Re: HD 189735

[Michael Koppelman <lolife@bitstream.net>]

I agree that this seems like a great candidate for a 
multi-observer campaign. As the unofficial campaign coordinator, 
I'd like to urge everyone to monitor this star. It would be 
great if we could get both normal ol' observers and the TASS 
systems pointed at this long enough to fill in the curve. I 
think it will be a very interesting curve. Please send me your 
data and I will happily distribute it to whomever requests it. 
As John point out, this will be interesting in color, too, so 
please take filtered data. It is bright enough:

B=11.4
V=9.76
R=10.2
I=9.34

...according to TASS and USNO A2. Tycho-2 says it has "suspected 
intrinsic variability". I wonder if ROTSE or any of the other 
surveys have picked this one up? There are no references to it 
in NASA ADS.

Cheers,
Michael K.


> On Tuesday, September 10, 2002, at 05:29  AM, postbag@freeuk.com wrote:
>
>
> Michael and each
>
> I'd been looking at this one.
>
> The TASS data says it's an RS CVn variable caught at one secondary
> minimum and also with the maximal wave sampled too over several
> different nights.  The eclipse gets bluer, so it is secondary.  Primary
> eclipse may end up being as much as a mag.
>
> You are a long way off folding the current data into anything.  RS CVn
> light curves need serious and complete sampling, and can vary over time
> for various reasons (though more usually over the longer term) so
> folding isn't entirely safe.
>
>
> Probably ought to check with Dirk re nature (B-V may be a bit too
> "early" for RS CVn identification) and import: I believe RS CVn objects
> are not that common.  Period is gonna be a day or more, with a lot more
> also being possible.  Could be a significant find and worthy of a
> multi-observer campaign.  A good light curve gives rotation rate of
> secondary star as well as orbital period, though the vast majority of
> these stars are synchronous (or "pseudosynchronous" if the orbit is
> elliptical), so there should be could be no difference twixt the two.
> Showing whether object is asynchronous or not is an important part of
> collecting the light curve.  Collecting lightcurves at times over many
> years allows solar-type cycle to be assessed.  A good lifetime project
> one.
>
> Strangely no hint of xray source.  As you say, not previously known.
>
> Cheers
>
> John