Historical light curve of the black hole binary V4641 Sgr based on the Moscow and Sonneberg plate archives

TL;DR

This study digitized and analyzed archival photographic plates of the black hole binary V4641 Sgr, revealing historical outburst activity and refining its orbital period using combined archival and CCD data.

Contribution

It provides the first extensive analysis of archival photographic plates for V4641 Sgr, improving orbital period measurement and documenting historical outburst activity.

Findings

Confirmed a single outburst in 1978.

Lower outburst activity compared to post-1999 CCD data.

Refined orbital period to 2.81728 days.

Abstract

We performed digital processing of a large set of photographic plates for X-ray binary system V4641 Sgr containing a black hole. A total of 277 plates were found in archives dated between 1960 and 1992. Photographic observations revealed lower level of outburst activity if to compare with CCD data after the large 1999 outburst. Only single outburst which happened in 1978 was confirmed. If archive photographic data are used along with contemporary CCD observations, the orbital period may be improved, and its value is 2.81728 +/-0.00004 day.