Dear dr. Kimura,

Currently we are monitoring Swift J1727.8-1613 from ROAD in the BVRI and clear filters. We are limited by the longitudinal coverage, but the object is still brightening and cyclical variations in several filter over a timescale of several hours appear.

It is possible that the phenomenology of the variations will be different from what has been detected in V404 Cyg before.

Warmest regards,

dr. Siegfried Vanaverbeke

Op vr 25 aug 2023 om 22:46 schreef Mariko Kimura <mkimura@kusastro.kyoto-u.ac.jp>:

Swift J1727.8-1613: black-hole binary and V404 Cyg-like object ?

Swift and MAXI detected an outburst in Swift J1727.8-1613.
This is a candidate for a black-hole binary and possibly similar to
V404 Cyg, a unique object known as a source of rapid variability.
A few seconds variability was already found in X-rays.
The most violent variability would be ~2 mag in several tens of min.
This is very bright. Currently, ~13 mag.
The position is (RA)17:27:46 (DEC)-16:12:53 reported by Swift.
Follow-up observations are strongly encouraged.
https://www.astronomerstelegram.org/?read=16205
https://www.astronomerstelegram.org/?read=16208

- Mariko Kimura at Kanazawa Univ. in Japan