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

Cseh, D.; Kaaret, P.; Corbel, S.; Grisé, F.; Lang, C.; Körding, E.; Falcke, H.; Jonker, P. G.; Miller-Jones, J. C. A.; Farrell, S.; Yang, Y. J.; Paragi, Z.; Frey, S.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society: Letters, Volume 439, Issue 1, p.L1-L5

Advertised on:
3
2014
Number of authors
13
IAC number of authors
1
Citations
52
Refereed citations
48
Description
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 × 1039 erg s-1 that is associated with a time-averaged isotropic X-ray luminosity of at least 4 × 1039 erg s-1. Our results suggest that Holmberg II X-1 is powered by a black hole of MBH ≥ 25 M⊙, that is inferred to be accreting at a high Eddington rate with intermittent radio activity.
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