68 replies to this topic

[Dan Crowson]

There’s a bright nova in Perseus:

 

Nova Per 2020

 

J2000.0
04 29 18.85 +43 54 23.0  (67.32854 +43.90639)

 

I get mag 8.738 V tonight near the big moon.

 

Dan

[KMAO]

Although my charts were ready a few days ago
clouds prevented me to observe
this Nova Per 2020 sooner.
So it was my first observation also.
20201128 at 7pm EST.
Nova was quite bright but moonlight
did interfere a bit.
Reported visual magnitude 8.6mV
using 6inch f10 Jaegers refractor
and 30mm XW Pentax eyepiece.
Best regards
KMA

ps
looks like this nova did reach maximum ???

[robin_astro]

Proving a popular target for spectroscopists

http://www.spectro-a...php?f=36&t=2674

My small contribution covering the H alpha and He 6678 region though it is evolving rapidly 

 

 

(As an aside, the little absorption line at 6613A is rather interesting. It is from interstellar absorption (The nova is heavily reddened by interstellar dust) and although this line has been known for many years, what produces it still appears to be unknown. It is suspected to be molecular in origin but the molecule that produces it remains identified.)

 

Cheers

Robin 

[vakulenko_sergiy]

Observed N PER 2020 just a ~ hour ago. Local weather were so generous so I able to capture only one 1sec frame  between the clouds.

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[cometchaserde]

Hi,

I image the Nova on Nov. 30th. with a 8" f=2.8 Newtonain, 6 x 60 sek. ATIK 383L+ from Southern Germany.

I measured 9.3 mag. with Astrometrica.

 

More https://www.cometcha...a-Per-2020.html

 

 

Stefan

[Rich (RLTYS)]

Have yet to observe N Per 2020 (V1112 Per) weather has been terrible. 

[KMAO]

Because of bad weather
only 2 observations in 9 days.
Hope it will get better soon....
Best regards
KMA

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[mwr]

Proving a popular target for spectroscopists

 

Due to the strong and broad emission lines that are now visible this nova is also a rewarding object for SA 100 users:

 

 

 

A comparison with ProAm spectra shows that the SA 100 delivers good results, even in the NIR region where intense OI emission peaks are detectable :

 

 

[mwr]

Nova Per 2020 (V1112 Per) shows a striking similarity to the Nova Scuti 1989 (V443 Scuti): http://adsabs.harvar...ApJ...376..721W

 

Based on this paper I could assign some more emission lines. Not surprisingly, mainly additional Fe I lines could be detected in the spectrum of this beautiful 'Fe II' class nova:

 

 

If the assumption is correct that this Nova will evolve like Nova Scuti, it has now passed its maximum (AAVSO data seem confirm this), featuring strong Balmer and Fe lines, in addition to Na I D with a P Cygni profile and is now in the P^o_fe phase. The O I 8446/7773 intensity ratio is considered as a good density diagnostic for the gas that forms the spectrum during decline and it will be interesting to follow the evolution of these lines in the NIR.

 

 

[KMAO]

Nova Per 2020
is still rather bright....
Best regards
KMA

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[descott12]

I finally got a chance to look at this one...glad it is still blazing away. I was surprised at how much the emissions stood out in the field of many star spectra - so easy to identify the right one!

 

The H alpha emission seemed so bright that I was convinced it was interference from a background star.  A single frame was identifiable but noisy so this is a stack of six 10-second frames.

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Edited by descott12, 15 December 2020 - 04:07 PM.

[PeterAB]

Hi,

 

Clouds cleared for a half hour this PM.    I have been following N Per 2020, so I took a look first thing.    My visual brightness  estimate is  m10.5 (2000 CST 12/17/2020).    See it while you can!

 

Peter

[msvtrove]

Saw it on December 16 th, that day it was a shade brighter than star HD276383 as observed visually with 200mm f/6 Dobsonian. My first nova ever. Since 16th dec it’s cloudy here, desperately want to have a look at it again before it becomes out of capability of my scope. 

[mwr]

 The O I 8446/7773 intensity ratio is considered as a good density diagnostic for the gas that forms the spectrum during decline and it will be interesting to follow the evolution of these lines in the NIR.

With the continuing expansion of this nova the emitting gas becomes less dense and the line at 8446 A, which is generated by the hydrogen Lyman/OI photoexcitation is becoming more intense with respect to the O I line at 7773 A. This phenomenon could be observed using the SA 100 in the Near Infrared:

 

 

Because of the low resolution of my setup I have "validated" the observation by using a ProAm spectrum from the ARAS database for comparison:

 

 

Beyond 9000 A there are more lines detectable but it would be daring to give assignments for these lines without a high resolution reference. Is somebody aware of NIR data of this nova beyond 9000 A ?

