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Nova in M31

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George Carey's picture
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Nova in M31

I spotted a new object in M31 on the 26th November. The Liverpool telescope confirmed a nova spectrum for the object, so far designated AT 2018jas. The magnitude is now about 16.4 so would be a good target for amateur spectroscopy.

Coordinates: 00:43:44.560 +41:27:52.40

When first detected the magnitude was 18.5, so it was caught well before the maximum brightness. 

This comparison image shows the increase:

Jeremy's picture
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New nova

Congratulations George: well done for discovering another nova in M31!

Rob Januszewski's picture
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Nova M31

Well done George - Yet another discovery in M31.

George Carey's picture
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AT 2018jas

 Thanks Rob and Jeremy,

Now confirmed as a nova: http://www.astronomerstelegram.org/?read=12245

Remote image from Spain last night gave magnitude 15.6.

Robin Leadbeater's picture
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spectrum

Went for a spectrum last night with the ALPY 200 but found that a series of power cuts during the storm yesterday had corrupted the observatory computer drive. 15.6 is bright for an M31 nova so definitely worth trying for even with a standard ALPY and novae spectra still show strong emission features later on even when they start to fade in measured brightness.

Robin

George Carey's picture
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Remote images from Spain with

Remote images from Spain with poor sky show magnitude on 29th Nov to be 16.3

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Images from La Palma

Images from La Palma last night are being analyzed right now but I'm still learning how to do that.  Results (possibly preliminary) will be edited into this post.  Nova certainly very obvious on the 3000s stacked image but the background from M31 is very bright and precision photometry will need to take that into account.

FWIW, I'm about to download GAIA-DR2 positions and magnitudes for analysis purposes as I don't have a finder chart and comparison magnitudes.  I'm hoping this is satisfactory ...

Results are undoubtedly preliminary because I'm still learning how to drive the tool set and much data reduction has been done by hand..  Comparing my V-band mags with GAIA's G-band gives satisfactory results (less than 0.05 mags at mag 16) so I'm fairly confident that the nova was at mag 16.50 +/- 0.05 at 2018-11-30 02:40UT.

Now to improve my skills and tools.

George Carey's picture
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Mag 16.8 Friday 30th

Difficult to miss tonight.

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George. Congrats on another

George. Congrats on another nice discovery. I'm getting 17.4 unfiltered (UCAC-4 R band) tonight (see attached). I think the photometric apertures that you are using in Astrometrica may be a bit small. This may lead to some problems with it estimating the sky background.

George Carey's picture
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Thanks Nick

I have the centroid at radius 3. 

These are values I get when I change the radius:

centroid magn.
radius
1 18.0
2 16.9
3 16.5
4 16.5
5 16.4
6 16.3
7 16.2
8 16.2

At radius 3 it looks like all of the nova is in the circle.

I am never sure what is best.

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Are you using background from

Are you using background from PSF or background from aperture? I think you should always use the latter since the PSF background estimator needs a much biffer photometric aperture to work properly. They often give very different magnitude zero points.

George Carey's picture
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I tried Aperture today - very

I tried Aperture today - very similar results. Mag 16.6.

If I increase the aperture the mag rises to 16.3. 

Pinpoint gave fairly consistent values at 16.8

George Carey's picture
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Magnitude using Maxim

I put the data from last night into Maxim. Much more involved procedure.

Average value= 17.11

Robin Leadbeater's picture
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finally a spectrum

Here  is a raw spectrum image from tonight (ALPY 600, 6600s total exposure.) It is very faint but the broad H alpha emission is clear. I will try to reduce it to see what else I can pick out

Robin

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reduced spectrum

Here is the reduced spectrum.  (red, filtered to R~300 resolution)

mag ~17 is the faintest target I have attempted with the ALPY600 setup and the SNR is very low. The broad H alpha line is obvious though and other Balmer lines are present too. I have also marked the Fe II curtain lines though they are only marginally detected above the noise.

Cheers

Robin

George Carey's picture
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Most impressive Robin!

Most impressive Robin!

George Carey's picture
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Photometry for AT 2018jas

I have filled in gaps in my data with remote observations using iTelescopes in Spain, and filtered images from Sofia University (Atel #12268).

The nova is now near the limit for my equipment so not much more can be obtained.

George Carey's picture
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Update

Also photometry from ATLAS_Bot1 and ZTF_AMPEL_MSIP.