Possible nova in Centaurus, PNV J13544700-​5909080, 03 Dec 2013

[Chochawker]

Oh yes, excellent point.

I think I was attributing everything to the atmosphere when at least a chunk of it could well have been impatience on my part.

[Merlin66]

Terry,
Glad to see your data!
The weather has changed for the worst done here....

[Rob_K]

Low-res spectrum from last night. Also an image of the nova last night, cropped from a stack of five 10-sec subs taken at 55mm, Canon 650D. Still visible naked-eye from here before moonrise, last night & the night before.

Cheers -

[Terry B]

Verg good Rob
Cloud here but no rain. The worst combination.

[Merlin66]

Well done, Rob!
Keep them coming.....
I hope to be back up and running later today...
(Rebuild of spectroscope and change to the guide camera)

[malclocke]

Attached is the first light spectrum with my L200 from the 22nd Jan. It's not possible to get focus across the full range at this dispersion with the L200, the red end is a bit soft and hence the Ha line has probably been broadened slightly and lost some intensity as a result.

7x15s unguided with an unmodified DSLR (Canon 550D), slit gap ~ 40 microns.

I will try for longer exposures next time to increase SNR. Lots to work on but happy with this for first light.

[Jon]

Nice work Malc! If i get as good a result first up with my L200 when it arrives I'll be delighted.

[Merlin66]

Congratulations on your first light!
Well done!
More exposure and may be a narrower slit gap....
Well done, anyway - things get even more challenging (and interesting) from here on in.
Onwards and Upwards.

[Jon]

Finally the clouds have cleared in the Canberra night sky and I have been able to get some more photometry and a low-res spectrum of V1360 Cen.

A lot has changed in a week. The forbidden lines of [NII] 5755 and [OI] 6300 are very much stronger. What looks like the H gamma having grown considerably in a week is in fact, I'm sure, the [OIII] 4363 growing in intensity.

I'm reluctant to take the huge spike in OI 8446 at face value, something so far in the infrared where the camera response could be an issue. On the other hand in the spectrum image itself it's very clear.

NaI at 5889 has been there since soon after the fireball phase. But now it has been joined by a new emission to the redward side - NII at 5937-41?

TO the best of my understanding these features might be signalling that the nova may be entering its transition phase. The light curve perhaps suggests the same - we are finally getting a consistent drop in visual magnitude as the flux peak shifts towards the UV.

[Merlin66]

Jon,
Very interesting result and observations....
I was hoping to get some data last night but clouded out (again!)
It will be interesting to hear Steve's next "instalment"
keep the data coming.....
(That [OI] at 8446 looks pretty real - I'd need the sort filter to confirm...)

[Terry B]

Excelent.
Im away in Qld til Monday but will try when I get back. We have had cloud and a pathetic amount of rain over the last few days.

[Chochawker]

Wow, that is quite a change!

Still cloudy here at the moment, but the weekend isn't over yet.

[Jon]

A bit of a further update:

In terms of the light curve, we've had increasingly rapid oscillations since around 6 Jan, with an amplitude of 0.5-1 mag and a period of 1-1.5 days. *Possibly* these are smoothing out recently into a steadier decline, although I'm not betting on it.

The first image below shows the spectra from one of the maxima (8 Jan, V=c.4.5) and one of the minima (V=c.5.1). The lines visible in the two spectra are essentially the same - but the relative intensity of the Balmer lines (especially Ha) is much greater at minimum. These are normalised spectra, not flux calibrated - in other words, we're comparing relative intensity of spectral features, not absolute intensity. So at minimum, the emission lines are relatively stronger compared to the stellar continuum. This lends support to the theory that these oscillations are a product of changes in the optical thickness of the ejecta. As the ejecta fireball becomes optically thin, we see a greater relative intensity of the ionised gas shell (emission lines) and of the UV/FUV radiation from the white dwarf itself. Well, we don't actually "see" the latter, which is why the visual-wavelength magnitude drops.

In the last week, everything has begun to change. The second attachment compares spectra from 17-25 Jan. All the forbidden lines are growing in intensity while the "iron curtain" of FeII emisison lines are beginning to fade in relative intensity. Some other significant changes (marked with triangles):

1) [OIII] at 4363 has emerged - although in my low-resolution spectrum this merges with H gamma at 4340. Good to get a higher-res picture of this area.
2) An entirely new line has emerged around 4670-80. Is this He II? That's not implausible
3) OI at 8446 has gone nuts. According to one theory (e.g. Williams, 2012), this is a product not of the white dwarf emission itself, but of interaction with the material coming off the secondary star.

I won't begin to speculate as to the astrophysical causes. But the spectra and photometry at least suggest we may be entering the transition phase of the nova.

Cheers

Jonathan

[Merlin66]

Actually looking promising for tonight...
I'll fit up a sort filter (>7000A) and have a look at that [OI] line as well as the 4363/ 4670 region.

[Galah]

Can someone please explain, I am OK with (e.g.) V = 5.50 - but what is "V=c.4.5"

Patrick.

