The high-frequency–peaked BL Lacertae object Markarian 180 ( Mrk 180 ) was observed to have an optical outburst in 2006 March , triggering a Target of Opportunity observation with the MAGIC telescope .
The source was observed for 12.4 hr , and very high energy \gamma -ray emission was detected with a significance of 5.5 \sigma .
An integral flux above 200 GeV of ( 2.3 \pm 0.7 ) \times 10 ^ { -11 } \mbox { cm } ^ { -2 } \mbox { s } ^ { -1 } was measured , corresponding to 11 % of the Crab Nebula flux .
A rather soft spectrum with a photon index of -3.3 \pm 0.7 has been determined .
No significant flux variation was found .