AO Her in 2021 and anomaly in visual observations
Prompted by BAA VSS Circular No. 196, I checked the past
light curve of the R CrB star AO Her. The observations by
two most prominent visual observers around the 2021 fading
did not agree at all with CCD observations. They (and also
Jose Ripero, as I suggested in vsnet-alert regarding other
objects) didn't notice the start of the July-Aug. fading
for more than two weeks. They reported unreal fading in Apr.-June.
They also didn't notice …
[View More]the brightening in the later half
of 2020. The reported values, however, agreed very well
between these observers (but no correlation with CCD
observations). A naive interpretation of this strange
phenomenon would be that these observers were copying
other persons' observations each other. They were not
correlated with actual variations and researchers should
pay attention when using any database (e.g. AAVSO)
containing observations of these observers.
Of course, I had noticed the sign from the past
(already in 1996 in V705 Cas, which was interpreted as
a "telephone effect" by Gary Poyner if I remember correctly),
but the present case and other cases are too apparent
with sufficient evidence in the presence of modern CCD data.
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No.121 2023 Jul.
SDSS J183131.63+420220.2: AM CVn star showing ER UMa-type behavior and
long standstill
Taichi Kato
http://vsolj.cetus-net.org/bulletin.html
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Seiichiro Kiyota
VSOLJ
No 0.1-d period in V2491 Cyg
https://ui.adsabs.harvard.edu/abs/2011A%26A...530A..70D/abstract
"On the progenitor system of Nova V2491 Cygni"
No such period was detected in the ZTF data. Two time-resolved
runs in the ZTF data did not show any sign of such a period.
The detection by this paper was probably spurious.
There was no sign of the reported possible spin period
(see Zemko et al. 2015).
No.120 2023 Jul.
ASASSN-22ak: La Belle au bois dormant in a hydrogen-depleted dwarf nova?
Taichi Kato, Franz-Josef Hambsch, Berto Monard and Rod Stubbings
http://vsolj.cetus-net.org/bulletin.html
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Seiichiro Kiyota
VSOLJ