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[vsnet-gcvs 241] (fwd) Probable new faint variable star in Scorpius

(fwd) Probable new faint variable star in Scorpius

From: "Mati Morel" <morel@ozemail.com.au>
Subject: Probable new faint variable star in Scorpius

 I have been working on a project to extract better positions for about 400
 variables in Scorpius and Oph. The stars were announced in Harvard
Bulletins
 857, 862 and 863.  Finder charts were published in  HB 887 in 1932.  They
 were announced as HV 4200 through to HV 4636.  In the GCVS they are named
CS
 Sco onwards, and BR Oph onwards. I have been using GSC-ACT and USNO-A2.0
 data in Guide 8. Most variables are rather faint, and the published finder
 charts are of rather small scale, and don't show many variables clearly.
 Nevertheless, using the original positions (of limited precision), and
notes
 for many stars it has been possible to identify about 80% of stars in GSC
or
 USNO-A2.0.  Mira variables show up often in the A2.0 catalogue with their
 very pronounced b-r color. Other stars turn up much brighter than expected,
 even appearing in the GSC.
 New Variable near EF Sco.
 One star which caused a problem was EF Sco, range 13.3-14.4p. The Guide8
 display puts it way off the nearest 13mag star, which happens to be GSC
 6821-01679, at 16h51m40.36s -29 41'25.5".  The notes in HB857 state that
 HV4231 = EF Sco
 was observed 30 times in 1926, sufficient to derive a period of 0.6056d.
So,
 while the Harvard position is poor, I surmise that the nearby star GSC
 6821-01679 is EF Sco. It appears to have a close companion to the east.
 While checking a DSS first generation plate I noticed that one USNO-A2.0
 star is missing (or nearly missing). The star's position is
 16h51m41.64s -29 42'0.5".   Photometric data :
 r = 14.7
 b = 16.9
 V = 15.5
 At this place on DSS1 (blue) I find a tight arc of three stars. None of
them
 are brighter than b = 20. On the latest DSS2 red plate the tight pair which
 closely matches the USNO position are somewhat brighter at r = 18.  Various
 catalogues have been checked. The star cannot be found in MSX5C, IRAS,
 2MASS-J, 2MASS-H etc. Nor is it in GCVS or NSV.
 However the star _does_ appear in the latest GSC 2.2 catalogue, at
 16h51m41.674s  -29 41'58.87"   at R = 16.05.

 Is it this apparent variation real?  Or have the A2.0 and GSC2.2 scans been
 fooled by the presence of close companions?

 Cheers,
 Mati Morel

 morel@ozemail.com.au
http://vsnet.ozemail.com.au/~morel

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