[vsnet-const 4] Re: V449 Sco

[Fraser Farrell <fraser@trilobytes.com.au>]

G'day all,

Sebastian's message illustrates the value of re-investigating stars for
long term changes in their behaviour.

My first thought after reading his observations was "maybe he was unlucky
and kept seeing the same phases in the lightcurve?"  However a bit of
arithmetic shows that this thought is difficult to prove.  Or disprove.
Many thousands of cycles have elapsed since the original ephemerides were
determined, so any small errors have accumulated...or real changes may have
occurred.

Below are Sebastian's observations; to which I have added the supposed
phase of the lightcurve at which they were made.  The first column assumes
a constant period of exactly 13.7 days since epoch, the second a period of
13.71 days.  As usual, a phase of 0 or 1 is the primary minimum, 0.5 is the
secondary minimum:

                                       13.7   13.71
                                      -------------------
    19980228.2868   70      0.86    0.37
    19980301.2409   70      0.93    0.43
    19980331.2090   70      0.12    0.62
    19980409.1770   70      0.78    0.27
    19980420.1701   70      0.58    0.07
    19980428.2152   70      0.16    0.66
    19980501.2013   70      0.38    0.88
    19980505.1722   70      0.67    0.17
    19980720.0215   70      0.20    0.70
    19980813.1458   70      0.97    0.46

This exercise can be repeated for any period near 13.7 days to produce
almost any phase numbers you want.  Sebastian may have been unlucky after
all !

I haven't read the original article (and I probably couldn't, as I know
zero Spanish), but I would guess that the 13.7 day period was a first
approximation and the authors planned further observations to get a better
value.  I can only speculate as to why this didn't happen.  We can also
speculate about orbital changes, postulate perturbations by a third object,
invoke pulsations in either or both components, etc, etc.

But the real answer to this mystery will (of course) come from a new
observing campaign.  I presume Sebastian has a chart and will make it
available?  If vsnet's storage space has been conquered by its own mail
archives ;-) then I can place it on my server instead.

And maybe the latest GCVS classification is simply the result of a lack of
recent and/or definitive observations?  I'm reminded of all those years
that we collectively ignored what is now V854 Cen....


cheers,
Fraser Farrell

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