[Bräumer]

That are some really nice spectra there!

But how is the O I 8446/7773 intensity ratio an indicator for the density of the gas?

 

And I didn't quite get this: 

 

 

With the continuing expansion of this nova the emitting gas becomes less dense and the line at 8446 A, which is generated by the hydrogen Lyman/OI photoexcitation is becoming more intense with respect to the O I line at 7773 A. This phenomenon could be observed using the SA 100 in the Near Infrared.

 

What does the Lyman photoexcitation have to do with the OI line?

[mwr]

That are some really nice spectra there!

 

Thanks! I'm always surprised about the good performance of the Star Analyser 100 in combination with a modified DSLR camera and relatively slow optics (focal ratio 9.4). 

 

 

What does the Lyman photoexcitation have to do with the OI line?

 

 The process is called "PAR" in spectroscopy: H Lyß/O I Photoecitation by Accidental Resonance. Jim (alias OrganicAstrochemist) has recently educated me about this process that is also of relevance in Be star disks :

 

"It just happens that oxygen, O I, has a transition at 102.6 nm, so O I in the disk could absorb Ly-ß and re-emit at 844.6 nm (by fluorescence). If a Be star has the disk density and inclination angle favorable for Ly-ß to produce H-α, it should also produce O I at 844.6 nm. Ly-ß could also cause emission at [O I] 630.0 nm and 634.6 nm (by fluorescence), but the density would have to be much lower to avoid collisions so this doesn't happen in Be disks." https://www.cloudyni...ars/?p=10654734

 

 

 

But how is the O I 8446/7773 intensity ratio an indicator for the density of the gas?

 

 

The O I 7773  line is connected to the O I 8446 line because of a non-negligible intercombination transition coupling the pumped level at 8446 Angström and the upper level of the 7773 Angström line. Optical thickness decreases the fluorescent line intensity (8446 A) relative to the non-fluorescing line intensity (7773 A). Decreasing the optical thickness by decreasing the density of the gas has the reverse effect, which can be observed during the evolution of this nova. The effect is described in the following paper that contains some illustrative Grotrian-diagrams: http://adsabs.harvar...ApJ...439..346K

 

Special greeting to Hessen! (I was born in Wiesbaden) 

[Bräumer]

Thanks for the explanation! 

I can't wait to make my first Nova spectrum with the SA100. But for now I need more experience with it and stick to stars brighter than 5 mag.

 

Vielen Dank  

 

Gruß

Kalle

[BrooksObs]

I find the lightcurves of this and a great many other recent novae surprisingly atypical of the scores of common novae I've observed long-term in years past. Throughout the 1960's and 70's, even in the 1980's, the vast majority of novae rose to a sharp peak and almost immediately began to rapidly decline. There were certainly exceptions, like HR Del in 1967, which exhibited a very protracted maximum phase and gained much notoriety by doing so, but such instances were rare. Yet, in recent years it seems that the majority of novae are of, or similar to, those of the so-called "iron" class of novae  in their lightcurves, showing months of prolonged near maximum brightness with only relatively minor fluctuations,or declining only very slowly, if at all, for weeks on end.   

 

Just an observation and obviously more a matter of some manner of observational selection rather something new transpiring.

 

BrooksObs

Edited by BrooksObs, 21 December 2020 - 12:08 PM.

[Organic Astrochemist]

Thanks! I'm always surprised about the good performance of the Star Analyser 100 in combination with a modified DSLR camera and relatively slow optics (focal ratio 9.4). 

 

 

 The process is called "PAR" in spectroscopy: H Lyß/O I Photoecitation by Accidental Resonance. Jim (alias OrganicAstrochemist) has recently educated me about this process that is also of relevance in Be star disks :

 

"It just happens that oxygen, O I, has a transition at 102.6 nm, so O I in the disk could absorb Ly-ß and re-emit at 844.6 nm (by fluorescence). If a Be star has the disk density and inclination angle favorable for Ly-ß to produce H-α, it should also produce O I at 844.6 nm. Ly-ß could also cause emission at [O I] 630.0 nm and 634.6 nm (by fluorescence), but the density would have to be much lower to avoid collisions so this doesn't happen in Be disks." https://www.cloudyni...ars/?p=10654734

 

 

 

The O I 7773  line is connected to the O I 8446 line because of a non-negligible intercombination transition coupling the pumped level at 8446 Angström and the upper level of the 7773 Angström line. Optical thickness decreases the fluorescent line intensity (8446 A) relative to the non-fluorescing line intensity (7773 A). Decreasing the optical thickness by decreasing the density of the gas has the reverse effect, which can be observed during the evolution of this nova. The effect is described in the following paper that contains some illustrative Grotrian-diagrams: http://adsabs.harvar...ApJ...439..346K

 

Special greeting to Hessen! (I was born in Wiesbaden) 

Great posts.

