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  #81  
Old 19-12-2013, 05:18 PM
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Quote:
Originally Posted by cometcatcher View Post
Wow that Ha spike is amazing. It looks about mag 5 in the visible, what magnitude would it be if we could see Ha? (If that makes any sense)
Actually, I thought of taking an image of the star field using my Ha narrowband filter, just to get a sense of that.
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  #82  
Old 19-12-2013, 05:30 PM
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IMHO I think, looking at the continuum, most of the visible energy is in the hydrogen emissions....let's say 80% in the Ha =<0.5 mag below current visual.
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  #83  
Old 19-12-2013, 06:35 PM
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Originally Posted by Merlin66 View Post
IMHO I think, looking at the continuum, most of the visible energy is in the hydrogen emissions....
In it's present state with that huge Ha spike, why doesn't it look more red? Last night in binos I couldn't see any colour.
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  #84  
Old 20-12-2013, 03:47 AM
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FINALLY got some clear skies!!!!!!
Still processing some medium res spectra (Spectra-L200/300, R=1000)
I'm not sure that the Ha is as bright (?) (spectra to follow)
The region around Hb looks interesting - need to confirm the emission lines.
I'm just thankful to have had a hour or so between the clouds.
More to follow.
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  #85  
Old 20-12-2013, 04:09 AM
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Originally Posted by Merlin66 View Post
FINALLY got some clear skies!!!!!!
Still processing some medium res spectra (Spectra-L200/300, R=1000)
I'm not sure that the Ha is as bright (?) (spectra to follow)
The region around Hb looks interesting - need to confirm the emission lines.
I'm just thankful to have had a hour or so between the clouds.
More to follow.
Nice to have some medium res stuff at last! More clouds on the way I'm afraid, Ken.

Here's mine of this morning. Certainly the Ha line is less prominent relative to the other emission lines, I think.
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  #86  
Old 20-12-2013, 08:47 AM
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Great work guys! I'm finally home again but haven't even unpacked my gear yet - cloudy, and probably continuing...

Cheers -
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  #87  
Old 20-12-2013, 08:29 PM
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Quote:
Originally Posted by Merlin66 View Post
IMHO I think, looking at the continuum, most of the visible energy is in the hydrogen emissions....let's say 80% in the Ha =<0.5 mag below current visual.
Ken
Im sure this would be the case.
With nova Del, I was able to take 30sec exposures early on when there was mostly a continuum but it was about mag 4
By the time it had dropped to mag 7 I was restricted to 5 sec exposures to prevent saturation of the Ha line. I was stacking 30 x 5 sec exposures using Isis with good results.
Im back in Oz but won't be home til the 26th. Then I have to be awake enough to get up at 3am to take some spectra. It probably will only happen on the weekend. I hope the clouds will stay away then.
Terry
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  #88  
Old 21-12-2013, 08:51 AM
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Clouded out down here...did anyone manage to get a spectrum last night???
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  #89  
Old 21-12-2013, 09:13 AM
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Originally Posted by Merlin66 View Post
Clouded out down here...did anyone manage to get a spectrum last night???
Still under it down here, haven't got anything since the 14th Hoping for some clear weather over the holidays.

Have just bought the second hand L200 that was recently advertised on the astro_spec list Maybe it will get here in time to get some data on this nova ...

Interesting developments with the AAVSO light curve, looks like it may be on the up again. Looking at the literature oscillations during the decline are quite common, and it looks like this could be what this one is up to.
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  #90  
Old 21-12-2013, 12:45 PM
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Originally Posted by Merlin66 View Post
Clouded out down here...did anyone manage to get a spectrum last night???
No. Wall-to-wall clouds. Clouding over again now, looks like it will be no break in the clouds in Eastern Australia till Christmas.

Quote:
Originally Posted by malclocke View Post
Have just bought the second hand L200 that was recently advertised on the astro_spec list Maybe it will get here in time to get some data on this nova ...
Nice, I've got one on order with JTW. Fingers crossed it will come soon.

Quote:
Originally Posted by malclocke View Post
Interesting developments with the AAVSO light curve, looks like it may be on the up again. Looking at the literature oscillations during the decline are quite common, and it looks like this could be what this one is up to.
Interesting data from the visual guys. Looks to go up, then comes straight back down. All within tolerance of simple estimation error. I was as keen to do some photometry as I was to take some spectra. I have a little 3.30 am routine: 12 SA spectra, shift the camera to the guidescope, 12 V exposures, 12 B exposures, by which time twilight is upon us ...
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  #91  
Old 24-12-2013, 08:33 PM
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Sigh. More clouds.

