mag 15 possible SN in NGC3147 - spectrum required

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mag 15 possible SN in NGC3147 - spectrum required

Postby Robin Leadbeater » Sun Feb 11, 2018 12:21 pm

Patrick Wiggins reports a possible supernova in NGC3147
https://wis-tns.weizmann.ac.il/object/2018rv
though there is a faint object visible in DSS and Pan-STARRS reference images so it may be a galactic CV/Nova

Spectrum required !

Robin
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Re: mag 15 possible SN in NGC3147 - spectrum required

Postby Robin Leadbeater » Mon Feb 12, 2018 1:07 am

This is probably an outburst of Dwarf Nova CP Dra
http://simbad.u-strasbg.fr/simbad/sim-b ... BAD+search

Robin
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Re: mag 15 possible SN in NGC3147 - spectrum required

Postby Forrest Sims » Tue Feb 13, 2018 4:31 am

Hi Robin and all,

I thought I would have a go at this target before the clouds set in on Sunday night. It was difficult to find at this magnitude. Part of the problem I had was where exactly to look. The Transient Name Server link gives an RA 10:15:39.90 and a DEC +73:26:04.83 but lower down in the link from Patrick Wiggins is the Value of DEC of +73:26:08.83. So I do not know if one or the other was a typo or just an updated value. Using the AAVSO chart tool I was able to find a star very close to this location which is also very close to the location SIMBAD lists for CP Dra and that is RA 10:15:39.84 and DEC +73 26 05.0. I took up to 30 sec exposures at binning =2 with my LodestarX2 guide camera and one and only one star clearly showed at or near these positions. I was able to get it positioned on my LISA slit or maybe I should say in the slit and guided on the Mag 14.9 star AUID (000-BBR-295) at RA 10:16:05.79 and DEC 73:27:01.0.

I took 7 600sec target images and used HD065900 as my Reference star.

After cottoning onto the fact that this might be CP Dra I was surprised at what I ended up with for a spectrum.

Not sure what I got, any ideas?

Cheers!
Woody
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Re: mag 15 possible SN in NGC3147 - spectrum required

Postby David Boyd » Tue Feb 13, 2018 9:06 am

In case it's of any help, here is a field image which shows CP Dra during an outburst of the star at mag 15.5 on 29 March 2009.

David

CP Dra + NGC3147 marked.jpg
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Re: mag 15 possible SN in NGC3147 - spectrum required

Postby Robin Leadbeater » Tue Feb 13, 2018 12:48 pm

There is now a spectrum on TNS showing H alpha in emission and other Balmer lines in absorption at zero redshift, screen shot attached

Cheers
Robin
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Re: mag 15 possible SN in NGC3147 - spectrum required

Postby Robin Leadbeater » Tue Feb 13, 2018 1:28 pm

Forrest Sims wrote:The Transient Name Server link gives an RA 10:15:39.90 and a DEC +73:26:04.83 but lower down in the link from Patrick Wiggins is the Value of DEC of +73:26:08.83. So I do not know if one or the other was a typo or just an updated value.


I have just checked with Patrick and Dec 73°26’04.83 is the correct location so coincident with CP Dra

Cheers
Robin
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Re: mag 15 possible SN in NGC3147 - spectrum required

Postby Forrest Sims » Tue Feb 13, 2018 9:08 pm

Hi David,

I am pretty certain that the star your arrow points to is the star I put on the spectrograph slit. A little hard to tell but I think it might have been a little bit fainter than the mag 15.5 value you show in your image. (I meant to save a targeting image taken with the LodestarX2 but forgot.)

Woody

Hi Robin,

I used this DEC 73:26:04.83 value to generate my AAVSO chart. So I must have been on the right target. The mag 14.7 star (AUID 000-BBR-277) just to the right in David’s image was near the slit but when I put our target star (AP Dra?) on the LISA slit I think that the mag 14.7 was sufficiently off the slit. Hoping that the only spectrum light I was getting was from our target. My spectrum is rather featureless/noisy even with 7 x 600sec frames. I tried numerous binning settings for the aperture for the target and the subtraction zones. None of this made a noticeable difference in the shape of the continuum but it did affect to some degree the sharp emission/absorption spikes. When I zoom in using PlotSpectra on my profile I can see an absorption feature at Hbeta and an emission line at Halpha although they do not exceed the general noisiness of the continuum. I have been unable to find a spectrum of CP Dra to compare. Probably just don’t now where to look. I am guessing my data is discardable…

Thanks guys!
Woody
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Re: mag 15 possible SN in NGC3147 - spectrum required

Postby Robin Leadbeater » Fri Feb 16, 2018 5:43 pm

Hi Woody,

I reckon your spectrum is consistent with the one posted on TNS, just more noisy. (H alpha emission, H beta absorption). I would suspect hot pixels/cosmic rays hits or artifacts from sky line subtraction for the very sharp features. Can you see anything in the spectrum image at these locations ?

Cheers
Robin
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