PNV J20233073+2046041 mag 6.8

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Re: PNV J20233073+2046041 mag 6.8

Postby Ernst Pollmann » Sat Aug 31, 2013 8:32 am

Francois and Christian,
would you be so friendly, to describe your communication about line flux in English?

Ernst
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Re: PNV J20233073+2046041 mag 6.8

Postby Ernst Pollmann » Sat Aug 31, 2013 11:41 am

Corresponding my considerations (on page 14 this forum), here further evaluations regarding the intrinsic Halpha line flux (see attachment):

Fig. 1: Halpha EW versus JD (trivial)

Fig. 2: Vmag (550 nm) versus Halpha EW
Obviously a clear inverse correlation between both: an increase of the continuum brightness (here V mag at 550 nm) will yield a smaller EW and vice versa.

Fig. 3: Halpha line flux versus JD (see page 14)
The variability of the EW is caused by variations of the continuum flux and by variations of the line flux, the latter is caused by variations in the wind density. While the EW in Fig. 1 is continuously increasing, the line flux (wind density) seems to decrease since JD 2456529.

Comments are welcome!

Ernst
Attachments
novadel_overview_2.jpg
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Re: PNV J20233073+2046041 mag 6.8

Postby Paolo Berardi » Sat Aug 31, 2013 12:06 pm

Absolute flux calibration and Ernst "true EW" calculation and analysis seems to me the final frontier of spectroscopy, congratulations! I have already learned a lot from you and I also hope to learn new things like these.

Robin, your great effort in observing campaigns is known! The modification of 2400 l/mm grating holder to reach IR is a thing of great value! Indeed we should use it for this subject...

Concerning double peak, I'm also curious to know the mechanism of its formation. If I don't wrong, it should be a dual emission Vrad separated, not an absorption on a single emission line. Now it is visible on almost all enlarged emission lines (whatever the element/state that produce them). In some lines the intensity ratio seems stronger, in other less. Main emission peak seems showing a blu-shifted component. The other peak is more (red) shifted.

On 29 august François bulletin I read about the complex ejecta structure deduced from NOT spectrum Fe II lines. Can we affirm that the same phenomenon is observed in other emissions like some H Balmer, OI, CaII line? Is this a demonstration of bipolar ejecta structure? We see this now because of increased transparency of ejecta?

It comes to mind the strange shapes of some planetary nebulas... Steve phrase "...just like a planetary nebula in fast forward!" is fantastic!

Sorry for so many question...

Clear sky!
Paolo
Last edited by Paolo Berardi on Sat Aug 31, 2013 12:30 pm, edited 1 time in total.
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Re: PNV J20233073+2046041 mag 6.8

Postby Robin Leadbeater » Sat Aug 31, 2013 12:15 pm

Hi Ernst,

My results derived independently show the H alpha flux still rising (see attached)

I think there are two significant differences between our data which produce the difference

1. The relationship between the Vmag flux and the flux in the continuum at Halpha is not constant but varies as the nova continuum cools

2. The V mag values you are using are significantly different from the mean values in the AAVSO database

I calculated the correction factor from V mag to H alpha continuum by multiplying the spectra (previously normalised at H alpha) by the normalised V mag filter response and taking the average of the result over the Vmag passband.

Cheers
Robin
Attachments
novadel2013_halpha_corrected_relative_flux.png
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Last edited by Robin Leadbeater on Sat Aug 31, 2013 1:12 pm, edited 1 time in total.
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Re: PNV J20233073+2046041 mag 6.8

Postby Ernst Pollmann » Sat Aug 31, 2013 12:32 pm

... why should the visual (estimated) brightness of the AAVSO data base be more correct (better suitably) than the photometric CCD values?

You wrote:
1. The relationship between the Vmag flux and the flux in the continuum at Halpha is not constant but varies as the nova continuum cools

... can you demonstrate this?

Ernst
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Re: PNV J20233073+2046041 mag 6.8

Postby Robin Leadbeater » Sat Aug 31, 2013 1:32 pm

Hello Christian,

Christian Buil wrote:Here the classic BVRI Bessel filter transmission

Image

Now the product of August 29.8 Alpy spectrum and the filters transmission:

Image

For the classical photometry we integrate the signal of each spectral band. This give raw BVRI magnitude.
But photometry fails to explain the complex phenomena of a nova.



