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Date: Fri, 2 Jul 93 12:33:38 CDT
From: gav@astro.as.utexas.edu (Gerard de Vaucouleurs)
Subject: SN93J Comparison stars
For transmission to all interested observers. G. de Vaucouleurs and
H. Corwin have prepared the following table of the present status of
the comparison stars. We still need good photoelectric magnitudes and
colors for the brighter five stars in the table which are important
for a proper reduction of the visual and CCD observations of the first
two-three days (April 27-30). These are essential to define onset
time and the first maximum. Also to decide whether or not there was
a 'halt' in the rise the day following the discovery. Please inform
the authors of any discrepancy, correction and addition. Thanks
for your attention.
*****************************************************************************
>From G. de Vaucouleurs and H. Corwin (6/25/93):
REVISED ESTIMATES OF COMPARISON STARS (6/25/93)
Star labels are, except where otherwise noted, as marked by the Spanish (MAA)
M1 group on copies of the AAVSO and TB charts. Cross-identfications with the
GSC, Neff, Sandage and Corwin numbers are provided. Good photoelectric V
magnitudes and colors are still needed for the first four stars to help reduce
the early visual and unfiltered CCD observations.
===============================================================================
Star AAVSO T-B MAA SAO GV* Ripero GSC V# Other ID
Carvahal "V" B-V
-------------------------------------------------------------------------------
SAO 15020 8.9 8.9// 8.9 8.7 (8.8)* 7.97 - DM 69.542 (8.5) =
= GSC 0848 8.55 HD85458(8.7v,9.1pg)
SAO 15018 10.4 10.4// 10.5 (10.6): - - AAVSO B =
= GSC 1127 E 9.8: AGK3 427 (10.9pg)
SAO 15017 10.5 10.5// 10.5 (10.7): - - AAVSO C =
= GSC 1127 W 9.9: AGK3 426 (10.9pg)
SAO 15026 9.4 9.4// 9.4 8.8 (9.4)* 8.67 - DM 69.544 (9.0) =
= GSC 0738 9.23 MAA A; SAO(9.8pg)
B 10.3 10.3// 10.4 10.95 10.45 W of M 81
= GSC 0150
B1 10.3 10.3/ 10.3 10.32 SA-19
= GSC 0860 0.39
C 10.7 10.7// 10.8 11.05 11.4 11.01 AAVSO D
= GSC 0698 (var?) 11.28 0.55: (Skiff)
C1 10.8 .... 10.8 10.9 10.82 AAVSO rev.
= GSC 0384 1.1: (Skiff)
D (MAA) 11.7 11.6 11.7 11.25 11.7 11.65 S of M81
= GSC 1031 11.55 0.51 HC-3 = Neff B
D1 11.8/ 11.8 11.9: 11.85 NE of M 81
= GSC 0224 1.31 HC-6 = SA-8
E 11.4/ . 11.4/ 11.4/ 11.40 Richmond A
= GSC 0565 0.55
F 11.9/ /11.9 11.9/ 11.9/ 11.90 Richmond B =
= GSC 0928 [Primary local standard] 0.50 HC-4
G 11.8 /11.8 11.8 11.75 11.9: 11.78 HC-2
= GSC 0308 0.69
AAVSO G .... 14.1// .... 14.44
= GSC 0574 1.0: (Skiff)
H 12.4 12.4/ 12.4 12.15 12.45 HC-1
= GSC 0434 0.63
I 12.9 13.0// 12.9 12.88 W of M81
= GSC 0863 0.9:
I1 12.9 12.9/ 12.9 12.89 ENE of M81
= GSC 0935 0.73 SA-14
J 13.0/ 13.0 12.99 SA-15
= GSC 0244 1.20
K 13.6 /13.6 13.6 13.65 SSE of M81
= GSC 1123 0.57 HC-5
L 13.7 13.7/ 13.7 13.71 SA-1
= GSC 1028 0.77
GSC 0340 14.0 14.0// var? 14.48 25"SW of SN
0.56 (Herbst)
GSC 1037 14.1 14.1 14.1 14.06 SW of 1031
0.97 Neff-A
============================================================================
Notes: GV*: For first four stars the magnitude was derived from BD corrected
to V via V = 7.2 + 1.2(m - 7.2) [formula in S And paper (ApJ 295, 267, 1985)].
For the close pair SAO 15017, 15018 combined, the DM69.541 mag (mv = 9.4) was
corrected to V (9.88) and split between the two nearly equal components (the
western one is ~ 0.1 mag fainter, thus 10.6 and 10.7).
For *B to *H, magnitude was derived a posteriori from V(SN) and detailed step
comparisons of M1(MAA) group members, in particular of equality.
GSC: first line is the GSC v magnitude, second line is corrected to V via
V = 12.87 + 0.969(v - 12.43), found generally applicable in the M 81 field
with a few exceptions. SAO 15017, 15018, with a combined GSC magnitude of
8.53 was corrected to V = 9.09, and then split as above to give 9.8 and 9.9.
V# photoelectric magnitudes from Neff, Sandage, and Corwin, and SN observers
(Herbst, Prugniel for *A, Skiff for *B, *C = AAVSO *D, and C1).
B-V photoelectric color index from the same sources.
AAVSO *D, marked var. on the revised AAVSO chart (NW of M 81), was initially
used as a comparison star with m = 10.7 (T-B), labelled *C by the Spanish
M1 group. After this star was suspected of variability they transferred the
label C (as C1) to a 10.8 mag star NNE of M81 near the edge of the AAVSO and
T-B charts. These two stars were measured by Skiff as, respectively,
V(C) = 11.01 and V(C1) = 10.82. Both need to be checked.
****************************************************************************
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