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Special Notice #425: FO Aqr XMM-Newton observations scheduled

November 9, 2016: Further to AAVSO Alert Notice 545, time series observations of the intermediate polar cataclysmic variable FO Aqr are requested to provide simultaneous coverage of XMM-Newton observations scheduled for 2016 November 13 19:43 UTC to November 14 8:13 UTC.

Dr. Colin Littlefield (University of Notre Dame) writes on behalf of his colleagues and himself: "We'd be grateful for simultaneous time-series photometry by AAVSO observers in support of these observations. Our primary objective for the AAVSO observations is to see how FO Aqr's X-ray behavior correlates with its optical variations.

"...FO Aqr is the subject of an ongoing AAVSO campaign to monitor its recovery from the first-ever faint state in its observational history. A number of AAVSO observers were co-authors on our first paper about FO Aqr's faint state [Littlefield et al., 2016, accepted for publication in ApJ; https://arxiv.org/abs/1609.01026].

"We would ask that observers use a cadence of 60 seconds or less. Regarding the bandpass, we would prefer either Johnson V or unfiltered with a V zeropoint. It is also important that observers ensure the accuracy of their computer clocks [to within a few seconds]."

After the XMM-Newton observations are over, please continue the time-series observations until the end of 2016. Observations in the AAVSO International Database show that FO Aqr is brightening from its faint state; Dr. Littlefield feels it will likely return to its original brightness of V~13.4 within a month, and says that he and his colleagues would appreciate the data continuing for a few weeks after that.

Coordinates (2000.0): R.A. 22 17 55.38  Dec. -08 21 03.8

Charts: Charts with a comparison star sequence for FO Aqr may be created using the AAVSO Variable Star Plotter (VSP). For observers who have been following FO Aqr as part of the CBA program, the comparison stars used for that program have been retained.

Please submit observations to the AAVSO International Database using the name FO AQR.

This campaign is being monitored on the AAVSO Observing Campaigns webpage. There is a discussion thread on the Campaigns and Observation Reports forum at https://www.aavso.org/content/fo-aqr-campaign .

This AAVSO Special Notice was compiled by Elizabeth O. Waagen.

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