[Jon]

Sorry - just shorthand. "V is approximately 4.5"

[Jon]

Very little change from last night. Which at least confirms that some of the new things in last night's spectrum were real not artifacts of my clumsy processing or technique.

The only real change seems a slight slant to the blueward. When we have seen this before, it has been when the nova has been rebrightening. Don't tell me we could be on our way up again?!?

[Merlin66]

Jon,
gathering data around Hb >4670A as I type....
I'll go down to the Hgamma region before fitting the sort filter for Ha and, if I can, out to the [OI] at 8446.
So far so good.

[Merlin66]

Still processing...
Had some issues trying to get out to 8446A - may need to redo.
Here are the Ha and Hb regions in medium resolution (R=6000/5000)
The P Cyg profiles seen earlier are diminishing and the ragged tops, I'm sure, may mean something???
I have more in the pipeline.

[Merlin66]

Around the Hgamma [0III] region.
Resolution is poor due to lack of good focus!

[Jon]

Very interesting Ken. It looks as though there are 4-5 different absorption lines superimposed on a broadening emission line. As you say, P Cyg profiles have given way to this more ragged feature.

Back to my Steve Shore reading list!

[Jon]

Definitely looks like an H gamma peak at 4340 plus an [OIII] bulge at 4363.

[Merlin66]

Hmmm
The emission line peaks seem to have moved to the red.....

My limited exposure of 8446A didn't seem to show the emission as bright as Ha???!!???

[Jon]

THe SA100 spectrum I got had 8446 dropping below Ha too. It seemed a short outburst ... what is the "OI flash"? I've seen references to it. Honestly, understanding these novae evolution seems a combination of science, intuition, and witchcraft :-)

[Merlin66]

Another night...more nova spectra.
I'm taking a series of med-res spectra from Hb through to Ha.
So far so good.........

[Terry B]

I took spectra last night with my LISA. Very strong Ha.
I will upload them later today.
The conditions were terrible with a 20Knot easterly blowing making the stars about 20 pixels wide as the scope was buffeted around.

[Terry B]

Spectra from last night. It was very windy and this made guiding a challenge.:P

My measurements from last night 27/1/14
B = 6.026 (err 0.05)
V = 6.097 (err 0.035)
V = 5.178 (err 0.05)
I = 5.121 (err 0.039)

The spectra shows an overall decrease in the continuum since my last spectra (18/1/14) in absolute flux.
There has been an increase in both relative and absolute flux of th eHa line but not the other H lines.
The P Cyg absorption features have now gone.

[Jon]

It's a bit like that :-) Here are the last two nights SA100. Little change.

[Merlin66]

Jon,
No attachments???

[Jon]

Oops. Fixed now, thanks Ken.

[Merlin66]

Sorry for the delay - some calibration issues....
The central wavelength is listed, each has approx. 140A coverage and R from 4000 to 7000.
These show some interesting detail in the various emission lines....

[Jon]

Lot's of detail there to look at, Ken. Were you using a 1200 line grating?

[Merlin66]

Jon,
Yes, the Spectra-L200 with the 1200 l/mm grating.......
The hot night meant that the camera cooling was struggling and I didn't have a set of darks for the temp.
I used an old set of darks for a lower temp....

[malclocke]

Some belated results from the 27th. Terribly noisy I'm afraid. Still no guiding and I tried to narrow the slit gap slightly which made things worse, plus battling with various other technical issues. Shame as it was an incredible night down here, best we've had in months.

Close up of the Hb and FeII lines show similar structure to Ken's recent results, particularly the redward skew on the Hb line.

[Merlin66]

Malc,
Good one!
I think until you come to terms with guiding you'll need more exposure!

[Merlin66]

I've sent some copies to Steve Shore - let's see if there are any comments....

[Terry B]

From last night (29/1). Slight drop in Ha compared with 27/1.
V mag has slightly risen to 6.008 from 6.097.
Terry

[malclocke]

Based on these I get the feeling we are moving into a different phase. Although the velocities have slowly increased, the absorption systems have maintained pretty much the same profile since they were first picked up. However here there's a definite change.

Great work Ken, keep them coming.

[malclocke]

I wonder what drives this? In your spectra, the decrement from H beta -> gamma -> delta seems quite normal, but the drop from alpha -> beta is enormous.

[Terry B]

I don't know but the same effect was seen in the spectra of nova del last year. The relative strength of the Ha line got up to 120.
Terry

[malclocke]

After thinking about it I realised I'm naively thinking about it in terms of absorption where n=2 is the starting point for all the balmer transitions.

For emission conditions may be favouring n=3, and not the levels for the other balmer lines. We will see the 3 -> 2 transitions (ha) but the 3 -> 1 transition is in the Lyman series (UV).

So it's not such a mystery why the lines are so imbalanced.

