SN 2018hna

[Peter Somogyi]

Hello,

This SN seem to have also reached amateur range (http://www.rochesterastronomy.org/snimages: today 13.7 mag).
After almost 2 months of this SN's discovery, last night I've put it on the list as the 2nd larger target for the case if weather allows (30 cm f/4 Newton, Alpy 600, 18 micron slit, ATIK 414, 3 x 1800 sec, 2019.01.19.112, R~670), cutting Gelato's comparison as the 2nd match:

gelato_asdb_sn2018hna_20190119_112.jpg (84.06 KiB) Viewed 16580 times

Gelato says 100% type II, however much more type IIP matches. With SN2012 (Type IIP) it estimates phase~50d that is close to the reality, with 1st match 1994N (Type II only) it tells 35.6d. Looking at these matches, my speculation that it's more like Type IIP, though not understanding classification system enough yet.

BTW, I can see Robin's first entry on TNS estimating type II the earliest:
https://wis-tns.weizmann.ac.il/object/2018hna

If I understand correctly, does the "Type II" label mean the subtype is yet unclear?

Cheers,
Peter
Attaching the fit:

asdb_sn2018hna_20190119_112.zip

(9.02 KiB) Downloaded 1458 times

[Robin Leadbeater]

Hi Peter,

Nice spectrum. It is a good reminder not to forget supernovae which are discovered early when faint. I think this must have been an unusually bright type II.
(EDIT I misread the z for this galaxy (it is faint but nearby) so the brightness now is in fact fairly typical of a type II at maximum brightness at this distance)

There was not enough evidence in my spectrum to decide if it was a normal type II or a possibly an early IIb. Others on TNS also classified it as type II but it is not clear if they eliminated the possibility of a IIb. Your later spectrum eliminates a type IIb which show only weak Hydrogen lines. IIP (plateau) are most easily distinguished by their light curve which has a pause. I have not looked at the light curve but I suspect since it is still bright after 2 months is could well be a IIP

Cheers
Robin

[Robin Leadbeater]

Actually, checking the light curve, it has been steadily rising for ~80 days since discovery so an odd light curve for a supernova.
https://lasair.roe.ac.uk/object/ZTF18acbwaxk/

Robin

[Robin Leadbeater]

I have asked around and it definitely is unusual behaviour for a type II but not unique, perhaps similar to SN1987A for example
https://purcell.ssl.berkeley.edu/~korpe ... img62.html
It will be interesting to see if any professionals are following this and what they make of it

Robin

[Peter Somogyi]

Hi Robin,

Thank you for looking after the info and light curves, I've had some readings by now, and assume profs should be waiting for a decline before judging any subtype.
The last 13.7mag reported on rochesterastronomy is standing out, maybe just an error (14 mag is the trend).
Let's see how it continues.

Peter

[Robin Leadbeater]

Hi Peter,

The light curve is already very different from the usual type II or IIP and similar to various suspected Blue Supergiant type II supernovae (including 1987A). See this paper for example
https://arxiv.org/pdf/1101.1298.pdf
Thanks to Emmanuel Conseil on the isn_chat group for the link to the paper

Cheers
robin

[Robin Leadbeater]

This supernova is now fading. See the ASAS-SN light curve here
https://asas-sn.osu.edu/light_curves/bf ... 9d23cec0c8

Despite its unusual very slow rise to maximum (~80 days) , the spectrum still closely matches match that of a normal type IIP SN at the same age. See attached ALPY 600 spectrum and example GELATO match

Cheers
Robin

gelatoplot.png (73.5 KiB) Viewed 16218 times

[Peter Somogyi]

Hi Robin,

I suspect the Vmag data is polluted now by the large absorption feature in the middle of green (Na I D ?), yet reading articles what is it exactly.
Here is my result (6 x 1800 sec) from last night, after spending 3 weeks without usable weekend-sky:

gelatoplot_1995ad.png (54.86 KiB) Viewed 16202 times

Althoguh Gelato offers the SN 1992H IIP even to me as a first match, I believe the Balmer velocities - with the blue end altogether - matching so perfectly, unlike 1992H that is showing well elaborated RV differences.
1995ad telling Phase=96.8d, whilst the 1992H match shows Phase=118.5d:

gelatoplot_1992H.png (50.78 KiB) Viewed 16202 times

Cheers,
Peter

asdb_sn2018hna_20190208_891.zip

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[Peter Somogyi]

Fresh result from this weekend, no big change except the H-alpha peak increase:

asdb_sn2018hna_20190216_956.png (55.13 KiB) Viewed 16064 times

- Peter

asdb_sn2018hna_20190216_956.zip

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