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ASTRO: Nova Delphini 2013 revisited 25 days later



 
 
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  #1  
Old October 14th 13, 08:38 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Posts: 3,085
Default ASTRO: Nova Delphini 2013 revisited 25 days later

I originally imaged Nova Delphini 2013 on August 29. I've tried several
time since to reimage it to see if it changed but the weather has made a
mess of all attempts. Now with it being over a month later and the moon
in the area, I went through all the attempts and found one that was sort
of usable. Seeing was poor by comparison so stars are much larger.
This makes them appear brighter but I've actually processed them
virtually the same. The difference is just due to seeing and changes in
transparency. The second attempt was taken September 23 so 6 days shy
of a month later. Two differences are obvious. First it has changed
color. This was rather expected. Many nova (but not the previous nova
in Delphinus in 1967) blow out huge shells of hydrogen gas that glows in
typical hydrogen alpha red and weaker hydrogen beta blue-green. Since
the red dominates the star appears to turn red though it is actually the
as yet unresolved hydrogen shell it expelled that gives it the red
color. The star is still blue hot from the eruption. The other change,
also as expected (but again not the case with the 1967 nova in
Delphinus) is that it has gotten fainter. I've included a side by side
comparison as well as the full frame from September. Both the August
and September images were taken precisely the same way in order to try
and preserve comparability.

I should add that while the nova appears to have a red halo about it
that is just glare from the star being so bright. This is the same as
the blue glare around the earlier image but colored by the H alpha
shell. The actual hydrogen shell is still an unresolved point source
same as the star itself.

14" LX200R @ f/10, RGB=1x10' each, STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

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  #2  
Old October 14th 13, 10:53 PM posted to alt.binaries.pictures.astro
Stefan Lilge
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Posts: 2,269
Default ASTRO: Nova Delphini 2013 revisited 25 days later

Rick,

the change in colour is quite astounding...

Stefan

"Rick Johnson" schrieb im Newsbeitrag
. com...

I originally imaged Nova Delphini 2013 on August 29. I've tried several
time since to reimage it to see if it changed but the weather has made a
mess of all attempts. Now with it being over a month later and the moon
in the area, I went through all the attempts and found one that was sort
of usable. Seeing was poor by comparison so stars are much larger.
This makes them appear brighter but I've actually processed them
virtually the same. The difference is just due to seeing and changes in
transparency. The second attempt was taken September 23 so 6 days shy
of a month later. Two differences are obvious. First it has changed
color. This was rather expected. Many nova (but not the previous nova
in Delphinus in 1967) blow out huge shells of hydrogen gas that glows in
typical hydrogen alpha red and weaker hydrogen beta blue-green. Since
the red dominates the star appears to turn red though it is actually the
as yet unresolved hydrogen shell it expelled that gives it the red
color. The star is still blue hot from the eruption. The other change,
also as expected (but again not the case with the 1967 nova in
Delphinus) is that it has gotten fainter. I've included a side by side
comparison as well as the full frame from September. Both the August
and September images were taken precisely the same way in order to try
and preserve comparability.

I should add that while the nova appears to have a red halo about it
that is just glare from the star being so bright. This is the same as
the blue glare around the earlier image but colored by the H alpha
shell. The actual hydrogen shell is still an unresolved point source
same as the star itself.

14" LX200R @ f/10, RGB=1x10' each, STL-11000XM, Paramount ME

Rick
--
Prefix is correct. Domain is arvig dot net

  #3  
Old October 15th 13, 01:40 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
external usenet poster
 
Posts: 3,085
Default ASTRO: Nova Delphini 2013 revisited 25 days later

I've seen this quite often with Nova. For a while they get redder as
the star still has sufficient UV light and shell's density reaches
optimum values. Then the red and the star fade back to obscurity. I
may have caught it when color was near max. It was fainter in earlier
images and cloudy since so haven't seen what it has done since the 23rd.
GK Persei was an exception since the star has stayed bright in UV (and
visible light) it continues to light up its ejecta over 100 years later.
That is an exception however. Nova Cygni 1975 was pretty well faded
to nothing in just a month's time yet hit magnitude 2 at maximum. It
was about magnitude 6 or fainter when the shell was most obvious only a
week or so later. It will be interesting to see how long this one hangs
in there. The 1967 Delphini nova showed no hydrogen and was brighter
months after it blew rather than dimmer. I stayed as bright or brighter
than its first peak for many months. It is still there at mag 13 or so
though it was much fainter prior to the eruption. Like GK Persei it is
a variable star since the nova. Maybe in 100 years it too will have a
"fireworks burst" nebula around it. Maybe I should image it to see get
a base image in case something shows up.

Rick

On 10/14/2013 4:53 PM, Stefan Lilge wrote:
Rick,

the change in colour is quite astounding...

Stefan

"Rick Johnson" schrieb im Newsbeitrag
. com...

I originally imaged Nova Delphini 2013 on August 29. I've tried several
time since to reimage it to see if it changed but the weather has made a
mess of all attempts. Now with it being over a month later and the moon
in the area, I went through all the attempts and found one that was sort
of usable. Seeing was poor by comparison so stars are much larger.
This makes them appear brighter but I've actually processed them
virtually the same. The difference is just due to seeing and changes in
transparency. The second attempt was taken September 23 so 6 days shy
of a month later. Two differences are obvious. First it has changed
color. This was rather expected. Many nova (but not the previous nova
in Delphinus in 1967) blow out huge shells of hydrogen gas that glows in
typical hydrogen alpha red and weaker hydrogen beta blue-green. Since
the red dominates the star appears to turn red though it is actually the
as yet unresolved hydrogen shell it expelled that gives it the red
color. The star is still blue hot from the eruption. The other change,
also as expected (but again not the case with the 1967 nova in
Delphinus) is that it has gotten fainter. I've included a side by side
comparison as well as the full frame from September. Both the August
and September images were taken precisely the same way in order to try
and preserve comparability.

I should add that while the nova appears to have a red halo about it
that is just glare from the star being so bright. This is the same as
the blue glare around the earlier image but colored by the H alpha
shell. The actual hydrogen shell is still an unresolved point source
same as the star itself.

14" LX200R @ f/10, RGB=1x10' each, STL-11000XM, Paramount ME

Rick



--
Prefix is correct. Domain is arvig dot net
 




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