Eruption of the Recurrent Nova RS Oph!

[JeremyS]

Yes, definitely changing colour. I saw it 2 nights ago through an 8-inch SCT and it was distinctly orange.

have a look at this animation by Mazin Younis: https://britastro.org/observations/observation.php?id=20210814_032310_ebea8a7f20407930

[Muc]

Tonight it's much redder and comparable to HD162834, so around 7th mag. Lovely glow from it

[Nik271]

I just managed a quick look in my finder. It's become much dimmer, I estimate it at mag 8. I only had seconds to view it between gaps in clouds, the only reason I spotted it quickly is because it is deep red. Amazing to see such a rapid change in colour!

[lunator]

Managed a quick look in the 15x70 Binos. 

It is slightly fainter then HD162834 but still slightly brighter than HD162506. 

I estimated mag 7.5. 

Cheers

Ian

[JeremyS]

Currently around 8th mag. AAVSO LC:

[Xilman]

Observed last night. Still need to reduce the data ...

Grrr. Saturated even at 5s exposure.  Not accurately measurable but somewhere near V=7.5

Perhaps tonight with a 1 or 2 second exposure.

[JeremyS]

With really bright stars, I’ll sometimes stop my C11 down using a cardboard mask to get more manageable exposures.

[Xilman]

14 hours ago, JeremyS said:

With really bright stars, I’ll sometimes stop my C11 down using a cardboard mask to get more manageable exposures.

Good idea. Minor problem is getting hold of a sheet of cardboard significantly larger than 40cm in diameter. Might be good for solar work, though, if the hole is fitted with a metallic film filter. However, the SX 814 camera allows exposures as low as 1ms so it may not be necessary.

The Bahtinov mask was made out of the tray in which a replacement kitchen oven was delivered.  Never thought I would rule a diffraction grating with a craft knife but it works just fine, especially with the Bahtinov Grabber app for attaining critical focus.

Sorry to go slightly off-topic.

[Nik271]

I had clear, slightly hazy skies last night and had a good look at RS Oph with 10x50bins. It seems similar brightness to the nearby HIP 87396 so magnitude 8.  The colour was not showing very well perhaps because of the high haze/mist.

[lunator]

Hi Nik same here. I had a look at 22.30 last night. 

There was a bit of haze/contrails around making things a little tricky.

In my 15x70's RS Oph was fainter than HD162488 7.98 but slightly brighter than HD162506 8.38 so my best estimate is mag 8.2.

The colour did seem more muted last night and I think the haze was the issue.

Cheers

Ian

[michael.h.f.wilkinson]

Will try and have a visual shot again today (weather permitting)

[lunator]

I had a much better view last night.

Using the grab and go ST80 set up the colour was more apparent. It has gone from the golden yellow colour similar to HD162834 to a reddish colour. Brightness was similar to  HD162488. So probably about mag 8.1. 

The haze last night did make it look slightly dimmer.

Cheers

Ian

 

[Muc]

Caught with this again last night. It amazing how the view in my 9x50 finder is different now as the mag has dropped. On par mag wise with HD 162488 I would say. Harder to see colour tone now but hint of red

[Xilman]

On 21/08/2021 at 19:18, Xilman said:

Observed last night. Still need to reduce the data ...

Grrr. Saturated even at 5s exposure.  Not accurately measurable but somewhere near V=7.5

Perhaps tonight with a 1 or 2 second exposure.

A 2s exposure worked beautifully.

At DATE-OBS= '2021-08-22T22:23:33', it was measured as V = 7.865 ± 0.003

It has taken me so long to analyze because gout has crippled me for several days and it is hard to concentrate on work 😧

[robin_astro]

11 hours ago, Xilman said:

A 2s exposure worked beautifully.

 

Having a related problem doing spectroscopy tonight. The H alpha emission is so intense that the raw signal at  H alpha  is now something like 3000x greater than that in the continuum in the violet. I am having to take big stacks of short(ish) exposures to get a vaguely decent signal/noise in the violet while avoiding saturating at H alpha

Robin

[rl]

Absolutely massive H alpha peak last night; raw data.

This is raw data where the instrument is less sensitive at the alpha line compared to the beta..

I expect the Purkunjie effect will be a serious issue now doing visual magnitude estimates.

[robin_astro]

The flux calibrated spectrum from 2021-08-25. Red shows the full height of the H alpha line and  blue at 20x scale shows the detail in the weaker lines.

See this annotated high resolution spectrum in the ARAS forum for identification of the lines

https://www.spectro-aras.com/forum/viewtopic.php?f=36&t=2804&start=60#p15994

though a few other high ionisation lines have appeared since that spectrum was taken

The peak intensity of the H alpha line is currently ~120x compared with the continuum at 5500 A in the green. Approximately 50% of the total light in the visible range 4000-7000 Angstrom comes from the H alpha line.

Cheers

Robin 

 

Edited August 27, 2021 by robin_astro
comment about new lines

[Xilman]

6 hours ago, rl said:

I expect the Purkunjie effect will be a serious issue now doing visual magnitude estimates.

Very likely. Fortunately I, and many like me, make observations through photometric filters.

[robin_astro]

7 hours ago, Xilman said:

Very likely. Fortunately I, and many like me, make observations through photometric filters.

Interestingly the AAVSO data shows the visual observers are doing just fine 

[lunator]

12 hours ago, robin_astro said:

Interestingly the AAVSO data shows the visual observers are doing just fine 

I have been following RS Oph quite closely. It is the 1st variable I really paid attention too. From a visual perspective at 8th mag it is still bright enough to show colour even in a small scope. I have been using an ST80. It does show "flashes" of red when I am observing it but the change in colour does not seem to have changed the overall magnitude as far as it appears to me. 

Cheers

Ian

[Littleguy80]

Finally got this tonight. The weather has not been on my side for seeing this Nova. I’ve had a few failed cloud dodging attempts up until now. With the 80mm frac and APM 30mm I was surprised by how strongly the orange came through. It was almost red. Really neat looking. This makes it 4 Novas in 2021 for me. Before this year I’d seen 2 in 4 years of observing. I was really keen to see this one because of it’s history. I wonder if I’ll see any more eruptions of Rs Oph in my lifetime!

[lunator]

I got my OMC250 on this last night. The magnitude was still similar at around 8.2. 

The red was much more apparent using the 250mm vs the 80mm. 

Neil, based on the previous eruptions the average is about 15 years but varies between 9 & 26 years so there is a good chance to see it go again. The biggest issue could be if it happens when the Sun is in the same part of the sky and it gets missed.

I am going to go out on a limb and say the next Outburst could be less than ten years.

The previous outbursts are noted as 1898,1907,1933, 1945, 1958,1967,1985,2006,2021

The gaps are 9,26,12,13,9,18,21,15. If you take the 1907,1933,1945,1958 you get 51 years. If you take 1967,1985,2006,2021 you get 54 years. It may be just co-incidence but I wonder if there is a third component in the system with ~50 year orbit having an effect.

I might be completely and utterly wrong tho'

Cheers

Ian

[JeremyS]

Munari and Valisa have published an article on "The 2021 outburst of RS Oph. A pictorial atlas of the spectroscopic evolution: the first 18 days" on ArXiv today.

[JeremyS]

Latest light curve from BAA VSS. The eruption continues:

[lunator]

i   managed a quick look at this last night. 

Conditions weren't great, transparency was quite poor.

RS has continued to fade.

it looked fainter than HD162488 but brighter than the other field stars.

I couldn't see any colour.    

my rough estimate was mag 8.6

cheers

Ian