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at2020nvb a bright transient in NGC4457

PostPosted: Wed Jul 01, 2020 4:37 pm
by Robin Leadbeater
Koichi Itagaki reports a bright (mag 13 C) transient in NGC4457, discovered 4 hours ago
https://wis-tns.weizmann.ac.il/object/2020nvb

Robin

Re: at2020nvb a bright transient in NGC4457

PostPosted: Wed Jul 01, 2020 5:52 pm
by Jaroslaw Grzegorzek
Hi,
Yes. I was happy to see this at TNS (congratulations to Koichi Itagaki) ... but why RA=12 and low DEC again !!! :( Virgo targets are "mission impossible" for me now.
Observers who are more to the south will manage it. Waiting for results. Good luck!

Re: at2020nvb a bright transient in NGC4457

PostPosted: Wed Jul 01, 2020 8:02 pm
by Robin Leadbeater
Jaroslaw Grzegorzek wrote:Hi,
why RA=12 and low DEC again !!!


Another one too low in a bright sky for me too :(

Re: at2020nvb a bright transient in NGC4457

PostPosted: Fri Jul 03, 2020 12:09 am
by Peter Velez
Not too far south for me - if anything, its a bit too far north. :D

Made a start on this last night but the observatory roof closed on me due to high humidity. Will give it another go in the next few days.

Pete

Re: at2020nvb a bright transient in NGC4457

PostPosted: Sat Jul 04, 2020 1:51 am
by Peter Velez
I managed to collect 2 hours of data on this SN last night.

Here is the spectrum produced with PlotSpectra. I'm still learning how to annotate and measure with the program.

Matched with Gelato to a Type 1A SN - best fit is 2003du 9.9 days before maximum. However the next nearest best fit is to 1992A only 5 days before maximum so I am not confident on the time to maximum yet. The response curve is a bit ropey as I used a reference star at the beginning of the imaging run so it drifted over the 2 hours. Gelato plot is also attached.

Its reported to have a Si II velocity of 12,500 km/s which matches nicely with the dip at 6031A in my data.

https://wis-tns.weizmann.ac.il/astronot ... e/2020-130

Lastly, I attach a screenshot taken with my guider. The SN is quite bright and I needed to tweak the contrast to tease it out from the galaxy.

Looks like I have a target for the next week or 2 to play with.

Pete

Re: at2020nvb a bright transient in NGC4457

PostPosted: Sat Jul 04, 2020 1:24 pm
by Robin Leadbeater
Excellent !

If you like you could sign up to the BAA spectroscopy database and add your spectra there. (You do not need to be a BAA member)
https://britastro.org/specdb/index.php

(You will see all my spectra including supernovae there)

Cheers
Robin

Re: at2020nvb a bright transient in NGC4457

PostPosted: Sat Jul 04, 2020 1:32 pm
by Robin Leadbeater
Or if you post the 1D fits or dat file here (as a zip file so the forum accepts it)
I could run it through SNID for you which might give a better estimate of age

Cheers
Robin

Re: at2020nvb a bright transient in NGC4457

PostPosted: Sun Jul 05, 2020 12:31 pm
by Peter Velez
Thanks Robin

here is the .fit file - zipped. Let me know if this is not what you need.

I'll look at submitting this to the BAA database tomorrow.

Mount issues here today so no new data - will give it another go tomorrow if I can wrangle the rig.

Pete

Re: at2020nvb a bright transient in NGC4457

PostPosted: Sun Jul 05, 2020 6:14 pm
by Robin Leadbeater
Thanks Peter,

SNID suggests -1.3 days from max but with an uncertainty of +-4.8 days. (Itagaki first spotted it at 15.5 mag C on 2020/06/24.50 )

I see there are now two spectra on TNS, the earliest one is by the Italian amateur team also using an ALPY600 but the professionals reported first so get the credit for the classification even though they did not publish their spectrum at first :(

Cheers
Robin

Re: at2020nvb a bright transient in NGC4457

PostPosted: Mon Jul 06, 2020 1:25 pm
by Peter Velez
Thanks Robin

How odd - priority based on professional status rather than time of publication.

Managed another decent session on this one tonight. Will process and, if usable, will post in the am

Pete