Hope that makes sense :/

[Merlin66]

Steve Shore has replied:

""
I'll send something this weekend, Ken. Thanks very much for all of
this. It's really a delight to have this window, for the moment
there's nothing coming in from CTIO or ESO (although I heard we got
something with FEROS I haven't seen the data). You're right that
there are still absorption systems present, the optical depth of the
ejecta remains high even now that the oscillations have stopped. The
development is now more along the lines of V339 Del but slower. The He
I absorption feature is very neat, you see that the detached absorption
is persistent. That again indicates a high opacity in the UV. So
more this weekend, I promise, in the hope it'll be encouraging.
""

[Jon]

Here is my SA100 spectrum from last night. I had a cloud issue, was playing with exposure times and may have saturated the Ha so I wouldn't read anything into the low Ha level.

The forbidden lines at [OIII] 4363, [NI]5755 and [OI] 6300 are really growing.

[Jon]

Malc, there's a good bit on the causes of relative changes in Ha/Hb (the "Balmer decrement") in the Keith Robinson book. As you say it's often to do with the relative optical thickness of the ejecta (in this case) to photons at the energy level to produce Lyman vs Balmer transitions.

There's also something going on here to do with a recombination front, which I think I just about understand :-) Along the lines of - recombination takes place, a 3->2 transition happens emitting an Ha photon, but then the Hydrogen immediately absorbs another photon of the same energy level bumping it back up to 3, because of the density of the Ha at this point in the nova evolution (unlike a nebula, for instance, where the much less dense Hydrogen will be more likely to continue to cascade down to 1).

Something like that.

[Terry B]

Spectra from last night. Essentailly no change in 2 days except a slight rise in Ha. The V mag is unchanged as well at V = 5.961
Seeing was terrible.

[malclocke]

The above makes sense. Although I would expect the same to hold true for the other Balmer lines, so I can't see how this would explain the different intensities of the Balmer series.

I imagine (without any grounding) that it would be more likely to be simply temperature dependent, where the visible ejecta is at a temperature that favours excitation to n=3 and hence the 3->2 H alpha transition is dominant. In much the same way that the temperature of an A class star puts a lot of the hydrogen into n=2 and thus favours absorption in the Balmer lines. That could also account for the decrease in H beta, as the temperature decreases, less and less of the hydrogen is excited to n=4.

Unrelated to the discussion of the relative intensities of the Balmer lines, I don't have a grasp on what mechanism could drive this recombination front outwards through the ejecta. It must be doing this if we ascribe to the idea that the absorption systems are from the ejecta, that there is a velocity gradient embedded in it, and that this recombination front is the cause of the changing observed velocity of the absorption system.

I would imagine the 'sweet spot' for recombination to be highly temperature dependent, and therefore would expect it to migrate inwards to lower velocity over time, not outwards, as the ejecta expands and cools.

Clearly there is some fundamental part of this that I don't get :(

[malclocke]

A bit of nova trivia - given we are now on around day 60, and that we have observed expansion velocities (if that is what they are) of around 2000 km/s, the ejecta should now have a radius of around 70 AU, almost twice the orbit of Pluto!

Using the small angle approximation (θ = D x 206265/d, where D is the size of the object and d is the distance), this figure combined with the estimated distance from the ATCA of 3.3 kpc, this gives an angular size of 0.04 arcseconds.

Anyone fancy trying direct imaging :)

[Rob_K]

LOL, even 0.04 arcminutes is still a couple of orders of magnitude too small for anything I've got! :lol:

Cheers -

[Jon]

Same pattern tonight. Ha still increasing over Hb.

Malc, you pose some interesting questions. I had a stab at why the processes seem inside out on the ARAS forum. I found some papers on the idea of the recombination front, as I agree it seems counterintuitive. I think the key is the optical thickness at various wavelengths. That's not so much about us seeing the photons from the centre of the nova; it's about the atoms in the periphery of the nova "seeing" the photons at particular wavelengths coming from the centre, getting ionised, then cascading back down. Which is how it moves from inside out not outside in. If you see what I mean.

Actually, reading that back, I'm sure you don't. It's late, I'll have a crack at being coherent in the morning :-)

[Chochawker]

My attempt from last night.

Various issues, the most significant of which was power supply related, meaning that I wasn't using any cooling.

Anyway, for what it is worth, this was from 11:10 pm last night.

[Jon]

OK, let me try again half awake. I hope you don't mind my trying to respond to these questions - I don't for a moment pretend that I have the answers but it helps my emerging understanding to bat these back and forth with you like this.

A) OK, so imagine we have a hot but static star surrounded by an envelope of ionised gas. This would have a "recombination front" which is a sphere, the radius of which is the point at which the temperature is low enough to allow recombination. This point wouldn't change.

B) Now, change the model to one that has a nova-sized thermonuclear runaway at the centre - an enormous burst of energy into the gas, energy which eventually finds its way out into space through radiation at various wavelengths. In this, slowly cooling model, the recombination front gradually contracts as the "sweet spot" gets closer to the star. As you suggest. Let's call this rate of contraction owing to cooling C.

C) However, add the ballistic expansion into the model. The ionised gas expands at 2000 km/s. Call this B. If B>C then already we have an expanding recombination front. I have no idea whether B>C in a typical nova; but it's a factor.

