[vsnet-chat 3901] V438 Pup and MP TrA new elements

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

Dear friends:
                   Yesterday when I sent my eclipse observation of V438
Puppis, I mentioned that it would probably be not possible to find a period
based on the sparse data available. But fortunately I was wrong: my
observation made it possible.

V438 Puppis turned out to be a very interesting object. First of all it was
very difficult to find a period because both primary and secondary eclipses
are almost identical and they are easily misidentified.
Second, as I mentioned earlier, Hipparcos Catalogue suggested period of
5.699 days can be thrown out using only the own Hipparcos data, because some
eclipse observations are not taken as such when they actually are.
Third, it's very interesting to note that secondary eclipse occurs at phase
0.696. Is it an extreme case of eccentricity or there are other cases?
When I noticed this, I tried to find a shorter period, but they were all
impossible based on Hipparcos data.

New elements are the following:

V438 Puppis - EA

JD 2448381.042 + 4.934978 x E (min I)

Primary eclipse lasts 0.32 days (approximately).
Amplitude:  5.907 - 6.14 Hp ( V= 5.97 - 6.20:)*

JD 2448634.227 + 4.934978 x E (min II)

Secondary eclipse lasts 0.36 days (approximately).
It happens 3.434 days after primary eclipse (phase 0.696)
Amplitude:  5.907 - 6.114 Hp ( V= 5.97 - 6.18:)*

These elements can be checked out any day, because the star allows eclipses
to be visible often.


MP TrA is another interesting star. No period was suggested for this one,
although it could be easily found in the Hipparcos data.
Lots of observations (including an almost three full-days run of
observations difficult to find for Hipparcos objects) show two eclipses
similar in duration and something interesting: an evident O'Connell effect
in the secondary eclipse, that makes maximum almost 0.02 mag. brighter than
before and after primary eclipse.

New elements:

JD 2448077.9076 + 2.0697312 x E (min I)

Primary eclipse lasts 0.167 days.
Amplitude:  7.785 - 7.896 Hp (V= 7.81 - 7.90:)*

JD 2448619.0004 + 2.0697312 x E (min II)

Secondary eclipse lasts near 0.17 days (= min I) and happens at phase 0.431
( 0.893 days after primary minimum) almost the same as in the delta Velorum
case.
Amplitude:  7.771 -  7.847 Hp (V= 7.79 - 7.86:)*

* : V minimum (converted from Hp) depends on how the color index of the star
changes while eclipsed.


Well, I've already got 5 or 6 periods. I'll be posting a list soon to make
easier the comparison between HIP and new data.

Best regards,
Sebastian.








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