The RCB star V0482 Cyg is going into a fade. Looking at the light curve, it looks like there are two distinct sets of observations creating a “two track” fade. I wonder if this is a case of two sequences being used or misidentified comparison stars. The sequence seems to have been revised sometime around the spring of 2022(?). It looks like it used to be a CCD Henden sequence and is now mostly an APASS sequence. The two stars that I could find in common (BCK-011-000 and BCK-090-000) have pretty close V magnitudes.
In any event, this is a pretty rich Milky Way field and observers should be sure to identify their comparison stars carefully.
Hi all,
Actually this is not the explanation.
Look at the VSX remark: 13.7 mag. star 7" to the SW.
One observer is not properly solving the red companion. That’s why the difference grows as the star fades, because one observer is seeing the variable as it fades while the other is observing the blend as it approaches the combined magnitude of both (or at least the blended magnitude in his aperture).
Always be sure to check VSP Notes (although now they do not dislplay on charts, something that I hope we can correct in future versions) about companions, and if you can’t solve the stars properly, I recommend not observing them. Or add a remarl mentioning that it is a blended magnitude, although I think that trying to solve them is always the best option (e.g. by reducing the photometric aperture size).
One more thing, this is not so red as the typical carbon stars, these hydrogen deficient stars are part of another group of C-type stars that paralel the G and K stars in the HR diagram. They were just labelled as R before, now I see them labelled as C-R.
So this one looks more like a reddened [E(B-V)= 0.56] R-type star.
Further checking reveals that at least two different observers are reporting blended magnitudes. As the star keeps fading this will be an even worse issue.
So please check your images.
Thank you so much Sebastian. I’ll raise my hand and plead guilty to reporting the blend. I should have read the VSX entry. I’ll try to mathematically subtract the companion from my observations and delete and re-submit.
It is even more difficult!: I had to add it to VSX (as 2MASS J19594210+3359241) since, as most red giants, is also variable. A small amplitude (0.3 in g) short period SRS.
This makes subtracting its magnitude an almost impossible task. No useful V measures to provide (only ZTF data) but I calculate that in V the amplitude should be around 0.2 between 13.7 and 13.9.
You can try with a mean V= 13.8 but you won’t be able to get rid of the intrinsic variability of the red giant, that, however, will be almost unnoticeable around the maximum of V0482 Cyg. The real problem is during the fadings.
Hi Sebastian, yes I saw the 16.1 in my survey search. I presumed it was in everyone’s measurement aperture. I didn’t have time to see if the star fades to that magnitude. It might be a case for PSF photometry for high resolution systems.
I see something similar in the current fade of DY Per. Both V482 Cyg and DY Per are in crowded fields with nearby companions, when I take a good look at the charts. This is probably causing my too bright measurements, as I am using a SeeStar S50 with a relatively wide field that is unable to resolve the nearby companions.
I think I have to drop these stars, at least when they are fading, and I will have to take a closer look at the other stars I am observing, especially in Milky Way fields.