[vsnet-alert 18793] Re: New CV DDE 36 = 1RXS J202427.7+331629 36' from V404 Cyg

[FIDRICH Róbert]

Dear Denis,

What is the maximum brightness of DDE 36?

I made several photos of the V404 Cyg field with a 300mm (zoom) 
telephoto lens + DSLR camera in the past few years.
I wonder whether it is worth to check my images for faint transient 
candidate. (My limit is usually around 14.3-15.0TG).

Clear skies,

Robert


2015-06-25 16:20 keltezéssel, Denis Denisenko írta:
> I have serendipitously discovered another CV within 6" of the faint
> ROSAT source 1RXS J202427.7+331629 (flux=0.0210+/-0.0066 cnts/s
> HR1=1.00+/-0.33 HR2=0.31+/-0.31) with a 16" error circle in 1RXS.
> Actually I was checking the default 15'x15' DSS plate finder field of
> _another_ X-ray source with HR1=1.00 HR2=1.00 (see [vsnet-alert 18771]
> for the description of idea which keeps on being fruitful), namely
> J202435.9+332044. Nothing obvious was found near the plate center, but
> a large-amplitude variable with a distinct proper motion appeared
> ~4.5' to the south of center and only ~1.5' S of red variable VSX
> J202430.0+331759 = IRAS 20225+3308 = NSVS 8503179. There are two faint
> X-ray sources 4.5' from each other, and the southern one shows an
> obvious variability.
>
> The star was in outburst on 1989-06-30 and 1989-07-06 blue plates and
> at quiescence on other 10 DSS images. The animation of 1951 and 1989
> POSS plates shows the variability and notable proper motion (about 2"
> in 38 years): http://hea.iki.rssi.ru/~denis/DDE36-POSS-Blue-anim.gif
>
> The new variable is:
>
> 1RXS J202427.7+331629 (flux=0.0210+/-0.0066 cnts/s HR1=1.00+/-0.33
> HR2=0.31+/-0.31)
> USNO-B1.0 1232-0517211 (20 24 27.832 +33 16 35.24  B1=19.04 B2=17.43)
> 2MASS J20242785+3316333 (J=15.283+/-0.047 H=15.042+/-0.09 K=N/A)
>
> Color-combined DSS finder chart:
> http://hea.iki.rssi.ru/~denis/J2024+3316-BRIR5x5.jpg (2x zoom).
>
> The INT Photometric H-Alpha Survey has the star at quiescence as IPHAS
> J202427.84+331633.1 (20 24 27.84 +33 16 33.1 rmag=20.41+/-0.05) with
> no detection in H-alpha and i band.
>
> Proper motion in PPMXL: 20 24 27.854 +33 16 33.43 pmRA=5.0 pmDE=-57.6
> B1=19.04 B2=17.43. I note that pmRA may be wrong: from the plate
> inspection it should have the negative sign. pmDE looks good. With
> 0.06"/yr this variable is among Top 30 highest proper motion CVs. If
> quiescent M is about 11, then the distance is ~400 pc (M-m=8) and the
> tangential velocity - about 110 km/s.
>
> Another remarkable thing about the new variable is that DDE 36 resides
> within 36' from V404 Cyg, so it may fall inside the FOV of some
> telescopes observing its current outburst!
>
> I have submitted the new variable to AAVSO VSX as DDE 36. It is
> awaiting the approval by VSX Admin.
>
> Denis Denisenko
> Sternberg Astronomical Institute of Moscow State University
>
>