[vsnet-alert 10661] Fwd: re CSS081007:030559+054715 [ATEL 1825] - was Re: KP Cas superhumps update

[bydra at Safe-mail.net]

-------- Original Message --------
From: bydra at Safe-mail.net

...

> Whatever the case, filtered photometry tucked away in arxiv 
> somewhere may well be timely for future studies of this thing.

err, that should read _archives_ not arxiv.

The thing's a bit faint, around 16th mag at present, so not many amateurs are going to be able to do filtered stuff on this thing.

Whilst I'm at it, no one's mentioned the SDSS nor GALEX progenitor mags for this thing, so I'll link them.  Also, examination of the POSS II J plates suggests the USNO B1.0 B2 magnitude, and the GSC2.3.2 magnitude, is/are spurious, it looks no fainter nor brighter to speak of twixt POSS I and POSS II when comparison of all stars is made, and the POSS II blue image is certainly not showing an object of 20th mag and less.

Here's the SDSS summary page with mags :-

<http://cas.sdss.org/astrodr7/en/tools/explore/obj.asp?ra=046.49393&dec=+05.78740>

this is from the recently (All Hallows' Eve) made publicly available SDSS data release 7, _however_ the data was in SDSS prior to that, but you had to search through the SEGUE I interface, as this star wasn't included in the DR6 data.  Nor is all dr6 data in the vizier holdings.  Folk have to remember to watch out for stuff like that.

Those magnitudes, the SDSS ones, are for December 2004.  You'll note that the POSS I ~(1950's) blue and red mags via USNO A2.0 and the B1 and R1 mags vis USNO B1.0 ain't that much different from the g' and r' mags in December 2004.  As stated above, the USNO B1.0 B2 and R2 mags don't tally with what the images are saying.  Feel free to check for yourselves via the NOFS ppm server or Aladin, former better in this particular instance.

GALEX data has two exposures, there's a difference in FUV mag between the two exposures, and consequently also in FUV-NUV colour.  At these mags the difference of a coupla tenths or so of a mag between GALEX exposures is not really meaningful [ie might not be real], but usually the scatter is in tandem, without a colour difference, both fuv and nuv are usually similary offset if separate exposures don't concur exactly.  But then again the colour difference is only 0.2 in the FUV-NUV colour index, ie a brightening of about 0.2 in FUV (NUV agrees in the two exposures to 0.012 of a mangitude, but FUV differs by  0.192) so could just as easily mean nothing.

Click on the object IDs as linked at left of page to get the separate summary pages.

<http://archive.stsci.edu/xcorr.php?target=%2046.4938%20%205.7875&missions[]=GALEX&radius_GALEX=0.2&outputformat=HTML_Table&max_records=10&action=Search>

Basically, poss i, poss ii and sdss say a quite colourless 18 and a half ish mag object in the past, mid 1950s, mid 1990s and late 2004.

Cheers

John

John Greaves