D) Finally, and most importantly, the ionised gas is still being pumped with UV and higher energy from the star at the centre. As the inner layers of ejecta expand, they become optically thinner to increasingly bluer (more energetic) wavelengths. This means that more energy is getting to the outer layers, which get hotter than they were at the time of the initial explosion. As the (denser, slower) fireball close to the star expands and thins, more UV gets through, so the temperature of the (less dense, faster) outer shells of the expanding ejecta increases, so thus recombination "sweet spot" moves outwards.

I think this is how it works.

[malclocke]

Just got my credentials through for the TOCP system yesterday, only took a month and a half :)

[Merlin66]

A bit cooler down here last night.
Was going to use PHD2 and the new AA5 slit-guiding...couldn't get either of them to work for me - probable operator error...
Back to PHD 1.13
The Ha emission is very strong and shows some absorption features? The Fe also have some deep absorption and the P-Cyg profiles diminishing.

[malclocke]

Very nice Ken. Some interesting structure appearing in the Balmer lines. Also odd that the P-Cyg has gone from H alpha but still present in H beta.

Here's my belated effort from 2nd Feb. Left my t-ring at home so had to use a different one and subsequently the imaging camera focus was off, about double the normal FWHM on the reference lamp lines :(

Got the guide camera in the imaging train though, which is progress. Unfortunately guiding didn't work, but having the guider image was a huge help in finding the slit.

I think the nova is fading faster than my skills are improving.

Close up is of H beta line.

[Terry B]

Mine from last night compared with 31/1
The V mag has dropped to 6.21. This has dropped the overall flux. My continuum in the blue may be a bit off as it was very windy with passing cloud.

[Merlin66]

Terry,
It's good to see the continuous monitoring of this nova with different resolutions....
I sincerely hope we can continue to collect data all the way as it starts to fade.
Hopefully we'll get some "insights" from Steve Shore soon....

I would urge all members with access to a grating or spectroscope to monitor this nova. This could be an opportunity of a lifetime ( the only thing better would be Eta Car kicking in!!!!)
We, in the southern hemisphere are in a privileged position, this can't be seen or recorded by our colleagues in the north. This one's ours!!!!

[Jon]

Here's my spectrum from last night.

[malclocke]

My effort from 6th Feb. A huge thanks to Andrei Cotiga (acotiga here on IIS) for getting guiding operational. Managed to get multiple 60 second exposures and the impact on the SNR is dramatic. Only quibble is I didn't take the time to ensure I got H beta and H alpha in the frame, and only got the latter.

Close up of the H alpha line, a good correlation with Ken's results.

[Terry B]

Really good Malc
The SN is certainly much better.
Well done

[Merlin66]

Well done Malc!
I think you're beginning to see the potential of the Spectra-L200.....
There's now around 70 spectra in the ARAS database for the nova, and hopefully more to come!
I'm sure Steve will be commenting soon....

(It looked promising down here last night, but by the time I got set up the cloud bank moved in....bumma!)

[Terry B]

From last night
Not much change in 4 days.
The mag continues to fall. Now V = 6.362
The absolute strength of the Ha line has increased a little but the relative strength is identical.

Terry

[Jon]

Nice stuff, Malc.

NI at 5679 and [NI] at 5755 really clear, for instance. The old SA has these two partly merged.

Can't wait for my L200 :-)

[Jon]

Nice and clear, Terry. HeII at 4666 (if that is what it is) seems to be slowly strengthening. Looks to be some internal structure in this line, too.

I'm glad you also had V down in the 6.3s. I had that too, and was worried it was discrepant. Big fall in the last couple of days, given the previous rate of decline.

If we are really down to 6.3 then we're getting close to being able to put a T3 figure on the nova - the time it takes to fall 3 magnitudes, important in its classification.

[Jon]

Here is my spectrum from just now. Spectrum from Thursday 5 Feb included (blue) for comparison. Almost no change - but perhaps HeII at 4686 and at 5890 are beginning to edge up?

[Merlin66]

Frustrating night....all set up, started guiding then the clouds built up....

[Terry B]

I had a clear still night and took spectra and photometry. I'll process them tonight after work.
I've had plenty of clear skies but there has been a 20k easterly wind come up most nights. This makes photometry very difficult as the stars jump around too much. Spectra are OK as the star moving off the slit just makes less through put but I still get an acurate spectra.
To be honest, I'd rather it rain than take spectra. Our last rain was Christmas day. Everything is now dead and my dams are nearly empty.

[Terry B]

From last night.
It has slightly increased in brightness over the lsat 2 days.
7/2/14 B =6.323 V= 6.362
9/2/14 B =6.238 V= 6.299
The spectra shows a continuing strengthening of the Ha line.

[Jon]

Even more interesting than that Terry. You and I had very close measurements for 7 and 9 Feb. But on 8 Feb I caught it up at 6.19 - moreover that was the minimum of one of its oscillations. It's still bouncing around.

[Terry B]

It certainly is bouncing around still. Too hot for me to bother taking images tonight.
I have played around with the spectra I have taken. Attached are graphs of the full spectra, Ha and Hb region all flux calibrated. It shows the evolution of the nova.

