Urgent photometry of AR UMa needed


We have an approved X-ray Timing Explorer target of opportunity program to study the high magnetic field AM Her binary system AR UMa in its high accretion state. Spectroscopy of AR UMa obtained over the past week by Gary Schmidt using the Steward Observatory 2.3-m telescope has shown a brightening of the star by perhaps a magnitude and the appearance of a rich emission line spectrum which is characteristic of a high accretion state.

We are in urgent need of some visual or digital magnitude estimates of AR UMa to supplement our spectroscopy. These observations will help us to decide whether AR UMa is in the high accretion state. Previous RoboScope observations (Remillard et al. 1994; Honeycutt, Robertson, and Turner 1996, private communication) have shown that AR UMa exhibits a bright optical state which corresponds to the high accretion state when it becomes brighter than about 14th mag.

AR UMa is located at:

alpha = 11:15:44.9
dec = +42:58:23     (2000)

If anyone can obtain some photometry of the star in the next 24 to 36 hours we would be very grateful. High precision is not required. A finding chart is in the Remillard paper (ApJ, 426, 288, 1994; Fig 2, plate 5).

Thanks in advance,

R. Mark Wagner (Ohio State U)
Gary Schmidt (U of Arizona)
Paula Szkody (U of Washington)

VSNET chart

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