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Re: [AAVSO-DIS] RU Vulpeculae and its star field
Woops! That should be an expected error of 0.05 (sigma) in the star 97
discussion.
Tom Droege
> [Original Message]
> From: Thomas Droege <tdroege2@earthlink.net>
> To: Skiff, Brian <brian.skiff@lowell.edu>; <gianluca_1@fastwebnet.it>
> Cc: <aavso-discussion@mira.aavso.org>; tass <tass@listserv.wwa.com>
> Date: 9/5/2004 10:39:26 PM
> Subject: Re: [AAVSO-DIS] RU Vulpeculae and its star field
>
> Tass has RU Vul at 309.719+23.258 Entering RU Vul into Vizier gets a GCVS
> position of 309.7196+23.2585
> or 20:38:52.9 +23:15:31 This is presently star 1941815 in the tass data
> base. The ID numbers are subject to change, the position is not.
>
> The tass data base found 33 measurement pairs, and the star looks variable
> with 100+ day period and a 0.6 mag variation in V. Somewhat less in I. .
> Not enough data to pin down the period. There is scatter in the data
> points but it is consistent with the published errors. Brian says "
> ...bearing in mind that the second is not always well-calibrated." I
would
> prefer to say that the scatter has been calibrated but is larger than
those
> living on mountain tops are used to seeing. Looking at the AAVSO plot
for
> RU Vul, I would estimate that the tass data has a factor of 4 less
scatter.
>
>
> My best estimate of the 97 star is a star at:
>
> 309.553+23.344 This is star 1941738 in the present tass data base. There
> are 24 measurement pairs. The scatter in V is 9.7 to 9.86. With a sigma
> claim of 0.5 for a star of this brightness, this is consistent with a
fixed
> star. OK, it is on the upper end of the probable error. More data is
> needed.
>
> My best estimate of the 105 star is at:
>
> 309.564+23.332 This is star 1941750. There are 24 measurement pairs.
The
> scatter in V is 10.49 to 10.68. This is again consistent with a fixed
> star.
>
> I did several plots of the tass data to try to compare it with the AAVSO
> chart. There are just too many stars in the tass plot to make sense of
it.
> This even after I removed all the stars with less than 20 measurements.
We
> need a program that plots stars as circles proportional to the magnitude
> (and with error bars). Possibly someone will work on this. Probably
> someone has already done it, but I could not find it. Michael built such
a
> program into his data base for the Mark III data. Michael, is it easy to
> export this program?
>
> Tom Droege
>
>
> > [Original Message]
> > From: Brian Skiff <Brian.Skiff@lowell.edu>
> > To: <gianluca_1@fastwebnet.it>
> > Cc: <aavso-discussion@mira.aavso.org>
> > Date: 9/5/2004 4:01:00 PM
> > Subject: Re: [AAVSO-DIS] RU Vulpeculae and its star field
> >
> > Given that the chart data are from no more recent than 1942, it is
> > not surprising to find that a particular comp star has inconsistent
> > values. You can check this yourself. First determine coordinates
> > using your Skymap program or some other method. Then look up the
star(s)
> > in the ASAS-3 and/or TASS MkIV query pages:
> >
> > http://www.astrouw.edu.pl/~gp/asas/asas3_catalog.html
> >
> > http://sallman.tass-survey.org/servlet/markiv/template/DataDownload.vm
> >
> > ...bearing in mind that the second is not always well-calibrated.
> > I would also look at the stars in Tycho-2 using the Strasbourg VizieR
> > catalogue-query utility:
> >
> > http://vizier.u-strasbg.fr/cgi-bin/VizieR
> >
> > ...where Tycho-2 is item I/259 in this system. If the Tycho-2 scatter
> > on the photometry is small and/or the scatter in the ASAS data is small,
> > then the star is most likely constant. The ASAS data also should give
> > a very good mean V magnitude that will be reliable to ~0.03 mag or so.
> > Likewise Tycho-2, though a small correction is necessary to adjust the
> > catalogue values to standard V.
> > It is helpful when posing queries such as this to provide
coordinates
> > for the stars rather than noting only "97var? on the chart for RU Vul".
> > You really can't dig into available data without _coordinates_ or a
> > principal name, such as HD or BD number.
> >
> > \Brian
> > _______________________________________________
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>
>
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