[vsnet-survey 33] (fwd) ASAS - GCVS vol V XIDs (Greaves)

[Taichi Kato <tkato>]

(fwd) ASAS - GCVS vol V XIDs (Greaves)

Date: Wed, 14 Jun 2000 15:53:21 +0000
From: JG <jgts@jgws.totalserve.co.uk>
Subject: ASAS - GCVS vol V XIDs [survey]

It seems that these have effectively been covered in vsnet-survey 16 by
Brian Skiff, so I will not be doing a cross check.

Another reason for not doing a straight catalogue to catalogue
comparison is that, after all, there are ambiguities and inaccuracies
for the ASAS data, especially in crowded fields.  Points regarding this
are covered by comments in the above noted posting.  Specific examples
where this is highlighted are commented on in vsnet-survey 13 by
somebody called John...

A specific LMC [ASAS-GCVSvolV] example follows:-

LMC V2139 = GSC 9162 0570 and has a GCVS vol V 31.96 day period

ASAS 052020-6902.4 = GSC 9162 0857 [=HD 269393] and is stated as having
a 31.86 day period.

GSC 9162 0570 lies about 18 arcsecs from GSC 9162 0857

It is my opinion that these stars are unresolved by the ASAS experiment,
and the pulsation of LMC V2139 has been picked up in the solution for
GSC 9162 0857 due to insufficient resolution.

This identification for this ASAS object differs from vsnet-survey 16,
so needs double checking, especially as the 1" RA and 0.1' Dec accuracy
for ASAS that I've used presents problems.  LMC V2139 does appear to be
near coincident in position to GSC 9162 0570, however.

I note two further points re this ID: first the GSC magnitude of GSC
9162 0570 [12.5 SERC V] seems more appropriate to LMC V2139 [13.5-14.9p]
(given that cepheids aren't _very_ red) than GSC 9162 0857's GSC
magnitude [10.1-10.2 SERC V], although differing passbands _do_ cause
problems.

Second the photographic magnitude range of LMC V2139 is 1.4 magnitudes,
whilst the amplitude of the ASAS object is given as 0.06 in the I band.
Although variables act differently at widely differing passbands, this
does not seem sensible, whilst fitting the "pixel poisoning" scenario
well enough.


Cheers

John

John Greaves
UK

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