Nova in M31

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  • #574190
    George Carey
    Participant

    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:

    #580292
    Jeremy Shears
    Participant

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

    #580295
    Rob Januszewski
    Participant

    Well done George – Yet another discovery in M31.

    #580297
    George Carey
    Participant

     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.

    #580298
    Robin Leadbeater
    Participant

    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

    #580301
    George Carey
    Participant

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

    #580303
    George Carey
    Participant

    Difficult to miss tonight.

    #580304
    Nick James
    Participant

    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.

    #580305
    George Carey
    Participant

    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.

    #580306
    Nick James
    Participant

    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.

    #580307
    Robin Leadbeater
    Participant

    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

    #580308
    George Carey
    Participant

    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

    #580302
    Paul Leyland
    Participant

    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.

    #580310
    George Carey
    Participant

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

    Average value= 17.11

    #580311
    Robin Leadbeater
    Participant

    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

    #580312
    George Carey
    Participant

    Most impressive Robin!

    #580392
    George Carey
    Participant

    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.

    #580393
    George Carey
    Participant

    Also photometry from ATLAS_Bot1 and ZTF_AMPEL_MSIP.

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