INTEGRAL observations of the gamma-ray binary 1FGL J1018.6-5856

Abstract

The Fermi-LAT collaboration has recently reported that one of their detected sources, namely, 1FGL J1018.6-5856, is a new gamma-ray binary similar to LS 5039. This has prompted efforts to study its multi-frequency behavior. In this report, we present the results from 5.78-Ms INTEGRAL IBIS/ISGRI observations on the source 1FGL J1018.6-5856. By combining all the available INTEGRAL data, a detection is made at a significance level of 5.4 sigma in the 18-40 keV band, with an average intensity of 0.074 counts/s . However, we find that, there is non-statistical noise in the image that effectively reduces the significance to about 4 sigma and a significant part of the signal appears to be located in a 0.2-wide phase region, at phases 0.4-0.6 (where even the corrected significance amounts to 90% of the total signal found). Given the scarcity of counts, a variability is hinted at about 3 sigma at the hard X-rays, with an anti-correlation with the Fermi-LAT periodicity. Should this behavior be true, it would be similar to that found in LS 5039, and prompt observations with TeV telescopes at phases anti-correlated with the GeV maximum.

Accepted for publication in Astrophysical Journal Letters; 6 pages, 1 figure

References in corpus (1)

• INTEGRAL observation of hard X-ray variability of the TeV binary LS5039 / RX J1826.2-1450

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• Discovery of variable VHE gamma-ray emission from the binary system 1FGL J1018.6-5856
• GeV detection of HESS J0632+057
• Swift observations of 1FGL J1018.6-5856
• NuSTAR Hard X-ray Observation of the Gamma-ray Binary Candidate HESS J1832-093
• Ten years of INTEGRAL observations of the hard X-ray emission from SGR 1900+14