Re: HD 189735

[Michael Koppelman <lolife@bitstream.net>]

300.2996279	7.981603488

aka

20:01:11.91 +07:58:53.77


On Tuesday, September 10, 2002, at 08:34  AM, Tom Droege wrote:

> I should have more data on this one.  If someone will remind me 
> of the decimal RA and Dec. I will look.
>
> Tom Droege
>
> At 10:29 AM 9/10/02 +0000, you 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
>
>