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arXiv · 1311.4867

Unveiling recurrent jets of the ULX Holmberg II X-1: evidence for a massive stellar-mass black hole?

D. Cseh·P. Kaaret·S. Corbel·F. Grise·C. Lang·E. Koerding·H. Falcke·P. G. Jonker·J. C. A. Miller-Jones·S. Farrell·Y. J. Yang·Z. Paragi·S. Frey
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Abstract

We report on the discovery of an apparent triple radio structure hidden inside the radio bubble of the ultraluminous X-ray source Holmberg II X-1. The morphology is consistent with a collimated jet structure, which is observed to emit optically thin synchrotron radiation. The central component has a steep radio spectrum and is brighter than the outer components indicating a renewed radio activity. We estimate a minimum time-averaged jet power of 2 x 10^{39} erg/s that is associated with a time-averaged isotropic X-ray luminosity of at least 4 x 10^{39} erg/s. Our results suggest that Holmberg II X-1 is powered by a black hole of M_BH \geq 25 M_sun, that is inferred to be accreting at a high Eddington rate with intermittent radio activity.

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D. Cseh, P. Kaaret, S. Corbel, F. Grise, C. Lang, E. Koerding, H. Falcke, P. G. Jonker, J. C. A. Miller-Jones, S. Farrell, Y. J. Yang, Z. Paragi, S. Frey. 2013-11-19. Unveiling recurrent jets of the ULX Holmberg II X-1: evidence for a massive stellar-mass black hole?. https://doi.org/10.1093/mnrasl%2Fslt166

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