Alert! Nova Cas 2021 mag 9

Alerts and Monitoring of Novae

Re: Alert! Nova Cas 2021 mag 9

Postby Francois Teyssier » Wed May 12, 2021 8:03 am

By chance (vey cloudy weather) , a new echelle spectrum secured this morning with the remote station SMM-SP equiped with a NOU-T spectrograph.

asdb_NovaCas2021_20210512_120.png


Significant evolution of the absorption system.

Fe II (42) 5018:
NovaCas2021_FeII_5018.png
NovaCas2021_FeII_5018.png (28.24 KiB) Viewed 1274 times


H alpha:
NovaCas2021_Ha.png
NovaCas2021_Ha.png (21.67 KiB) Viewed 1274 times


Na I D region:
Note the increase of Na I D and He I 5876 absorptions
(for beginners: the narrow lines are interstellar Na I)

NovaCas2021_NaID.png
NovaCas2021_NaID.png (33.44 KiB) Viewed 1274 times


Following Steve's suggestion, a comparison of H beta, Fe II, Na I D1:
showing that the maximum absorption of Na I D has the same radial velocity than Balmer and Fe II lines.

NovaCas2021_HaFeIINaID.png
NovaCas2021_HaFeIINaID.png (29.93 KiB) Viewed 1274 times


As suggested in my last post, daily coverage is strongly recommended, due to the fast changes observed.

Looking at the AAVSO V light curve, it seems that the nova is reaching a new plateau at mag 5.3

NovaCas2021_LC_2021-05-12.png
NovaCas2021_LC_2021-05-12.png (22.41 KiB) Viewed 1274 times
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Re: Alert! Nova Cas 2021 mag 9

Postby Christophe Boussin » Wed May 12, 2021 5:02 pm

Hello all,

For this time, here is my contribution to the monitoring of the Nova Cas 2021 at high resolution !
The following spectrum, centered on the Halpha line, was obtained the 12th of May at 1 h 03 TU (resolution of 12568, JJ = 2459346.5439) with my LHIRES III (grating of 2400 lines / mm) and an acquisition time of 60 min (6 x 600s):

novacas2021_20210512_044_Christophe Boussin_Halpha.png
Halpha line of Nova Cas 2021 on May 12th, 2021
novacas2021_20210512_044_Christophe Boussin_Halpha.png (16.9 KiB) Viewed 1246 times

Maximum absorption is observed at a velocity of approximately -686 km/s.

Clear skies to all !!

Christophe BOUSSIN
CBO (Newton 200 F/5 / Alpy600 / Atik 314L+ / Atik Titan + Mewlon 180 F/12 / LHIRES III 2400 / Atik 460EX / Atik 314 L+) @ ARAS database
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Re: Alert! Nova Cas 2021 mag 9

Postby Francois Teyssier » Thu May 13, 2021 7:11 am

Astronomer's Telegram

ATEL #14622 ATEL #14622

Title: V1405 Cas (= Nova Cas 2021) has entered a recombination phase
Author: S. N. Shore (Univ. of Pisa), F. Teyssier, O. Garde, S. Charbonnel,
M. Bajer, C. Boussin, H. Allen (ARAS Group)
Queries: steven.neil.shore@unipi.it
Posted: 13 May 2021; 03:09 UT


As a result of our continuing spectroscopic monitoring, described in ATel
#14577 (with resolutions ranging from 560 to 12568), we report that the slow nova V1405 Cas has now entered a new phase with the development of a strong recombination event coincident with the start of the optical brightening reported in ATel #14614.

On 2021 May 9.0 there was no detectable absorption on the Na I D lines other than interstellar (EW < 0.06 A, R ~ 11000) while on May 12.1 the two D lines showed strong, nearly identical absorption compoennts (EW =0.6A) at -670 km/s with FWZI ~ 250 km/s (the line depths, 0.25 of the continuum, suggests partial covering). Lower resolution (R~1500) show the absorption was already present on May 10.8 at a similar intensity. The He I lines (e.g. 4471, 5876, 6678, 7065 A) are all still present but with very weak P Cyg profiles; the absorption extends to -1100 km/s (width of 400 km/s, minimum at -800 km/s). Ca II H and K now display extremely strong absorption, extending to -1400 km/s, with weak emission wings extending to +1200 km/s.
All of the Balmer series continue to display strong P Cyg profiles but the visibility of the narrow emission at around 0 km/s has greatly diminished relative to the broader emission component, and is absent on Hgamma and beyond (maximum absorption velocity, -1200 km/s, maximum emission velociity
-1300 km/s). These velocities are quite similar to those on the Ca II H and K lines that now display extremely strong absorption, extending to
-1400 km/s, with weak emission wings extending to +1200 km/s. The same applies to Si II 6347, 6670 A and to all of the principal Fe II transitions whose emission component is now contiguous with the absorption. The He I lines (e.g. 4471, 5876, 6678, 7065 A) are all present but with very weak P Cyg profiles; the absorption extends to -1100 km/s (width of 400 km/s, minimum at -800 km/s).

