[vsnet-alert 4479] Re: (fwd) SN suspect in NGC 5128

[Hitoshi YAMAOKA <yamaoka@rc.kyushu-u.ac.jp>]

Dear Berto and all,

>The 11th magnitude star is indeed visible on your nice picture, just
>under (South of) the centre of the Southern bright starforming
>region.  The 12.5 star is not obvious and is located just South of
>the centre of the galaxy, just under the dust lane.  The two 14.5
>stars are in the region between the two described foreground stars,
>one is visible just NNE of the brightish 11th magnitude star.

  From my archive of vsnet-chat, there was some nice identifier of
this region given by B. Skiff (2 years ago).  For the reference, I
reproduce it below.  The "mag 11 star" would be CoD-42 8389, "the 12.5
star" would be star B.  Visible 14.5 star would be NGC 5128-V17.
Are they correct, Berto?

Sincerely Yours,
Hitoshi Yamaoka, Kyushu Univ., Japan
yamaoka@rc.kyushu-u.ac.jp

>Date: Wed, 11 Mar 1998 04:16:32 -0700
From: bas@lowell.Lowell.Edu (Brian Skiff)
Subject: [vsnet-chat 759] Position of NGC 5128-V17

     I found a few plates of NGC 5128 taken by Carl Otto Lampland in the
Lowell Observatory plate vault.  They were taken some 80 years ago with the
observatory's 1.1-m f/5 Newtonian (~37"/mm) located on Mars Hill.
     I have measured the star V17 and CoD-42 8389 as well as two others stars
superposed on the galaxy on two plates.  I used our venerable PDS machine and
a reference net of twelve PPM stars (including PPM Supplement stars).  The
mean residuals from a quadratic fit to the reference stars were ~0".1 in RA,
but about 0".5 in Dec.  I suspect this results from an incomplete compensation
for differential refraction in the solution (severe since the plates were
inevitably taken at high zenith distance).  No matter---this is a lot better
than what is evidently available for the stars!
     The average values are listed below, rounded to 1" precision.  Star "A"
is the bright star in the dark lane of the galaxy, near its geometric center.
Star "B" is the somewhat fainter star lying between V17 and the 'central star'
in a small dark patch south of the main rift.


                 RA  (2000)  Dec
CoD-42 8389   13 25 27.7  -43 02 17

V17           13 25 28.5  -43 02 05

A             13 25 23.8  -43 00 53

B             13 25 24.9  -43 01 28

For what it's worth, the positions are for the mean epoch of the plates, about
1917.9, but I'm sure any systematic errors from the imperfect net and 
reduction dominate any proper motion for these stars.
     There was really no challenge in measuring these stars, but it merely
required having a convenient original plate and a measuring machine.

\Brian

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