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Bright nova (mag. 6.4) in Hercules


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I was surprised by how much it had dimmed since Saturday night when I last looked. Just about visible in the 10x50 finder against the very bright summer sky, obvious through the scope. I made a couple of attempts to take an SA100 spectrum of it without any great success, although it clearly shows a nova.

Chris

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Last evening June 15 at 23.55 BST I had it a little brighter than star 94 (I.e mag 9.4) on the AAVSO 5deg chart I posted near the beginning of this thread. I thus estimated it at mag 9.2

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After a lot of faffing about learning how to use Vspec I got this spectrum from my data taken around midnight on the 12th - 13th June when it was at its short-lived brightest (X-axis in angstroms calibrated with a neon lamp):

image.png.d4404c63cc630e95ea223091fcd271e9.png

No idea how valid a result this is..did anyone else get a spectrum? Seems to ba a symmetrical dip and peak either sie of the Hydrogen Balmer line at 6563, plus other wide absorption lines. Six 10-minute exposures all gave the same result. 

 

 

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1 hour ago, rl said:

No idea how valid a result this is..did anyone else get a spectrum?

Looks good. Here are spectra by Hugh Allen and David Boyd at around the same time from the BAA spectroscopy database

https://britastro.org/specdb/data_graph.php?obs_id=9977%2C9978&multi=yes&mix_flux=yes

There are two clear broad lines with P Cygni profiles. H alpha with emission at 6563A   and another line with emission at ~6350A  (Si II ?) both with absorption at about 80A /3700km/s to the blue (P Cygni shape profiles)

The features to  the red of H alpha are mainly telluric absorption bands from O2 and H2O in our atmosphere

(Note the dramatic change   just 2 days later in my spectrum up the thread)

Cheers

Robin

Edited by robin_astro
added doppler shift of absorption component
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Paul Abel, reporting on the BAA Forum, noted that the nova 2 nights ago was exceptionally red. The reddest nova he has seen. Mind you, he was observing with a 30 cm scope. I didn’t see it especially red in my 10 cm OG.

Anyone else noticed the colour recently?

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On 16/06/2021 at 00:15, John said:

Managed to find it OK with the 120mm refractor tonight. My estimate is around magnitude 9.5 as well.

Got a bit distracted by the Summer Beehive cluster and Blue Raquetball planetary nebula before getting to the nova :rolleyes2:

 

Glad you managed to get it John 👍🏻

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1 hour ago, JeremyS said:

Glad you managed to get it John 👍🏻

Thanks. I didn't notice a red tint either though.

If it's still visible when next clear, I'll try the 12 inch dob on it.

 

Edited by John
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It's looking like a very clear night here, tonight. I'll set the dob up for it, as I still haven't had a chance to see it yet.

Looks like the nova in Cassiopeia is brightening again, too!

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Posted (edited)

Here's the latest light curve of Nova Her. This time it's the AAVSO version as there are more data. The open circles are visual obs, the green squares are CCD with V filter.

I note the visual obs are generally a bit brighter. I think this might be due to the reddish colour (V filter cuts out the red, whereas the eye sees it). Have seen similar trend in Nova Cas data

Note that the box with the laest measurement is a B measurement (blue) - B is  much fainter than visual for this object.

 

501811491_NovaHer2021_20210617.thumb.png.08b424e1b53e8f71642bff0dffc3449a.png

Edited by JeremyS
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3 hours ago, JeremyS said:

Paul Abel, reporting on the BAA Forum, noted that the nova 2 nights ago was exceptionally red. The reddest nova he has seen. Mind you, he was observing with a 30 cm scope. I didn’t see it especially red in my 10 cm OG.

Anyone else noticed the colour recently?

It was definitely very red on my images from 14/15th. 

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  • robin_astro
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  12 hours ago, rl said:

No idea how valid a result this is..did anyone else get a spectrum?

Looks good. Here are spectra by Hugh Allen and David Boyd at around the same time from the BAA spectroscopy database

https://britastro.org/specdb/data_graph.php?obs_id=9977%2C9978&multi=yes&mix_flux=yes

There are two clear broad lines with P Cygni profiles. H alpha with emission at 6563A   and another line with emission at ~6350A  (Si II ?) both with absorption at about 80A /3700km/s to the blue (P Cygni shape profiles)

The features to  the red of H alpha are mainly telluric absorption bands from O2 and H2O in our atmosphere

(Note the dramatic change   just 2 days later in my spectrum up the thread)

Robin, Jeremy, I'm going to do a proper writeup on this with all the details in. 