The May 10.8 spectrum was flux calibrated with a measured integrated value of 8.E-8 erg/s/cm^2 (3900-7300A). We confirm the DIB equivalent width measurements reported in ATel #14476 (3780 A: 0.32A; 3790: 0.08A; 6613: 0.11A) with a de-reddened flux of 5.1E-7 erg/s/cm^2 applying E(B-V)=0.51 (for standard Galactic extinction). It appears the rapid brightening reported in ATel#14614 #14615 is the signal of a recombination wave driven by the development of strong UV Fe-curtain absorption in the expanding ejecta.

Further high cadence observations arte strongly advised, ours will continue as weather permits.

ARAS Database: Novae: http://www.astrosurf.com/aras/Aras_DataBase/Novae
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Re: Alert! Nova Cas 2021 mag 9

Postby Francois Teyssier » Thu May 13, 2021 7:12 am

I forward a request of our colleague Pavol and Dr. Vladimir Zekovic.

This request is a new encouragement to undergo our intensive monitoring of this bright nova (currently mag V ~ 5.3)
At the date, we gathered 132 spectra.
Send spectra to francoismathieu.teyssier (at) gmail.com and a copy to arasdatabase for double check.
François


The international research team led by Dr. Vladimir Zekovic (University of Belgrade, Serbia) is working on the modelling of astrophysical shocks and related particle acceleration within the framework of particle-in-cell simulations and non-linear theory.
(https://ui.adsabs.harvard.edu/abs/2021A ... A/abstract) The present outburst of Nova Cas 2021 appears as an unique opportunity to test the theory and estimate the cosmic-ray production by the nova shock.
As the observed plasma temperature will be used in a shock modelling, the time evolution of H_alpha profile with ~1 day time resolution is needed. The resolution power shall be >8000. To accomplish such coverage, all observers with appropriate equipment are encouraged to do the observations as frequently as possible and submit them to ARAS
database:
http://www.astrosurf.com/aras/Aras_Data ... as2021.htm
It would be great to continue with the high-density coverage as long as the brightness of the target allows it. Of course, this effort will also have an impact in the understanding of novae themselves. Recently, it was found that shocks contribute significantly to the bolometric luminosity of novae (see for instance
https://ui.adsabs.harvard.edu/abs/2020N ... A/abstract)

Pavol A. Dubovsky
Vihorlat Observatory
Humenne, Slovakia


Vladimir Zekovic
Research Associate
Dept. of Astronomy
Faculty of Mathematics
Uniersity of Belgrade
Studentski trg 16
11000 Belgrade, Serbia
Last edited by Francois Teyssier on Sat May 22, 2021 11:28 am, edited 1 time in total.
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Re: Alert! Nova Cas 2021 mag 9

Postby Christophe Boussin » Wed May 19, 2021 6:33 pm

Hello all,

Finally a clear sky for a few hours ...
Here is my new contribution to the monitoring of the Halpha line of the Nova Cas 2021 at high resolution.
The following spectrum was obtained on May 18 at 23 h 14 TU (resolution of 12187, JJ = 2459353.4683) with my LHIRES III (grating of 2400 lines / mm) and an acquisition time of 60 min (6 x 600s):

novacas2021_20210518_968_Christophe Boussin_Halpha.png
Halpha line of Nova Cas 2021 on May 18th, 2021
novacas2021_20210518_968_Christophe Boussin_Halpha.png (17.64 KiB) Viewed 1010 times

The Halpha line profile has changed a lot since May 12 !

Clear skies to all !!

Christophe BOUSSIN
CBO (Newton 200 F/5 / Alpy600 / Atik 314L+ / Atik Titan + Mewlon 180 F/12 / LHIRES III 2400 / Atik 460EX / Atik 314 L+) @ ARAS database
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Re: Alert! Nova Cas 2021 mag 9

Postby Christophe Boussin » Sun May 23, 2021 11:23 am

Hello all,

And again a new "window" of clear sky !!
Here is a comparison between my last spectrum of the Halpha line of Nova Cas 2021 obtained at high resolution on May 22 at 00 h 00 TU (resolution of 14045, JJ = 2459356.5001, LHIRES III with grating of 2400 lines / mm, acquisition time of 60 min (6 x 600s)) and the previous one obtained on May 18 at 23 h 14 TU.

novacas2021_Halpha_Christophe Boussin.png
Halpha line of Nova Cas 2021 on May 18th and 22th 2021
novacas2021_Halpha_Christophe Boussin.png (23.86 KiB) Viewed 900 times

The change of line profile is once again very obvious in only a few days but the overall appearance remains the same.

