EX Hya

EX Hya is a well-known Intermediate Polar CV - that is, it has a strong magnetic field but one that is not strong enough to either disrupt the accretion disk or lock the spin and the orbital rotation of the system. We choose to observe this system because it is so well-studied already (https://asd.gsfc.nasa.gov/Koji.Mukai/iphome/systems/exhya.html), and would therefore serve as a good test for our analysis routines. The orbital period is 1.638 hr, and has been seen in both the optical and X-ray bands. The spin period of the white dwarf is 67 min, and has been seen in many optical and X-ray observations.

The amount of data collected on this source was significantly less, as can be seen from the image at left. However, we are reasonably confident we can pick out the spin period using Peranso - although not the orbital period.

The measured period of 1.06762 h was seen in multiple searches (LS, ANOVA, DCDFT, CLEANest), and the phase plot is reasonably convincing. Similar results were found for the VStar implementation of DCDFT.

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2024 Reanalysis with MPO Canoptus

In the summer/fall of 2024 the group undertook a study of the software package MPO Canoptus to determine if it was appropriate for our CV star research. Although we had previously done some initial testing of MPO, our impressions were that it was both a) too complicated and b) too expensive, as compared to AIJ + Peranso/VSTAR. The latest version, however, is free (https://minplanobs.org/BdwPub/php/v1012conversion.php ), so we felt it was worth another look. Here we present the reanalyzed data from MPO on this source. The basic result is "not very convincing", in a similar way to our initial approach, and it shown below. First the short period, then the longer one.

The period search above a minimum of 1 hr. There are several peaks, but they are not overly significant, similarly to the first figure from Peranso. The actual peak period here is 1.03 hr, 62 min.

The folded phase plot for the 1.03 hr signal. Not only not convincing, but the model looks more like twice this phase. It should be noted that the period search was no less convincing in Peranso, but the folded phase is much *more* convincing that we are actually looking at a periodic signal.

The period search for the short period with the longer period subtracted. Somewhat more significant, at 1.09 hr (65 min).

The folded light curve on the short period after subtracting out the longer period.

The period search for the long period. Again, not overly significant but at least cleaner than the shorter period. The result was 3.04 hr, so perhaps a harmonic of the known long period of 1.6 hr.

The folder phase plot of the longer period. This is more convincing then the shorter one, and the symmetry suggests that indeed we are looking at the first harmonic of the orbital period.

The period search with the shorter period subtracting, resulting in the same peak (3.04 hr), but a more significant result.

The folded light curve of the longer period with the shorter one subtracted. A slightly better model fit to the interpretation of a first harmonic.

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