PNV J20233073+2046041 mag 6.8

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Robin Leadbeater
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Re: PNV J20233073+2046041 mag 6.8

Post by Robin Leadbeater »

Ernst Pollmann wrote: 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.
Hi Ernst,

This is a correlation, not causation. The correlation is high because the H alpha EW is generally increasing as the nova fades. We already know that. What we are trying to establish is what the flux in the H alpha line is doing independent of the continuum level. To do this we need to express the continuum at Halpha (used as a reference for the EW measurement) in terms of flux. We can do this (as you have done) using the Vmag values as a reference. Your treatment however does not take into account the fact that the mean flux level in the Vmag passband changes with time relative to the continuum level at H alpha. That is what my correction factor takes into account. (This correction factor fell from ~1.7:1 to ~1.2:1 currently as the continuum flattened)

Cheers
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
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Christian Buil
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Re: PNV J20233073+2046041 mag 6.8

Post by Christian Buil »

Cette nova est l'occasion d'aller plus loin dans les techniques d'analyses

J’ai donc fait une page qui détaille la manière d’étalonner en flux nos
chers spectres :

http://www.astrosurf.com/buil/calibrati ... ration.htm

La méthode 2 est quasi celle évoquée par Steve Shore dans le
dernier message journalier de compte rendu qu’a fait passer François T.
sur la nova.

D'autres existent (François Teyssier teste une méthode mixte photométrie/spectrométrie
par exemple).

Si vous vous appropriez cela, vous serez de vrais champions de la spectro !
Et cela signifie que vous savez quasiment tout faire ;)

En vérité ce n’est pas très compliqué, et assez amusant.
Faites une tentative pour voir.

La chose peut rapporter gros aussi, car le résultat est bien plus riche
que la photométrie BVR classique sur le plan astrophysique. Il Faudrait
même que les photométristes si mettre... !

On touche vraiment au coeur de la spectro ici.

Pas trop le courage de traduire anglais, ni l’aptitude pour écrire les subtilités
de ces choses sans erreurs. S’il y a des volontaires (Robin, Olivier, ...).

J'ai ouvert un autre fil sur le forum pour discussion eventuelle car cela ne
concerne pas que la nova :

http://www.spectro-aras.com/forum/viewt ... 2900#p2900

-----------------------------------

A page about techniques for convert spectra un flux unit. Two methods are
proposed (4 spectra techniques, 2 spectre techniques – i.e. the classical).
Sorry the text is in french (but illustration in english). It is too difficult for
me to translate. Procedures are not really complex... but have a
great interest for some astrophysical studies:

http://www.astrosurf.com/buil/calibrati ... ration.htm


A new topic in the forum because it is a general problem and question in spectrography:

http://www.spectro-aras.com/forum/viewt ... 2900#p2900


Christian
Christian Buil
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Re: PNV J20233073+2046041 mag 6.8

Post by Christian Buil »

A direct application of flux conversion :

- comparison of Aug. 29.83 and Sept. 1.98 spectra in flux unit (erg/cm2/s/A)
- comparison of Aug. 29.83 and Sept. 1.98 spectra in relative intensity (normalization zone 66650-6680 A)

The magnitude difference between the two date measured from flux spectra is (numerical Bessel filters set):

0.51 in B
0.56 in V
0.45 in R

To be confirmed (new measures this night).

Christian
Attachments
_compa_flux_3.png
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_compa_flux_2.png (12.67 KiB) Viewed 6757 times
_compa_flux_1.png
_compa_flux_1.png (8.79 KiB) Viewed 6757 times
Robin Leadbeater
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Re: PNV J20233073+2046041 mag 6.8

Post by Robin Leadbeater »

Hello Christian,

The change in calculated V mag in 3 days seems larger than expected compared with the AAVSO data which is showing a slope of about 0.1 mag/day currently
Like Francois, I am also experimenting with flux calibration using V mag values. Is it possible to post the fits files of your flux calibrated spectra?

Cheers
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
http://www.threehillsobservatory.co.uk
Kevin Alton
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Joined: Sun Sep 01, 2013 1:48 am

Re: PNV J20233073+2046041 mag 6.8

Post by Kevin Alton »

I've been monitoring Nova Del 2013 since 21Aug2013 using a low resolution SBIG DSS-7/ST-402ME spectrophotometer and would like to share some of my results. Typical exposure times on a 20 cm SCT ranged between 40-50 sec using the narrowest slit (50 µm). Data reduction using HD 196544 as a reference was performed using RSpec. BTW, many thanks to Robin for helping me through the process. So far spectra have been generated on four separate days and can be seen below.
Attachments
Nova Del 2013_Overlays_v2.jpg
Nova Del 2013_Overlays_v2.jpg (93.25 KiB) Viewed 6743 times
Francois Teyssier
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Re: PNV J20233073+2046041 mag 6.8

Post by Francois Teyssier »

Excellent results Kevin.
I wainting for the fit files as soon as you'll have fix the head issues.
Welcom on the forum, the camapaign and spectroscopy world
Best regards
François
Jacques Montier
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Re: PNV J20233073+2046041 mag 6.8

Post by Jacques Montier »

Bonjour,

Dans la nuit du 2 au 3 septembre, le spectre au Lhires 2400 de H alpha montre un pic montant péniblement à 11 environ en valeur relative.
20130902_930_nova_del.png
20130902_930_nova_del.png (4.79 KiB) Viewed 6711 times
Vous confirmez ou c'est une fausse manip de ma part ?

Merci à vous,
Last edited by Jacques Montier on Wed Sep 04, 2013 8:15 am, edited 1 time in total.
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Jacques Montier
Societe d'Astronomie de Rennes
IAU code J23
Christian Buil
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Re: PNV J20233073+2046041 mag 6.8

Post by Christian Buil »

Jacques, regarde ta ligne de base (le continuum) : il n'est pas normalisé à 1, et donc
tu ne peux trouver la bonne valeur au pic. Faut commencer par normaliser, puis ensuite
on pourra évaluer.

Christian
Jacques Montier
Posts: 242
Joined: Sun May 13, 2012 2:46 pm

Re: PNV J20233073+2046041 mag 6.8

Post by Jacques Montier »

Christian Buil wrote:Jacques, regarde ta ligne de base (le continuum) : il n'est pas normalisé à 1, et donc
tu ne peux trouver la bonne valeur au pic. Faut commencer par normaliser, puis ensuite
on pourra évaluer.

Christian
Si, si Christian, la ligne de base était bien normalisée à 1, mais dans Isis -> Gnuplot, j'avais fait démarrer l'ordonnée Y1 à 0.5 au lieu de 0.
Ça induit en erreur car quelle que soit l'origine des y choisie dans Isis, Gnuplot affiche 0 sur l'axe des y...
C'est corrigé sur le post en mettant cette fois l'origine des Y à 0.

Amitiés,
--
Jacques Montier
Societe d'Astronomie de Rennes
IAU code J23
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