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Re: at2020nvb a bright transient in NGC4457

PostPosted: Mon Jul 06, 2020 11:18 pm
by Robin Leadbeater
Peter Velez wrote:How odd - priority based on professional status rather than time of publication.

Well the Italian spectrum was taken earlier but the pros posted their classification first but kept the spectrum private, which is allowed by the rules apparently. I agree it is a little odd though to allow a classification without making the evidence public. This is what the rules say:-

"For Class reps, it is possible to request a proprietary period separately for
the classification itself (typing+redshift), or for the uploaded spectrum.

With respect to the proprietary period options just mentioned, the formal
"discoverer" of a transient is defined to be the reporter/s whose discovery report
first turns to public (or was immediately so). Likewise for "classifier".

Re: at2020nvb a bright transient in NGC4457

PostPosted: Tue Jul 07, 2020 3:03 am
by Peter Velez
I managed just over 2 hours on this target last night. For some reason ISIS didn't like a few frames so I ended up with around 110 minutes of data.

Here is the latest spectrum (6 July) plotted against my data from 3 July in PlotSpectra. The Si II absorption suggests the ejecta velocity has dropped a bit - about 300 odd km/s.

Run through Gelato again, the 2 best matches were to the same SN - 1996X - one 3.7 days before maximum, the other only 0.8 days before maximum light. So take from that what you will. The SN is appreciably brighter than at the weekend. I was in too much of a hurry to get started that I didn't take an image with the guider to post. However, as you will see from the spectra, there is a lot less noise in last night's data.

An interesting feature is an emission line that looks like its developing at 5905 A. I suspected there were a few spikes that are due to airglow or some other sky contamination so I ran ISIS without subtracting the sky and confirmed that the spikes at 5576 and 6299 A are sky contribution as the spikes are accentuated at these points. I've attached a plot that highlights this. However, the peak at 5905 was not accentuated which suggests that there is something else going on here. Interstellar Na might be the culprit but I would have expected absorption not emission. It may be just noise - however, I do see it in the 3 July spectrum too, just not as prominent. I've attached a close up. Feel free to tell me I'm off beam with this one.

The weather doesn't look good for much of the rest of this week - but if there is a break in the clouds, I'll take another crack at this


Re: at2020nvb a bright transient in NGC4457

PostPosted: Fri Jul 10, 2020 11:53 pm
by Christian Buil
An UVEX spectrum taken the 8.864 July 2020 (45 mn exposure):


Christian Buil

Re: at2020nvb a bright transient in NGC4457

PostPosted: Sun Jul 19, 2020 2:16 am
by Peter Velez
Here is my latest on 2020nvb. The weather gods have not been smiling on me of late but I managed an hour on this target. Also included is my data from 8 July which was not that different from the last spectrum I posted.

The Fe II lines are becoming much more prominent.

Gelato matches this to a type 1a SN 9.4 days after peak brightness. This suggests that my data from 8 July was around the peak - which reflects the Gelato match to SN 1996X from that date.

I'll keep on this one as its still quite bright and easy to access early in the evening here in Australia


Re: at2020nvb a bright transient in NGC4457

PostPosted: Fri Jul 24, 2020 7:27 am
by Peter Velez
Another update

I've plotted data from 23 July and 18 July together. Both are adjusted for HRV and the redshift for the host galaxy. I've labelled the Fe II emissions - its quite clear how these are shaping significant sections of the spectrum.