I used a similar technique to improve Ernst's method of measuring H alpha flux, but for better accuracy should we correct the filter response to include the response of the sensor? This is hopefully a small effect at V but could be large I think at B where the typical CCD response is changing fast.

Cheers
Robin
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Re: PNV J20233073+2046041 mag 6.8

Postby Robin Leadbeater » Sat Aug 31, 2013 1:36 pm

Ernst Pollmann wrote:... why should the visual (estimated) brightness of the AAVSO data base be more correct (better suitably) than the photometric CCD values?

You wrote:
1. The relationship between the Vmag flux and the flux in the continuum at Halpha is not constant but varies as the nova continuum cools

... can you demonstrate this?

Ernst


Hi Ernst,

I used the photometric Vmag data in AAVSO (means of several observers) not visual estimates.

http://www.aavso.org/lcg/plot?auid=000- ... an=&vmean=

The relationship between the flux in the Vmag passband and the continuum at H alpha is calculated see the column labelled "correction vmag/Ha" The reduction in slope of the continuum with time is clear in the spectra. There is also an effect from the change in intensity of the many P Cygni lines, mainly from Fe in the Vmag passband. See for example the animation by Paolo here
http://quasar.teoth.it/html/spectra/novadel_15_21.gif

Cheers
Robin
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Re: PNV J20233073+2046041 mag 6.8

Postby Ernst Pollmann » Sat Aug 31, 2013 4:04 pm

Robin you wrote:
The relationship between the flux in the Vmag passband and the continuum at H alpha is calculated see the column labelled "correction vmag/Ha".The reduction in slope of the continuum with time is clear in the spectra.

This is what Fig . 2 in my analysis is saying (although for 550nm):
an increase of the continuum brightness (below Halpha) leads to a smaller EW and vice versa, proven with the correlation coefficient of better than 0.9.
In addition: as Christian´s Bessel plot shows, there is obviously no significant difference of the continuum level V (5500) to R (6500).

Ernst
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Re: PNV J20233073+2046041 mag 6.8

Postby Francois Teyssier » Sat Aug 31, 2013 5:18 pm

Just about the photometric method to compute absolute calibration of the spectra, here's a web page.

http://www.astronomie-amateur.fr/feuilles/Spectroscopie/Traitement.html

Two points :
- as I said in a post, you have to substract the emission lines (see Skopal, 2003,2007) The factor is x0.83 for yesterday spectrum
- you have to dereddened the spectrum E(B-V) =0.18

François
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Re: PNV J20233073+2046041 mag 6.8

Postby Robin Leadbeater » Sat Aug 31, 2013 5:47 pm

Ernst Pollmann wrote:Robin you wrote:
The relationship between the flux in the Vmag passband and the continuum at H alpha is calculated see the column labelled "correction vmag/Ha".The reduction in slope of the continuum with time is clear in the spectra.

This is what Fig . 2 in my analysis is saying (although for 550nm):
an increase of the continuum brightness (below Halpha) leads to a smaller EW and vice versa, proven with the correlation coefficient of better than 0.9.
In addition: as Christian´s Bessel plot shows, there is obviously no significant difference of the continuum level V (5500) to R (6500).

Ernst


Hi Ernst,

your Fig 2 appears to be a plot of H alpha EW against Vmag. I do not understand what this has to do with the correction I am making which is for the difference in flux between where the V mag brightness is measured and the continuum around H alpha where the spectra are normalised for the EW measurement. Are you seriously saying that the ratio of the mean flux in the Vmag passband to that in the continuum at H alpha has not changed during the past 2 weeks? The figures calculated from the spectra say otherwise (Including those made by Christian, who used the same technique as I did, though I do not see where this has been calculated explicitly)

The main difference between our measurements however is due to the difference in the Vmag values used. Do you know why the Vmag values you are using are significantly different from the values provided by other observers in the AAVSO database?

Cheers
Robin
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