[vsnet-alert 8485] V4641 Sgr

[Berto Monard]

I would like to confirm the likely end of the V4641 Sgr active state.

My observation (made through clouds),  after the eclipse mentioned by M Uemura, gave:

sgrv4641   050628.13   13.2CR 


On the previous night there was still a slow and low amplitude modulation and a 0.05 mag hump occured around UT June 27.028. 


Interesting to note is that the X ray flare picked up by the HETE team and mentioned in vsnet-alert 8477 "The HETE WXM instruments detected an untriggered burst H11603 at 04:05 UT on 26 June 2005" was actually predictable from my observations just preceding this time. Dawn and the setting of V4641 Sgr at my location prevented any observations past 03:40 UT. At that time V4641 Sgr had reached 10th magnitude and was apparently still brightening further. This might be a similar event as the one picked up by R Stubbings in 1999.

The other X ray maximum detected by HETE "examination of earlier data revealed another event at 03:01 UT on 26 June 2005" was not visible in my data but about 5 minutes later (June 26.129) there is a definite temporarily maximum brightness shown in my data. At time UT 03:01 there was a plateau of constant brightness just preceding the rise to this maximum. Probably it's all related...


True to tradition V4641 Sgr has shown its (his?) 50h big show and not much after that. ..


Regards,

Berto Monard
Bronberg Observatory / CBA Pretoria