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[vsolj-alert 512] M61 (SN1999gn) sequence

From owner-vsnet-alert@kusastro.kyoto-u.ac.jp Wed Dec 22 09:45 JST 1999
Date: Tue, 21 Dec 1999 17:33:23 -0700 (MST)
From: Brian Skiff <bas@lowell.edu>
To: aavso-discussion@physics.mcmaster.ca, isn_chat@supernovae.net,
        vsnet-alert@kusastro.kyoto-u.ac.jp
X-Distribute: distribute [version 2.1 (Alpha) patchlevel=24]
Subject: [vsnet-alert 3845] T&B sequence for M61
Content-Type: text
Content-Length: 1552

     I was a little surprised to find the situation for published photometry
of field stars near M61 is relatively poor.  The best bet for visual observers
of the current supernova is probably the sequence that appears on the Thompson
& Bryan search chart for the galaxy.  Since these are not widely circulated,
I show below coordinates for all the labelled chart stars, which were measured
by Ron Buta.  These are presumably V magnitudes, but given to only 0.1-mag.
precision.  For completeness I also show GSC magnitudes and the blue and red
magnitudes from USNO-A2.0 for the same stars.  As can be seen, the fainter GSC
magnitudes are similar to V, probably because the GSPC sequence is only about
1.5 degrees away at the same Dec.  The first two bright stars are unlabelled
but appear at the northwest periphery of the T&B chart.  The Tycho photometry
shown has small uncertainties for the mag. 8 star, but is 0.05 for the mag. 10
star, and so could be substantially in error.  

\Brian



T&B            RA  (2000)  Dec         GSC      mGSC   mb    mr     V    B-V
HD 107428   12 21 00.2  +04 32 16   0285-0616   8.01               8.22  1.12
BD+05 2618  12 21 14.2  +04 36 51   0285-0416  10.15              10.41  0.54
124         12 21 17.7  +04 27 21   0285-0914  12.37  13.2  12.3
131         12 21 49.4  +04 36 35   0285-0339  12.89  14.0  12.8
140         12 21 49.0  +04 26 22   0285-0572  13.89  15.0  14.1
155         12 22 04.1  +04 32 31                     16.0  14.8
161         12 21 48.1  +04 32 31                     16.9  15.0

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