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6th of October 2017
Multi-band search for the counterpart to 3FGL J0838.8-2829
(by Rea et al.)
3FGL J0838.8-2829 is a high-energy gamma-ray source discovered with NASA's Fermi satellite. The uncertainty in the position of the gamma-ray source is large enough to include several possible counterparts at lower energies. Rea et al. conducted a multi-wavelength campaign in the X-ray, infrared, optical bands, together with ATCA radio observations, finding three X-ray sources consistent with the position of the Fermi source. The brightest object, RX J0838-2827, is a magnetic cataclysmic variable, a class of object not previously detected at gamma-ray energies, and so is unlikely to be the counterpart. One of the other X-ray sources, XMM J083850.4-282759, showed variable X-ray emission, with a powerful flare lasting ~600s, similar to what is observed in transitional millisecond pulsars during the sub-luminous disc state, plausibly associating this source with the Fermi-LAT source.

The ATCA images above show the field of interest at 5.5 GHz (left) and 9.0 GHz (right) The large white circle is the 68% confidence level error circle for the gamma-ray source. The small black circle denotes the position of RX J0838-2827. While no radio emission is detected from XMM J083850.4-282759, this does not rule out an association with the Fermi source. Several unidentified radio sources are seen in the ATCA images, however the lack of an X-ray counterpart to these means it is unlikely that any of them is the counterpart to the Fermi source.

More details are given in the pre-print of the paper by Rea et al.

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