A 78 Day X-Ray Period Detected from NGC 5907 ULX1 by Swift

Walton, D.J.; Fürst, F.; Bachetti, M.; Barret, D.; Brightman, M.; Fabian, A.C.; Gehrels, N.; Harrison, F.A.; Heida, M.; Middleton, M.J.; Rana, V.; Roberts, T.P.; Stern, D.; Tao, L.; Webb, N.

Abstract

We report the detection of a 78.1 ± 0.5 day period in the X-ray light curve of the extreme ultraluminous X-ray source NGC 5907 ULX1 (${L}_{{\rm{X,peak}}}\sim 5\times {10}^{40}$ erg s−1), discovered during an extensive monitoring program with Swift. These periodic variations are strong, with the observed flux changing by a factor of ~3–4 between the peaks and the troughs of the cycle; our simulations suggest that the observed periodicity is detected comfortably in excess of 3σ significance. We discuss possible origins for this X-ray period, but conclude that at the current time we cannot robustly distinguish between orbital and super-orbital variations.

Citation

Walton, D., Fürst, F., Bachetti, M., Barret, D., Brightman, M., Fabian, A., …Webb, N. (2016). A 78 Day X-Ray Period Detected from NGC 5907 ULX1 by Swift. Astrophysical Journal Letters, 827(1), Article L13. https://doi.org/10.3847/2041-8205/827/1/l13

• Journal Article Type: Article
• Acceptance Date: Jul 22, 2016
• Online Publication Date: Aug 5, 2016
• Publication Date: Aug 5, 2016
• Deposit Date: Aug 19, 2016
• Publicly Available Date: Aug 23, 2016
• Journal: Astrophysical Journal Letters
• Print ISSN: 2041-8205
• Electronic ISSN: 2041-8213
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 827
• Issue: 1
• Article Number: L13
• DOI: https://doi.org/10.3847/2041-8205/827/1/l13
• Public URL: https://durham-repository.worktribe.com/output/1377674
• Related Public URLs: http://arxiv.org/abs/1607.07448