It is the sun, yeah. They use the Perseverance cams to monitor solar activity.

https://www.jpl.nasa.gov/images/pia26301-perseverance-views-sunspots/

The images you highlighted in your post are MastCam-Z images of the sun taken through neutral density (ND) filters that are used for solar imaging. Each of the MastCam-Z cameras has a pair of ND filters (590 ± 88 nm (ND6) and 880 ± 10 nm (ND5))

They image the sun on a regular basis, primarily to check the rover's internal navigation system, but they also use the cameras with those filters to measure sunspot activity, especially when Mars is on the far side of the sun, they have also measured the Martian moons transiting the sun, this can more accurately measure the rotation speeds and orbits of the moons compared with Earth based telescopes.

I'm assuming this set of images were acquired on sol 1944 for navigation checks. Basically the rover have a set of internal motion detectors, they are used during driving and at the end of each drive to record the position of the rover. That x, y & z data is returned to JPL shortly after each drive. That data permits the update of the rover traverse and location maps. However there can be minor inaccuracies (e.g caused by wheel slip on slopes or soft sand), but those small errors can accumulate over several drives where the rover's computer thinks it is in a certain location, but it's slightly off. So they use the sun to accurately check the actual position. The way I understand it (from MSL days) is that the rover points the camera at where it calculates the sun should be at a specific time of the day (if its navigation is accurate) and snaps a photo. If it is accurate the sun will appear in the center of the images, if the navigation is off (even by a little) the sun will be 'off-center' in the image and ground engineering team members can reset the x, y & z accordingly. The amount it is off-center can be used to accurately calibrate / correct its location. These sun checks are similar to how navigators sailed the seven seas back in the day with a sextant. The sun images are used in conjunction with end-of-drive images to determine accurate location :)

Credit: NASA/JPL

Which sols are the images you highlighted in the image in your comment?

It is possible that the rover returned metadata to show the pointing and the precise UTC timing of the capture by the camera when those 4 images were acquired. Such data can be used by experts to understand what star field camera was looking at, but that's a skill I have not acquired. The actual reason for the images will likely be detailed in the mission managers report for that sol, but if they are recent images, then you'll have to wait several months before that information hits the PDS / Analysts Notebook