[vsnet-alert 10339] ATEL 1622 candidate CV in GALEX

[bydra at Safe-mail.net]

http://www.astronomerstelegram.org/?read=1622

This thing's in GALEX, though pretty much near the limits of said, and one solution has an error as large as 0.4 mags in FUV.

The better solution has NUV 21.275 error 0.111 and FUV 22.663 error 0.269, so FUV-NUV +1.4 error 0.3 ish, which isn't all that good for a CV (BZ UMa = +0.4, +0.5; WW Cet -0.0; ER UMa 0.1; SU UMa 0.3, stuff like that), on the other hand it ain't bad for a white dwarf, somewhat contradictorily.  Yet the mags are faint and the errors unsmall.

Also, CVs and QSOs overlap a lot in UV colour space, and "3D" colour space is more informative (although they still overlap strongly then).

The POSS II blue colour in USNO B1.0 will be through a blue filter (POSS I O plates were unfiltered if I remember rightly so I don't mention that one), that's 21.1 in a Johnson B approximated plate magnitude, but only approximated, and USNO B1.0 magnitudes aren't good, especially not this faint, whilst GSC2.3.2 gives a J plate (blue plate) mag of 21.0, which is similar, but of course based on the same POSS image, but generally quiescence blue-NUV looks fairly white.

GALEX info doesn't really clarify the issue though.

Generally it hovers near the right sort of colour area for a CV, but not uniquely so.

There's some lensing surveys pointed towards M31, and extragalactic nova patrols, I don't know if any overlap a field this relatively far off though, or have accessible data.

VizieR gives nothing extra save several astrometric catalogues' interpretations of the POSS image(s) (usnos a2.0 and b1.0, gsc2.3.2 and apm north).

When it comes to faint stuff it's always pushing it to be able to say anything about it.

Cheers

John