Spectroscopic Observations of PNV J17184504-2454221 (Nova Oph 2017) as a Classical Nova in the Iron Curtain Phase
ATel #10975; Paul Luckas, International Centre for Radio Astronomy Research, University of Western Australia
on 16 Nov 2017; 01:35 UT
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PNV J17184504-2454221 (ATel #10959) has recently been announced as a nova candidate. We obtained a medium resolution spectrum (0.82A/px) using an Alpy600 spectrograph (two exposure, 600 sec, S/N of about 50 in the continuum from 4000-7000A) on 2017 Nov. 14.5 UT that confirm this identification and show that the ejecta are quite optically thick and at high expansion velocity. The wings of the Balmer alpha extend to greater than +/-3000 km/s with a narrower (FWHM ~ 2800 km/s) profile with two additional emission enhancements at about -360 km/s and +570 km/s, the latter being weaker by about 30 percent). The low ionization metal lines are all broad, Fe II 5018 and 5169A lines have maximum absorption (P Cyg) radial velocities of -1800+/-100 km/s with red wings extending to +2000 km/s. The Balmer lines do not show absorption (Halpha-Hepsilon) but show similar profiles with lower maximum emission velocity in the wings for the higher series members and asymmetric profiles with the blue core stronger than the red, suggesting possible asymmetric ejecta . Notably, Na I D displays a P Cyg profile with the emission being similar in form to the Balmer lines and the maximum absorption (depth of about 30 percent) at - 1500 km/slow velocity. Si II 6347,6374A are present with weaker absorption (no terminal edge is seen on any P Cyg profile) with a similar velocity to Na I, about -1500 km/s. Mg I 5173A is also present, with a HWZI of 2000 km/s and FWHM of 2600 km/s with similar structure on the emission as Na I. The [O I] lines are absent as are the He I lines. No strong forbidden metal ion lines were detected, and no lines have been seen from C I or C II. The spectrum is too weak below 4000A to say whether Ca II might be present. The spectrum is therefore typical of the opaque (Fe curtain) stage of the ejecta around or a bit after optical maximum and after the maximum of the recombination wave following the initial fireball. The strong neutral emission spectrum is, however, unusual and may indicate a more massive ejection. Unfortunately, the nova is likely to be unobservable from here on but it would be worth the effort to obtain a few more spectra before it is no longer visible.
ARAS Nova Spectroscopic Database