MBCAA Observatory

FO Aqr: 2017 season and a new fading

Observed: 7 June, 28 July, 21, 22 Aug, 12, 14, 24 Sep, 5, 14 Oct 2017

Michel Bonnardeau
8 Sept 2017
Updated 13, 14, 15, 25 Sep, 6, 16 Oct 2017


Observations of the intermediate polar FO Aqr are presented for 2017. They show that the object is fading.


FO Aqr is a cataclysmic system and an intermediate polar. These observations are a follow-up of my 2004-15 observations and of my 2016 observations.


The observations in the 2017 season are carried out with the same setup and the same comparison star as with the previous seasons.

For the differential photometry, the comparison star is GSC 5803-398 (UCAC4 409-138153 with V=10.921 mag). The check star is UCAC4 409-138161.

The following light curves are preliminary results:

The magnitudes are the differences with the comparison star. Red: FO Aqr, Blue: the check star shifted by +0.3 mag. The error bars are the quadratic sum of the 1-sigma statistical uncertainties on the variable and of the comparison star.

The check star magnitudes are shifted by +1.0 mag.

During Full Moon.


With the magnitudes averaged over each night:

The bars are +/- the standard deviations over each night.

The object is fading. This was reported by Littlefield et al (2017).

Fourier spectra

Fourier spectra obtained with the PERIOD04 software program (Lenz & Breger (2005)):

The main signal (at 69) is due to the spin of the white dwarf.

The following signals may be identified: 69 spin, 64 spin-orbit with an harmonic at 128, 5 the beat between the previous ones with several harmonics. See also Littlefield et al (2017).

The 4 highest peaks are, in increasing frequencies: orbit, spin-orbit, spin, 2(spin-orbit).


Lenz P. and Breger M. (2005) Comm. Asteroseismology 146 53

Littlefield C. et al (2017) ATEL #10703

Technical notes

Telescope and camera configuration.

Computer and software configuration.

Data processing.

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