[Merlin66]

Sorry for the delay guys, but the smoke haze has given me headaches in processing the spectra......
The Na Region from the 10th attached. Ha and Hb to follow.

[Merlin66]

Still not happy with the sky background removal.....I've tried various programs but still seem to end up with residual "absorption features" - Na etc.
Don't honestly know the answer to this one....may be I'll have to dump the data and try again when there's less smoke/ haze around.
Bumma.

[Merlin66]

Finally got some results which I think are OK.
Minor P-Cyg still there in Hb?
The Ha emission line certainly seems to have brightened - just look at the comparison ADU count between the Hb peak and the Ha peak!!!

The clouds have now set in for at least the weekend...anyone else managing to collect data???

[Terry B]

Cloudy here as well but unfortunatley not much rain. Only had 9mm total over the last few days.

[Glenpiper]

Ken,

Nice looking Ha and Hb spectra.

I suggest you should normalize your spectra (set continuum to unity at a given wavelength) as that would make comparisons easier and more meaningful, and conform to 'standard practice'.

You have erroneously headed the Hb spectra as Ha.

Cheers,
Bernard

[Glenpiper]

Oops ... I see that now the Hb header is correct.

Bernard

[Merlin66]

:thumbsup:

I'll look at the normalisation issue....finding a suitable "continuum" for the Hb/Na/Ha regions is interesting.....
Ken

[Glenpiper]

Ken,

Ha should not be problem. For Hb may I suggest normalizing over the range 509-510nm, and for Na you could use 562-562nm.

Bernard

[Glenpiper]

Typo ...> for Na I suggest 562-563nm.

Bernard

[Merlin66]

Steve Shore has just issued a note on the nova...
Too large a PDF to attach - email me for a copy.

The following is an extract for observers:

Extract from Steve Shores Notes of the 16th Feb 2014

On the other hand, V1369 Cen will remain, like V339 Del, a gift that keeps giving. At only _7 now, it’s still too bright to comfortably do with HST so the STIS pointing will be on hold while the V339 Del observation is still set for the observational window in April. At the current rate of decline and spectral change, any high resolution spectra of V1369 Cen, taken with a cadence of about once per week, will be very valuable with a special emphasis on the 4500 - 5200°A region for the N III 4636, He II 4686, Fe II transitions, 5400 - 6100°A for [O I] 5577, [N II] 5755, He I 5876, Na I 5890; possible [Ca V] and/or [Fe VII] 6086. Any spectra longward of 7000°A will be very important for the Ca II, O I, and He I lines and also to see how the Paschen lines develop. But the frequency isn’t pressing. Remember, these are legacy spectra. We have almost an embarrassment of riches here but this will remain, permanently, as a record. The more uniform the coverage, given all we’ve learned from the first campaign, the more valuable it will be for the future.
Don’t forget, this is real-time astrophysics and no event will ever repeat quite the same way. It is always a frustration, you know this yourselves, to go back through the literature with knowledge from the future and lament the lacunae of the past.
More will be coming and, always, thanks so much! .

[Jon]

Here is a spectrum from the 18th. Had to process two versions - one unstretched, in which you can see little detail other than the now huge Ha line, and one with a linear stretch applied that saturates Ha but allows the other lines to be seen.

Some movement in the last week. [Oi] 6300 grows, and now has a partner [OI] 6364. Na and some FeII lines fading.

[malclocke]

Was out at the observatory struggling away until 3am last night and got nothing at all, unable to get the nova on the slit :(

[Merlin66]

Jon,
The Hi sitting over us sounds promising for tonight....

Malc,
What set-up were you using? Beamsplitter/ Al's reticule/ PHD???
As I've mentioned previously, a bit of a fiddle to set-up but has proved to be very effective...
Hope you have more success soon.

[malclocke]

No Al's reticle yet, using a beamsplitter and the guiding from Maxim as I know it works. I can't leave the unit assembled between sessions so Al's reticle is not going to work for me at the moment.

Main problem is that the nova has faded to the point where it is not visible on my DSLR live view, which makes the whole process a lot more error prone. Seeing was fairly shocking and it was very windy too which didn't help matters. 15 minutes of getting the star centred on the zero order each time, then move the grating to position, expose ... nothing.

Need to decide whether to invest the effort into the beamsplitter guiding or just wait for the reflective slit upgrade. Whichever, I think I am going to have to focus on some brighter targets to get everything working.

[Merlin66]

Malc,
As long as the beamsplitter/ spectroscope remain together, then the "virtual slit" will always be in the same position.
You can calibrate the microhead/ wavelength on the sun during the day and pre-set the micro to the required central wavelength.
You don't need to use the zero order image all the time.
Certainly the reflective slit/ guiding is easier to use, but the beamsplitter on reasonable bright objects can work well.

[malclocke]

Thanks Ken. Unfortunately I have to disassemble everything after each session as it won't fit in the carry case assembled.

[Merlin66]

Malc,
I don't know what your pain threshold is like....but I think maybe the time has come to dump the storage case and leave the beamsplitter in place...
Just wrap the instrument in a towel for temporary storage.....life is too short.

