Millholland et al. (2016) present the possible detection of a non-transiting hot-Jupiter in a planetary system consisting of two low-mass transiting planet candidates with longer orbital periods. The technique employed to detect this non-transiting hot-Jupiter is a novel one which combines optical phase curve analysis and astrometric transit timing variations (TTVs). Optical phase curve analysis involves measuring the reflected light from the hot-Jupiter as its dayside rotates in and out of view.
The non-transiting hot-Jupiter in this study was detected around a Sun-like star identified as KOI-1858. Orbiting KOI-1858 are two known transiting planet candidates - KOI-1858.01 and KOI-1858.02. KOI-1858.01 has ~3.53 times the radius of Earth and has a 116.3 day orbital period. KOI-1858.02 has ~2.06 times the radius of Earth and has a 86.0 day orbital period. Both the observed optical phase curve and astrometric TTVs are mutually consistent with the presence of a non-transiting hot-Jupiter with 1.5 ± 0.4 times the mass of Jupiter and a 2.991 day orbital period.
Millholland et al. (2016), "On the Detection of Non-Transiting Hot Jupiters in Multiple-Planet Systems", arXiv:1602.05674 [astro-ph.EP]