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Chandra Probes the X-Ray Variability of M51 ULX-7: Evidence of Propeller Transition and X-Ray Dips on Orbital Periods

Vasilopoulos, Georgios and Koliopanos, Filippos and Haberl, Frank and Treiber, Helena and Brightman, Murray and Earnshaw, Hannah P. and Gúrpide, Andrés (2021) Chandra Probes the X-Ray Variability of M51 ULX-7: Evidence of Propeller Transition and X-Ray Dips on Orbital Periods. Astrophysical Journal, 909 (1). Art. No. 50. ISSN 0004-637X. doi:10.3847/1538-4357/abda49.

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We report on the temporal properties of the ultraluminous X-ray (ULX) pulsar M51 ULX-7 inferred from the analysis of the 2018–2020 Swift/X-ray Telescope monitoring data and archival Chandra data obtained over a period of 33 days in 2012. We find an extended low flux state, which might be indicative of propeller transition, lending further support to the interpretation that the neutron star is rotating near equilibrium. Alternatively, this off-state could be related to a variable superorbital period. Moreover, we report the discovery of periodic dips in the X-ray light curve that are associated with the binary orbital period. The presence of the dips implies a configuration where the orbital plane of the binary is closer to an edge-on orientation, and thus demonstrates that favorable geometries are not necessary in order to observe ULX pulsars. These characteristics are similar to those seen in prototypical X-ray pulsars such as Her X-1 and SMC X-1 or other ULX pulsars such as NGC 5907 ULX1.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Vasilopoulos, Georgios0000-0003-3902-3915
Koliopanos, Filippos0000-0002-1989-7984
Haberl, Frank0000-0002-0107-5237
Treiber, Helena0000-0003-0660-9776
Brightman, Murray0000-0002-8147-2602
Earnshaw, Hannah P.0000-0001-5857-5622
Additional Information:© 2021. The American Astronomical Society. Received 2020 November 18; revised 2021 January 8; accepted 2021 January 8; published 2021 March 4. The authors would like to thank the anonymous referee for their comments and suggestions that helped improve the manuscript. We would like to thank the organizers of the "Chandra Frontiers in Time-Domain Science" meeting that was held virtually in 2020 October. Presentation of M51 monitoring data and discussions that followed resulted in the current work. G.V. acknowledges support by NASA grant Nos. 80NSSC20K1107, 80NSSC20K0803 and 80NSSC21K0213. Software: HEASoft v6.26, CIAO v4.12.1, Python v3.7.3, IDL®.
Funding AgencyGrant Number
Subject Keywords:High mass x-ray binary stars; Neutron stars; Pulsars
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: High mass x-ray binary stars (733); Neutron stars (1108); Pulsars (1306)
Record Number:CaltechAUTHORS:20210308-082954334
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Official Citation:Georgios Vasilopoulos et al 2021 ApJ 909 50
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108336
Deposited By: Tony Diaz
Deposited On:08 Mar 2021 20:57
Last Modified:16 Nov 2021 19:11

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