The thing is up and down like a roller coaster. Back up to 4.5. The good news is, according o Payne-Gaposchkin, these oscillations in the early decline phase are almost always associated with the slower novae. So it should be around for a while.
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  #92  
Old 25-12-2013, 01:40 AM
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A clear night down here for a change....
Imaging Nova Cen in the background.
The Ha still looks very strong and the Fe lines at Hb seem a little more prominent. I'm also taking some spectra around the Na region....
Stay tuned!
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  #93  
Old 25-12-2013, 05:01 AM
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Quote:
Originally Posted by Merlin66 View Post
A clear night down here for a change....
Imaging Nova Cen in the background.
The Ha still looks very strong and the Fe lines at Hb seem a little more prominent. I'm also taking some spectra around the Na region....
Stay tuned!
I was lucky to catch it between the clouds this morning. My comments are in the other thread.

What would you place its magnitude and colour at?
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  #94  
Old 25-12-2013, 09:18 AM
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First chance since 16 Dec and I managed to obtain another spectrum last night. H-alpha line remains dominant (although it graphed poorly??); NaI line at 589nm and the various FeII lines have increased in relative intensity; H-gamma is weak but it could reflect the camera response, weak at that end.

The nova was a relatively easy naked-eye last night but because of the low altitude and sky gradients in that direction I didn't attempt an estimate. Definitely brighter than the mag 5s though.

Also attached is a Xmas card for those to whom it matters - to all others, have a safe and happy holiday season!

Cheers -
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  #95  
Old 25-12-2013, 02:51 PM
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Rob - love both your images :-). Look at the FeII lines! Rivalling the H beta.

Very little media coverage of this nova. I'd expect a few "Star of Bethlehem" pieces;-)
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  #96  
Old 26-12-2013, 03:34 AM
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Here's a quick one from this morning
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  #97  
Old 26-12-2013, 08:50 AM
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Rob, Jon,
Well done guys!
Weather permitting we seem to be keeping track of the nova.
I have some spectra which will show the same emissions as Jon's - hope to process them later today.
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  #98  
Old 26-12-2013, 11:30 AM
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OK guys, here's a stacked and cleaned up spectrum from this morning. Easily my best capture with the SA100. I've done a fair bit of research this morning on what I may be seeing. So here goes:

1) The Balmer lines remain prominent. However, they are less so relative to the continuum than on 19 December. This corresponds with a rebrightening of the nova - as the nova brightens, the SA100-measured Balmer lines decrease in relative intensity.

In a study of V5558 Sgr (2007), another nova with a series of rebrightenings after maximum, Tanaka et al (2011) found that the absorption component of the Balmer P Cygni profiles increased as the nova rebrightens. This is because the rebrightening is owing not to increased temperature, but to increased density, mass flow and photospheric radius of the stellar wind.

The SA100 does not have sufficient resolution to capture both absorption and emission components. The net effect of an increase of the absorption component would be a diminution of the measured emission component, as here. This seems to be an interpretation that is at least plausible.

2) The FeII emisison lines are extremely prominent across the spectrum.There is also evidence of CaII, NaI, NII, and possibly HeII and CII. These latter are less convincing, but are consistent with a FeII nova at this stage.

3) There is no evidence of any forbidden lines. Not unusual, but see below.

4) Perhaps the most interesting feature of the spectrum is OI at 7773. OI at 8446 is present in nearly all novae spectra, but OI 7773 can only form in conditions of a relatively dense wind. Williams (2013) discusses this in detail and proposes the 8446/7773 ratio as a means of classifying the wind environment of different novae. Williams suggests that where the 8446/7773 ratio is low (as here), and the wind relatively dense, then forbidden lines are (unsurprisingly) slower to emerge.

So there is is - even from a SA100 spectrum there's a bit of evidence from the rebrightenings and the 8446/7773 ratio that this is a nova with a particularly dense wind.
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  #99  
Old 26-12-2013, 01:26 PM
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Thanks Ken, and nice work again Jon! You're doing well and it's great to see areas that are way outside the response range of my camera!

Here's mine from last night.

Cheers -
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  #100  
Old 26-12-2013, 01:42 PM
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I've been working my way through Steve Shore's comments/ notes on Nova Del as a reference source:

The two first pages (Francois is still working on them) http://www.astrosurf.com/aras/novae/Nova2013Del.html

The notes are downloadable from : http://www.astrosurf.com/aras/novae/Images_NovaDel2013/SteveNotes.pdf
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