We report multi-wavelength observations of the unidentified Fermi object 2FGL J1653.6-0159. With the help of high-resolution X-ray observation, we have identified an X-ray and optical counterpart of 2FGL J1653.6-0159. The source exhibits a periodic modulation of 75 min in optical and possibly also in X-ray. We suggest that 2FGL J1653.6-0159 is a compact binary system with an orbital period of 75 min. Combining the gamma-ray and X-ray properties, 2FGL J1653.6-0159 is potentially a black widow/redback type gamma-ray millisecond pulsar (MSP). The optical and X-ray lightcurve profiles show that the companion is mildly heated by the high-energy emission and the X-rays are from intrabinary shock. Although no radio pulsation has been detected yet, we estimated that the spin period of the MSP is ~2ms based on a theoretical model. If pulsation can be confirmed in the future, 2FGL J1653.6-0159 will become the first ultracompact rotation-powered MSP.
@article{arxiv.1408.5162,
title = {Discovery of an ultracompact gamma-ray millisecond pulsar binary candidate},
author = {A. K. H. Kong and R. Jin and T. -C. Yen and C. P. Hu and C. Y. Hui and P. H. T. Tam and J. Takata and L. C. C. Lin and K. S. Cheng and S. M. Park and C. L. Kim},
journal= {arXiv preprint arXiv:1408.5162},
year = {2015}
}
Comments
5 pages, 2 figures; Accepted for publication in ApJL