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arXiv · 1208.2085

VLBI detection of the Galactic black hole binary candidate MAXI J1836-194

Jun Yang·Yonghua Xu·Zhixuan Li·Zsolt Paragi·Robert M. Campbell·Leonid Gurvits·Zhiqiang Shen·Xiaoyu Hong·Bo Xia
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Abstract

The X-ray transient MAXI J1836-194 is a newly-identified Galactic black hole binary candidate. As most X-ray transients, it was discovered at the beginning of an X-ray outburst. After the initial canonical X-ray hard state, the outburst evolved into a hard intermediate state and then went back to the hard state. The existing RATAN-600 radio monitoring observations revealed that it was variable on a timescale of days and had a flat or inverted spectrum, consistent with optically thick synchrotron emission, possibly from a self-absorbed jet in the vicinity of the central compact object. We observed the transient in the hard state near the end of the X-ray outburst with the European VLBI Network (EVN) at 5 GHz and the Chinese VLBI Network (CVN) at 2.3 and 8.3 GHz. The 8.3 GHz observations were carried out at a recording rate of 2048 Mbps using the newly-developed Chinese VLBI data acquisition system (CDAS), twice higher than the recording rate used in the other observations. We successfully detected the low-declination source with a high confidence level in both observations. The source was unresolved (<=0.5 mas), which is in agreement with an AU-scale compact jet.

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Jun Yang, Yonghua Xu, Zhixuan Li, Zsolt Paragi, Robert M. Campbell, Leonid Gurvits, Zhiqiang Shen, Xiaoyu Hong, Bo Xia. 2012-08-10. VLBI detection of the Galactic black hole binary candidate MAXI J1836-194. https://arxiv.org/abs/1208.2085

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