Proposal #453

Short-cadence time series observations of V0470 Cam.

V0470 Cam is an HW Virginis-type eclipsing binary with an orbital period of approximately 2.3 hours. According to the Variable Star Index, the object has CV magnitude ranging from 14.52 to 15.62. Several publications have been written about the V0470 Cam. Here are three examples:

- X. Mai and R. L. Mutel, "Eclipse timing modelling of three post-common envelope binaries: hybrid solutions",
- O. Sale et al., “Eclipse time variations in the post-common envelope binary V470 Cam”,
- D. Bogensberger et al., “Post-Common Envelope Eclipsing Binary V470 Cam”.

In July 2023, a monthly, time series photometry project was started for this object with a goal of providing continuous data for a period of at least a year – in order to re-examine hypotheses raised by the researchers in the past by measuring times of future minima. Observations were made in July, August and September 2023 using a 0.6 meter f/4.6 Newtonian telescope located at Obserwatorium Astronomiczne w Niedźwiadach. Due to the lack of suitable weather, no observations were conducted in October, and weather forecasts for the nearest future are not optimistic.

Finally, I request that one of the Faint Star Monitors conduct time series observations of this object. The preferred effective cadence would be less than 20 seconds. In order to achieve the best signal-to-noise ratio, they should be done using a clear filter (if not possible, Johnson V is the second preference). What is important, the camera clock should be well-synchronized so that its accuracy is better than few seconds of time (ideally, error < 1 second). I am interested in two primary minima (not necessarily consecutive ones) for the purpose of averaging and control checking. This could be achieved in one of two ways:

1. The first method involves conducting a single, non-stop 5-hour observation. In this way, two primary minima would surely be captured. This is a simpler method.

2. The second method would be to observe the two primary minima separately, whose approximate moment "T" should be possible to estimate using the ephemeris given below, where E is the primary eclipse number. Ideally, observations of a minimum should begin 30 minutes before the calculated moment of maximum eclipse phase and end 30 minutes after the calculated moment of maximum eclipse phase – in total, 60 minutes of imaging. This method is less time-consuming, as a total of 120 minutes would be spent this way instead of 300.

T= 2460203.5145 + 0.095646609 ·E
T = [Barycentric Julian Date]

For your information, the 0.6m f/4.6 telescope used 10s clear filter exposures with approximately 11s effective cadence - providing satisfactory results. During these observations, the average out-of-eclipse Source-Sky value (the aperture ADU counts minus sky background contribution value) of the target star was approximately 60000 ADU – similar value would be desired here. If this proposal is accepted, this information may prove useful when allocating the right telescope and choosing the right exposure time that is below 20 seconds.

I request that the images can be downloaded via FTP. If somehow more convinient, files could be shared via Google Drive, for example. I am open to any suggestions. The photometry would be performed using AstroImageJ. Therefore, I do not request the files to be uploaded into VPhot.

I would like the data to be kept proprietary for a period of one year. After that period they would be submitted to the AAVSO International Database.

The coordinates below are given for epoch J2000 (source: VSX).

If you have any questions, please do not hesitate to contact me at krzysztof.s.zielinski@gmail.com .

Regards,
Krzysztof Zieliński