(The attached screen dump shows PHD locked onto the Nova and the sequence of subs being "farmed")

[Terry B]

It was very windy last night but it was clear. I got a reasonable spectra that I will post tonight. Photometry was more of a challenge as the scope kept getting buffeted with wind gusts. I had to try to get exposures between gusts and limited exposures to 20secs.

[Glenpiper]

Hi guys,
(I first erroneously posted this the nova Sgr thread)

I'm new to this V1369 Cen discussion because, until last night, this nova hadn't risen above my urban obstacles to be seen by me at a convenient time.

I've only covered a 150A range (4595-4745A) at R=8700 (SNR~100), using a Lhires III with 2400 grating on a 0.28m scope, as that is where I'm working at for two other long running pro-am projects.

Given that one seldom sees 'high' res nova spectra in this HeII area it may be of interest to researchers and it is interesting to note the triangular profile ... which tends to question statements that this is a classic FeII nova. It is impossible to say if any NeIII or HeII is hidden in this zone but it is most likely that many of the FeII 37 and 38 multiplets are present ... which leads me to suggest this may be a hybrid (FeII b) nova. I've not followed the discussions of this nova here, or on other forums, so this topic may already have been well covered. Unless there are requests for further coverage of this wavelength (unlikely) this is probably my first and last spectra of this nova .. unless I add it to my echelle target list.

Cheers,

[Merlin66]

Bernard,
Good to see some hi-res spectra of the nova...
Your peak at 4649 (?) doesn't seem to match the HeII wavelengths I have - 4542/ 4686 ??
The NIII at 4838 seems evident?
Now it's observable can you continue the data farming?

[Merlin66]

Nova data collected last night shows the dramatic changes in the Ha emission from the 10th Jan......
The Velocity profile also looks interesting.

[Glenpiper]

Ken,

The peak at 4649A certainly isn't HeII 4686 ... most likely a composite of merged FeII lines (>20 in the 37,38 series) and possibly NIII 4640 and HeII 4646 lines included (depending on the phase) .. IF it is hybrid nova. There could even be Ne lines in the range 4704-4717. Anyway, my 150A wide range isn't wide enough to class the nova, but hopefully it helps. As you imply, more widely spread, high-res spectra are needed.

I can continue with the same setup (centred on HeII) but as I also need to continue with other projects I'm not prepared to hop around at different wavelengths ... too inefficient. If/when the central Vic weather improves (less windy) then I will try for high-res and wide cover with my echelle.

Cheers,

[Terry B]

Spectra from Sunday night. I was busy working last night so only processed them today.
It has dropped to mag V = 7.047 B= 7.004
The Ha line continues to strengthen relative to the continuum but it has dropped in absolute flux.

Cheers
Terry

[Merlin66]

After a bad spell of weather....finally a clear night.....
Hope to collect a full set of data on the nova tonight!
I hope others are getting the same chance.

[Merlin66]

The Ha is certainly maintaining it's strength!!

[Jon]

Still wall-to-wall cloud here ...

[Terry B]

I got spectra but only V photometry due to cloud. 30km/h winds make t
he star jump all over the place. The Ha is vastly stronger. It has almost doubled in relative strength in the last week.
I will post the data tonight. Cloudy at present.

[Terry B]

I have processed the spectra now. Mag has dropped from V=7.05 on 23/2 to V=7.86 last night(2/3/14)
The Ha strenght has not changed in absolute flux but the continuum has dropped significantly. This has made the relative Ha strength increase significantly.
Terry

[Merlin66]

My data from the 2nd March.
Now using the 600 l/mm grating (nominal, R=2500)

The Ha emission is VERY impressive!

Around the NII - 5755, I think there's also HeI @ 5876, then a blend of FeVI/5677, Na/5686, NII/5679

The Fe lines around Hb seem to be fading? The peak at 4640....could be NIII @4638????

[Terry B]

Data from last night.It is rapidly fading. Now V= 7.97
Ha is very strong.

[Jon]

I think we might be seeing the formation of dust. B is plummeting and now back fainter than V. R and I are holding up. AFAIK this is consistent with dust formation.

[Merlin66]

Out "data farming" tonight - bumped up the exposures to 2400 sec (600 l/mm gratings)....
Will get at least an Ha and Hb region....already I can see the Ha is VERY strong!!
The NIII region looks much brighter than the Fe emissions used to be....
Let's see what comes out.

[Merlin66]

Ha emission shows some absorptions in the blue side (-500 km/s) and emission in the red ( +300 Km/s) and absorption (+400 km/s)

The shape has certainly changed over the past couple of weeks.

Hb region added.....

[Terry B]

Spectra from last night also. I don't see the Ha absorption but this is probably due to my resolution being lower.
I has actually brightened in V.
V= 7.97 on 5/3
V= 7.82 on 8/3
The Ha has intensified slightly.
It was a crappy night here with strong winds making it very difficult to image. Cloudy tonight.
Terry

[Merlin66]

Terry,
That data is OK...
We need to be able to collect ANY spectra for as long as possible......

