[vsnet-chat 3036] RE: [vsnet-obs 28038] ETA CARINAE - Two years of observations

[Sebastián Otero <varsao@fullzero.com.ar>]

Hi, Stan and VSNET friends:
                                                Two straight cloudy nights
prevented me from watching Eta, but looking at Harry's measurements I found
that my visual estimates are almost always 0.15 magnitudes fainter than
PEP(V) no matter what time of the year we choose.  For example the last two
measurements are 5.11 and 5.12 and my visual estimates (before rounding them
to 5.3) were 5.28 and 5.30. If we take this difference as a fact, the star
would now be shining between 5.2 and 5.3. Maybe the star has just passed the
maximum of its SD phase and it's starting to decline slowly. It would be
great to do photometry as soon as possible to confirm it or disprove it.
                                                But I want to ask observers
about the colour of the star. I really find it redder than its B-V implies.
Maybe the colour of the envelope is more apparent visually than in UBV
photometry. What colour do you see?

Best regards,
Sebastián.

----- Original Message -----
From: William S G Walker <astroman@voyager.co.nz>
To: Bish Ishibashi <bish@howdy.gsfc.nasa.gov>;
<vsnet-chat@kusastro.kyoto-u.ac.jp>; <varsao@fullzero.com.ar>
Cc: Harry Williams <harryw@iconz.co.nz>
Sent: Wednesday, June 07, 2000 2:59 PM
Subject: [vsnet-chat 3032] Re: [vsnet-obs 28038] ETA CARINAE - Two years of
observations


> Hi Bish and Sebastian,
>
> I read the notes about eta Carinae with interest. As Bish knows, Harry
> Williams measures this star in Auckland from time to time using UBV
> filters. Your emails encouraged me to reduce his last two measures of May
2
> and 24. These seem to show (but to misquote - 'two measures don't make a
> decline') a pause in the brightening which has prevailed for some time.
The
> last dozen or so measures are set out below: JD-2400000, V, B-V, U-B.
>
> It's rather difficult to measure this star using pep and the errors are
> probably between 1% and 3%. There's obviously a case for continued
> measures. Maybe the 5.5 year cycle is now beginning to make its presence
> felt again. But I'd go along with Bish's comments - it's a very difficult
> visual object. For what it's worth the colour has reddened by 0.06 in B-V
> since 1972 and the U-B colour may have become a little stronger.
>
> Let's all keep looking!
>
> Regards,
> Stan
>
> 50847.9544,5.442,.642,-.284
> 50850.9404,5.41,.653,-.275
> 50856.9378,5.422,.672,-.268
> 51319.8457,5.218,0.664,-0.312
> 51322.8565,5.184,0.665,-0.315
> 51335.8660,5.217,0.672,-0.334
> 51336.8543,5.222,0.645,-0.318
> 51348.8614,5.217,0.678,-0.285
> 51349.8440,5.181,0.665,-0.293
> 51560.9347,5.125,.695,-.301
> 51606.8692,5.124,.695,-.332
> 51612.8989,5.128,.667,-.285
> 51620.8788,5.103,.673,-.304
> 51625.9255,5.1,.672,-.329
> 51627.8502,5.092,.699,-.299
> 51630.8758,5.096,.668,-.313
> 51635.8901,5.098,.677,-.321
> 51666.9385,5.11,.673,-.308
> 51688.822,5.12,.645,-.379
>

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