New transcient, perhaps a nova

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Re: New transcient, perhaps a nova

Postby Francois Teyssier » Tue Sep 12, 2017 2:59 am

With the help of Steve Shore, an ATel on the evolution of this peculiar nova and notably the rebrightning

http://www.astronomerstelegram.org/?read=10737

Continuing ARAS visible spectroscopic monitoring of the slow classical nova Sct 2017 = ASASSN-17hx

ATel #10737; Joan Guarro, Paolo Berardi, Umberto Sollecchia, Tim Lester, Terry Bohlsen, Paul Luckas, Fran Campos, Lorenzo Franco, Olivier Garde, Christian Buil, Jim Edlin, François Teyssier (ARAS Group)
on 12 Sep 2017; 01:37 UT
Distributed as an Instant Email Notice Novae
Credential Certification: S. N. Shore (shore@df.unipi.it)


We report the results of our continuing spectroscopic monitoring of the slow classical nova Sct 2017 = ASASSN-17hx (Atel# 10523, #10524, #10527, #10558, #10736) as part of the ongoing program by members of the ARAS group. Spectra span the interval from 2017 Jun 29.6 through Sep. 9 with resolutions ranging from from about 580 to 14000, depending on the spectrograph (Alpy600, LISA, LHIRES, eShel) covering ~3800-7200A and S/N of about 50-100) with exposure times ranging from 3500 to 10400 sec. The sequence spans the light curve interval starting at the plateau following the initial rise through the ongoing second maximum and we report here some preliminary results to indicate the richness of the growing archive and the complexity of the phenomenology. All lines have varied in strength and profile with what appears to be cycling coincident with light curve changes. The Balmer emission line wings varied in extent, first rto 1000 km/s until around Jul. 14, then narrow (500 km/s) through extending to about 500 km/s, showed a dramatic re-broadening to 1000 km/s around Aug. 2 and reaching 1300 km/s by Aug. 20. Although the core of the profile (|vrad|<500 km/s) has become more boxy (like Fe II), he low level extended wings have persisted. Balmer line absorption velocities ranged from -400 km/s (from discovery through Aug. 1), the wings expanded Aug. 13 through Aug. 19 with the narrow absorption at -400 km/s steadily decreasing through Sep. 5. High velocity absorption at -1000 km/s reappeared on Sep. 8 along with increased visibility of the -400 km/s feature, the main changes began around the time of rise to second visible maximum. The Si II 6347,6371 doublet showed strong P Cyg profiles from Jul. 10 through Jul 28, then only absorption through Aug.1, a new absorption features appeared at -800 km/s that persisted (width about 150 km/s) and the emission briefly reappeared through Aug. 7. Fe II 5169 (used as a proxy for the iron absorption spectrum) tracked the Si II lines through Aug. 12, thereafter developing a boxy, complex emission profile with absorption at The Si II doublet disappeared during the local visible minimum and reappeared as strong P Cyg on Aug. 7 with an wings extending to 800 km/s. The low velocity (-300 km/s) absorption reappeared on Sep. 8. The Na I D doublet displayed detached absorption at -300 km/s from around Jul 18 through Aug. 3, when a high velocity absorption appeared at -800 km/s that lasted only a few days, coincident with the appearance of He I 5876 in emission. Na I D absorption has remained otherwise invariant through out this interval. He I 5876 showed a P Cyg profile from Jul 16 through around Jul 18 and disappeared between around Jul 25 - Aug. 1, after which the high velocity absorption at -1000 km/s reappeared through Sep. 8. He I 6678 behaved similarly. No [O I] lines have yet appeared, nor have the C I 6828,7114 lines seen during the Fe-curtain stage of V339 Del and other CO novae. Observations are continuing, all spectra are publicly available though the ARAS database http://www.astrosurf.com/aras/Aras_DataBase/Novae/2017_NovaSct2017.htm

See also:http://www.astronomerstelegram.org/?read=10736

Thanks to all the contributors fot the excellent coverage
Of course, continuous observations are strongly encouraged


For similar novae, see V723 Cas, HR Del
and V5558 Sgr, very close :https://arxiv.org/pdf/1105.1614.pdf

V5558Sgr.PNG
V5558Sgr.PNG (88.43 KiB) Viewed 2885 times



François Teyssier
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Re: New transcient, perhaps a nova

Postby James Foster » Tue Sep 12, 2017 1:35 pm

Thanks for the head-up François on the ATel message for this interesting object!
Here is a spectra I took of this object from my high altitude (2500 meter elevation) dark sky site on 27Aug17:

Image

Shot with a 33cm aperture classical cassegrain telescope working at F/7.5 with LISA spectroscope using a 23micron slit.
According to the AASVO this object is continuing to rise in magnitude...up to V=9! I'll try to get more spectra after I re-tune the
LISA for my 45cm aperture telescope at home....alas under much worse conditions (15 km from downtown LA near sea level).

James
James Foster
eShel2
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope,
LISA IR/Visual Spectroscope (IR Configured Presently)
Alpy 600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
James Foster
 
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Re: New transcient, perhaps a nova

Postby Francois Teyssier » Tue Sep 12, 2017 3:38 pm

Hi James,

Nice spectrum! It is welcome in the data base, you've just to send it.

