Proposal #52

We propose to perform time-resolved photometry of the prototypical magnetic cataclysmic binary AM Herculis in support of joint simultaneous XMM-Newton/NuSTAR X-ray observations. AM Herculis has recovered from a year-long low state last fall which allowed us to trigger joint satellite observations. These will take place on April 6, 2015. XMM-Newton will begin to observe 2015-04-06 02:37:02 till 2015-04-06 15:07:02. The high-energy observations were granted to determine the energy budget of the accreting binary over an as large as possible wavelength range at high energies. The accretion picture would be incomplete without optical coverage. We thus ask for time-resolved photometry with full phase coverage of the 3.1 hour binary. If possible, the observations shall last as long as the XMM-Newton observations which would involve more than one telescope. The robotic telescope STELLA at Tenerife assigns time to our target and can observe till around 6:00 UT. It performs photometry through Johnson V and we ask for telescope time in the US to enlarge the time coverage. Exposure time shall be 10-30 seconds (dependent on the size of the scope) to achieve an as high as possible time resolution with acceptable signal/noise.