[Aavso-photometry] [AAVSO-DIS] SN 2009dd

[arne]

It is really tough to deal with a supernovae next to a galactic nucleus.
The nucleus does not have a stellar profile, so assuming that it has
a constant magnitude and can be subtracted out of an aperture that
includes both objects will usually give you the wrong result.  The
best approach is to wait a year until the supernova has faded sufficiently;
take another image and use that as a template for subtraction.  You have
to convolve with the seeing to ensure the subtraction works right.
Michael Richmond has a good paper that you should look at when performing
supernova photometry:  AJ 1995, 109, 2121

In general, I avoid SNe in confused regions whenever possible.
Arne
--------------
Richard Huziak wrote:
> Hi Mario
> 
> That's the procedure I understand.  You'd treat the nucleus & galactic 
> fuzz as a second star in the aperture and after the SN is gone, image 
> again.  To be consistent, the same aperture size should be used in the 
> reductions of different nights and the same area of the galaxy within 
> the aperture.  I guess the secret would to be try to keep all things the 
> same over all nights as possible.
> Just as an aside, can an 'unsharp masking' or similar nulling technique 
> be used on a raw image to subtract out the galaxy, then photometry done 
> after?  Just a thought.
> 
> rick
> 
> Mario Motta wrote:
>> Hello all,
>>
>>   I was away at the NEAF meeting with gary Walker, got back last 
>> night. I did take a set of images of NGC 4088, with the intent of 
>> deriving a magnitude. What I found was the SN os right on top of the 
>> core, just appears as a bump off the core. I have an image made which 
>> I will post at my ATMOB site later tonight, also have a raw stack 
>> unprocessed beyond flat and dark to derive a magnitude. however, not 
>> sure how to do in this case. Anyone have an idea? The magnitude 
>> derivation will be contaminated by the core of the galaxy. Do we have 
>> to wait a couple of months till gone and then subtract out the 
>> underlying galaxy?
>>
>> Mario Motta
>>
>> Richard Huziak wrote:
>>> Is anyone working on the light curve of 11th mag type II SN 2009dd in 
>>> NGC 4088, a very interesting, disturbed galaxy in UMa?  Tough 
>>> photometrically - it is basically on top of the nucleus (2"W, 5"S), 
>>> but short exposures might decrease the 'fuzz factor'.  Visually 
>>> estimates would be good.  There is no sequence around NGC 4088, though.
>>>
>>>
>>> Are all SN's added to VSX, btw?
>>>
>