The MAGIC very-high-energy ( VHE ) \gamma -ray astronomy collaboration recently reported the detection of the quasar 3C279 at > 100 GeV \gamma -ray energies .
Here we present simultaneous optical ( BVRI ) and X-ray ( RXTE PCA ) data from the day of the VHE detection and discuss the implications of the snap-shot spectral energy distribution for jet models of blazars .
A one-zone synchrotron-self-Compton origin of the entire SED , including the VHE \gamma -ray emission is highly problematic as it would require an unrealistically low magnetic field .
The measured level of VHE emission could , in principle , be interpreted as Compton upscattering of external radiation ( e.g. , from the broad-line regions ) .
However , such an interpretation would require either an unusually low magnetic field of B \sim 0.03 G , or ( in order to achieve approximate equipartition between magnetic field at B \sim 0.25 G and relativistic electrons ) an unrealistically high Doppler factor of \Gamma \sim 140 .
In addition , such a model fails to reproduce the observed X-ray flux .
Furthermore , both versions of leptonic one-zone models produce intrinsic VHE \gamma -ray spectra steeper than measured , even in the case of the lowest plausible extragalactic \gamma \gamma absorption .
We therefore conclude that a simple one-zone , homogeneous leptonic jet model is not able to plausibly reproduce the SED of 3C279 including the recently detected VHE \gamma -ray emission .
This as well as the lack of correlated variability in the optical with the VHE \gamma -ray emission and the substantial \gamma \gamma opacity of the BLR radiation field to VHE \gamma -rays suggests a multi-zone model in which the optical emission is produced in a different region than the VHE \gamma -ray emission .
In particular , an SSC model with an emission region far outside the BLR reproduces the simultaneous X-ray — VHE \gamma -ray spectrum of 3C279 .
Alternatively , a hadronic model is capable of reproducing the observed SED of 3C279 reasonably well , both in scenarios in which only the internal synchrotron field serves as targets for p \gamma pion production , and with a substantial contribution from external photons , e.g. , from the BLR .
However , either version of the hadronic model requires a rather extreme jet power of up to L _ { j } \sim 10 ^ { 49 } erg s ^ { -1 } , compared to a requirement of L _ { j } \sim 2 \times 10 ^ { 47 } erg s ^ { -1 } for a multi-zone leptonic model .