Clear skies to all !!

Christophe BOUSSIN
CBO (Newton 200 F/5 / Alpy600 / Atik 314L+ / Atik Titan + Mewlon 180 F/12 / LHIRES III 2400 / Atik 460EX / Atik 314 L+) @ ARAS database
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Re: Alert! Nova Cas 2021 mag 9

Postby Christophe Boussin » Fri May 28, 2021 5:45 pm

Hello all,

Is it finally the return of more frequent starry nights?
This seems to be the case for the next few days ...
Here is a new comparison between my last spectrum of the Halpha line of Nova Cas 2021 at high resolution on May 27 at 23 h 34 TU (resolution of 13096, JJ = 2459362.4819, LHIRES III with grating of 2400 lines / mm, acquisition time of 60 min (6 x 600s)) and the previous ones obtained on May 18 at 23 h 14 TU and on May 22 at 00 h 00 TU.

novacas2021_Halpha_Christophe Boussin.png
Halpha line of Nova Cas 2021 on May 18th, 22th and 27th 2021
novacas2021_Halpha_Christophe Boussin.png (32.45 KiB) Viewed 672 times

The line profile, especially in the “blue” part, has changed significantly in a few days !

Clear skies to all !!

Christophe BOUSSIN
CBO (Newton 200 F/5 / Alpy600 / Atik 314L+ / Atik Titan + Mewlon 180 F/12 / LHIRES III 2400 / Atik 460EX / Atik 314 L+) @ ARAS database
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Re: Alert! Nova Cas 2021 mag 9

Postby Peter Somogyi » Sun May 30, 2021 1:07 pm

Nice results Christophe, let me extend the H-alpha serie:
NovaCas2021_pso.png
NovaCas2021_pso.png (21.06 KiB) Viewed 584 times

The daily cadence looks reasonable.
Got rainy days, please continue!
Peter
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Nova Cas 2021 remarkable spectral evolution

Postby HughAllen » Mon May 31, 2021 11:36 am

Since Mar 22 I've captured a dozen Alpy spectra of this beautiful nova, the latest last night May 30. The slow decline in expansion velocity seemed to go into reverse in my spectrum of May 24 around the time that the nova began again to rebrighten. The decline in velocity has seemingly resumed based on last night's spectrum:

Nova Cas 2021 Evolution of velocity of absorption minimum.png
Nova Cas 2021 Evolution of velocity of absorption minimum.png (30.19 KiB) Viewed 507 times


The HeI emission seems to be returning, here's an offset relative flux plot of a few of my spectra since Marr 22:

Nova Cas 2021 Offset zoom 2021 03 22 - 05 24.png
Nova Cas 2021 Offset zoom 2021 03 22 - 05 24.png (91.43 KiB) Viewed 507 times


The star appears amazingly red, presumably due to the currently overwhelming relative intensity of the H alpha emission:

Nova Cas 2021 2021 05 24.png
Nova Cas 2021 2021 05 24.png (33.32 KiB) Viewed 507 times


This really is a wonderful object to follow in a spectroscope!
Cheers
Hugh
Hugh Allen
Alpy 600 user
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Re: Alert! Nova Cas 2021 mag 9

Postby Christophe Boussin » Tue Jun 01, 2021 8:29 pm

Hello all,

Very nice and interesting analysis Hugh, you get the most out of your Alpy !

Thank you Peter, great result too !
I hope that you will quickly find again clear skies and ... I will therefore continue the serie in the meantime ;-) !

Here is my new comparison between my two last spectra of the Halpha line of Nova Cas 2021 at high resolution on May 29 at 23 h 51 TU (resolution of 16788, JJ = 2459364.4938) and on May 31 at 23 h 35 TU (resolution of 14355, JJ = 2459366.4825) obtained with my LHIRES III (grating of 2400 lines / mm, acquisition time of 60 min for each spectrum (6 x 600s)) and the previous ones obtained on May 18, 22 and 27.

novacas2021_Halpha_Christophe Boussin.png
Halpha line of Nova Cas 2021 on May 18th, 22th, 27th, 29th and 31th 2021
novacas2021_Halpha_Christophe Boussin.png (42.12 KiB) Viewed 422 times

The overall appearance of the line profile has changed less over the past few days...

Clear skies to all !!

Christophe BOUSSIN
CBO (Newton 200 F/5 / Alpy600 / Atik 314L+ / Atik Titan + Mewlon 180 F/12 / LHIRES III 2400 / Atik 460EX / Atik 314 L+) @ ARAS database
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