AT2019hau - Possible nova (mag 14) in Cygnus

[Robin Leadbeater]

From: Transient Name Server
Sent: Friday, June 07, 2019 3:15 PM
Subject: TNS - New reports and classifications


The following new transient/s were reported on:
https://wis-tns.weizmann.ac.il/object/2019hau
RA=19:28:22.236, DEC=+55:32:01.28, Discovery date=2019-06-07 08:52:48, Discovery mag=14 ABMag, Filter: g - Sloan, Reporter: K. Z. Stanek, C. S. Kochanek, for the ASAS-SN team, Source group: ASAS-SN



Best Regards,
The TNS team

[Peter Somogyi]

Fresh result from last night, switching to the Alpy setup quickly when received the vsnet-alert:

star choice in the red cross

guide_asassn-19om_20190607_889.jpg (42.78 KiB) Viewed 10118 times

6 x 30 minute, 300/1200 Newton + Alpy 600 (18 micron slit), ATIK 414 EXm camera:

Strong and narrow Balmer and He I lines + HeII 4686 present, but the continuum is CV-like.
Uploaded spectrum to britastro specdb (https://www.britastro.org/specdb) under the name "ASASSN-19om".

Peter

[Francois Teyssier]

Nice spectrum on a faint target, Peter!

Yes, the continuum looks to that of a CV.
But the emission is inusual for a CV in outburst, the lines are faint, no absortions ...

Nova: The He I and (then He II) appears about two mags after the maximum ; there's no Fe II lines which would be the case for a low speed nova (with narrow lines)

It looks to be a symbiotic in outburst (TiO bands overhelmed), with a strong interstellar extinction (thus strong blue continuum)

New spectra are very welcome!
François

[Robin Leadbeater]

The rise was very rapid and from the latest ASAS-SN photometry, it may already be starting to fade
https://asas-sn.osu.edu/light_curves/9b ... d50528c720
https://lasair.roe.ac.uk/object/ZTF19aaxugwk/

I am not sure about high IS extinction. This would show as a reddening of the continuum I think. Also there is no obvious Na D absorption and the total galactic extinction E(B-v) is only ~0.1 in this direction

Cheers
Robin

[Robin Leadbeater]

I have pointed Kris Stanek/Jay Strader of the ASAS-SN team here. Perhaps they will have some suggestions

Cheers
Robin

[Peter Somogyi]

Glad to see it's an interesting object, yesterday night made a repeat with the same setup:

asassn-19om_20190607_vs_0608.png (10.45 KiB) Viewed 9946 times

I believe the target has faded a lot, hence the narrow spikes should be coming from noise on the new spectrum.
Verified also the continuum's blue fade validity (taken Iot Cyg 3 times in a before-mid-after fashion, starting at beginning of the night in both cases).
Uploaeded this new spectrum to britastro specdb.

Meanwhile received a comment from Steve Shore (for 1st spectrum):
"I'll bet a cataclysmic, likely a VV Pup-type system, perhaps an AM CVn
or AM Her. Very low extinction (no hint of Na I), and the Balmer lines
are pretty opaque."

Cheers,
Peter

[Robin Leadbeater]

I thought AM CVn systems were hydrogen poor ?
It looks rather like SDSS 0155 from this paper
https://iopscience.iop.org/article/10.1 ... /fulltext/
section 3.4 fig 9
which was suggested to be either an AM Her or SW Sex type.
@Peter - Can you see any sign of an eclipse in the emission line strengths between the individual exposures ?

Robin

[Peter Somogyi]

Hello Robin, no I can't find anything conclusive (besides the fact that of course, the intensities vary):

Ha_HeII4686_velocities_75pct.jpg (123.14 KiB) Viewed 9907 times

(In raw ADU unit, no response calibration - except flat/bias/dark, and disabled cosmic ray removal for this graph)
Other lines too noisy or obviously inconclusive to show.
Peter

[Peter Somogyi]

I've asked Tamas Tordai to prepare his simultaneous observation serie, covering also my time.
He has prepared for us these graphs (JUN.7 - JUN.11 at this time), he is mostly doing differential photometry with a clear filter:

Author: Tamas Tordai

Summary of first 3 days since alert:

Author: Tamas Tordai

Author: Tamas Tordai

ASASSN-19om_Tamas_Tordai_JD58645_CV--.png (41.01 KiB) Viewed 9813 times

Author: Tamas Tordai.

Based on these results, the outcome I've been told that it's most certainly a UGWZ-type dwarf nova.

Another update - 2 new spectra available, see:

https://wis-tns.weizmann.ac.il/object/2019hau

2019-06-09 22:08:32 UH88/SNIFS
2019-06-09 12:00:00 UH88/SNIFS
(the UH88 must be this 2.2 meter one at Mauna Kea: https://en.wikipedia.org/wiki/UH88 )

I think these spectra mostly match with mine, but their range 4870-5020 is unavailable by the graph - for any reason.

Cheers,
Peter

[Robin Leadbeater]

Hi Peter,

Yes I saw the report of super humps on vsnet but the the spectrum is perhaps unusual for a UGWZ outburst ?
I have had a comment back from Jay Strader "The H and He (especially He II) and lack of Fe or N lines makes it very likely to be a dwarf nova, though an unusual one to be sure." I found this reference though that suggests the spectrum can be very variable between absorption and emission
https://arxiv.org/abs/astro-ph/0401292

Cheers
Robin