[vsnet-id 425] re VX Dra & FU Dra

[crawl@zoom.co.uk]

Jochen Pietz schreiben:-

>during one of last observing nights I try to get a CCD image
>of VX Dra. But I found no star at the specified GCVS position (a POSS
>image show also no brighter object).
>
>VX Dra position in GCVS: 1950.0  RA: 153335. DE +623100
>Spectral type G5, Mag 11.1-11.6P, P=0.892d/n
>
>Nearby the star W UMa-star FU Dra ( GSC4181.673 = HIP76272 ) can be found.
>Position 2000.0 15h34m45.53s 62o16'44.1"
>
>Transforming the position of FU Dra to an epoch of ~1930.0 
>( 15h33m34s 62o30'38 ) results in a value
>nearly identical to the 1950.0 epoch GCVS value of VX Dra. Also the
>given spectral type G0, the amplitude of 0.52 mag is of the same order
>as in the case of VX Dra.
>
>Can VX Dra be identical to FU Dra?

SIMBAD gives a cross ID for VX Dra as AN 33.1921 , which means the 31st
variable star reported in Astronomische Nachrichten in 1921.  So the
position epoch will probably have been either the contemporary 1921, or
vaguely possible 1875.

Interestingly FU Dra appears to have a very large proper motion, with about
15 arcsec of difference between the 1984 GSC plate position and the 1991.25
epoch Hipparcos position, so this could well be interesting in light of a
1921 VX Dra position... ...however the declinations seem problematic,
unless the VX Dra declination carries a typographic error somewhere along
the line [a not unknown occurence].

Jochen Pietz noted other similarities between the two variables.  Another
more circumstantial one is that VX Dra is listed as a probable type Isa
variable in the GCVS, whilst FU Dra seems to more or less coincident in
position with a ROSAT Faint Source...

FU Dra is a "new Hipparcos" variable, and is supposed to have a mean period
of 0.3 days according to Hipparcos, but GCVS is quiet on this.  Spurious
periodicities for low amplitude erratic variables are often found in sparse
data, so I see no real problem 'tween this and the about roughly 0.9 days
mentioned for VX Dra.  Then again, it could still be an EW type, as
suggested in GCVS for VX and as assumed for FU in HIP: EW stars are well
represented amongst the RASS Faint Source catalogue.

Anybody got any 1921 Astronomische Nachrichtens?  Cos I reckon Jochen is
right!  They probably are the same object.

Cheers

John

John Greaves, UK

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