[vsnet-chat 4303] Re Confirmation and Reporting Observations

["Peter F Williams" <pfwilliams@onaustralia.com.au>]

Hello All,

I have just returned home from a week's holiday to find many recent
postings on reporting of observations 'after the event', seeking
confirmation and reporting all observations (including negative ones).

I am certainly guilty of not reporting all of my observations through the
vsnet.  They are, however, all reported through my parent organisation, the
VSS RASNZ, and more recently through the AAVSO as a copy of my VSS dbf data
file (though I am not sure if the AAVSO actually process these).  My
reporting to the vsnet is usually of specific observations of potentially
interesting events and only sometimes include other observations made on
the same date.  This is also related to my having some concerns about
duplication of observations within the various international data bases. 
Additionally, I would hope researchers of variable stars would seek
observational data from all of the international groups and not just rely
on data posted, for example, only to the vsnet.  Any thoughts on this
duplication?

Reporting for me is most often related to a simple lack of time on my part
- I usually key my hand written observations into the PC many days later -
and have yet to start on my April observations.  I admire guys like Rod
Stubbings and Andrew Pearce (to mention a local few) who obtain their
observations, key them and report them seemingly all in the one motion.

Regarding posting observations after the event, my guilt relates to recent
observations of V4018 Sgr in which I was endeavouring to establish a better
timing for the onset of decline of this under observed ZAND star.  The
following observations of CU Vel may be of more interest.

VELCU	20010217.7173	<145	WPX
VELCU	20010219.5173	148	WPX
VELCU	20010221.4451	<145	WPX

The positive observation was essentially at the limit of visibility for me
and none of these observations were reported through the vsnet (but were
included in my usual VSS monthly report).  They appear to show a
short-lived flare rather than a true outburst.  Interestingly, some 35 days
later the vsnet carried reports of an outburst of CU Vel which peaked near
magnitude 11.2 about March 26.  Perhaps many similar flares have been seen
by other observers who at times seek private confirmation or simply do not
report them?  I recall several years ago seeing a similar flare in CU Vel
prior to an outburst.

The vsnet postings have not yet made reference to such flares.  After
encouragement from Nikolaus Vogt, these events were investigated by Frank
Bateson of the VSS RASNZ a number of years ago and three papers resulted in
the Publications of the VSS RASNZ under the title 'Do Some Dwarf Novae Have
Short-lived Flares or Precoursers to Outburst'.  These appear in Publ 16
(1991) pp75-80, Publ 17 (1991) pp74-75 and Publ 19 (1994) pp 54-55, and
discuss events seen in the southern stars V442 Cen, OY Car, TU Men, Z Cha,
TW Vir and TU Ind.

These papers note the following intervals between the flares and true
outburst, with due regard to the long cycle period for OY Car and TU Men:

V442 Cen 4 to 14 days (average 8.8 days)
OY Car 16 to 174 days with one observer reporting a decline of 12.3 to
<13.5 in 5 minutes.
TU Men 20 to 222 days
Z Cha 5 to 100 days (average 36 days)
TW Vir 4 to 8 days
TU Ind 11 days

I understand observations at wavelengths other than the visual have since
confirmed the existence of these events.  Has a similar investigation been
made into more northerly stars?

Regards (and sorry for the long post)

Peter Williams
Heathcote NSW

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