[vsnet-ecl 335] Re: DK Cam

["Sebastian Otero" <varsao@fullzero.com.ar>]

> Dear VSNETTERs
>
> From the Hipparcos data of DK Cam and the recent visual minimum observed
> by Kari Tikkanen we find a very likely period of 12.218 days. Fractions of
> this period do not look very likely. The next few eclipses are given in
> the ephemeris and interested observers are encouraged to forward their
> observations to us. The eclipse lasts for about 7 hours and is not very
> deep so observations with a CCD or photometer will be most valuable.


Hi, Chris:
              We seem to be coming up with the same periods every time!!.
Two days ago I wrote a message to Kari tellimg him about a 12.21857 days
period.
The message went like this:

>I search thorugh the data and could find a
> very possible period of 12.21857 days for DK Camelopardalis.
>              This is based on just three eclipses observed by Hipparcos,
but
> we have several facts on our side:
> Duration of the eclipse is long enough to account for a relatively long
> period.
> This long period let us do some especulations without a very large error
> accumulation.
> And it is easier to establish a relationship between minima this way.
> Eclipses took place at 2448074.50, 2448160.03 and 2448660.99, as seen by
> Hipparcos.
>
> There are 7 and 41 cycles between the different eclipses.
> There is a possible secondary minimum by 2449045 but that observation is
> probably a wrong measurement so it would be better not to take it in
> account.
> Periods of 6 and 4 days have been discarted by using Hipparcos data.
>
> From Hipparcos data it is possible to say that eclipse lasts 0.48 days or
so
> (that's 11 1/2 hours from beginning to end). Given the short amplitude of
> the variation the extreme parts of the eclipse probably remain undetected
> visually.
> V range is 7.57 - 7.79 (7.62 - 7.84 Hp) assuming no major color changes at
> minimum (that could interfere in the transformation from Hp to V, which is
> actually not possible for an EA with an amplitude thsi short...)
>
> One of my favourite projects is to work with these "unsolved" EA Hipparcos
> variables. I had discovered the periods for 5 or 6, two of them with
> recently observed eclipses but the rest just by looking at Hipparcos rich
> (but not always well-used) data.
> I could even find a perfect secondary eclipse and the presence of
O'Connell
> effect on MP TrA, a 2 day period short amplitude eclipser!!!

>I have a prediction to confirm a 35 day period for
> FM Leonis, which I think it is going to be in eclipse next wedneday night.
(MESSAGE ABOUT IT TOMORROW)

Well, Chris, let's compare our results:
Yours:

>To=2448380.0000 +  12.21760000xE

My results are: To= 2448160.03 + 12.21857 x E

This means that we are almost a day off.
My predicitions are:
2452020.0010  April 20.5010
2452032.2195  May  2.7195
2452044.4380  May 14.9380
2452056.6565  May 27.1565

>           JD       Year  Mo   Date     UT   Min Cycle
>      2452020.8448  2001   4  21.3448   8:16  I    297
>      2452033.0624  2001   5   3.5624  13:29  I    298
>      2452045.2800  2001   5  15.7800  18:43  I    299
>      2452057.4976  2001   5  27.9976  23:56  I    300
>
> Regards
>
> Chris Lloyd
> Kari Tikkanen

It's an important difference that should be solved by observations during
April 20 and 21.

Regards,
Sebastian.


PS: I am preparing charts for the 0.5 mag. eclipse of FM Leo next wedenesday
night.






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