Nova in Cassiopea (nova Cas 2020)

[Benjamin Mauclaire]

Il serait serait bien maladroit d'aborder ainsi un suivi d'évolution.
Les multiplots sont plutôt utiles pour la detection de motifs comme le realise Valerie dans sa newsletter.
A l'instar de la photométrie où les images d'étoiles ne sont pas comparees pas entre elles mais plutôt les mesures de flux, c'est avec la mesure de grandeurs spectrales qu'un monitoring de l'évolution des convultions de l'étoile peut être réalisée.
Encore faut-il une grandeur independante de la resolution comme la largeur equivalente par exemple.

Alors oui cela fait faire encore des graphes, deja que l'on manipule des courbes (profils de raies) et que l'on est dans un espace frequenciel (on ne voit pas d'etoiles bien rondes).
Mais des graphes ont le merite de debrousailler les choses car il y a tellement de richesse dans un spectre qu'il faut faire des choix sur ce que l'on veut regarder, de l'activite a la vitesse d'expansion...

Benjamin

[Christophe Boussin]

Hello all,
For information, a new telegram about the spectroscopy of Nova Cas 2020 in the infrared :
http://www.astronomerstelegram.org/?read=14034

Christophe BOUSSIN

[John Coffin]

What is the cause of the P Cygni profile in what appear to be sodium lines? I think I can identify these on recent spectra. Is the sodium interstellar? If so, is it photoexcitation by UV from the white dwarf that causes the emission lines or some other mechanism?

nova cas stacked 4200 to 6500.png (80.7 KiB) Viewed 8836 times

[Robin Leadbeater]

A quick look under a full moon with the ALPY200 (R~130)
The contamination from the second order is minimal because of the low flux in the blue so I included the IR end in the same spectrum

Cheers
Robin

v1391castelrem_20201001_877_Leadbeater.png (21.77 KiB) Viewed 8762 times

V1393_Cas_ALPY200.png (5.75 KiB) Viewed 8762 times

[Forrest Sims]

Nova Cas 2020 continues to change rapidly and is well worth following. Here are recent flux calibrated spectra taken just two days a part. Nova Cas 2020 has dimmed by nearly 3 magnitudes in the V band in the past week.

Here is a plot of changes in Halpha over the past 5 weeks.

novacas2020_series Ha.png (40.28 KiB) Viewed 8471 times

Here is a plot that shows changes in [OI] 6300Å and [OI] 6364Å over the same time period.

novacas2020_Series [OI] 6300.png (48.77 KiB) Viewed 8471 times

Woody

[Olivier GARDE]

Nice results Woody !!!

[Peter Somogyi]

Good catch of this event, Woody! Looking at your flux graph, my result suggests a tendency H-alpha is shrinking day by day very quickly:

I've used wide slit (1 x 600 sec) for flux calibration.
At OI 7772 region, I've got only very low signal (SNR~10, no flux calibration):

OI_7772.png (51.39 KiB) Viewed 8413 times

Note that the N I 7423,7442,7468 features gone below noise or absent.
Peter

[Forrest Sims]

Last nights spectrum of Nova Cas 2020. It is fading fast now. I measured it at about V magnitude 17.2 with large error bars as it is really dim for my photometry kit. David Boyd measured it at mag 16.7 about 12 hours earlier. I needed 10 second guider exposures to see the star and it was really tricky to put the star on the spectrograph slit. Fortunately my mount was able to keep it there long enough that I was able to guide on a nearby star. This is all I could see in my spectrum raw images to confirm that I still had the star on the slit.

And here is the resultant spectrum of (9) 900 second exposures. Halpha and Hbeta are still detectable as well as [O I] 6300Å and [O I]6364Å although they both appear shifted blueward around 5Å.


Woody

[Robin Leadbeater]

After fading to ~mag 20 Nick James (BAA) reports Nova Cas 2020 (V 1392 Cas) has re-brightened to mag 17.8 currently
https://britastro.org/observations/obse ... d0b45369c3

Cheers
Robin