July 2023 - vsnet-chat - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-chat 9429] AO Her in 2021 and anomaly in visual observations
by Taichi Kato 20 Jul '23

20 Jul '23

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 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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[vsnet-chat 9428] VSOLK bulletin no.121
by meineko 18 Jul '23

18 Jul '23

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 -------- Seiichiro Kiyota VSOLJ

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[vsnet-chat 9427] No 0.1-d period in V2491 Cyg
by Taichi Kato 13 Jul '23

13 Jul '23

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).

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[vsnet-chat 9426] ASASSN-19ir in AAVSO VSX
by Taichi Kato 05 Jul '23

05 Jul '23

https://www.aavso.org/vsx/index.php?view=detail.top&oid=687324 You may have missed vsnet-chat 9423.

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[vsnet-chat 9425] VSOLJ Variable star bulletin No.120
by meineko 01 Jul '23

01 Jul '23

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 --------------- Seiichiro Kiyota VSOLJ

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