[vsnet-id 413] (fwd) V391 Sct position

[Taichi Kato <tkato>]

(fwd) V391 Sct position

From: "Bruce Sumner" <b.sumner@bom.gov.au>
Date: Tue, 13 Mar 2001 12:40:50 +1100
Subject: [vsnet-chat 4130] V391 Sct position

Berto,

	You make a good point. I had a lot of trouble making the 
identification that now appears on the Henden/Sumner chart, 
but my reasoning can be found in the notes that I include in
all Henden/Sumner sequences. These full sequences can be found 
at:
      http://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/sumner/

	If you check the sequence for V391 Sct there you will find my 
reasoning for calling the red star the variable rather than your 
blue star. If you cannot access that site, here are the relevant 
notes:

2. Downes, Webbink and Shara, in their 1997 catalogue, consider this
variable to be lost and not able to be identified. However precessing 
the discovery position (P. Maffei, IBVS, 12 April 1975, object M64) 
to J2000 reveals that M64=GSC 6266-2259=V391 Sct.

3. Examination of this star on the available Schmidt pixel imagery 
shows that on three occasions in three separate years, namely 1982, 
1984 and 1986, V391 Sct was at maximum at about magnitude 14.0. 
However on Palomar red and blue exposures taken on 23 August 1952 
V391 Sct is very faint, and is estimated at 21R and <21B.

4. All images reveal that V391 Sct is the northern component of 
a very close double star, with the southern red component having 
an estimated magnitude of V=15.8 and B=17.6 and a separation of 
approximately 4 arcsec SW of V391 Sct.

5. The evidence suggests that Maffei's estimated minimum of I=17.0 
actually refers to the southern companion, and not V391 Sct itself. 
The double nature of V391 Sct would most likely not have been 
resolvable on his imagery.  
 (End of notes)
	
	The bottom line is that the real position of V391 Sct is not yet 
known for certain. I would keep the immediate vicinity under scrutiny 
in case I am wrong, which is quite possible.

Bruce

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