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Nova in Cas

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Jeremy's picture
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Nova in Cas

According to ATel 13904, the 12.9mag (unfiltered with V zero-point) optical transient TCP J00114297+6611190 was identified on 2020-07-27.9302 UT by S. & K. Korotkiy and spectroscopically confirmed as a Fe II type classical nova on 2020-07-29.025 with the 2.5m Sternberg Astronomical Institute telescope by the team of Kirill Sokolovsky.

Nova Cas 2020 has coordinates (J2000.0): R.A. 00 11 42.96 Decl. +66 11 20.8

Observations and spectroscopy urgently required. An AAVSO chart and sequence are available.

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N Cas latest obs

David Swan has an image on his Members page of the nova taken last night.

I've seen CCD and Vis observations from the early hours of this morning (30th) placing it between mag 13.5 and 13.9.

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Picture a bit dark

For some reason the uploaded pic has come out a bit dark. It is, I suspect, something to do with the fact that I saved the image first as a png in Maxim. The file was still a bit large though, so I opened that in Photoshop and did a web compression. I'll have a look this eve at putting something slightly better up. I also need to test whether the boxcar or the bayer pane setting for flat calibration works best with this particular calibration frame set.

Anyway, I was keen to have a look at the nova! I am actually planning to revisit low res spectroscopy with the StarAnalyser in a much more rigorous way: dark and flat calibration and then instrument response correction using a standard star at a similar altitude.

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slitless spectrograph flats

Hi David,

I would not bother attempting flat correction of slitless spectra. Normal flat correction techniques do not work because each point is a mix of spectral and spatial information. (The technique used on professional setups is complex and involves generating effectively a "flat cube"  for each wavelength at each point in the field.) My advice would be to take a conventional flat beforehand to check for any obvious dust donuts etc and place your target and reference star zero orders as near as possible on the same pixel avoiding any dust spots so any gross flat effects eg vignetting etc cancel.

Cheers

Robin

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How to use the StarAnalyser

Thanks Robin, I'll do as you advise. Here's a not so egregiously black-clipped image. I'll have a look at the pixel brightness values to see if I can get anything reliable from the green pane.

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Image from Chelmsford

https://britastro.org/node/23563. I get 12.6 unfiltered last night using Gaia DR2 G mags. 

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Nova Cas

My first opportunity to see Nova Cas '20.  In a grotty sky using the AAVSO sequence, visual 13.4 on Jly 30.938.

The first Nova (detected) in Cassiopeia since V723 Cas (Nova 1995), which is still visible around 16.5 mag.

Gary

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Spectrum of Nova Cas 2020

Here is a spectrum of Nova Cas 2020 recorded with a LISA spectrograph on a C11 SCT and calibrated in absolute flux using a concurrently measured magnitude of V = 13.395. Using PlotSpectra, the integrated absolute flux of the H-alpha and H-beta lines are 3.53E-12 and 2.52E-13 erg/cm2/sec respectively. These results are consistent with the values 3.54E-12 and 2.54E-13 reported in ATel 13905. The apparent FWHM of the H-alpha line is 508 km/s and there is evidence of weak P Cyg absorption on the blue side of H-alpha extending to -800 km/s relative to the peak of emission. There are also emission lines of Fe II 5018, Fe II 5169, [O I] 5577 and an unidentified emission line at ~6160 A.

David

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a bit higher resolution spectrum

Here is the region from H beta and redwards covering the "Fe curtain" region at R~1950 with the LHIRES and 600l/mm grating

The H beta FWHM is ~360km/s after correcting for the spectrograph resolution but there may be some higher velocities redwards in the line profiles

Cheers

Robin

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Nova still brightening?

I saw the nova last night and estimated the mag. to 12.7. 

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brightening

Yes Lars, it looks as if it's getting a little brighter.  I had 13.0 visual in a cloud break just after dark last night (31st)

Gary

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From 1 Aug UT 09:39 T5 iTelescope

I find the following from this morning using T5 (250 mm) in New Mexico at JD 2459062.902. I used AstroimageJ

With V filter, nova was 12.9 using 11.2 ,14.3, and 12.6, reference stars in AAVSO chart

With R filter, nova was 12.4 using 12.6 in AAVSO chart

With B filter, nova was 13.3 using 12.6 and 13.7 in AAVSO chart

Seems quite bright through the red filter. Stewart

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Nova brightness

Excellent, thanks Stewart. I'm waiting on clear skies to acquire a low res spectrum of the object. At this brightness, it should be doable with my scope.

