INTEGRAL Picture Of the Month
July 2005

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Murphy's law and the OMC

Until Sunday June 26 no Gamma-Ray Burst (GRB) in the field of view of the Optical Monitoring Camera (OMC) onboard INTEGRAL had been been observed. This is not too surprising given the much smaller field of view of the OMC compared to the gamma-ray instruments.

However, an automated system is in place since launch, which will make a triggered observation with the OMC based on the coordinates which are provided by the on-ground software IBAS (the INTEGRAL Burst Alert System).

Last Sunday a GRB triggered IBAS and an OMC observation was started just 1m48s after the GRB brightened.

And here Murphy comes in to action....

Unfortunately this GRB occurred only a couple of arc minutes away from one of the brightest stars in the sky: Alpha Crucis; a magnitude 0.8 star. The region where the GRB took place is severely affected by saturation by this very bright star.

The chance of such an event occurring so close to such a bright star (Alpha Crucis is the 13th brightest star in the sky) is very small. And it tells us that also astronomers have to face Murphy's law.

Hopefully the next GRB in the field of view of the OMC will not be affected by an extremely bright star.

The figure shows the position of the GRB (red cross and green circle representing the error circle) and the saturared image of Alpha Crucis.

Credits: J. Miguel Mas-Hesse (LAEFF) and OMC-team

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