 

I was wrong when I said that [O I] at 630.0 nm and 634.6 nm would be produced by fluorescence; that would be phosphorescence. The paper you cited talks a lot about the non-fluorescent nature of [O I]. I think my basic argument is correct, that all these emissions can be caused by pumping from Ly-ß and that [O I] requires longer time for decay and hence lower densities. But the paper you cites says [O I] is independent of the photoexcitation by accidental resonance. I don't think I understand all the differences between fluorescence and phosphorescence. 

Edited by Organic Astrochemist, 21 December 2020 - 01:49 PM.

[mwr]

Great posts.

 

I was wrong when I said that [O I] at 630.0 nm and 634.6 nm would be produced by fluorescence; that would be phosphorescence. The paper you cited talks a lot about the non-fluorescent nature of [O I]. I think my basic argument is correct, that all these emissions can be caused by pumping from Ly-ß and that [O I] requires longer time for decay and hence lower densities. But the paper you cites says [O I] is independent of the photoexcitation by accidental resonance. I don't think I understand all the differences between fluorescence and phosphorescence. 

Hi Jim,

 

the theory behind the evolution of emission lines in novae is really puzzling but nevertheless highly interesting. I haven't focused yet on the forbidden lines of oxygen that will become more prominent when the nova enters into the nebular phase but at that time the magnitude will most probably pass the critical limit that can be reached with my old and noisy DSLR.  However, Howard Mooers and William Wiethoff presented a 125-day spectral record of the bright Nova Del 2013 using the SA-100/R-Spec and could nicely demonstrate the appearance of the forbidden lines of O II that accompanied the disappearance of O I lines at the transition to the nebular phase (even at a resolution below 100). A really nice work that was published in JAAVSO: https://www.aavso.org/ejaavso421161

Edited by mwr, 22 December 2020 - 09:42 AM.

[descott12]

I captured the nova again last night. Here is a comparison to Dec 14, 2020. It appears the emission at 8446 mentioned above by mwr is, in fact,  a bit taller. Otherwise the spectra match very closely other than a small difference around 4500 A

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[descott12]

It just occurred to me to ask why we aren't seeing anything blue shifted? It seems that the expanding shell of gas should be rushing towards us....

[robin_astro]

It just occurred to me to ask why we aren't seeing anything blue shifted? It seems that the expanding shell of gas should be rushing towards us....

It is also expanding sideways and away from us so on average the emission is roughly symmetric around the rest wavelength and the width gives a measure of the expansion velocity. It is possible to see  blue shifted absorption lines in the material coming directly towards us,  illuminated from behind. This is rather weak now as the continuum is so faint. It was much stronger early in the outburst. eg as here 

 

https://www.cloudyni...020/?p=10689414

 

The emission and absorption make the classic P Cygni shape profile. You can just see the absorption component in H alpha in Paolo Berardi's spectrum here, though it is almost completely swamped by the relative strength of emission

http://www.spectro-a...start=70#p15151

 

Cheers

Robin

Edited by robin_astro, 22 December 2020 - 07:10 PM.

[descott12]

It is also expanding sideways and away from us so on average the emission is roughly symmetric around the rest wavelength and the width gives a measure of the expansion velocity. It is possible to see  blue shifted absorption lines in the material coming directly towards us,  illuminated from behind. This is rather weak now as the continuum is so faint. It was much stronger early in the outburst. eg as here 

 

https://www.cloudyni...020/?p=10689414

 

The emission and absorption make the classic P Cygni shape profile. You can just see the absorption component in H alpha in Paolo Berardi's spectrum here, though it is almost completely swamped by the relative strength of emission

http://www.spectro-a...start=70#p15151

 

Cheers

Robin

Ah yes...the width. That makes sense. Thanks for the explanation

[mwr]

 

 

Beyond 9000 A there are more lines detectable but it would be daring to give assignments for these lines without a high resolution reference. Is somebody aware of NIR data of this nova beyond 9000 A ?

James Foster has recently uploaded some excellent NIR spectra of various objects into the BAA database (I'm impressed by his incredible productivity). Among these, there is also a spectrum of Nova Per 2020 that covers the NIR up to 9580 Angström (the spectrum is discussed in the ARAS forum http://www.spectro-a...start=80#p15194

Based on this intermediate resolution spectrum (R=870) I could assign some more lines in my low resolution spectrum. Although there is a difference of 10 days between the acquisition dates, I'm quite confident about the detection of C I and O I (neutral carbon and oxygen) beyond 9000 Angström.