[vsnet-alert 5319] Delta Velorum next eclipses

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

Dear friends:
                       In response to Dr. Sonja Vrielmann's request I've
prepared a new ephemeris.
I took some aspects in account.


PART 1 - Period

First of all, according to Galileo's star scanner, the observed eclipse was
deepest between JD 2451714.77 and 2451715.10.
That means 0.33 fraction of a day. So mideclipse should be 0.165 days away
from this dates.
That is: 2451714.94

According to Galileos' data, the star took several hours to regain its full
brilliance. "Disappearance" for Galileo means more than 0.2 mag. dimming ,
in this case= 2.15

If we take a look at Hipparcos data we'll see the following:

2448806.05313    2.212 Hp
2448806.06746    1.949 Hp

Which is pretty interesting... and dissapointing. Too fast recovery!!!!
Unless the first measurement has been made just at the time the eclipse was
ending. Then 2.15 would take place near 2448806.055

If Hipparcos eclipse is real, then the period should be 5.88877 days and
give the following predicted and observed eclipses (deepest part):

JD - Begin predicted  -  End predicted   -
Observed--to         -
Observation by

2448805.72               2448806.06
2448806.0531----
HIPPARCOS

2450631.25               2450631.58
2450631.4375----2450631.5417
My visual observations

2450831.47               2450831.80
2450831.6409----2450831.7688
My visual observations

2451308.45               2451308.78
2451308.4618----2451308.7014
My visual observations

2451714.77               2451715.10
2451714.77--------2451715.10
GALILEO

The 67.7 day-period gives great residuals in the order of two or three days
for the first and third eclipses.

Paul Fieseler, Sequence Integration Engineer of the Galileo Mission, Jet
Propulsion Laboratory of NASA, has kindly submitted more data from the
Galileo star scanner.
He has prepared a chart based on the 5.9 day period and it seems there is a
hint of eclipses going round.
However, it's not enough for a confirmation since most of the eclipses
should occur just during gaps in the data.

This, along with the refined period and the excellent fitting reported
above, seems to indicte the shorter period is correct.


PART 2 - Ephemeris


I've been preparing a schedule for the following observations and hte
conclussion is: BE PREPARED.

Yesterday at 4 AM local time I could observe the star and it is high enough
to make a reliable brightness estimate, even earlier.

So, taken the 5.88877 day- period, we should see an eclipse from South
America and South Africa next Monday, before sunrise.


Predicted beginning ----  ending               South America       South
Africa
Australia/ New Zeland

2451832.54---2451832.88     10/14-15     22.00--06.00         03.00-11.00
11.00-19.00/13.00-21.00
2451838.43---2451838.77     10/20-21     19.30--03.30         00.30-08.30
08.30-16.30/10.30-18.30
2451844.32---2451844.66     10/26-27     16.45--00.45         21.45-05.45
05.45-13.45/07.45-15.45
2451850.21---2451850.54     11/01-02     14.00--22.00         19.00-03.00
03.00-11.00/05.00-13.00


If the period is 67.7 days (if so, Hipparcos eclipse and the 2451831 eclipse
would be left aside) then the following eclipse would be:

2451850.2---2451850.5       11/01-02      14.00--22.00        19.00-03.00
03.00-11.00/05.00-13.00


It's interesting to note that if the first one is correct, Australia and New
Zeland have no chance of detecting it while in the second option, South
America 's got in the way.
South Africa has the cahnce to catch both events but near the beginning and
near the end.

We'll see what happens.

Thanks again to JPL, NASA.


Best regards,
Sebastian.

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