[vsnet-chat 3729] NEW AND VERY LIKELY PERIOD FOR DELTA VELORUM

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

Dear observers:
                            Some things can play tricks on us, we know that.
And some things, as the Hipparcos data, can be randomly mistaken in such a
way that it can make a perfect fit - as the previously 5.88877 day period-
in our data and make us believe we have something when we don't.
                            Surprisingly I came to the conclussion that the
Hipparcos measurement is an spurious one.
Three reasons for this: 1) the recovery from eclipse to normal is just 20
minutes!!! 2) Galileo's very good data of 1989 (with another eclipse) shows
a longer eclipse and a slow light curve. 3) This new information doesn't fit
with a 5.9 day-period "forced" by Hipparcos "eclipse".

                           The thing is that I found another eclipse in my
old data based on a new ephemeris according to Galileo's measurements. And
another picture of the system is suggested now: some of the eclipses
observed are secondary eclipses. The question is which (only photometry
could solve the question)
                          First of all, thanks to Paul Fieseler, Sequence
Integration Engineer of the Galileo Mission at the Jet Propulsion
Laboratory, NASA for making all Galileo's data available. Without it, all
these coincidences would have never been noticed.


SO:  We have two stars rather similar. One of the stars was eclipsed in JD
2450631 (my data)  and 2451308 (my data) and 2451714 (Galileo's data). While
the other was eclipsed in JD 2447850 (Galileo's NEW data), 2450831 (my data)
and 2451147 (my "NEW"old data).
Let's supposed the first sets of eclipses corresponds to the primary events.
Then secondary minimum would occur at phase 0.43 (20 days after primary).
The period I'm referring to is 45.16 days. This figure would explain why the
variability wasn't discovered before.

So Danie Overbeek, you were right: nothing happened last saturday!!!!

We need to refine this but I think this new ephemeris are very reliable:

JD 2451850.4   PRIMARY ECLIPSE?  November 01/02  21.30 UT
JD 2451870.3   SECONDARY ECLIPSE?  November 21/22  19.00 UT
JD 2451895.5   PRIMARY ECLIPSE?  December 16/17  01.00 UT
JD 2451915.5   SECONDARY ECLIPSE?  January 5/6  23.30 UT
JD 2451940.7   PRIMARY ECLIPSE?  January 30/31  05.00 UT
JD 2451960.6   SECONDARY ECLIPSE? February 19/20  03.30 UT
JD 2451985.9   PRIMARY ECLIPSE?  March 17  09.00 UT
JD 2452005.8   SECONDARY ECLIPSE?  April 5  07.30 UT


The eclipses probably last more than 0.7 days (17 hours) so observations
should be made several hours before and after the times predicted.

November 01-02 eclipse won't confirm the period since 5.9 and 67.7 also work
for that date, but the next one on November 21 will be conclusive.

I hope South Africa and Australia enjoys clear skies because I'll probably
miss the eclipse from Buenos Aires..:-(((

Best regards,
Sebastian Otero.
LIADA.
Buenos Aires,
Argentina.

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