RL

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Anyone, whats the comparison between a ccd L filter and a V filter ? Is there a standard relationship or an experimental way of determining one, without having a V filter to hand ?

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1 hour ago, rl said:

Robin, Jeremy, I'm going to do a proper writeup on this with all the details in. 

RL

For anyone specifically interested in the details of amateur spectroscopy of Novae and possibly contributing, the ARAS forum have followed several in international collaboration with professionals. Nova Del 2013 was the first major example

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

and the current threads monitoring Nova Cas 2021 and Nova Her 2021 can be found here

https://www.spectro-aras.com/forum/viewforum.php?f=36

Cheers

Robin

Edited by robin_astro
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9 minutes ago, robin_astro said:

For anyone specifically interested in the details of amateur spectroscopy of Novae and possibly contributing, the ARAS forum have followed several in international collaboration with professionals. Nova Del 2013 was the first major example

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

and the current threads monitoring Nova Cas 2021 and Nova Her 2021 can be found here

https://www.spectro-aras.com/forum/viewforum.php?f=36

Cheers

Robin

The BAA also offer a mentoring service for members looking to bring their spectroscopy up to  research standard for inclusion in the BAA spectroscopy database

The BAA spectroscopy resources page can be found here

https://britastro.org/node/19378

Robin

Edited by robin_astro
added BAA spectroscopy link
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Used the dob tonight and found it!

Blimey - that took a lot of peering at charts to compare the view and find it. It's pretty faint and hard to find with the light skies here. Waited to 1am to get the best view.

I reckon it's the same brightness as HD 230191 - Mag 10.0

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I finally got a go at this one. No eyepieces used though!

Got a slack handful of 30 second subs through my 127 Mak. It does look red in previews but I'll process it later and post it. 

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Had a last look last night before I have to go back to Bortle 8 skies - was really only just visible in the Z73.

I have used both the 35mm TMB clone (12x) and 17.5mm Morpheus (25x) over the last few nights viewing the nova.Although the 35mm gives good context with the other stars around it, it also had a bit of background sky brightness which meant at this point the nova was pretty much invisible, so the Morpheus was a better option. 

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Finally got a chance to look for this last night, but what a struggle. Sky was still quite bright at 1 am and even in the Dob it took more than 30 minutes to locate. At first I was unsure if I actually had found it but constant returns to the finder chart finally convinced me. Estimating mag was difficult, but I estimate it as slightly dimmer than mag 10, perhaps around 10.2. 

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Here it is, close up and personal. Quick stack of 30 sec subs. ASTAP photometry, by my wonky hand, gives a magnitude of 9.9. I think my eggy stars throw things off a bit.

This is a very narrow field, about 12 x 17 arc mins, So don't try looking for any of the usual reference stars!592486368_NOVA_HER2021-06-1716x30LEQMODHEQ56ZWOASI178MC_stacked.thumb.jpg.a16bad06738dc6af11905208872fa46c.jpg

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A spectrum from last night.  We can see  from this why the Nova looks so red, particularly in images. By digitally filtering the full spectrum (Blue) by multiplying it by the response of a photometric V filter (Pink) we can see the light that would pass through the V filter (Green). If we measure the area under the green curve and compare it with the area of the H alpha line (between the two dotted lines) we find that there is over twice as much light in just the H alpha line compared with all the light passing through the V filter.

Nova_Her_2021_20210617_ALPY600.png.c60f5ab659f89ca5c0bbf3cb043f00c4.png

Cheers

Robin

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5 hours ago, Astro Noodles said:

Are there any suggestions or opinions as to why this event happened so quickly?

Depends on amount of energy released and speed of expansion of then eruption.

The eruption occurs when sufficient material lands on the white dwarf star (from the secondary donor star) to cause a thermonuclear runaway. The material is then blasted away into space and the eruption declines. A slow nova has ejection speeds of ca 500 km/sec. Fast is ~ 2000 km/sec so the brightness declines more quickly 

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