[Jon]

It continues to, brighten in V and B. Now (last night) V=7.57. R and I stayed constant during the dip and re-brightening. Looks like dust as far as I can see

[Terry B]

I took more images last night as well (11/3)
I measured
V = 7.700
B = 7.666
R and I continue to decline despite the rise in B and V.
the spectra has changed over the 3 days as well. Ha has slightly reduced but there has been a significant strengthening and broadening of the line at 4640 that I assume is NIII but may be blended with other lines like Fe II
Interesting changes.
Terry

[Merlin66]

I'm finally pleased to say I managed to get the latest AstroArtV5 "slit guiding" set-up to work!!!
My problems were related to the EQMod settings!
I'd like to thank Paolo and Fabio for the support, help and assistance.

Reasonable night down here - bright moon but nova pretty easy to guide on with 1sec and the Lodestar. "data farming" at Hb, Na and Ha.

[Terry B]

Ken
I don't have astroart so haven't tried the new slit guiding. I have downloaded the trial and might give it a go.
The nova has brightened again.
I took spectra on 17th and 18th. It has brightened over the 2 weeks significantly.
5/3 V= 7.97
8/3 V= 7.82
11/3 V= 7.70
17/3 V= 7.59
18/3 V= 7.53

It continues to strengthen in Ha.
I have made a couple of graphs all in absolute flux. The first just compares 11/3 to 18/3. This shows a big rise in the strength of the Ha line.
To demonstrate how much of the overall flux is from the Ha line I graphed 18/3/14 and 28/12/13
The V mag on 28/12 was V= 4.27 compared to 7.53 on 18/3.
This is over 3 mag fall but the Ha flux has only reduced by about 50%. The continuum flux has fallen significantly more.
:)

[Merlin66]

Terry,
Thanks for the update!
I didn't manage to get any Ha on the 16th - clouded out!
I'm "data farming" right now......

[Rob_K]

Fantastic work Terry! And good luck with your new arrangement Ken! :thumbsup:

Cheers -

[Merlin66]

Rob,
Thanks!
AA5 and the Lodestar seem to be working well together....
The bright moon doesn't help much!!

[Merlin66]

The continuum is certainly fading....
I'm having to run 4800 sec for the Na region to get a half decent SNR....

[Merlin66]

Ha region from last night....
Still some absorption features

[Terry B]

Data from last night 22/3
It is slightly brighter in V again. Now V= 7.511
The Ha contribution has fallen though.

[Jon]

Interesting behaviour. Since March 5, R has stayed virtually constant, I has faded 0.2, while V has brightened 0.5 and B slightly more.

[Merlin66]

I'm clouded out down here....
Anyone getting data on the nova??

[Merlin66]

I had a problem with the observatory laptop and lost some data before I could backup.....
The attached image shows the dramatic rise of the Ha emission in Nova Cen during the month.

[Merlin66]

OK, finally clear weather and opportunity comes together...
Collecting some Ha data, and hopefully will move onto NII and Hb.....

[Merlin66]

The attached images show to significant drop in the Fe and the growth of the NII/[OIII] as well as the continued Ha activity.
It seems to change in a few days......

[Jon]

Wow! Where has the Fe gone?

A month of cloud here.

[Merlin66]

Yeah, some dramatic changes there....
Looks like the "Iron Curtain" has finally cleared and we're moving towards the nebula phase.....
Who says astronomy is boring!

[Merlin66]

Any other comparison spectra available????

[Terry B]

Ive taken spectra over the last 2 nights but haven't uploaded them yet. I have uploaded spectra from 30/3 and 3/4 to http://www.astrosurf.com/aras/Aras_DataBase/Novae/Nova-Cen-2013.htm

I will process them tonight hopefully.
Terry

[Merlin66]

Interesting...
Your 3/4 spectrum seems to show very strong FeII emission at 4352A as well as the increasing NII/[OIII]

Clouded out down here for the next few days by the look of it.....

[Terry B]

There hasn't been much change in the spectra over the last few weeks. The magnitude has fluctuated a bit(see graph)
The spectra from 8th April is compared to 22nd March.
Terry

[Jon]

One of the things I'm finding interesting about this one is the way the I is dropping steadily even while BVR rebrighten. Anyone got an explanation?

[Merlin66]

Could be the loss of the "iron curtain" and the change in the energy levels...
Or just that the Ha continues to grow!!
First results from last night - shows the consistent absorptions in the Ha and the increased strength....

[Merlin66]

Here's the Hb Region from the 15th.
Hmmmm
I think the [OIII] at 4959 and 5007 are beginning to develop.
The others could be NII (5001), NIII (4638) and HeII (4686)

Every spectrum seems to show more and more features......

[Terry B]

I took spectra last Thursday but am away for a week so can't upload them. Good to see your data.

[Rob_K]

Nice work Ken! Sorry I missed you at NACAA, I didn't get there till Saturday morning. Would have loved to have met you and had a chat.

Cheers -

[Chochawker]

First time in months that I've been able to play with the telescope, so here is a low-res from me.

This is from a stack of 10 x 15 second exposures a little after 7 this evening.

