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observations of U Gem needed now

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Details will be forthcoming in an AAVSO Special Notice, but visual and multicolor observations of U Gem are needed now through at least December 11. HST/COS will be observing U Gem on 2013 December 7, now that the recent outburst is over, and it is essential to have good coverage from AAVSO observers. These HST observations are a continuation of the campaign announced last year in AAVSO Alert Notice 475 and followed up on in AAVSO Special Notices #327 and #328.

Good observing  -  Elizabeth Waagen, AAVSO HQ

U Gem for HST
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Hi Elizabeth!

I observed and submitted IRVB data for U gem for 06Dec13 for UT times 09:08:47.9 to 11:25:22.9.  Hope this helps the research for this interesting dwarf nova!

James Foster-Los Angeles, CA

p.s.  I notice I'm not seeing the AASVO moniker next to my name in the plots.  Is this because I joined  "officially" only 3 weeks ago?

U Gem for HST
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Hope this isn't too hard on the eyes. Here's a colorful little graph I made of the VBRI data I took last night:

Backround image of U Gem is from "Darkly" at Deviant art: http://darky-face.deviantart.com/art/S-Doradus-245309265#/art/U-Geminorum-245310457?_sid=58754c29

Unusual Color?
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I was looking at the LCG of U Gem, and noticed that B and V are quiescent at about 15th mag.  U and Ic are brighter at 13th.  I am not surprised to see the Ic brighter, but to see both the Ic and the U brighter surprised me.  Is this normal for U Gem?  Is this normal for this type of star? 

If its clear tonight, I might try it, and I do have a U filter. 

 

WGR

Observations U Gem needed now
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I wanted to shoot it in the U, but the filter I thought was U was actually a non-standard IR.  Nice observation!  I think that most of the radiation is coming from Ic (red star?) and U(white dwarf& accetion disk?). Time to buy another $150+ filter! :(

FJQ

p.s.  Just submitted 08Dec13's data, not much else different than 2 days before.

Unusual color
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Hi Gary,

Remember that CVs are composite objects, consisting of a white dwarf, an accretion disk, and a donor star.  Each has a different temperature, and so the resulting spectrum does not look like any kind of a normal star.  If the donor star (which is almost always quite red) is bright, then it will dominate in the Ic band.  If the white dwarf is hot and bright, then U-band will be particularly bright.  The mid-wavelengths are almost always dominated by the accretion disk, especially during outburst.  So what you get depends strongly on the relative contribution of each object.

Now that we are back at quiescence (14.5 mag), I would expect U-band to be about 14th mag, which is very difficult with an amateur telescope.  I'd give it a try just to see what happens, and then be ready for the next outburst.  Watch out for red leaks - U filters are known for this.  The Astrodon U filter is blocked to 1.1 micron and so should be ok.  One good way to test for a red leak is to image S Ori, a very red but bright star.  It should be fainter than the B-band measurement; if brighter, then you have a leak.

Arne

indicating affiliation on LCG
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Hi James,
Thank you so much for your multicolor observations of U Gem during the current campaign - and for joining the AAVSO! We very much appreciate your observations and your support. I apologize for not answering you sooner - I was away from my email from the 5th until last night. In order for the Light Curve Generator to indicate your affiliation with the AAVSO, you need to specifiy it in your profile. It's very easy to do: log in to the website and click on 'My account' in the upper right corner. When your page comes up, click on 'View My AAVSO Profile' and when your profile appears, click on 'Edit your information'. Go down to the Affiliation line and choose AAVSO from the drop-down menu of organizations. Save your edit (click 'Submit' near the bottom of the screen) and that's it! If you have questions about or difficulties with this, just let us know.

Thank you again, and good observing, Elizabeth

Unusual color
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RE:"Watch out for red leaks - U filters are known for this. The Astrodon U filter is blocked to 1.1 micron and so should be ok. "

I'll keep that in mind when getting the photometric U filter...thanks for the great feedback Dr. Arne!

James Foster

Los Angeles, CA

indicating affiliation on LCG
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To:  Elizabeth,

Thanks for the direction.  I'm seeing this on the plotted charts now:

 

FJQ FOSTER, JAMES US, AAVSO

Hope to make my 30,000 CCD photometric measurement by the end of 2013!

 

James

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484