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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.

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


D.J. Walton

F. Fürst

M. Bachetti

D. Barret

M. Brightman

A.C. Fabian

N. Gehrels

F.A. Harrison

M. Heida

M.J. Middleton

V. Rana

D. Stern

L. Tao

N. Webb


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.


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.

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
Related Public URLs


Published Journal Article (436 Kb)

Copyright Statement
© 2016. The American Astronomical Society. All rights reserved.

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