[vsnet-chat 2593] Re: VS-Chat 2587,90-92

[JG <jgts@jgws.totalserve.co.uk>]

Re VS-Chat 2591 on VS-Chat 2587

Fair enough: as I said it was just a thought.  And I am indeed glad of
feedback.

I often wonder how good/accurate/useful the plethora of catalogues that
are available nowadays actually are.

There can not be many people on the planet nowadays who actually have
access to _primary_ sources! This added information definitely puts the
F spectra into the very dubious category!

In general, I suppose the old rule applies: SAO is an ASTROMETRIC
catalogue, and a _compilation_. HD is a spectrometric catalogue.  It can
often be seen that people will take SAO magnitudes and spectra if they
can't find them anywhere else (at least it used to happen pre-Hipparcos,
with Tycho and Hipparcos themselves having been misused on the
photometric front from time to time).
The old rule?  Well, basically, only use a catalogue for what it was
intended!  Subsequently, I tried to point out that these F spectra were
iffy, prior to the extrapolations!

(As an added obfuscation, there seems to have been some disagreement
over the years as to whether or not CGCS 2086 = FK Puppis _is_ SA0
198860, I _think_ the current viewpoint is that it is!  As VS-Chat 2592
implies the area is a bit confusing.  NSVS 17753 = IRAS 08074-3615 lies
about 7' South and a bit East, GSC 7133-3997 4' North and a bit East.  A
busy area)

More importantly, however, is Mr Skiff's point that the LSR is mostly
useless. This is important information.

I'm confused though.  The "regions" are based on IRAS "colour" [ie 12.5
micron etc] photometry, and the LSR was merely indicative of SiC
emission at 11.3 micron (the '4' bit of 45) at strength 5 on a 1 to 9
scale (the '5' bit of 45).  The stars marked within region II lay in
"blue", ie more negative, regions of a colour diagram, defined by colour
indices based on the 60 micron and 25 micron IRAS bands in the one case,
and the 25 micron and 12.5 micron ones in the other.  The authors of the
paper (noted in VS-Chat 2587) stressed they'd only used _photometry_ of
suitable quality in freshly deriving these colour results, excluding
those without.  Hence no assignment of region for SAO 198860 and
251015.  Region II was predominantly filled with "blue" young oxygen
stars, carbon stars should have been in region VII, though admittedly
there are no hard and fast rules.  Stars will do what they want, no
matter how much it scuppers the theorists!

Even without the 'F' stars, there are 4 carbon stars in VC region II, so
are they anomalously "photometrically" hot, even if spectroscopically
normal (which which is what the LSR=45 and Val=c classifications
suggested anyway)?

I wish I hadn't mentioned the F spectra now!  Although it has led to
Mati Morel getting an answer.

Re VS-Chat 2590: CGCS 1045

In VS-Chat 2590 I used the Alladin Java interface to examine DSS and
SERC  red and blue plates for CGCS 1045. Using a link at lowell.edu I
was able to get red and blue mag data for it from USNO A2.0, which
suggested a B-V of 2 and a half and V around 18.

Coincidentally, whilst checking V713 Mon references, I found BVR
photometry for this star in:-

Groenewegen et al (1993), A+AS [Astron.Astrop.Sup.Series] 101, 267

Which gave a (then) recent photometry and a V mag (and CCD finder image)
for this object, of around mag 18.

Which suggests that this object is pretty faint and constant in V and
not necessarily worthy of further investigation, contrary to the hopes
expressed in VS-Chat 2590.

V713 Mon on the other hand was discovered as a Mira-esque variable in:-

Le Bertre (1992), A+AS 94, 377

_BUT_ only in infra-red wavebands, so there's still a possibility that
no-one's seen it vary in the visible as yet (first noted in Namelist 73,
of 1995 vintage, with only M band details).  [Some of us haven't got
password account access to SIMBAD, unless access rules have lessened].


All very intriguing, and possible confusing, but that's why we are
interested in variable stars, and don't just draw pictures of the moon!

Cheers

John

John Greaves
UK

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