  We report on multi-wavelength observations taken in quiescence and during the
first detected outburst of the ~60 min orbital period AM CVn system SDSS
J113732+405458. Using X-ray and UV observations we determined an upper limit on
the duration of the event, which was around one year. The amplitude of the
outburst was remarkably small, of around one magnitude in r and 0.5 magnitudes
in g near the peak. We have also investigated the color variations of SDSS
J113732+405458 and other long period AM CVns in outbursts and identified a
track in the color-magnitude diagram that is not compatible with the one
expected under the disk instability model, suggesting that the outbursts in
long period AM CVns do not have a disk instability origin, but rather are
caused by enhanced mass-transfer. To our knowledge, these are the first studies
of the color evolution in AM CVn systems. During quiescence we detected SDSS
J113732+405458 as an X-ray source, with an X-ray luminosity of ~3E29 erg/s in
the 0.5-10 keV band. This indicates a very low accretion rate, in agreement
with the disk instability model for long period systems. In the same state we
identified an infrared excess that can be attributed to the donor star. This
makes SDSS J113732+405458 the second AM CVn for which the donor has been
directly detected.
