319

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