[vsnet-chat 4223] DK CAM and DE DRA

[Kari Tikkanen <ktikkane@mail.student.oulu.fi>]

>From: "Sebastian Otero" <varsao@fullzero.com.ar>
>To: "Kari Tikkanen" <ktikkane@mail.student.oulu.fi>
>Subject: Re: [vsnet-chat 4182] How I get Hipparcos data of DK CAM ?
>Date: Sat, 14 Apr 2001 04:23:58 -0300


>> >>Subject: How I get Hipparcos data of DK CAM ?
>> How I get single HIP magnitude measurements of DK CAM with HJD's ?
>
>Hi, Kari:
>             Well, John has answered properly that question.
>But, prompted by your request 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.

Hi, Sebastian:

I have now observed two minima of DK Cam:
  I GJD 51996.433 +-0.013 d and
 II GJD 52013.53  +-0.03  d

MinI with Hipparcos minima data gives period 12.2176 d.
With period P=12.2176 d the second looks minII with phase 0.400+-0.03 
which is suspicuously close 2/5 .. 
.. but P'=4.8794 d doesn't fit Hipparcos data.


---- DE DRA ----
>From: "Sebastian Otero" <varsao@fullzero.com.ar>
>To: "Kari Tikkanen" <ktikkane@mail.student.oulu.fi>,
>        <vsnet-chat@kusastro.kyoto-u.ac.jp>
>Subject: Re: [vsnet-chat 4185] DK CAM hipep.. THANKS!
>Date: Sat, 14 Apr 2001 17:01:20 -0300

>> Also DE DRA is EA but
>> I've found also strange ~ 90 d cycle,
>> DE DRA or its compare reddish star varies.
>>
>> With Best Regards,
>>  Mr. Kari A. Tikkanen
>
>Dear Kari:
>                Hipparcos did not catch any eclipse of DE Draconis which is
>at V= 5.72 at maximum.
>The GCVS lists it as an EA/DM star based on a 1979 paper by L. Meinunger.
>Amplitude is 0.16 magnitudes.
>Epoch is 2442626.2861 and period is 5.2980361 days.
>But using this ephemeris, no eclipse is seen by Hipparcos when it should:
>2428231.60 is the predicted date. And Hipparcos found:
>2448231.55    5.71V
>2448231.565  5.71V
>
>Maybe a small error in the period could have accumulated with years and this
>results in a wrong prediction, but new observations are probably needed.
>Maybe someone else knows something about this bright star.
>
>The star is a B9V, a main sequence dwarf, so the 90 day cycle is probably
>not for this one. Hipparcos photometry doesn't show variability of any kind.
>If your comparison is HD 194298, this is probably a K5III giant
>microvariable (5.68 - 5.72V). NSV 25126.
...

I observed couple minima of DE DRA in Aug 2000 visually. They are
on my logbook but not yet tapped onto file into my computers.
I use RANDOM method for these small "milli"variables. (It means
without ephemeris).

My comp stars for DE DRA are:
 e  TYC 4236-2502-1  HIP 99500 F5V    T48= W  
 b  TYC 4236-2503-1  HIP 98962 K3III  
 

With Best Regards,

  Mr. Kari Tikkanen, OULU, FINLAND            
  http://vsnet.student.oulu.fi/~ktikkane/astrov.html

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