Lightcurve and stellar occultation observations of asteroids with the Unistellar's network of citizen astronomers

The recently developed Unistellar’s eVscope/eVscope2 and eQuinox telescopes have been delivered to more than 5,000 customers around the globe. These telescope owners already represent the largest worldwide network of potential citizen astronomers. Due to the unified design and user-friendly operation via a smartphone app, several types of useful scientific observations are enabled and supported by Unistellar.

Each individual frame is stored in the telescope and can be accessed in 12-bit TIFF format by the user for the following data processing and analysis. Moreover, the user can upload the data to Unistellar for further processing, which is the main concept of the campaign mode: Any owner of an eVscope can receive notifications on their smartphone of transient events visible in the sky, such as comets, supernovae, asteroid flybys, stellar occultations by asteroids, or other targets of interest, perform the observations and upload the data to Unistellar’s server.

In this contribution, we focus on

(i) light curve observations of asteroids, and

(ii) stellar occultations by asteroids.

Light curves represent the temporal changes of asteroids' brightness within the typical night observational window, which takes usually several hours. Light curve observations allow us to study asteroidal physical properties - rotation period, rotation axis, and the 3D shape model.

During the stellar occultation, the asteroid is passing in front of a bright star, which is occulted, the duration of this event is directly related to the asteroid's dimension. Various observers distributed on the ground can sample different parts of the asteroid, which can lead to an accurate size estimate, and possibly even to a shape model refinement.

In 2021 and 2022, we initiated several observing campaigns aiming at obtaining light curve data of several near-Earth asteroids (NEA) that were having close approaches to the Earth - e.g., NEAs 1999 AP10 and 2000 PQ9. Dozens of citizen scientists provided their observations. Here we show the initial results obtained by analyzing these optical data. We will also discuss the quality of the photometric data and the significance and potential of the eVscope network for the study of the physical properties of asteroids.

We selected asteroids that get bright enough for at least one month, which provides a sufficiently wide window of opportunity for the eVscope users that are often limited by the weather conditions. Also, these targets have unknown or poorly constrained physical properties, which results in the opportunity to contribute to the better characterization and understanding of the population of asteroids.

Within the Unistellar's eVscope network of citizen astronomers, we are targeting stellar occultations in order to estimate their dimensions with an accuracy non-achievable by commonly used techniques such as thermal modeling. This task is quite challenging, however, we will report the first successful observations of these events.

Acknowledgments

The work of JH and JD has been supported by the Czech Science Foundation through grant 22-17783S.