[vsnet-alert 2562] 3C279 comparison sequence summary

[bas@lowell.Lowell.Edu (Brian Skiff)]

     Given the recent notices about activity in 3C 279, here is a summary
of available BVRI photometric sequences in the field.  There are three such
series, mostly overlapping, all published within the last two years.  The
individual data from each paper are reproduced below along with a table of
averaged values.
     The first list shows the averaged photometry along with coordinates and
GSC identifications.  I have adopted the numbering scheme of Raiteri and
Smith & Balonek.  All the positions come from USNO-A2.0.  The next three
blocks show the lists from Villata et al., Raiteri et al., and from Smith &
Balonek, and at the bottom the means from these three sources.  All three
papers give data in BVRI magnitudes rather than as magnitudes and colors, as
are shown in the top list.  Comparison among the three sources suggests the
means should have external accuracy in the 0.01-0.03 mag. range in each color.
     N.B. that Villata star 'B' is a large-amplitude variable, which the
Villata group have called "Simona"; see the Raiteri paper for comments.
The position of 3C 279 itself for equinox 2000 is:  12 56 11.17  -05 47 21.5.
     Finally, a chart of the field can be found at:

http://quasar.colgate.edu/~tbalonek/optical/3C279compstars.gif

...which is at Tom Balonek's Web site on active galaxies.  This small .gif 
image has most of the comparison stars labelled, but the numbering scheme is
different than in the list below.  You'll have to compare relative positions
to get things correct---or look in either of the recent papers by Raiteri or
Smith & Balonek!
     If anyone finds errors in my arithmetic, I'll be pleased to know about it!

\Brian



Summary table

Name                  RA  (2000)  Dec    s     GSC       V    B-V   V-R   V-I
3C 279 1           12 56 10.3  -05 50 14 A  4956-1119  12.42  0.61  0.37  0.72
3C 279 6           12 55 48.6  -05 44 21 A  4956-1151  12.81  0.61  0.37  0.69
3C 279 2           12 56 28.5  -05 44 22 A  4956-0858  12.99  0.75  0.43  0.82
3C 279 3           12 56 26.6  -05 45 22 A  4956-1102  14.89  0.59  0.34  0.69
3C 279 Villata C   12 56 04.5  -05 51 14 A             15.14  1.23  0.70
3C 279 4           12 55 58.0  -05 44 18 A             15.66  0.87  0.53
3C 279 5           12 56 14.5  -05 46 47 A             15.96  0.86  0.50  0.96

"Simona"           12 56 08.5  -05 44 35 A  large-amplitude variable



Villata et al. 1997 A&AS 121,119
               B     V     R     Remarks
1253-055 A   16.84 15.84 15.46   = Raiteri 5
1253-055 B   17.31 16.71 16.74   = Raiteri S; variable!
1253-055 C   16.37 15.14 14.44
1253-055 D   13.05 12.39 12.06   = Raiteri 1


Raiteri et al. 1998 A&AS 130,495
               B     V     R
3C 279 1     13.02 12.42 12.05
3C 279 2     13.73 12.99 12.56
3C 279 3     15.49 14.87 14.53
3C 279 4     16.53 15.66 15.13
3C 279 5     16.79 15.98 15.47


Smith & Balonek 1998 PASP 110,1164
               B     V     R     I     Remarks
3C 279 1     13.01 12.41 12.05 11.70   = Raiteri 1
3C 279 2     13.74 12.99 12.55 12.17   = Raiteri 2
3C 279 3     15.47 14.90 14.53 14.20   = Raiteri 3
3C 279 5     16.82 15.94 15.45 15.00   = Raiteri 5
3C 279 6     13.42 12.81 12.44 12.12


means:
               B     V     R     I     Remarks
3C 279 1     13.03 12.42 12.05 11.70
3C 279 6     13.42 12.81 12.44 12.12
3C 279 2     13.74 12.99 12.56 12.17
3C 279 3     15.48 14.89 14.55 14.20
3C 279 C     16.37 15.14 14.44
3C 279 4     16.53 15.66 15.13
3C 279 5     16.82 15.96 15.46 15.00   Villata discrepant V omitted

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