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Relativistic baryonic jets from an ultraluminous supersoft X-ray source

Liu, Ji-Feng and Bai, Yu and Wang, Song and Justham, Stephen and Lu, You-Jun and Gu, Wei-Min and Liu, Qing-Zhong and Di Stefano, Rosanne and Guo, Jin-Cheng and Cabrera-Lavers, Antonio and Álvarez, Pedro and Cao, Yi and Kulkarni, Shri (2015) Relativistic baryonic jets from an ultraluminous supersoft X-ray source. Nature, 528 (7580). pp. 108-110. ISSN 0028-0836.

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The formation of relativistic jets by an accreting compact object is one of the fundamental mysteries of astrophysics. Although the theory is poorly understood, observations of relativistic jets from systems known as microquasars (compact binary stars) have led to a well established phenomenology. Relativistic jets are not expected to be produced by sources with soft or supersoft X-ray spectra, although two such systems are known to produce relatively low-velocity bipolar outflows. Here we report the optical spectra of an ultraluminous supersoft X-ray source (ULS) in the nearby galaxy M81 (M81 ULS-1; refs 9, 10). Unexpectedly, the spectra show blueshifted, broad Hα emission lines, characteristic of baryonic jets with relativistic speeds. These time-variable emission lines have projected velocities of about 17 per cent of the speed of light, and seem to be similar to those from the prototype microquasar SS 433 (refs 11, 12). Such relativistic jets are not expected to be launched from white dwarfs, and an origin from a black hole or a neutron star is hard to reconcile with the persistence of M81 ULS-1’s soft X-rays. Thus the unexpected presence of relativistic jets in a ULS challenges canonical theories of jet formation3, 4, but might be explained by a long-speculated, supercritically accreting black hole with optically thick outflows.

Item Type:Article
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URLURL TypeDescription ReadCube access
Bai, Yu0000-0002-4740-3857
Wang, Song0000-0003-3116-5038
Gu, Wei-Min0000-0003-3137-1851
Cao, Yi0000-0002-8036-8491
Kulkarni, Shri0000-0001-5390-8563
Alternate Title:An ultraluminous supersoft X-ray source in M81 as a microquasar with baryonic relativistic jets
Additional Information:© 2015 Macmillan Publishers Limited. Received 17 June 2015; Accepted 11 September 2015; Published online 25 November 2015. We thank K. Blundell, R. Narayan, Z. Li, T. Wang, F. Yuan, X. Fang, J. Irwin, T. Maccarone and D. Swartz for helpful discussions. We acknowledge support from the Chinese Academy of Sciences (grant XDB09000000), from the 973 Program (grant 2014CB845705), and from the National Science Foundation of China (grants NSFC-11333004/11425313). This work is based partly on observations made with the Gran Telescopio Canarias, installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, on the island of La Palma. Some of the data were obtained at the W. M. Keck Observatory, which is operated through a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. This Observatory was made possible through the financial support of the W. M. Keck Foundation. Author Contributions: J.-F.L. proposed the observations. J.-F.L., Y.B., S.W. and J.-C. G. reduced the optical and X-ray data and carried out the analysis. J.-F.L., S.J., Y.-J.L. and R.D.S. discussed the results and drafted the manuscript. A. C.-L., P.A., Y.C and S.K. helped with the observations. All authors commented on and helped in improving the manuscript.
Funding AgencyGrant Number
Chinese Academy of SciencesXDB09000000
Chinese Academy of Sciences2014CB845705
National Science Foundation of ChinaNSFC-11333004
National Science Foundation of ChinaNSFC-11425313
W. M. Keck FoundationUNSPECIFIED
Issue or Number:7580
Record Number:CaltechAUTHORS:20150922-214601520
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:60425
Deposited By: George Porter
Deposited On:01 Dec 2015 16:33
Last Modified:23 Apr 2020 22:41

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