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AAVSO Special Notice #425

November 9, 2016

FO Aqr XMM-Newton observations scheduled

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 

"...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;].

"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 

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) at 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 at

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

It’s all about the  standstills, those episodes where the star gets stuck at a mid-point between maximum and minimum. If it doesn’t exhibit standstills it isn’t a Z Cam star.

AM Her stars in need of further investigation

Data from Catalina Real Time Survey 
Drake et al. 2009, ApJ, 696, 87

Northern CVs brighter than 17th magnitude here.

Southern CV's brighter than 17th magnitude here.


New outbursts and unusual activity reported in the last 72 hours

Last updated 16:41 UT December 06, 2016


DT Aps
BE Oct

# indicates a noteworthy or unusual outburst
:  indicates confirmation required
'Activity At A Glance' is gleaned from observations reported to AAVSO MyNewsFlash, BAAVSS-Alert, CVnet-Outburst, VSObs-share and VSNET-outburst. We sincerely thank all the observers who contribute timely observations and reports of activity to these email lists.


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