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Still brightening as of Aug 5 at 01:43

I make it 11.8 mag through V filter this morning, Aug 5th at 01 :43. (T18, Nerpio, Spain.)

I make it 11.1 mag through the R filter.

For both measurements the reference star was 11.2 on the AAVSO chart. I'll try to get these uploaded via Muniwin once I get the hang of it.

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N Cas 2020 continues to brighten

I took images last night through a V filter and measured a calibrated stack in Maxim (AAVSO X25582AO) 

N Cas 2020 measured 11.548 CCD-V

REF 112 set 11.186

CHK 126 measured 12.599

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Spectrum is changing

This is a spectrum from the early hours of 12th August. It looks very different from those of the 30th and 31st July in this thread. The H alpha line is much reduced and there appears to be a P Cygni profile, presumably due to expansion of the nova. I haven't tried to identify the other broad absorption features. I would be interested in other people's comments on what this spectrum tells us about the evolution of the nova. I see from the database that others have also noticed the changing profile.

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Evolution of nova spectra

Hi John,

There was an excellent detailed commentary on the evolution of nova spectra by Prof Steve Shore during the Nova Del 2013 ARAS campaign here

http://www.astrosurf.com/aras/novae/Nova2013Del.html

He has also issued an ATel on the current nova based on amateur spectra

http://www.astronomerstelegram.org/?read=13939

Cheers

Robin

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Evolution of novae

Thanks Robin, very useful.

John

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N Cas brightening

Observations from last night and this morning suggest Nova Cas is rebrightening after a very short four day decline.

At this stage the light curve resembles several other Nova I have observed over the years - V1493 Aql (N Aql 1999#1), V2274 Cyg (N Cyg 2001) and the Fe II Nova V2362 Cyg (N Cyg 2006), although the time scales of fading and rebrightening are different.

The light curve below is from visual observations and unfiltered CCD from SLOOH.  Thank goodness for remote scopes - the night sky here in Brum has been very cloudy of late, although I did have a forty minute gap last night (17th).

Gary

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H alpha prominent in spectrum again

The H alpha line has become very prominent again and the P Cygni profile has disappeared. There appear to be emission lines for Fe II, He I and [O I]. The spectrum was recorded around midnight on 18th/19th August with an Alpy 600 and the resolution is ~ 550.

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N cas spectrum

Snap!

I took this at about the same time (been away for a few days so only processing now...)

Reassuring to see close similarity.

I have some accompanying photometry so aim for flux calibration soon...

Kevin

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oops

...removing duplicate - apologies..

Kevin

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Latest ATel

Interesting passing comment in the latest ATel 13967 on the nova:

Quote:    "...dust formation will almost certainly take place sometime in the next several weeks."

So I guess a dramatic fade can be expected??? Well worth watching at every opportunity.

Mike.

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N Cas

The Nova is now fading from it's second maximum, very slightly fainter than the first.   Most unusual.  Reminds me of V5558 Sgr (Nova Sgr 2007).

Gary

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H alpha emission line still prominent.

H alpha is still prominent, possibly even brighter. It needs someone cleverer than me to do a flux calibrated spectrum. I've attached a plot of three spectra taken over the last three weeks to show the changes. This object continues to fascinate me. Any interpretation of what we are seeing would be welcome.

 

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If ever we get a clear sky in

If ever we get a clear sky in Leicester, I’ll take a look. My 12” Newtonian should pick it up.

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V1391 Cas

This nova has received the official VS designation, V1391 Cas.

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Flux calibrated spectra

John,

I calibrated your 3 spectra in the BAA database in absolute flux using V magnitudes interpolated at the times of your spectra from V magnitudes in the AAVSO photometric database. I have labelled the main emission lines which include the Balmer series of hydrogen recombination lines and collisionally excited lines of singly ionised iron Fe II. The latter have strengthened during the recent rebrightenings of the nova. There are also forbidden lines of oxygen [O I] formed in the lower density expanding nebula.

David

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Flux calibrated spectra

Thanks very much for that. Maybe next year you will be able to teach us how to do this, perhaps in another spectroscopy workshop.

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P Cygni profiles again

Last nights spectrum shows P Cygni profiles in He I, Fe II, Na I and [O I] which have deepened or appeared since 5th September.

1920p