[vsnet-alert 7344] Re: V4641 Sgr: eclipse!?

[Gianluca Masi <gianmasi@fr.flashnet.it>]

Dear Taichi,
I was just having a look at Berto's run and actually was captured by the
shape of the feature you point out in your message. Such a deep (around
0.5 mag) fading is very different from the other features visible on the
same curve, having a shorter timescale. Also, at the bottom part of the
eclipse, there is an interesting feature (0.1 mag), which should be
interesting to investigate.

A very close observation os this fashinating star is definitely urged!

Regards,
Gianluca


Taichi Kato wrote:
> 
> V4641 Sgr: eclipse!?
> 
> Dear Colleagues,
> 
>     We have received two new data sets from Berto Monard (see vsnet-alert
> 7342).  On May 21/22, the system underwent a deep fading between May 22.0
> and 22.1 UT.  This timing agrees with the expected inferior conjunction
> (ephemeris from Orosz et al. 2001; updated by Uemura et al. 2002).
> During this fading, strong flickering activity virtually disappeared!
> Such behavior could be reasonably explained if the (compact) flickering
> body was eclipsed by the secondary (first case in microquasars, if
> confirmed).  There was an indication that flickers rapidly emerged
> when the system brightened from this fading.  During the declining branch,
> flickering was less apparent than on the brightening branch.
> 
>     On May 22/23, the strong ultra-short-period flickering were always
> present in high-speed photometry (5-s integratrations), as on May 20-21.
> 
>     Expected times of inferior conjunctions (likely eclipses), in geocentric
> UT.  Times are approximate (to 1 hr or so) owing to the unavoidable
> uncertainty in the epoch and period.
> 
>   20020519 06:39:14
>   20020522 02:15:53
>   20020524 21:52:33
>   20020527 17:29:15
>   20020530 13:05:57
> 
>     If this interpretation is correct, the object is expected to remain
> active until late May 24.  Continuous coverage is most urgently needed.
> More detailed analysis, together with newly available data, will be
> later presented by Uemura-san.  The Kyoto team is planning to make
> high-speed (1s) photometry at Ouda tonight, depending on the conditions.
> You will hear more from Uemura-san about the progress of the observation
> and data analysis.
> 
> Regards,
> Taichi Kato
> VSNET Collaboration team

-- 
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* Gianluca Masi                           "Two things fill the soul   *
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