Dear colleagues,
It seems to me that there is a little doubt with V482 Cyg's sequence. My opinion is that comparison stars marked as 121 and 128 N and NW from V482 Cyg are not correct (the source is an AAVSO chart which was made before the early 80's).
The field is as below (south is up):
* V482
5'
. 128 [--------------]
. 121
The magnitude difference visually does not look 0.7 magn. I have found them in the Guide Star Catalog as GSC 2678.771 (='128') and GSC 2678.1450 (='121') with the same brightness which is 11.6.
On the other hand, I have looked at V482 Cyg's light curve based on Hungarian observations and I have found very large scatter during its last minimum in the 80's exactly in this brightness region, as one can see below:
JD mg. obs. JD mg. obs.
47702 125 SCH 47720 122 FID
47707 120 FID 47721 131 RIP
47708 131 PPS 47721 123 FID
! 47709 120 FID 47722 131 RIP
! 47709 130 PPS 47723 126 SCH
47713 123 FID 47725 122 FID
47713 126 MZS 47727 125 SCH
! 47714 131 RIP 47728 123 SCH
! 47714 123 FID 47729 123 FID
47715 131 RIP 47729 130 MZS
47715 125 SCH 47732 132 RIP
47716 131 RIP 47733 123 SCH
47720 126 SCH 47733 132 RIP
47720 131 RIP 47734 132 RIP
These observers are very experienced and they used the same chart. Of course there are many more possibilities to cause such scatter but I think it would be quite useful to look at these stars. Unfortunately there are different sequences too, which make visual estimates almost uncomparable.
Because of the recent fading of V482 Cyg it would be important to find a more reliable reference.
Sincerely,
Laszlo Kiss.
(vsnet 678, Taichi Kato)
My recent CCD measurements and a photovisual sequence in AJ 109, 538, on which my zero-point depends, are as follows for the denoted stars and one more of similar magnitude. (All mags are shown on the VSNET chart.)
AAVSO mag. pv mag VSNET V-mag
------------------------------------------
12.1 11.70 11.66
12.8 11.60 11.63
11.9 -- 11.87
Yes, I also suspect up to 1 mag difference for these comparison stars have been responsible for large scatters. The fainter AAVSO sequence seems to be in better agreement with the CCD one.
VSNET chart: ftp://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/charts/V482_Cyg.ps
Regards,
Taichi Kato
VSNET chart
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