AAVSO Alert Notice 598 announces a campaign on the intermediate polar FO Aqr, which is undergoing only the second fading episode recorded in its observational history. V/CV photometry is needed beginning immediately. Please see the notice for details and observing instructions.
Many thanks, and good observing,
Elizabeth Waagen, AAVSO HQ
On behalf of my colleagues, I'd like to thank everyone who has observed FO Aqr during this fading event; your photometry has been very useful to us. It establishes that although FO Aqr's overall brightness leveled off from early September until early-to-mid October, the fading has since resumed at an erratic rate. Moreover, power spectral analysis of the AAVSO data, in conjunction with my group's photometry, reveals that the relative strengths of the periodicities in the light curve have changed significantly during this fading event. This gives us critical information about how the gas from the donor star accretes onto the binary's white dwarf, and it's central to our research objectives.
As thankful as we are for what you've already done, we'd like to encourage you to continue observing FO Aqr. In the past month, there haven't been as many observations, so I'd like to reiterate just how valuable your observations are to us. I realize that the nature of our request for observations -- multi-hour time series of the same star for several months -- is very time-consuming and potentially monotonous, but if you can find the time to get a time series at least once or twice a week, we will be further indebted to you.
My colleagues and I are thankful for your extensive coverage of FO Aqr. In 2017 alone, you've contributed 210 hours of time-series photometry of this object. If you can continue observing for as long as the weather permits, it would be helpful to us.
Recent time-series observations by several observers indicate that FO Aqr is starting to brighten again. I have attached an updated light curve of the ongoing low state. Each point indicates the average magnitude during a time series, and the different marker styles correspond to different observers.
I know that it's getting close to solar conjunction, but please continue observing FO Aqr until it becomes infeasible from your site.