The forecast is currently looking promising for tomorrow evening, so I'll try again tomorrow and am very happy to take any suggestions for the next attempt.

I tried to get better focus on one of the absorption lines in Spica when I was setting things up, but given that the emission lines in the spectra are so bright, I wonder if it makes more sense to get the focus right on one of those instead?

[Jon]

Nice work Malcolm. Yes, Ken is right - the [OIII] at 5007 is definitely growing. The emissions seem strongly nebular now, and the magnitude has plateaued at around 7.5-8. Which is good news, as it will still be around when my L200 arrives!

I've given up SA100 spectra of it recently, in favour of BVRI photometry where I think there's more need. Accidentally last night I left my Ha narrowband filter in the imaging sequence - as you can imagine in Ha the nova outshines everything else by a long shot! So, just for a bit of fun (and as a sort of "souvenir" of the long nights I've spent with this object) I put together an image, using the BVRI data as RGB and blending in the Ha at the right wavelength over the top. I guess this particular starfield will be pretty familiar to those of us who have got all the way to page 20 of this thread!

[Chochawker]

Nice souvenir Jon, and yes, that looks vaguely familiar.

Here are the results from last night (about 7:10 pm Sydney time), along with a comparison with what I saw in February.

[Merlin66]

Malc,
Good results there....
Your current focusing technique looks OK.
I think the peak you show around 5018 may actually be a blend of OIII (5007) and HeI (5016) - the Fe emissions have effectively gone and being replaced by the nebula lines.....

[Chochawker]

Thanks very much Ken!

That's a good point about the change, I mostly left the labels from 2 months ago.

I'll produce an updated version and see if I can replace the original.

[Merlin66]

Ha region from last night...looking more and more like an emission/ nebula feature...

[Terry B]

I took a spectra last nightas well. It was almost identical to the one I took on 17th.

[Merlin66]

Here a cloud interrupted Hb region from the 9th....
Clearly shows, when compared with the 15th April, the continued growth in the O[III] emissions.....

[Rob_K]

Great work Ken! You must have a terrific archive on this nova now, top stuff! :thumbsup:

Cheers -

[Merlin66]

Thanks Rob!
I'll continue "data farming" V1369 Cen for as long as I can....

The Ha from the 9th May shows little difference from previous...

[Terry B]

I've been continuing to take spectra of this nova on a regular basis and the spectra are on the ARAS database.
The spectra continues to change. The Ha line had become very strong but has started to weaken now.
The 5007 [OIII] line continues to strengthen and in my raw spectra is now the line that limits my exposure length. It will saturate with a 15 sec exposure.
The graph shows a comparison between 28/4/14 and 17/5/14 in absolute flux.
Terry

[Merlin66]

Always glad to see your results!
I'm surprised that the magnitude of the nova has continued to hover around 8 mag for so long....
Weather permitting I'll continue the "data farming" for as long as I can....

[Jon]

Yes, the longevity at this brightness is unusual, isn't it?

Here's an SA100 spectrum from ten days ago. I'm getting almost no continuum now. [OIII] 5007 very strong. They are all nebular lines now.

[Terry B]

I have continued to take spectra of this nova.
As of last night it is V mag 7.99 and has dimmed significantly in I and measures 8.27
I have attached a graph of the magnitudes I have measured.
The spectral that is brightest now has changed from Ha to [OIII] 5006.8
I have attached graphs showing the change over 5 weeks and over the last week. All are calibrated in absolute flux.


Terry

[Merlin66]

Well done Terry!
I hope to get back on the job after a brief holiday to WA...
The continued development of the nebula phase is interesting.

Looking at the latest report from ARAS the V1369 Cen spectrum looks very similar to previous nova.

[Terry B]

A new spectra for an old thread. This star is still quite visible with a V mag of 9.66
Almost all of the light is now being emitted from the [OIII]5007 line.
The spectra is attached. It is certainly now in the "nebula phase"

[Merlin66]

Thanks for that Terry!
It's good to see that the Nova is still being monitored.
Such a dramatic change from last year.

[Terry B]

I'm still monitoring this nova occasionally. It now has a V mag of 10.07 using my filters. Most of the light is being emitted from the [OIII] 5007 line with much smaller contributions from the hydrogen lines. It is slowly fading in a mostly linear pattern. There are still lots of metal lines above the continuum but when I graph it these lines are hidden because of the enormous [OIII] emission. The relative strength of the [OIII] line is about 800x the continuum.
The attached graphs show the entire spectrum with the Y axis reaching to 800 as well as one with 2 different ranges to show the much weaker lines.
I have also included a standard B9 star for comparison. This is the standard star I use to correct the continuum of the nova.

[Terry B]

I haven't looked at this nova for nearly a year so I thought I would last night.
It is now mag V=11.34 and the spectra shows that almost all of that flux comes from the [OIII] 5007 line.

Terry

[Terry B]

Another update of this now old nova in Centaurus V1369 Cen
It has been about a year since I last took a spectra. It has not changed much but has now dimmed to V= 12.27.

[beren]

:thumbsup: very nice.....great thread to catch up on