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There is a suggestion that the RCB star V482 Cyg may be fading. The star has been pretty much inactive since June 1996 when it faded to magnitude 13.0 and recovered to maximum brightness 12 months later (a deeper fade to magnitude 15.0 occured in 1990). Since then there have been small amplitude variations of 0.5 mag either side of magnitude 11.0. Latest magnitude in the AAVSO database is 11.9mv.
Position 19 59 42.57 +33 59 27.9
Charts are available from both BAAVSS and AAVSO.
Further observations are requested.
Gary
Very interesting- thanks Gary! I’ll take a look if ever we get a clear sky! Tuesday is looking promising.
Cheers,
-PaulCloudy here in Birmingham last night/this morning, but clear at SLOOH Tenerife…
V482 Cyg May 24.149UT 11.84CV
V482 Cyg May 24.149UT 12.02TGObservations should be made every night if possible please, and reported to the BAAVSS as soon as possible. There is no way of knowing how deep V482 Cyg will go if it continues to fade, but observers should be careful of a close 13.7 mag star 7″ to the SW if V482 Cyg approaches mag 14.0
Gary
I mentioned this star during the Sky Notes at the BAA meeting in London today. Here is an image taken when I got home. It is unfiltered so the star is still quite bright. I assume that, a bit like R CrB, it will be quite red when it fades.
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Thanks for mentioning it Nick. I’m looking forward to watching the meeting on YouTube over the weekend.
V482 Cyg seems to have paused in it’s decline at the moment (according to V, mv values), but it’s worth keeping an eye on over the next few weeks to see what happens.
I assume it will get redder as it fades, but it’s been so long since it did anything that there are only visual data covering the fades. Looking at the AID, the first V measures occured in 2000 and after.
Gary
This star has now faded to around mag 15. Gary prompted me to look at my images since my magnitude estimates of this star were too bright as it faded. One of the problems with automating everything is that I don’t often look at images or the data derived from them and there is a fairly bright star only 7 arcsec to the SW which was within my photometric aperture. The AAVSO VSX does warn about this. Looking in detail at my unbinned images tonight there is also a 15th mag star only 3 arcsec to the NW of the variable and this will generate significant errors at the current level. This is not mentioned anywhere and I haven’t seen it on other images since it is normally swamped by the bright variable. It is in Gaia EDR3 (a demonstration of how good the optics in that spacecraft are). It is worth considering if you are doing photometry of this star at the moment.
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Since the point spread function of each of these stars would be expected to be similar, is it possible to use some kind of psf fitting technique to separate the flux from each component instead of aperture photometry ?
PSF photometry works well in crowded fields but the separation of these stars is only 2.9 arcsec so getting good enough focus and tracking to ensure that the PSF of each object is not too blended needs a bit of work with an amateur telescope from sea level in the UK. My image was at a scale of 0.28 arcsec/pix and had a star FWHM of 2.2 arcsec so the stars are reasonably well separated but that was on a night of good seeing. CMOS cameras allow selective stacking a lot of short exposures so a strategy similar to that used by planetary imagers is probably worth trying.
I ran source extractor on this image and it showed that V482 Cyg was about 0.2 mag fainter than the companion so probably about 15.2 unfiltered at the moment. The star is likely to be very red though.
The seeing seemed quite stable here tonight so I thought I’d have a go tonight at doing a set of very short exposures of V482 Cyg and selecting the best ones to stack. This gives very high resolution and allows a clear separation between the variable and the 15th mag star to the NW. The variable has certainly brightened relative to that star since the image I posted on Aug 13. This image is only 3 arcmin square with a pixel resolution of 0.14 arcsec. Given that I’m not on a mountain this is probably as good as I can get.
The FWHM is around 1.5 arcsec and the circles are apertures of 1.7 arcsec radius centred on the Gaia catalogue position. This is unfiltered so the variable is likely to be quite a bit brighter than V would give.
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