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[vsnet-campaign-deltavel 4] New period for delta Vel
Sebastian kindly sent me his visual observations, the Galileo eclipse
timings and the Hipparcos data of delta Vel so that I could have a look
for a period. I downloaded the Hipparcos data from ESA so that I could see
the flags and was immediately suspicious of the 'eclipse' measurement, as
it is flagged and has by far the largest error. As the next value, taken
shortly afterwards, is back at the constant level, I think the Hipparcos
eclipse is a dud.
With so much data it is surprising that the period is difficult to find,
which suggests that we might be seeing two eclipses in an eccentric
binary. As well as the periods that have been proposed so far I have also
found a new series around 135, 45 and 27 days all of which are eccentric.
For all of these it is difficult to find a period in which there are no
'constant' values within the eclipse, however, given that these are mostly
visual observations there is bound to be some blurring of the edges. Of
them all 45.164 days looks very promising. The uncertainty on this period
is very subjective, depending on what you are prepared to accept, but it
begins to fall apart at +/- 0.002 days.
The total width of the eclipses are about 0.02 cycles or 0.9 days, but for
visual observers to see anything it will probably be less than half of
this, so about +/- 5 hours of the minimum. The ephemeris for the next two
cycles is given below and suggests that South Africa is the best place to
be.
Ephemeris for delta Vel 2451714.94 + 45.164xE
JD Year Mo Date UT Min Cycle
2451850.4320 2000 11 1.9320 22:22 I 2
2451870.3042 2000 11 21.8042 19:18 II 2
2451895.5960 2000 12 17.0960 2:18 I 3
2451915.4682 2001 1 5.9682 23:14 II 3
If someone could dust off their old photoelectric photometer in the next
week or so we might have a light curve to look at.
Cheers Chris Lloyd
vsnet-adm@kusastro.kyoto-u.ac.jp
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