€3 systems have recently
been discovered with binary periods
<10 min (600 sec)! Small enough to fit within Jupiter
RXJ1914.4+2457 9.5 min Cropper et al (1998)
(V407 Vul)
RXJ0806.3+1527 5.4 min Ramsay, Hakala & Cropper (2002) Israel et al (2002)
KUV01584–0939 10.3 min Warner & Woudt (2002)
(ES Cet)