The identification is globally correct. Of course, He I 4922 is blended with Fe II 4924 (42)
But, not for [Fe VI], for two raisons:
1) The ejecta is still optically thick, very thick, so no "forbidden" lines (collisionnaly excited lines) which require much lower density
2) The hot object (expended envelop of the white dwarf) isn't sufficiently hot at this stade to produce high ionization
Fe VI needs 100 eV photons (about 100 000 K)
Late August, T* is about 20000 K at a first order
See http://www.astronomie-amateur.fr/Documents%20Spectro/Ionisation.pdf

All the best,

François
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Re: New transcient, perhaps a nova

Postby Joan Guarro Flo » Tue Sep 12, 2017 8:01 pm

Hi,
These is a new graphic of Nova Sct 2017.
Joan.
Attachments
novasct2017_20170911J. Guarro.png
novasct2017_20170911J. Guarro.png (38.91 KiB) Viewed 2860 times
novasct2017_20170911J. Guarro2.png
novasct2017_20170911J. Guarro2.png (61.34 KiB) Viewed 2860 times
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Re: New transcient, perhaps a nova

Postby Tim Lester » Wed Sep 13, 2017 6:57 am

Hi all,

Here is nova sct 2017 for Sept 13th.
novasct2017_20170913_024_tlester.png


Halpha and Hbeta for the last 4 nights.
novasct2017_20170913_024_Halpha_tlester.png
novasct2017_20170913_024_Halpha_tlester.png (36.07 KiB) Viewed 2850 times

novasct2017_20170913_024_Hbeta_tlester.png
novasct2017_20170913_024_Hbeta_tlester.png (50.01 KiB) Viewed 2850 times


Tim
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Re: New transcient, perhaps a nova

Postby James Foster » Wed Sep 13, 2017 1:33 pm

Nice high resolution Ha & Hb spectrum Tim!
I was wondering how you compute the velocity plots for the Ha & Hb spectra?

Do you compensate for any rotation and/or RV before you plot multiple dates?
Its one of the items I need to teach myself as I start to use the Lhires III I'm ready to work with.

I'll shoot one or two more LISA spectra of this star then experiment with the 2400 and 1800 mm/l gratings
I have with the Lhires III.

James
James Foster
eShel2
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope,
LISA IR/Visual Spectroscope (IR Configured Presently)
Alpy 600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
James Foster
 
Posts: 395
Joined: Sun Jan 24, 2016 7:14 am

Re: New transcient, perhaps a nova

Postby James Foster » Wed Sep 13, 2017 1:38 pm

To: François,

RE:"See http://www.astronomie-amateur.fr/Docume ... sation.pdf"

Thanks for this! I added it to my collection of important spectral notes. I will of course send you my Mt. Pinos spectra data as soon as I QC it for compliance with BeSS.

James
James Foster
eShel2
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope,
LISA IR/Visual Spectroscope (IR Configured Presently)
Alpy 600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
James Foster
 
Posts: 395
Joined: Sun Jan 24, 2016 7:14 am

Re: New transcient, perhaps a nova

Postby Tim Lester » Wed Sep 13, 2017 8:07 pm

James,

I use the velocity plot feature of PlotSpectra and simply choose the listed Halpha or Hbeta as the center point on the chart settings dialog.
I do correct for Heliocentric radial velocity when I process the spectra with ISIS but generally nothing more.

PlotSpectra is available here: https://1drv.ms/f/s!AvXqhKI5kEGRjEhdaQ6jaj8AHx_L

Tim
Tim Lester
 
Posts: 167
Joined: Fri Apr 04, 2014 6:31 pm
Location: Arnprior Ontario

Re: New transcient, perhaps a nova

Postby James Foster » Thu Sep 14, 2017 11:19 am

To: Tim,

Thanks for the feedback! I've used PlotSpectra as well (see spectra of ASASSN-17hx above).

All I've done with this software, with respect to spectra, is to display a 2nd extended (scaled) y-axis, display the more common emission lines, and perhaps
correct for some cosmological shift in SN on the X-axis.

I cant find any documentation to apply spectra for RV analysis. I guess I'll have to do some more reading elsewhere to derive RVs from the spectra like you do.
Thanks for the great diagrams and time variation on this object.

James
James Foster
eShel2
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope,
LISA IR/Visual Spectroscope (IR Configured Presently)
Alpy 600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
James Foster
 
Posts: 395
Joined: Sun Jan 24, 2016 7:14 am

Re: New transcient, perhaps a nova

Postby umberto sollecchia » Thu Sep 14, 2017 1:14 pm

Bonne journée à tous, place le profil de la nuit du 13-09-2017, pris avec un spectroscope construit par notre cher ami amateur Joan Guarro Flo.
Umberto

asassn-17hx_20170913_788_Umberto Sollecchia.png
asassn-17hx_20170913_788_Umberto Sollecchia.png (23.1 KiB) Viewed 2803 times


asassn-17hx_20170913_788_Umberto Sollecchia crop.png
asassn-17hx_20170913_788_Umberto Sollecchia crop.png (18.47 KiB) Viewed 2803 times
umberto sollecchia
 
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