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AG VIR is indeed an EW-type binary star (W Ursa-Majoris), which is actually two stars in contact, orbiting each other around a common center of mass and eclipsing each other from our field of vision. According to the AAVSO catalog, VSX, they are also of type KE, meaning contact binaries with a spectral type described as hotter (A to O).

In fact, we are dealing with two stars, A7 and A9V (according to the VSX), with temperatures of approximately 7500-7920 Kelvin. There is an exchange of matter between the two, and this exchange of matter implies a change in mass, a shared envelope, and therefore subject to changes in orbits, even a change in type depending on the star's evolution.

This is why they must be monitored periodically to observe these changes.

(See: Algol Paradox). (* Ref: https://sites.uni.edu/morgans/astro/course/Notes/section2/spectraltemps.html)

During the night of April 30, 2022, observations began at 02:25 UT and ended at 05:50 UT, a total of 3 hours and 25 minutes. Since the star's period is 0.6426505 days (15.42361 hours) (VSX), the observation time corresponds to only about 1/5 of the complete period.

Data was collected using multifilter photometry (B, V, R, I) and then in low-resolution spectroscopy (Alpy-600).

In Spectroscopy:
I combined one of the spectra taken at 2:40 UT (in green), then another at 05:42 UT (in blue), and placed them on the same graph to see the differences and, more importantly, to determine if we could detect a shift caused by one of the elements. However, although the Alpy spectrograph works wonders for obtaining a visible spectrum image of a star, its resolution isn't high enough to detect the shift caused by a binary or double star. The Alpy-600 has an approximate resolution of R=600; a resolution of R=15,000 or higher would be needed to have any chance of detecting binary stars.

Here, although the instrumental correction was well executed, a difference is noticeable in the star's continuum and in certain elements of its composition... Minimal, but still present.

The two components, which are almost of the same spectral type, are therefore difficult to distinguish at this scale and given their proximity.
From a photometric perspective, it quickly becomes apparent that we were observing the star's minimum.

It is interesting to note, however, the differences between the curves due to the various filters, which create a separation of the different spectral responses.

(See attached file on the photometric filters used).

AG VIR - P. 108 - Binary stars _ a pictorial atlas -- Dirk Terrell, Jaydeep Mukherjee, R_E_ Wilson; with foreword 

Graphique O-C 2024:

https://www.as.up.krakow.pl/minicalc/VIRAG.HTM

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JBD Juin 2022 - Révision 2025