J2045

SRGA J204547.8+672642

Observations

SRGA J204547.8+6726422RXS J204548.4+672629 is a CV star that is Identified as “possible IP”. Using a Moravian camera and a 20” Ritchey-Criterion telescope located at Merrimack College to record the period of J2045. VStar was then used to determine the period, frequency, and light curve for CV star. There are a total of two sets of images taken, one was done using a V filter, the second set we used a Luminance filter. The period for the V filter was 47.52mins and for the Luminance filter was 18.288mins. Combining the filters and subtracting the difference, a time of 46.368mins was recorded. We were unable to confirm these periods, due to limited information NASA provided from the catalog.

We conducted a reanalysis of this source in early 2024, which can be found at the bottom of this page. We were able to find these same periods again, in a more consistent manner, but the combined data is still inconclusive.

Luminance Filter

V Filter

Combined Data of Both Filters

Period Analysis (Combined)

All images set with a min of 0.005d and a max of 0.05d.

We also ran the Period through a different application, Peranso, and the period found was 46.863 minutes long. This is without subtracting the V filter from the luminance filter.

Phase Plot (Combined)

Frequency (Combined)

Frequency range was 48 minimum, 300 maximum, and a resolution of 1.

Individual Observation of Luminance and V filters

Luminance Filter

All 99 images were taken on 20230601 at 30 seconds exposure.

V Filter

All 153 images were taken on 20230610 at 30 second exposure. Using the same comparison stars from the Luminance filter.

Light Curve with Luminance Filter

Light Curve with V Filter

Phase Plot (V Filter)

Phase plot of 153 images set with a min period of 0.005d and a max of 0.05d.

Period Analysis (V Filter)

Period analysis of the 153 images set with a with a min period of 0.005d and a max of 0.05d.

Frequency (V Filter)

Frequency range was 48 minimum, 300 maximum, and a resolution of 1.

Period Analysis (Luminance Filter)

Period analysis of 153 images set with a min period of 0.05d and a max of 0.2d.

Light Curve (Luminance Filter)

Light curve of the 153 images set with a with a min period of 0.005d and a max of 0.05d.

Frequency (Luminance Filter)

Frequency range was 48 minimum, 300 maximum, and a resolution of 1.

Our Data

20230601

20230610

2024 Reanalysis

In this reanalysis, we were more careful and systematic with both the photometry and the periodogram. For example, since the AAVSO does not have a sequence for this source, we had to construct our own set of comparison stars. In this reanalysis, we followedthe J/K to V strategy found here: http://brucegary.net/dummies/method0.html, and we used the V mag to perform differential photometry on the luminance filter (for 20230602) as well. Our results follow.

In the first two observations, peaks were found just under 50 Hz and around 85 Hz, corresponding to 18 min and 27 min. The longer period may be present in the last observation as well.

Analysis of the complete set was complicated by the fact that the filter changed between the first and second observation. In this figure we normalized the three observations to have the same mean, and we again see peaks in the 40 1/d and 85 1/d region. In addition, there is a larger peak at very small frequency, corresponding to 11.1 1/d (130 min). The problem with this analysis is that there is a clear and very obvious 2.98 hr period, found in Kepler data (https://ui.adsabs.harvard.edu/abs/2022A%26A...661A..39Z/abstract), which we would not be sensitive to this crude normalization.

In this analysis, we left the offset in, in an attempt to see the 2.9 hr period. However, that peak is at 3.45 hrs. That phase plot is shown below.

However, the 2.9 hr period is quite convincing in the Kepler data, so we are not making the argument that this period is more significant. Likely the change in the filters is impacting the analysis.

Shown at left is the residual plot, after the 3.4 hr period has been subtracted. Although the highest peak does have a period close to the others we found, we've also indicated the 1% FAP, which tells us there are several significant peaks in the data. Thus, there is no simple interpretation of these results. It may be that the relatively large number of peaks over the 1% FAP is telling us that the null hypothesis is false here, but it is unlikely to be demonstrating to us that major peak is significant.

We should also note that we tried a similar analysis with the 2.98 hr period, and although the details vary (the ~55 1/d peak becomes subdominant to a ~17 1/d peak), the problem with the FAP remains. Those two images are found below.

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