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Unfortunately, I cant monitor this Nova Cas 2021 from home, but I recently went to Mt. Pinos (2,500 meters elevation) and was able to capture Alpy600 and LISA-IR data.
Here is the latest I've done from the nights of 13&14May2021, stitched together with as many lines as I could identify with PlotSpectra software:

[NOTE: all non-balmer lines identified are speculative]

I will get more data this coming week when I return to Mt. Pinos, CA.

James

Hello all,

After a few very cloudy nights, the clear skies seems to be back for this week...
Here is my new comparison between my two last spectra of the Halpha line of Nova Cas 2021 at high resolution on June 1 at 23 h 34 TU (resolution of 18277, JJ = 2459367.4824) and on June 6 at 22 h 54 TU (resolution of 17957, JJ = 2459372.4542) 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, 27, 29 and 31.
Clear skies to all !!

Christophe BOUSSIN

Hello all,

It was a good week to observe the Halpha line of the Nova Cas 2021 at high resolution almost daily !

Here is my new comparison between my four last spectra of the Halpha line of Nova Cas 2021 at high resolution on June 7 at 23 h 04 TU (resolution of 18453, JJ = 2459373.4611), on June 8 at 23 h 13 TU (resolution of 18668, JJ = 2459374.4672), on June 10 at 23 h 03 TU (resolution of 18761, JJ = 2459376.4604) and on June 11 at 23 h 15 TU (resolution of 18499, JJ = 2459377.4689) with my LHIRES III (grating of 2400 lines / mm, acquisition time of 60 min for each spectrum (6 x 600s)) and the previous ones.
The following animation shows the impressive evolution of the Halpha line between May 18 and June 11 : The overall appearance of the line profile is roughly the same since early June, but this week the relative intensity of the line has increased !

Clear skies to all !!

Christophe BOUSSIN

Hello all,

Here is my new comparison between my three last spectra of the Halpha line of Nova Cas 2021 at high resolution on June 15 at 1 h 16 TU (resolution of 17539, JJ = 2459380.5531), on June 16 at 0 h 56 TU (resolution of 18726, JJ = 2459381.539) and on June 19 at 1 h 02 TU (resolution of 18674, JJ = 2459384.5428) and the previous ones obtained with my LHIRES III (grating of 2400 lines / mm, acquisition time of 60 min for each spectrum (6 x 600s)).
The overall profile of the Halpha line now remains very similar from day to day.
However, we can note the variation in the relative intensity (increase between 11 and 15, decrease between 15 and 16 and increase between 16 and 19 June) :
Clear skies to all !!

Christophe BOUSSIN

Christophe Boussin wrote: However, we can note the variation in the relative intensity (increase between 11 and 15, decrease between 15 and 16 and increase between 16 and 19 June)

Hi Christophe

You can only measure changes in the intensity of emission lines if you calibrate your spectra in absolute flux. The change in relative intensity in H alpha could be because the continuum brightness is changing.

For example the V magnitudes for your last 4 spectra from AAVSO are 7.1, 7.4, 6.8, 7.1 If we assume the continuum at H alpha follows V magnitude this will make the H alpha line look ~30% stronger in relative magnitude on 6/15 and ~30% weaker on 6/16

Cheers
Robin

Hi Robin,

Thank you for your comment !
Yes, I'm aware that the brigthness of the continuum can vary and that is why I'm talking about relative intensity.
Therefore, the variation in the relative intensity of the Halpha line does not indicate, of course, the variation in the intensity of the line but only a variation with respect to the continnuum.

I can't, for the moment, measure the V magnitude at the moment of the acquisition of the spectrum, so I limit myself to presenting it in relative intensity.
But, of course, the spectrum can be, a posteriori, calibrated in absolute flux with the measurements from AAVSO for example as you indicate it

Spectroscopically,

Christophe

Here is my observations of Nova Cas 2021 (V1405 Cas) with my LhiresIII, as seen in this animated .gif:


The Nova is still very bright...will post IVB magnitudes latter that I took near simultaneous with by LhiresIII spectra.
2021 might be known as the year of NOVA!

James

Hello all,

Nice spectra James !
Yes, indeed, 2021 is a great year for the observation of novae ... as well as 2020 !

Finally a clear sky for a few hours to fill the gap since June 19...
So, here is my last spectrum of the Halpha line of Nova Cas 2021 at high resolution on June 29 at 0 h 24 TU (resolution of 18771, JJ = 2459394.517) and the comparison with the previous ones obtained with my LHIRES III (grating of 2400 lines / mm, acquisition time of 60 min for each spectrum (6 x 600s)).
In ten days, the relative intensity of the Halpha line shows a very clear variation !
And, as the animation of the spectra of James shows very well, the absorption around -1200 km/s becomes more and more obvious :
According to the AAVSO website, the brightness of the Nova increases again !!
(Johnson V : green squares)
Clear skies to all !!

Christophe BOUSSIN

Hello all,

Between the clouds , with some luck and perseverance, I succeeded to find a clear sky...for 2 hours  !
So, here is my last spectrum of the Halpha line of Nova Cas 2021 at high resolution on July 1 at 23 h 17 TU (resolution of 18654, JJ = 2459397.4701) and the comparison with the previous ones obtained with my LHIRES III (grating of 2400 lines / mm, acquisition time of 60 min for each spectrum (6 x 600s)).
The following animation shows the evolution of the profile of the Halpha line between May 18th and July 1st : Evolution over the last 2 weeks : ... and a more detailed view of the profile in the “blue” part : According to the AAVSO website, the brightness of the Nova drops again !!
Is this the start of more regular oscillations ?
(Johnson V : green squares) Clear skies to all !!

Christophe BOUSSIN

Hello all,

A new small “weather window”...to follow the evolution of the Halpha line of the Nova Cas 2021 !
Here is my two last spectra at high resolution obtained on July 7 at 1 h 07 TU (resolution of 18932, JJ = 2459402.5464), at 23 h 13 TU (resolution of 18662, JJ = 2459403.4672) and the comparison with the previous ones obtained with my LHIRES III (grating of 2400 lines / mm, acquisition time of 60 min for each spectrum (6 x 600s)).
Evolution between June 29 and July 7 : Note the evolution of the profile in the “blue” part : According to the AAVSO website, after a one magnitude drop between June 29 and July 1, the brightness of the Nova remained more or less the same between July 1 and July 7.

(Johnson V : green squares) Clear skies to all !!

Christophe BOUSSIN