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Main
Date: 27 Jul 2007 05:59:46
From: Rob Johnson
Subject: Variable or Nova?
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I took a couple of pictures of the Dumbbell Nebula, M27, a couple of
years apart:
<http://www.whim.org/nebula/astro/dumbbell20050903.html >
<http://www.whim.org/nebula/astro/dumbbell20070715.html >
In both, the Goldilocks Variable is apparently at a minimum (I'm not
sure of its period). However, in the latter, there is a star which
is not in the former. It is not an anomalous speck, since it appears
in all 10 of the images I took at the time (only 4 were used), and at
different positions on the sensor (I have some flexure problem that I
need to resolve). In the larger image on the latter page, the star
is at pixel (5,861), where y is positive down. It is near the edge
due to cropping to center the nebula. In the preprocessed images, it
is fully in the shot.
I estimate the star to be about magnitude 12.3, at RA 19:59:41.9
Dec +22:33:50.4 (2000.0); very close to the same as the Hubble Guide
Star GSC2 N0312032-155635, a variable, aka V418 Vulpeculae, which
goes from 13.6 to 16.0, so unless I have misestimated the magnitude,
what I saw is 3.3x brighter.
Does anyone have a suggestion as to the best place to check whether
this is a nova or just the variable mentioned above?
Thanks in advance for any help.
Rob Johnson <rob@trash.whim.org >
take out the trash before replying
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Date: 27 Jul 2007 22:57:31
From: Greg Crinklaw
Subject: Re: Variable or Nova?
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Rob Johnson wrote:
> I estimate the star to be about magnitude 12.3, at RA 19:59:41.9
> Dec +22:33:50.4 (2000.0); very close to the same as the Hubble Guide
> Star GSC2 N0312032-155635, a variable, aka V418 Vulpeculae, which
> goes from 13.6 to 16.0, so unless I have misestimated the magnitude,
> what I saw is 3.3x brighter.
It's rather easy to be off by 1.3 magnitudes unless you do your
photometry carefully. Did you do accurate V-magnitude photometry? Not
only that, by the magnitudes listed in the GCVS can be in error (for
instance it might incorrectly identify the filter used) or this Mira
variable may simply be brighter than usual.
Sorry--but I think you likely just caught this variable at maximum.
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com
To reply take out your eye
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Date: 29 Jul 2007 18:13:38
From: Rob Johnson
Subject: Re: Variable or Nova?
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In article <ea1bc$46aaccbb$4212a552$8071@TULAROSA.NET >,
Greg Crinklaw <theskyhoundyoureye@yahoo.com > wrote:
>Rob Johnson wrote:
>> I estimate the star to be about magnitude 12.3, at RA 19:59:41.9
>> Dec +22:33:50.4 (2000.0); very close to the same as the Hubble Guide
>> Star GSC2 N0312032-155635, a variable, aka V418 Vulpeculae, which
>> goes from 13.6 to 16.0, so unless I have misestimated the magnitude,
>> what I saw is 3.3x brighter.
>
>It's rather easy to be off by 1.3 magnitudes unless you do your
>photometry carefully. Did you do accurate V-magnitude photometry? Not
>only that, by the magnitudes listed in the GCVS can be in error (for
>instance it might incorrectly identify the filter used) or this Mira
>variable may simply be brighter than usual.
>
>Sorry--but I think you likely just caught this variable at maximum.
Yes, indeed, this is the variable star that I mentioned above. So I
have not discovered anything new. It was discovered in August 1997
by Gianluca Masi. My image of M27, and some links which lead to
Gianluca's site can be found at
<http://www.whim.org/nebula/astro/dumbbell20070715.html >
Thanks for everyone's help.
Rob Johnson <rob@trash.whim.org >
take out the trash before replying
to view any ASCII art, display article in a monospaced font
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Date: 27 Jul 2007 09:05:47
From:
Subject: Re: Variable or Nova?
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On Jul 27, 5:59 pm, r...@trash.whim.org (Rob Johnson) wrote:
> I took a couple of pictures of the Dumbbell Nebula, M27, a couple of
> years apart:
>
> <http://www.whim.org/nebula/astro/dumbbell20050903.html>
> <http://www.whim.org/nebula/astro/dumbbell20070715.html>
>
> In both, the Goldilocks Variable is apparently at a minimum (I'm not
> sure of its period). However, in the latter, there is a star which
> is not in the former. It is not an anomalous speck, since it appears
> in all 10 of the images I took at the time (only 4 were used), and at
> different positions on the sensor (I have some flexure problem that I
> need to resolve). In the larger image on the latter page, the star
> is at pixel (5,861), where y is positive down. It is near the edge
> due to cropping to center the nebula. In the preprocessed images, it
> is fully in the shot.
>
> I estimate the star to be about magnitude 12.3, at RA 19:59:41.9
> Dec +22:33:50.4 (2000.0); very close to the same as the Hubble Guide
> Star GSC2 N0312032-155635, a variable, aka V418 Vulpeculae, which
> goes from 13.6 to 16.0, so unless I have misestimated the magnitude,
> what I saw is 3.3x brighter.
>
> Does anyone have a suggestion as to the best place to check whether
> this is a nova or just the variable mentioned above?
>
> Thanks in advance for any help.
>
> Rob Johnson <r...@trash.whim.org>
> take out the trash before replying
> to view any ASCII art, display article in a monospaced font
I guess you could try the AAVSO:
http://www.aavso.org/
Bill
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